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Therapeutic Potential of N-Acetyl Cysteine (NAC) in Preventing Cytokine Storm in COVID-19: Review of Current Evidence

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Therapeutic Potential of N-Acetyl Cysteine (NAC) in Preventing Cytokine Storm in COVID-19: Review of Current Evidence European Review for Medical and Pharmacological Sciences 2021; 25: 2802-2807 Therapeutic potential of N-acetyl cysteine (NAC) in preventing cytokine storm in COVID-19: review of current evidence R.R. MOHANTY, B.M. PADHY, S. DAS, B.R. MEHER 1Medicine All India Institute of Medical Sciences, Bhubaneswar, Odisha, India 2Pharmacology IMS & SUM Hospital, Bhubaneswar, Odisha, India Abstract. – Since November 2019, SARS death is mostly acute respiratory distress syn- 2 Coronavirus 2 disease (COVID-19) pandemic has drome (ARDS) . There are data suggesting the spread through more than 195 nations world- role of excessive immune activation and cytokine wide. Though the coronavirus infection affects storm as the cause of lung injury in COVID-193,4. all age and sex groups, the mortality is skewed The excessive immune activation and cytokine towards the elderly population and the cause storm usually occurs due to an imbalance in of death is mostly acute respiratory distress 5 syndrome (ARDS). There are data suggesting redox homeostasis of the individuals . Important the role of excessive immune activation and factors responsible for an imbalance in redox cytokine storm as the cause of lung injury in homeostasis are prolonged oxidative stress in COVID-19. The excessive immune activation and inflammation, increased reactive oxygen species cytokine storm usually occurs due to an im- (ROS) production, and decrease in glutathione balance in redox homeostasis of the individu- level6. Many antioxidants like Zinc, Vitamin C, als. Considering the antioxidant and free radical and NAC are being explored individually or in scavenging action of N acetyl cysteine (NAC), its use might be useful in COVID-19 patients by de- combination as a therapeutic agent in the man- 7 creasing the cytokine storm consequently de- agement of COVID-19 worldwide . Considering creasing the disease severity. Therefore, we re- the antioxidant and free radical scavenging action viewed all the available resources pertaining to of NAC, it has been used in a variety of condi- the role of reactive oxygen species (ROS) in cy- tions like acetaminophen poisoning, liver can- tokine storm and the mechanism of action of cer, polycystic ovarian syndrome6. In addition, NAC in preventing ROS. We also reviewed the 8-11 use of NAC in COVID-19. many studies have demonstrated the utility of NAC in variety of lung conditions like Influ- Key Words: enza, community-acquired pneumonia, acute Immune activation, Reactive oxygen species (ROS), exacerbation of the chronic obstructive pulmo- Oxidative stress, Redox homeostasis, Free radicals. nary disease, ventilator-associated pneumonia. Ergin et al12 demonstrated that addition of NAC to the fluid resuscitation improves renal oxy- genation in acute kidney injury in the rat by Introduction decreasing free radicals like nitric oxide (NO). Lee et al13 showed a decrease in the production Since November 2019, SARS Coronavirus of IL17 and improvement in transplant-free 2 disease (COVID 19) pandemic has spread survival in patients with acute liver failure oth- through more than 195 nations worldwide. Ac- er than acetaminophen poisoning. Along with cording to the world health organization (WHO) antioxidant activity, NAC has also anti-inflam- coronavirus disease (COVID-19) dashboard, ap- matory and anti-bacterial activity. As the treat- proximately 20 million people were infected and ment for COVID 19 is still emerging, the use 0.7 million succumbed to death till August 15, of NAC might be useful in COVID-19 patients 20201. Though the coronavirus infection affects by decreasing the cytokine storm consequently all age and sex groups, the mortality is skewed decreasing the disease severity. Though guide- towards the elderly population and the cause of lines throughout the world have not mentioned Corresponding Author: Rashmi Ranjan Mohanty, MD; 2802 e-mail: [email protected] Therapeutic potential of NAC in preventing cytokine storm in COVID-19 NAC as a treatment option in COVID-19, it is strated the antioxidant property of NAC. The being used as an off-label treatment at many antioxidant property of NAC can be attributed to centers14. three mechanisms a) direct antioxidant activity Therefore, we searched all the available re- b) indirect antioxidant activity, and c) disulfide sources in PubMed, Cochrane library on the use bond-breaking activity17. The direct antioxidant of NAC to review two key objectives, i.e.,: activity of NAC against reactive oxygen species Therapeutic potential of NAC in decreasing the like H2O2, ONOOH, O2 , HO, HO(X), and NO2 immune activation and cytokine storm. due to the presence of thiol group in it has been Efficacy of NAC in management of COVID-19. established in both in vitro and in vivo stud- We also reviewed all the studies registered in ies18-23. NAC has highest antioxidant activity 17 clinical trial.gov on the use of NAC in COVID 19. towards NO2 and HO(X) in vivo . It exhibits indirect antioxidant activity by increasing the Reactive Oxygen Species Induced glutathione level at the site of inflammation24,25. Cytokine Storm Meyer et al26 demonstrated that NAC increased Excessive production of ROS due to oxidative the level of glutathione to almost normal levels stress and decreased antioxidant level plays a in lung fluid in patients with pulmonary fibro- central role in the development of cytokine storm sis. NAC also exerts mucolytic activity in the during infections2,15. Many predisposing factors lungs in inflammatory conditions by its disulfide like diabetes, inflammaging, decrease glutathione bond-breaking action17. The breakdown prod- level with aging triggers ROS production, and ucts increase free thiol which exhibits antiox- results in cytokine storm due to increased oxida- idant action by directly inhibiting the reactive tive stress2. ROS causes cell death by apoptosis oxygen species (ROS) and indirectly by increas- and increases the release of pro-inflammatory ing the glutathione level. The pathogenesis of cytokines like IL-2, IL-6, and TNF-α by activat- the cytokine storm and the action of NAC has ed macrophages15. The rise of IL-2 and IL-6 has been depicted in Figure 1. been well documented in COVID-19 in the hy- per-inflammatory stage of the disease. There is a Therapeutic Potential of NAC in decrease in CD4, CD8 lymphocytes and increase Decreasing the Immune Activation neutrophil to lymphocyte ratio (NLR) in severe and Cytokine Storm COVID 19 along with a rise in monocyte mac- N-acetyl cysteine has been used as an antioxi- rophages leading to a rise in pro-inflammatory dant in clinical practice for decades, but its uses cytokines IL-6, IL-23. This hyper-inflammatory are mostly off-label. However, there is ample immune response leads to the production of ROS evidence in preclinical and clinical studies that by epithelial cells. ROS stimulates the synthesis it can attenuate immune activation and prevent of (NOD)-like receptor protein 3 inflammasome; cytokine release. Davreux et al27 demonstrated (NLRP3) and nuclear factor kappa-light-chain- that lipopolysaccharide-induced increased lung enhancer of activated B cell (NF-κB) which prop- permeability and lung injury is significantly agates the cytokine production4. These pro-in- attenuated by NAC in a rat model. In the same flammatory cytokines increase the release of study, although NAC did not affect the migra- nitric oxide (NO) which causes vasodilatation, tion of neutrophils to the site of injury, it sig- hypotension, vascular leakage, and organ dam- nificantly decreased the activation and cytokine age. Thus, in the latter part of COVID-19, these production by neutrophils. In another study by cytokines and free radicals play a major role in Ungheri et al28, NAC significantly decreased the disease pathogenesis rather than the virus itself. mortality in influenza affected mice by decreas- ing the production of ROS and cytokines like NAC As an Antioxidant TNF and IL-6. Similarly, Ergin et al12 and Ga- N-acetyl cysteine (NAC) is a safe and in- rozzo et al29 demonstrated the beneficial effect expensive medication commercially available of NAC in influenza and acute kidney injury in since 1960. It is the N-acetyl derivative of the the rat model. Animal studies showing the anti- natural amino acid L-cysteine and has been used oxidant effect of NAC in inflammation depicted in a variety of conditions including lung diseas- in Table I. es6. However, only USFDA approved indication From the above studies, it is evident that NAC of NAC is as an antidote for paracetamol poi- has therapeutic potential in decreasing the im- soning. Many studies8,16 in humans have demon- mune activation and resultant cytokine storm. 2803 R.R. Mohanty, B.M. Padhy, S. Das, B.R. Meher Figure 1. The pathogenesis of the cytokine storm and the action of NAC (COVID-19 causes increased ROS production and immune activation which in turn leads to cytokine storm in the hyper-inflammatory stage of the disease. Oxidative stress and low glutathione level predispose to the condition: NAC has a potential role in down regulating the cascade of the event by direct and indirect antioxidant activity). The clinical utility of NAC in various diseas- The addition of NAC to the standard treatment es has been proved by many studies8-11. Study protocol decreases the severity of many acute characteristics and its outcome of NAC use in respiratory conditions like influenza, communi- different lung diseases in humans are depicted in ty-acquired pneumonia (CAP), ARDS, ventila- Table II. tor-associated pneumonia (VAP) mostly by atten- Table I. Animal studies showing the antioxidant effect of NAC. Study Study hypothesis Observation Mechanism of action Davreux et al27 NAC might attenuate lung injury Significant decrease in lung Scavenging of free radicals 1997 following an intratracheal permeability due to and decrease in the neutrophil challenge with endotoxin lipopolysaccharide (LPS) oxidative burst (lipopolysaccharide; LPS) induced lung injury in mice (p < 0.5) Decrease neutrophil activation in NAC group.
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