The Possible Effects of Non-steroidal Anti-inflammatory Drugs (NSAIDs) on the COX-2 Pathway of Skeletal Muscle Repair Megan Obarowski*, Sarah Cooper, John Daley and Randy Tammara *Corresponding Author: [email protected] HAPS Educator. Vol 21, No. 2, pp. 28-35. Published August 2017. doi: 10.21692/haps.2017.012

Obarowski M. et al. (2017). The Possible Effects of Non-steroidal Anti- inflammatory Drugs (NSAIDs) on the COX-2 Pathway of Skeletal Muscle Repair. HAPS Educator 21(2): 28-35. doi: 10.21692/haps.2017.012 The Possible Effects of Non-steroidal Anti-inflammatory Drugs (NSAIDs) on the COX-2 Pathway of Skeletal Muscle Repair

Megan Obarowski1, Sarah Cooper MEd2 , John Daley PhD3, and Randy Tammara, PharmD4 1Gwynedd Mercy University, Accelerated BSN Program, 1325 Sumneytown Pike, Gwynedd Valley, PA 2,3Arcadia University, Department of Biology, 450 South Easton Road, Glenside, PA 19038 4Arcadia University, Masters in Public Health Program, 450 South Easton Road, Glenside, PA 19038 [email protected], [email protected], [email protected], [email protected]

Abstract Non-steroidal anti-inflammatory drugs (NSAIDs) are thought to play a role in the process of muscle repair. However, the mechanism by which they function remains poorly understood. Recent studies have focused on the link between the COX-2 pathway of muscle repair and anti-inflammatory drugs. This article examines representative studies by Oak et al. (2014) and Lu et al. (2015), who have investigated this process in-depth and found differing results regarding the effects of COX inhibitors on the repair of skeletal muscle after injury. These studies also demonstrate that NSAIDs operate within the COX-2 pathway, which is a necessary pathway for muscle repair. doi: 10.21692/haps.2017.012 Key Words: Non-steroidal anti-inflammatory (NSAIDs), COX-1, COX-2, sports-related injury, muscle repair

Introduction Non-steroidal anti-inflammatory drugs (NSAIDs) are among damage over time (AGA 2017). For reasons that are not yet the most commonly used pain relief medications in the world. understood, NSAID use can trigger allergic reactions in certain More than 30 million Americans use NSAIDs each day for relief people who have asthma (AGA 2017). from common discomforts such as headache, arthritis, athletic COX-2 inhibitors were designed to alleviate pain while injuries, tissue swelling and the reduction of fever (American avoiding the gastrointestinal problems associated with other Gastroenterological Association AGA 2017, Schoenfeld 2012). NSAIDs by blocking only the COX-2 enzyme, which is not In the United States alone, approximately 30 million children associated with the production of prostaglandins that protect and teenagers participate in organized sports, resulting in the lining of the GI tract. However, levels of COX-1 and COX 3.5 million sports-related injuries and 775,000 children under 2 enzymes are normally balanced in the body and blocking the age of 14 treated in hospital emergency rooms each year only one of them may result in unexpected problems. For (Johns Hopkins Health Library 2017). Sprains and strains are example, COX-1 enzymes are responsible for making the the most common sports-related injuries. prostaglandin derivative thromboxane, which is associated with blood clotting (Caughey et al. 2001). This substance is When an injury such as a sprain or strain occurs, damaged normally kept in check by prostacyclin, which is synthesized tissues release prostaglandins that cause tissue swelling and with the help of COX-2 enzymes. When only COX-2 enzymes amplification of electrical pain signals. NSAIDs block the are blocked, prostacyclin levels decrease while the influence COX (Cyclooxygenase) -1 and COX-2 enzymes that play an of COX-1 enzymes on thromboxane production continues important role in prostaglandin production. The results are unchecked causing the risk of heart attack and stroke to less pain and reduced swelling at the site of injury (Bondesen increase (Caughey et al. 2001). This risk was considered to be et al. 2004). so high that a COX-2 inhibitor known as Vioxx was removed from the market in 2004 (Lesher 2004). There are side effects associated with habitual NSAID use, Given this history of side effects associated with COX-1 and however, the most common of which are gastrointestinal COX-2 inhibitors, and the prevalence of sports-related injuries, problems such as ulcers. For example, an array of it is not surprising that questions have been raised with prostaglandins produced by gastric epithelial cells, which respect to the effect of long term NSAID use on muscle repair. the COX-1 enzyme helps to produce, protects the stomach Muscle Injury lining by having stimulatory effects on gastric mucus and The two most common types of muscle injuries are classified bicarbonate production (Wallace 2008). Blocking the COX- as shearing injuries (strains) and in situ necrosis injuries 1 enzyme by continuous use of NSAIDs slows down the (Järvinen et al. 2013). A shearing injury (strain) occurs production of this prostaglandin, which may result in an when the muscle fiber, the surrounding basal lamina and increased rate of acid-induced damage to the tissues of the the neighboring capillaries are all damaged. An in situ gastrointestinal tract. NSAIDs can also raise blood pressure necrosis injury can occur, for example, in response to limb by reducing blood flow to the kidneys, which results in compression or the interruption of blood flow by a blood fluid build-up in the blood stream and may lead to kidney clot; in these situations, the muscle fibers are partially

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necrotized but there is no damage to the basal lamina or form of prostaglandin, known as PGH2 (Bondesen et al. the neighboring capillaries (Järvinen et al. 2013). Shearing 2004, Ricciotti and FitzGerald 2011). This inactive form is

injuries are the most common type of muscle injury. They then metabolized into an active form of PG2, PGF2α, PGI2, or

are classified as mild, moderate or severe based on the extent PGD2 (Ricciotti and FitzGerald 2011, Bondesen et al. 2004). of the muscle fiber damage and the size of the hematoma Active prostaglandins are moved out of the cell where they associated with the injury (Järvinen et al. 2013). subsequently bind to G-protein coupled receptors or nuclear peroxisomes receptors associated with target cells (Bondesen Myogenesis et al. 2004). Any type of muscle injury triggers an inflammatory response The most abundant PG in the body is PGE , which is involved in the body. Muscle injury results in damage to the cellular 2 in producing the typical signs of inflammation such as pain, make-up of the muscle fiber and the muscle becomes heat, redness and swelling (Riciotti and FitzGerald, 2011). incapable of normal contraction (Järvinen et al. 2013). Muscle PGE acts on the neurons of the spinal cord and brain that regeneration, myogenesis, re-creates a working muscle fiber 2 cause pain and is found in high concentrations in the synovial (Bondesen et al. 2004). fluid. Both isoforms of the COX enzyme, COX-1 and COX-2, catalyze the production of inactive PGH , which leads to the The three phases of the muscle healing are destruction, repair, 2 production of the same bioactive PGs (Bondesen et al. 2004). and remodeling (Järvinen et al. 2013). During the destruction The difference between the two isoforms is in the amount of phase, the injured muscle fibers become necrotic. Necrosis each bioactive prostaglandin that is produced. is stopped by the formation of a new sarcolemma and the area between the two ends of the new sarcolemma fills with a COOH hematoma. The formation of the hematoma signals the start Arachidonic of the inflammatory response (Järvinen et al. 2013). acid NSAIDs COX-1 & COX-2 During the second phase of the muscle healing process, the O COOH repair phase, monocytes and macrophages phagocytize PGH2 damaged muscle fibers and basal lamina in order to make O

room for the regeneration of new fibers (Arnold et al. 2007, OH Järvinen et al. 2013). Following phagocytosis, satellite cells, which are exposed when the basal lamina ruptures, differentiate into myoblasts (Bondesen et al. 2004, Järvinen Tissue-speci c isomerases et al. 2013). Committed stem cells form myoblasts through

a direct process, while undifferentiated stem cells produce COOH O O HO HO COOH COOH COOH COOH

more stem cells, which are stored in the newly formed O O HO O HO HO muscle (Järvinen et al. 2013). Myoblasts form a myotube OH OH OH OH OH that punctures and expands into the scar tissue of the injury. TxA2 PGD2 PGE2 PGI2 PGF2 The muscle regains its blood flow as capillaries are replaced EP1, EP2, (Järvinen et al. 2013). EP3*, EP4 TP, TP DP1, CRTH2 IP FPA, FPB *up to 8 splice In the final stage of the process, the remodeling phase, variants Platelets, VSMCs, Mast cells, brain Brain, kidneys, Endothelium, Uterus, airways, myotubes mature into contractile muscle fibers and newly macrophages, airways VSMCs, platelets VSMCs, platelets, VSMCs, eyes formed muscle fibers insert themselves into the tendon. A kidney kidney, brain small area of scar tissue remains between the two halves of the newly formed muscle fibers (Järvinen et al. 2013). Each of Flow chart shows the derivation of five prostaglandins from the three major steps of myogenesis is controlled by different arachidonic acid in the presence of COX-1 and COX-2. Adapted from Ricciotti and Fitzgerald 2011. Illustration by Kelly Paralis, factors such as chemoattractants, growth factors, and Penumbra Design, Inc. prostaglandins (Bondesen et al. 2004).

NSAIDs Prostaglandins NSAIDs can be bought over the counter at low dosages or Prostaglandins (PGs) act as modulators of the inflammatory prescribed by medical professionals in higher dosages. They response in muscle tissue and other body tissues. They can either be selective COX inhibitors or non-selective COX are also involved in many important stages of myoblast inhibitors. Selective COX inhibitors act on only the COX-2 development (Bondesen et al. 2004). Prostaglandins, which enzyme. Non-selective COX inhibitors act on both isoforms are up-regulated when tissue is inflamed, are synthesized of the enzyme. Well-known NSAIDs include: ibuprofen, when COX enzymes convert arachidonic acid, which is flurbiprofen axetil, celecoxib, and licofelone (Table 1) (Lu et secreted by prostaglandin membranes, into an inactive al. 2015, Oak et al. 2014). Ibuprofen is a non-selective COX

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inhibitor that is available over the counter. It is used for The ability of NSAIDS to reduce prostaglandin production has pain management and inflammation due to muscle injury, effects within the body in addition to their ability to reduce headache, or menstrual cramps and to reduce fever. It is also pain and inflammation (Ricciotti and FitzGerald 2011). Many effective in reducing post-operative pain. Flurbiprofen axetil, studies have shown the importance of PGs in the biological another nonselective COX inhibitor, is typically administered processes of healing muscle such as their impact on the intravenously by medical professionals (Yamashita et al. 2006). activation of the muscle stem cells found in the basal lamina Celecoxib is a selective COX-2 inhibitor that also targets the of myofibers, precursor cell activation, myoblast proliferation, Na+, K+, and Ca++ channels in muscle cells. It is often used to myoblast fusion, and the synthesis of muscle proteins (Prisk treat arthritis and acute pain (Frolov et al. 2011). and Huard 2003, Schoenfield 2012). If NSAIDs are blocking the action of the COX enzyme, one would hypothesize that Recent research that suggested that the protective effects there will be significant effects on the regeneration of muscle of COX-2 inhibitors might not be as significant as was after injury. This has led to additional investigations of the originally thought, led to the development of a new class effectiveness of NSAIDs in treating muscle injury. of drugs, 5-LOX inhibitors, to control inflammatory diseases (Celotti and Durand 2003). In general, these drugs are Recently, a link has been found between COX enzymes formulated as balanced inhibitors of 5-lipoxygenase (5-LOX) and the repair of injured muscle tissue (Oak et al. 2014, Lu and cyclooxygenase (COX-1 and COX -2). 5-LOX inhibitors et al. 2015). A link has also been found between the COX- combined with COX inhibitors block the formation of all the 2 isoform and NSAIDs suggesting that NSAIDs may have a enzymatically arachidonic acid-derived metabolites, COMPARISON OF COMMONLY USED NSAIDs AND THEIR ASSOCIATED RISKS both prostaglandins and COX-2 leukotrienes (Celotti and DRUG SELECTIVITY GI Risk Cardiovascular Risk Durand 2003). These (In vitro) drugs have been shown to possess a high degree Aspirin Low Moderate Low of anti-inflammatory efficacy without serious Celecoxib (Celebrex) High Low Moderate to high side effects. Licofelone is both a 5-LOX and a non- Diclofenac (Voltaren) High Moderate High selective COX inhibitor. It Flurbiprofen (Ansaid) Low High Data not available possesses powerful anti- inflammatory, analgesic and Ibuprofen (Motrin, Advil) Moderate Low Moderate to high anti-asthmatic effects at doses that are low enough Indomethacin (Indocin) Low Moderate to High Moderate to not cause significant gastrointestinal side effects Ketoprofen (Orudis) Low Moderate Data not available (Celotti and Durand 2003). Any of the NSAIDs can be Ketorolac (Toradol) Low High Data not available used for the treatment of Licofelone Data not available Data not available Data not available pain and inflammation due to muscle injury. Meloxicam (Mobic) High Low Moderate

Nabumetone (Relafen) Moderate Low Data not available

Naproxen (Anaprox DS) Low Moderate Low to Moderate

Oxaprozin (Daypro) Low High Data not available Table 1. Comparison of Commonly Used NSAIDs and Piroxicam (Feldene) Moderate High Low their associated risks. Pharmacist’s Letter 2015; 31(9):310902 Pharmacist’s Letter 2011; 27(11):271106 Therapeutic Research Center 3120 W. March Lane, Stockton, CA 95219, Tel:(209) 472-2240 Fax:(209) 472-2249

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complex effect on the healing of muscle injuries characterized difference seen in the cross-sectional area (CSA) of the muscle by early signs of improvement followed by subsequent samples. There was, however, a 36% size reduction seen late impairment in functional capacity and histology of in both type I and type IIA fibers present in the licofelone muscle tissue (Prisk and Huard 2003). Studies are currently treated muscle. The number of type IIB fibers doubled in the investigating the underlying effects this link may have on the drug-treated muscle, which accounted for the appearance of regeneration of muscle fibers after injury. With these new unchanged muscle mass, while the number of type IIX fibers findings, questions regarding the efficiency of NSAIDs and the decreased by half (Oak et al, 2014). treatment of inflammation associated with muscle injury are being examined (Oak et al. 2014, Lu et al. 2015). To test the contractility of the muscle, muscle fibers were isolated and placed in a solution to relax the fibers, which Link Between the COX-2 pathway and NSAIDs ultimately allows for a complete contraction. The muscle was then attached to a servomotor and a force transducer. Non-steroidal anti-inflammatory drugs are thought to The results of these contractility experiments showed no play a role in the process of muscle repair. However, the differences in the CSA. Maximum isometric force and specific mechanisms by which they function are poorly understood. force of the licofelone treated muscle displayed a significant Recent studies have focused on the link between the COX- decrease of 27% and 23%, respectively (Oak et al. 2014). 2 pathway of muscle repair and anti-inflammatory drugs. Studies by Oak et al. (2014) and Lu et al. (2015), have examined To analyze gene expression, messenger RNA was isolated this process in-depth and found differing results regarding from the muscle using a miRNeasy kit (Oak et al. 2014). the effects of the COX-2 pathway on the repair of skeletal Analysis of the adipogenesis and lipid storage transcripts muscle tissue after injury. These studies also demonstrated showed no clear pattern with a significant decrease in PPAR-γ, that NSAIDs operate within the COX-2 pathway, which is a perilipin 1, and FSP27 and a significant increase in DGAT1, necessary pathway for muscle regeneration (Oak et al. 2014, perilipin 5, FIT1, ACAT. Inflammation and atrophy related Lu et al. 2015). genes showed an increase in COX-2, IL-10, embryonic myosin heavy chain (eMHC) but no increases any of the others in COX Inhibitors Improve Healing in Rat Model this group. The autophagy test showed significant increase The COX-2 pathway operates as a pro-inflammatory pathway in each of the genes measured: beclin-1, Vps34, ATG16L1, that occurs after a muscle has been injured (Bondesen et al. and ATG5. For the extracellular matrix synthesis and fibrosis 2004). Anti-inflammatory drugs such as NSAIDs target and markers, increases were seen in MMP8 and scleraxis (Oak inhibit this pathway by acting as competitive inhibitors of et al. 2014). There were no significant differences seen in the COX-2 enzyme. By doing this, NSAIDs reduce swelling, macrophages and fatty macrophage accumulation (Oak et al. redness, and pain levels (Ricciotti and FitzGerald 2011). In 2014). a study done by Oak et al. ( 2014) the effects of the anti- inflammatory drug, licofelone, on the repair of an injured The content of hydroxyproline, an amino acid associated with rotator cuff were examined. The goal of this study was to collagen, was also examined. Hydroxyproline is often used determine if the presence of licofelone had a positive or as a biomarker for collagen in muscle tissue (Oak et al. 2014). negative effect on the ability of muscle fibers to produce The results showed that half the amount of hydroxyproline force following repair. Any reductions in force production was present in the licofelone treated muscle, compared to would be interpreted as problems relating to the repair of that of the control muscle (Oak et al. 2014). Following the muscle fibers. This study examined the supraspinatus muscle hydroxyproline assessment, triglyceride and phospholipid of the rotator cuff of Spague-Dawley rats, which had been levels of the muscles were examined. The results showed a surgically torn using the deltoid-splitting technique and then 78% reduction in the triglyceride levels in licofelone treated repaired with Mason-Allen sutures (Figure 2) (Oak et al. 2014). muscles while levels of phospholipids were similar in both samples (Oak et al. 2014). A 40 mg/kg dose of solid licofelone was dissolved in hydroxpropyl methylcellulose (HPMC) to make a liquid The last part of the experiment performed by Oak et al. (2014) solution that could be administered to the rats via a stomach involved gross anatomical analysis and biomechanical testing. tube. The control rats were given HPMC without licofelone Anatomical testing of the enthesis of samples showed at the same rate as the experimental group. At the end of a increased redness, inflammation, and size (Oak et al. 2014). 28 day recovery period, the torn and repaired muscles were Biomechanical testing was done using Electroforce ELF3200 removed from the rats and a combination of biological assays uniaxial testing system with a 100 N load per cell, which is was performed in order to determine the role of NSAIDs in a standard load. For all biomechanical tests, the humerus muscle repair (Oak et al. 2014). with the supraspinous muscle still attached was used. The maximum load to yield, the peak stress, peak stiffness, and The results showed no differences in muscle mass measured CSA data were obtained as well. The results showed that by gross anatomical examination. There was also no there was no difference in the tendon CSA of the muscle

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samples and no differences in the displacement to yield The ibuprofen group received 10 mg·kg−1·d−1 of ibuprofen in amount. There was a 62% increase in the maximum load, their normal food post-operatively for seven days (Lu et al. a 51% increase in peak stress, and 73% increase in the peak 2015). Flurbiprofen axetil, was administered intravenously to stiffness of the licofelone-treated muscle samples (Oak et al. another group of rabbits for seven postoperative days at a 2014). dose level of 2 mg·kg−1·d−1 per day. The third group of rabbits received 8 mg·kg−1·d−1 of celecoxib in their food for seven The authors concluded that when a non-selective COX post-operative days (Lu et al. 2015). After a recovery period, inhibitor was present during the rabbits were sacrificed and the muscles were removed. Of muscle fiber regeneration, there was a stronger bone-tendon the twelve rabbits in each treatment group, eight were tested attachment, less inflammation, and stronger load to failure at each post-operative time point: three weeks, six weeks, and levels. This suggests that the use of NSAIDs can have a twelve weeks. Histological and biomechanical analyses were positive effect on the regeneration of muscle after injury. done on all sample muscles (Lu et al. 2015).

COX Inhibitors Impair Healing in Rabbit Model For biomechanical testing, the supraspinatus muscle was dissected, isolated from other nearby muscles, and placed In a study done by Lu et al. (2015) the effects of both selective into the MTS-858 biomechanical testing system. The sample and non-selective COX inhibitors on the process of post-injury was loaded to a 2.5 N cell, which is a low load cell, and load muscle regeneration in rabbits were studied. Ibuprofen and to failure was tested at a speed of 1 mm/s (Lu et al. 2015). flurbiprofen axetil were used as non-selective COX inhibitors For this test, the maximum load at failure and percentage and celecoxib was used as a selective COX-2 inhibitor (Lu et al. of maximum load were recorded. The results showed that 2015). The goal of this study was to determine the effects of the percentage of maximal load to failure decreased on he use of COX inhibitors on the repair of injured muscle tissue. the surgically repaired side of the muscle as compared to the normal side. After three weeks, there were significant Ninety-six New Zealand white rabbits were used as the animal differences between the celecoxib and flurbiprofen axetil model for this study because of the anatomical similarity of groups and the control group. There was no difference seen the rabbit shoulder to the human shoulder (Lu et al., 2015) between the ibuprofen and the control group. At week six, and the fact that shoulder injuries are among the top four there was only a significant decrease seen in celecoxib group injuries that occur along with hand, knee, and ankle injuries. compared to the control group. Flurbiprofen and ibuprofen The rabbits were divided into four groups and randomly did not show any significant differences. The same results assigned to one of three experimental COX inhibitor groups were observed at week twelve (Lu et al. 2015). or the control group. The supraspinatus muscle was surgically torn using the A B deltoid splitting approach and repaired using Mason-Allen sutures (Figure 2) Ssp (Lu et al. 2015). The rabbits were given post-operative penicillin for three days GT to prevent infection. Following this precautionary step, NSAID treatments Ssp were begun (Lu et al. 2015). GT

C D

Figure 2. Surgical technique for tearing and repairing the Supraspinatus muscle (Ssp) in Ssp rabbits. The tendon of the Ssp was removed from the greater tubercle (GT) of the bone using the deltoid splitting technique (A) and Isp (B). A Mason-Allen suture was used to close the wound (C) and biomechanical testing was done with the SSp muscle loaded to a MTS- 858 system (D). Infraspinatus (Isp) positioned and labeled. Adapted from Lu et al. 2015. Illustration by Kelly Paralis, Penumbra Design, Inc.

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Histological analysis was carried out in order to view the inhibiting anti-inflammatory drugs have on the process of fibrovascular granulation, fibrocartilage formation, and muscle repair following injury. The Oak et al. study (2014) presence of Sharpey’s fibers and to quantify the amount of suggested that the non-selective inhibition of COX-2 leads collagen at the bone to tendon attachment (Lu et al. 2015). to the production of muscle tissue that has less scar tissue The results of this study at three weeks indicated poor and lipid accumulation, increased levels of maximum load fibrovascular granulation tissue in all of the drug treatment to failure, and reduced levels of inflammation on both the groups. The ibuprofen and control groups showed little gross anatomical and the cellular gene expression levels. osteoclastic activity and cartilage formation. At six weeks, These results indicate that the muscle is stronger after repair there was similar fibrocartilage formation and Sharpey’s in the presence of NSAIDs. These results are very different fibers were observed in ibuprofen, flurbiprofen axetil, and from the results obtained by Lu et al. (2015) when a selective control groups but not the COX-2 inhibitor was used as celecoxib group. At twelve an NSAID. The Lu et al. (2015) weeks, there were hypercelluar study showed that there was and fibroblastic cells present decreased muscle strength in ibuprofen, flurbiprofen and detrimental structural axetil, and control groups. The differences in collagen and celecoxib groups showed no the enthesis in the presence of cartilage and no new bone NSAIDs. formation (Lu et al. 2015). Interestingly, the negative Quantification of collagen effects of the inhibition of COX- levels revealed that there 2 on muscle tissue repair were was less collagen I in the supported by Shen et al. (2005) celecoxib and flurbiprofen and Schoenfeld et al. (2012). axetil groups compared to the Shen et al (2005) reported control while there were no fewer regenerating myofibers, significant differences seen more scar tissue accumulation, when ibuprofen groups were higher levels of transforming compared to the controls. growth factor (TGF)-β1, and At six weeks, there was less lower amounts of neutrophil collagen I in the celecoxib than and macrophages in muscle in the control groups, but there fibers treated with NSAIDs . were no differences seen in They suggested that the lack ibuprofen and flurbiprofen axetil groups. The same results of new muscle fibers after injury made room for scar tissue to were seen at week twelve (Lu et al. 2015). accumulate over time. The high levels of TGF-β1 observed in this study are indicative of fibrosis and the presence of muscle The Lu et al. (2015) study found that there were decreased tissue fibrosis is also supported by the increased amount levels of maximum load to failure in the mechanical testing of scar tissue. The study done by Shen et al. (2005) used phase. These results conflicted with the findings from Oak et the selective COX-2 inhibitor NS-398. The use of a different al. (2014). This may be due to the fact that different NSAIDs COX-2 inhibitor may be why these results differ from the were used in the studies. Licofelone, a non-selective COX findings of Oak et al. (2014), which found decreased amounts inhibitor, showed an increase in muscle strength (Oak et al. of scar tissue and increased numbers of fibers. Selective 2014) while celecoxib, a selective COX-2 inhibitor, showed COX-2 inhibition strongly suggests that the COX-2 pathway is a decrease in muscle strength (Lu et al. 2015). These results necessary for the proper repair of muscle fibers. may indicate the importance of the COX-2 pathway in the process of regenerating a functioning muscle and suggests Additional results regarding the effects that inhibition of that functional muscle may not be produced when the COX- COX-2 pathway by a selective inhibitor are evident in a study 2 pathway is inhibited. The results of Lu et al. (2015) also completed by Schoenfeld et al. (2012) This study suggested indicated that both selective and non-selective COX inhibitors that a reduced number of stem cells were activated in injured impact the repair of muscle after injury. This conclusion muscle tissue in the presence of NSAIDs. The study results was supported by both the histological and biomechanical held true when NASIDs were used over time. If NSAIDs lead to analysis. a decrease in the activation of myogenic stem cells over time, this could lead to the production of abnormal muscle tissue Summary (Schoenfeld, 2012). The studies done by Oak et al. (2014) and Lu et al. (2015), present conflicting results regarding the effects that COX-

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The effect of specific COX-2 inhibition on muscle repair was Illustration courtesy of stronger than the effect of non-specific COX-1 inhibition Kelly Paralis, Owner (Lu et al. 2015, Oak et al. 2014, Shen et al. 2005, Schoenfeld Penumbra Design, Inc. 2012). The difference in the results between the inhibition 143 North Sylvania Avenue, First Floor of non-specific COX/LOX and specific COX-2 inhibition may Rockledge, PA 19064 have been due to the specific role that each pathway has Tel: 215-379-2832 on the regeneration of muscle. COX-1 is responsible for homeostatic responses such as maintaining the integrity About the authors of the gastrointestinal mucosa, mediating normal platelet Megan Obarowski graduated from Arcadia University with function, regulating blood flow through the kidney and acute a Bachelors of Arts in Biology in the spring of 2017. She is inflammation (Crofford 1997). COX-2 is pro-inflammatory and enrolled in an Accelerated Bachelors of Science in Nursing in animal models of inflammatory arthritis, COX-2 increases program at Gwynedd Mercy University for the fall of 2017. along with PG production and the progression of clinical After completing the BSN program, she plans to continue her inflammation. Increased COX-2 expression has been observed education in nursing to become a nurse practitioner. in models of endothelial cells, chondrocytes, osteoblasts, and macrophages in vitro following the introduction of Sarah Cooper is an Associate Professor of Biology at Arcadia proinflammatory cytokines, such as interleukin 1 (IL-1) and University and Editor-in-Chief of the HAPS Educator. She tumor necrosis factor-alpha (TNF-alpha). COX-2 is also has taught human anatomy and general biology at Arcadia increased in some types of human cancers, particularly colon University since 1981. She is the pre-nursing adviser and the cancer. (Crofford 1997). COX-1 is expressed continually, while coordinator of the interdisciplinary science courses at Arcadia COX-2 is expressed only when needed (Bondesen et al. 2004). and she has served as a member of the Arcadia University Judicial Board since 1984. There are more side effects associated with the use of non- selective COX inhibitors (COX-1) because the enzymes are John Daley, PhD is an Assistant Professor of biology at produced regularly (Ricciotti and FitzGerald 2011). There Arcadia University where he serves as the coordinator are fewer side effects associated with the use of selective of the Introductory Biology courses. He teaches Junior COX inhibitors (COX-2), which is why they are prescribed Seminar, General Biology I and II, and microbiology labs for chronic use with patients struggling with rheumatoid and is an active participant on departmental and university and osteoarthritis (Ricciotti and FitzGerald 2011). Since committees. non-selective COX inhibitors affect more than one pathway, the effects may not be as strong as direct inhibition by a Randy Tammara is a pharmacist who has been working in selective NSAID. Non-selective COX inhibitors primarily the Philadelphia area for twenty-five years. He is a certified inhibit the COX-1 isoform with only a slight inhibition of COX-2 diabetes educator who gives presentations to care-givers (Bondesen et al. 2004). The slight inhibition of COX-2 allows through Northampton Community College, Bethlehem, PA for the production of some prostaglandins, which means where he is an adjunct faculty member in the Community the inflammation pathway will still be initiated. Selective Education Division. He is currently enrolled in the Masters in COX-2 NSAIDs fully inhibit any prostaglandin production by Public Health program at Arcadia University. the COX-2 isoform, which is what leads to the effects on the muscle regeneration (Bondesen et al. 2004). These differences in inhibition may account for the variation in the observed Literature cited results for selective and non-selective COX inhibiting NSAIDs. Arnold L, Henry A, Poron F, Baba-Amer Y, van Rooijen N, The overall effect of anti-inflammatory drugs on the COX-2 Plonquet A, Gherardi RK, Chazaud B (2007) Inflammatory pathway of muscle regeneration remains unknown. More monocytes recruited after skeletal muscle injury research is needed to fully understand the effects of the switch into antiinflammatory macrophages to support inhibition of the COX-2 pathway on muscle repair following myonecrosis. J Exp Med 204 (5):1057-1069. injury. Future research should include studies that use American Gastroenterological Association (AGA) www.gastro. commonly prescribed selective COX-2 NSAIDs, studies that org Accessed May 14, 2017 examine the use of NSAIDs over extended periods of time, and studies that incorporate higher doses of NASIDs than are Bondesen BA, Mills ST, Kegley KM, Pavlath GK (2004) The typically prescribed by physicians. These types of studies will COX-2 pathway is essential during early stages of skeletal help to more fully elucidate the effects of NSAIDs on the COX- muscle regeneration. Am J Physiol Cell Physiol 287: 2 pathway in the repair of skeletal muscle following injury. C475-C483.

34 • HAPS Educator Journal of the Human Anatomy and Physiology Society Volume 21, Issue 2 August 2017 The Possible Effects of Non-steroidal Anti-inflammatory Drugs (NSAIDs) on the COX-2 Pathway of Skeletal Muscle Repair

Celotti E and Durand Y (2003) The metabolic effects of Schoenfeld BJ (2012) The use of nonsteroidal anti- inhibitors of 5-lipoxygenase and of cyclooxygenase 1 and inflammatory drugs for exercise-induced muscle damage: 2 are an advancement in the efficacy and safety of anti- implications for skeletal muscle development. Sports Med inflammatory therapy. Prostaglandins Other Lipid Mediat. 42(12): 1017-1028. (3-4): 147-62. Shen W, Li Y, Tang Y, Cummins J, Huard J (2005) NS-398, a Caughey Gillian E, Leslie G Cleland, Peter S Penglis, Jennifer cyclooxygenase-2-specific inhibitor, delays skeletal R Gamble and Michael J James (2001) Roles of muscle healing by decreasing regeneration and Cyclooxygenase (COX)-1 and COX-2 in Prostanoid Production promoting fibrosis. Am J Pathol 167(4): 1105-1117. by Human Endothelial Cells: Selective Up-Regulation of Wallace JL (2008) Prostaglandins, NSAIDS, and gastric mucosal Prostacyclin Synthesis by COX-2. J Immunol. 167(5): 2831- protection: Why doesn’t the stomach digest itself? 2838. DOI: https://doi.org/10.4049/jimmunol.167.5.2831 Physiol Rev 88(4): 1547-1565. Crofford (1997) COX-1 and COX-2 tissue expression: Yamshita K, Fukusaki M, Ando Y, Fujinaga A, Tanabe T, Terao implications and predictions. J Rheumatol Suppl. 49:15-9 Y, Sumikawa K. 2006. Preoperative administration of Frolov RV, Ignatova II, Singh S (2011) Inhibition of hERG intravenous flurbiprofen axetil reduces postoperative potassium channels by celecoxib and its mechanism. PLoS pain for spinal fusion surgery. J Anesth 20:92-95. ONE 6(10): 1-7. Järvinen TA, Järvinen M, Kalimo H (2013) Regeneration of injured skeletal muscle after the injury. Muscle, Ligaments and Tendons Journal 3(4): 337-345. Johns Hopkins Health Library (2017) Lesher BA (2004) Pharmacist’s Letter. Therapeutic Research Center. 3120 West March Lane, Srockton, CA 95219. 20(11):201102. Lu Y, Li FL, Li X, Zhou HW, Jiang CY (2015) Do different cyclooxygenase inhibitors impair rotator cuff healing in a rabbit model? Chinese Med J-Peking (128)17: 2354-2359. Oak NR, Gumucio JP, Flood MD, Saripalli AL, Davis ME, Harning JA, Lynch EB, Roche SM, Bedi A, Mendias CL (2014) Inhibition of 5-LOX, COX-1, and COX-2 increased tendon healing and reduces fibrosis and lipid accumulations after rotator cuff repair. Am J Sports Med 42(12): 2860-2868. Pharmacist’s Letter (2015) 31(9):310902. Therapeutic Research Center 3120 W. March Lane, Stockton, CA 95219, Tel:(209) 472-2240 Fax:(209) 472-2249. Pharmacist’s Letter (2011) 2711):272206. Therapeutic Research Center 3120 W. March Lane, Stockton, CA 95219, Tel:(209) 472-2240 Fax:(209) 472-2249. Prisk V and Huard J (2003) Muscle Injuries and Repair: the role of prostaglandins and inflammation. Histol Histopathol. (4):1243-56. doi: 10.14670/HH-18.1243. Ricciotti E and FitzGerald GA (2011) Prostoglandins and inflammation. Aterioscelr Thromb Vasc Biol 31(5): 986-1000. doi: 10.1161/ATVBAHA.110.207449

35 • HAPS Educator Journal of the Human Anatomy and Physiology Society Volume 21, Issue 2 August 2017