Role of PI3K/Akt/GSK-3 Pathway in Emesis and Potential New Antiemetics
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https://www.scientificarchives.com/journal/journal-of-cellular-signaling Journal of Cellular Signaling Commentary Role of PI3K/Akt/GSK-3 Pathway in Emesis and Potential New Antiemetics Zhong W, Darmani NA* Department of Basic Medical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, 309 East Second Street, Pomona, CA 91766, USA *Correspondence should be addressed to Nissar A. Darmani; [email protected] Received date: August 24, 2020, Accepted date: September 18, 2020 Copyright: © 2020 Zhong W, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Keywords: Chemotherapy, Emesis, Ca2+, Emetic emesis research using smaller vomit-competent-species nuclei, PI3K, Akt, GSK-3 such as least shrews (Cryptotis parva) [9] or house musk shrews (Suncus murinus) [10]. Such receptor-selective Nausea and vomiting are protective defense mechanisms or non-selective specific emetogens include agonists of by which vomit competent species avoid ingestion of serotonin type 3 (5-HT3R) (e.g. 2-Methyl-5-HT or 5-HT)- potentially toxic substances. More specifically, vomiting , substance P neurokinin type 1 (NK1R) (e.g. GR73632)-, is the act of forceful expulsion of gastrointestinal contents dopamine D2 (D2R) (e.g. quinpirole or apomorphine)-, through the mouth, whereas nausea is an unpleasant and muscarinic 1 (M1R) (McN-A-343 or pilocarpine)- painless subjective feeling that one will imminently vomit. receptors, as well as Ca2+ channel regulators comprising Severe or chronic vomiting can become detrimental the L-type Ca2+ channel (LTCC) agonist FPL64176 [11], and due to significant loss of fluid and ion imbalance. The the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) act of vomiting is usually preceded by retching, where inhibitor thapsigargin [12]. Based on our Ca2+-dependent the gastrointestinal tract contents are forced into the emesis hypothesis [9], we have demonstrated the broad- esophagus, without the vomitus being expelled [1]. While spectrum antiemetic nature of two of the selective LTCC significant knowledge exists on the neurotransmitter and inhibitors, nifedipine and amlodipine, against the above anatomical basis of vomiting [2-4], nausea is the neglected discussed diverse emetogens [11-13]. symptom and its anatomical neurochemistry remains to be fully defined. In this laboratory we have focused on investigating intracellular emetic signals evoked by the above The major emetic sites involved in the process of vomiting discussed specific emetogens. Indeed, our recent include: i) the brainstem dorsal vagal complex (DVC) findings have well established that ERK1/2 is a common containing the central emetic nuclei such as the area emetic signal in the mediation of vomiting elicited by postrema (AP), nucleus tractus solitarius (NTS) and dorsal intraperitoneal administration of diverse emetogens motor nucleus of the vagus (DMNX); and ii) the peripheral [12,14-18]. Moreover, our group has demonstrated a time- emetic loci such as neurons of the enteric nervous system dependent upregulation of phosphorylation of protein (ENS) and enterochromaffin cells (EC cells), as well as kinase B (Akt) downstream of phosphoinositide 3-kinase vagal afferents carrying input from the gastrointestinal (PI3K) signaling in the least shrew brainstem following tract (GIT) to the brainstem DVC [5,6]. Cisplatin-like administration of either the selective LTCC agonist cancer chemotherapeutics cause vomiting via release of FPL64176 [19] or the emetic NK1R agonist GR73632 multiple neurotransmitters [e.g. dopamine, serotonin [14]. Following PI3K activation, phosphatidylinositol (5-HT), substance P, etc] from the EC cells and/or the (3,4,5)-trisphosphate (PIP3) accumulates at the cell brainstem [7]. In the past, non-specific emetogens such as membrane which then leads to the recruitment of Akt copper sulfate or cisplatin were often used to determine to the plasma membrane where Akt is phosphorylated the antiemetic potential of drugs in relatively large animal at Thr308 together with Ser473 which ensures full Akt models of vomiting including dogs, cats, or ferrets [8]. activation [20,21]. Multiple cellular experiments have Recently, more specific emetogens are frequently used in shown that the PI3K inhibitor LY-294002 can inhibit the J Cell Signal. 2020 Volume 1, Issue 4 155 Zhong W, Darmani NA. Role of PI3K/Akt/GSK-3 Pathway in Emesis and Potential New Antiemetics. J Cell Signal 2020; 1(4): 155-159. activity of its downstream target protein, Akt, therefore it the brainstem DVC emetic nuclei as well as the jejunal is more often described as a PI3K/Akt inhibitor [20-22]. ENS. The selective ERK1/2 inhibitor U0126 (10 mg/kg, In a recent study we found that LY-294002 at 20 mg/ i.p.) prevented MK-2206-induced vomiting, suggesting kg (i.p.) dose, could reduce both: i) the vomiting evoked ERK1/2 signaling contributes to emesis in response to by the neurokinin NK1R selective agonist GR73632 pharmacological inhibition of Akt. Our finding is in line in least shrews, and ii) the GR73632-evoked ERK1/2 with several published studies that demonstrate PI3K/Akt phosphorylation and Akt phosphorylation at Ser473 in inhibition leads to the RAF/MEK/ERK pathway activation. the shrew brainstem protein extracts. These findings Indeed, PI3K inhibitors wortmannin or LY-294002 as suggest an important role for the PI3K-Akt pathway in well as Akt inhibitor VIII, significantly potentiate ERK1/2 NK1R-mediated emesis [14]. However, the role of Akt in phosphorylation at the cellular level [30]. Moreover, the evoked vomiting appears to be complex and is under upregulation of phosphorylated ERK1/2 has also been continued investigation. Indeed, our recent unpublished observed following exposure to MK-2206 [31,32], which is findings indicate that PI3K/Akt pathway inhibitors are consistent with our findings. potent emetogens in the least shrews when administered systematically, which we further discuss in the following Based on the essential role of intracellular Ca2+ paragraph. mobilization in the process of vomiting evoked by diverse emetogens [9], we evaluated the antiemetic potential The PI3K/Akt pathway hyperactivation occurs in several of the LTCC blocker nifedipine against MK-2206- and types of cancers and inhibitors targeting this pathway perifosine-induced vomiting. Nifedipine provided potent are under development as potential armamentarium for and total (100%) protection against the vomiting caused cancer treatment which have been extensively reviewed by both Akt inhibitors perifosine (50 mg/kg, i.p.) and MK- [23,24]. When treating cancer patients with PI3K/ 2206 (10 mg/kg, i.p.). At this dose nifedipine could only Akt pathway inhibitors, nausea and vomiting are among partially protect shrews from vomiting evoked by the above their common impending side-effects [25]. Indeed, discussed diverse emetogens, including that caused by GSK2636771, the potent, orally bioavailable, adenosine LTCC activator FPL64176 [11]. Thus, Akt inhibitor-evoked triphosphate-competitive and selective inhibitor of emesis is highly sensitive to the LTCC blocker nifedipine, PI3Kβ, not only causes dose-dependent nausea (40%) and extracellular Ca2+ entry through LTCCs plays a major and vomiting (31%) in cancer patients, but also reduces role in both perifosine- and MK-2206- induced emesis. the phospho/total Akt ratio [26]. In our one of our Our preliminary results support the involvement of current animal studies, we observed that a larger dose serotonergic 5-HT3Rs, neurokinin NK1Rs and dopamine of the PI3K-Akt inhibitor LY-294002 (40 mg/kg., i.p.) D2Rs in vomiting evoked by the Akt inhibitor MK-2206. caused vomiting in up to 71% of tested shrews, whereas In fact, according to the antiemetic efficacy profiles of its lower dose (20 mg/kg) has limited emetic potential. the selective 5-HT3 receptor antagonist palonosetron, Such anti/proemetic effect with small versus larger doses NK1R antagonist netupitant, and the selective D2R of other antiemetics, such as the selective 5-HT3 receptor antagonist sulpiride, we propose that release of emetic antagonist tropisetron, has also been observed against neurotransmitters serotonin, substance P and dopamine GR73632-evoked NK1 receptor-mediated emesis [27]. In are involved in MK-2206-evoked emesis. Further studies addition, Akt inhibitors, perifosine and MK-2206, appear are to be performed in our laboratory to address their to be more efficacious proemetic than LY-294002. In fact, underlying mechanisms. clinical trials demonstrate that perifosine evokes vomiting in up to 63% of cancer patients [28]. Likewise, relative A downstream target protein for Akt signaling pathway, to perifosine, MK-2206 is a more potent and efficacious glycogen synthase kinase-3 (GSK-3), is a constitutively proemetic chemotherapeutic in cancer patients [29], active protein involved in diverse physiological processes which mirrors the findings of our studies in least shrews. including metabolism, cell cycle, and gene expression In fact, while MK-2206 induced vomiting in all tested least [33-38]. GSK-3 is also involved in a wide range of shrews at 10 mg/kg (i.p.) dose, perifosine evoked emesis pathologies such as diabetes, inflammation, some types in ~90% of tested shrews at 50 mg/kg (i.p.). Moreover, of cancer, neurodegeneration and mental illness [39]. MK-2206-evoked emesis led