The anti-asthmatic drug pranlukast suppresses the delayed-phase vomiting and reverses intracellular indices of emesis evoked by cisplatin in the least shrew (Cryptotis parva)

Mechanisms of Nausea and Vomiting: Current Knowledge and Recent Advances in Intracellular Emetic Signaling Systems

Nausea and vomiting are common gastrointestinal complaints that can be triggered by diverse emetic stimuli through central and/or peripheral nervous systems. Both nausea and vomiting are considered as defense mechanisms when threatening toxins/drugs/bacteria/viruses/fungi enter the body either via the enteral (e.g., the gastrointestinal tract) or parenteral routes, including the blood, skin, and respiratory systems. While vomiting is the act of forceful removal of gastrointestinal contents, nausea is believed to be a subjective sensation that is more difficult to study in nonhuman species. In this review, the authors discuss the anatomical structures, neurotransmitters/mediators, and corresponding receptors, as well as intracellular emetic signaling pathways involved in the processes of nausea and vomiting in diverse animal models as well as humans. While blockade of emetic receptors in the prevention of vomiting is fairly well understood, the potential of new classes of antiemetics altering postreceptor signal transduction mechanisms is currently evolving, which is also reviewed. Finally, future directions within the field will be discussed in terms of important questions that remain to be resolved and advances in technology that may help provide potential answers.

Role of leukotriene pathway and montelukast in pulmonary and extrapulmonary manifestations of Covid-19: The enigmatic entity

Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2), the responsible agent for the coronavirus disease 2019 (Covid-19), has its entry point through interaction with angiotensin converting enzyme 2 (ACE2) receptors, highly expressed in lung type II alveolar cells and other tissues, like heart, pancreas, brain, and vascular endothelium. This review aimed to elucidate the potential role of leukotrienes (LTs) in the pathogenesis and clinical presentation of SARS-CoV-2 infection, and to reveal the critical role of LT pathway receptor antagonists and inhibitors in Covid-19 management. A literature search was done in PubMed, Scopus, Web of Science and Google Scholar databases to find the potential role of montelukast and other LT inhibitors in the management of pulmonary and extra-pulmonary manifestations triggered by SARS-CoV-2. Data obtained so far underline that pulmonary and extra-pulmonary manifestations in Covid-19 are attributed to a direct effect of SARS-CoV-2 in expressed ACE2 receptors or indirectly through NF-κB dependent induction of a cytokine storm. Montelukast can ameliorate extra-pulmonary manifestations in Covid-19 either directly through blocking of Cys-LTRs in different organs or indirectly through inhibition of the NF-κB signaling pathway.

Construction of trisubstituted chromone skeletons carrying electron-withdrawing groups via PhIO-mediated dehydrogenation and its application to the synthesis of frutinone A

The construction of the biologically interesting chromone skeleton was realized by PhIO-mediated dehydrogenation of chromanones under mild conditions. Interestingly, this method also found application in the synthesis of the naturally occurring frutinone A.

The pivotal role of glycogen synthase kinase 3 (GSK-3) in vomiting evoked by specific emetogens in the least shrew (Cryptotis parva)

Glycogen synthase kinase 3 (GSK-3) is a constitutively active multifunctional serine-threonine kinase which is involved in diverse physiological processes. GSK-3 has been implicated in a wide range of diseases including neurodegeneration, inflammation, diabetes and cancer. GSK-3 is a downstream target for protein kinase B (Akt) which phosphorylates GSK-3 and suppresses its activity. Based upon our preliminary findings, we postulated Akt's involvement in emesis. The aim of this study was to investigate the participation of GSK-3 and the antiemetic potential of two GSK-3 inhibitors (AR-A014418 and SB216763) in the least shrew model of vomiting against fully-effective emetic doses of diverse emetogens, including the nonselective and/or selective agonists of serotonin type 3 (e.g. 5-HT or 2-Methyl-5-HT)-, neurokinin type 1 receptor (e.g. GR73632), dopamine D₂ (e.g. apomorphine or quinpirole)-, and muscarinic 1 (e.g. pilocarpine or McN-A-343) receptors, as well as the L-type Ca²⁺ channel agonist (FPL64176), the sarco/endoplasmic reticulum Ca²⁺-ATPase inhibitor thapsigargin, and the chemotherapeutic agent, cisplatin. We first determined if these emetogens could regulate the phosphorylation level of GSK-3 in the brainstem emetic loci of least shrews and then investigated whether AR-A014418 and SB216763 could protect against the evoked emesis. Phospho-GSK-3α/β Ser21/9 levels in the brainstem and the enteric nerves of jejunum in the small intestine were upregulated following intraperitoneal (i.p.) administration of all the tested emetogens. Furthermore, administration of AR-A014418 (2.5-20 mg/kg, i.p.) dose-dependently attenuated both the frequency and percentage of shrews vomiting in response to i.p. administration of 5-HT (5 mg/kg), 2-Methyl-5-HT (5 mg/kg), GR73632 (5 mg/kg), apomorphine (2 mg/kg), quinpirole (2 mg/kg), pilocarpine (2 mg/kg), McN-A-343 (2 mg/kg), FPL64176 (10 mg/kg), or thapsigargin (0.5 mg/kg). Relatively lower doses of SB216763 exerted antiemetic efficacy, but both inhibitors barely affected cisplatin (10 mg/kg)-induced vomiting. Collectively, these results support the notion that vomiting is accompanied by a downregulation of GSK-3 activity and pharmacological inhibition of GSK-3 protects against pharmacologically evoked vomiting.

Involvement of leukotriene pathway in the development of sevoflurane-induced pica in rats

We previously reported that sevoflurane-induced pica, kaolin ingestion behavior, in rats has the potential to reflect postoperative nausea and vomiting (PONV) in humans. It is well-known that corticosteroids, which inhibit both prostaglandin and leukotriene syntheses due to phospholipase A₂ inhibition, are effective for reducing PONV; however, the precise mechanisms remain unclear. We investigated the involvement of the prostaglandin or leukotriene pathway in the development of sevoflurane-induced pica. We found that sevoflurane-induced pica was effectively inhibited by pretreatment with a leukotriene receptor antagonist (montelukast) or an inhibitor of 5-lipoxygenase (zileuton), rather than an inhibitor of cyclooxygenase (flurbiprofen). Furthermore, we observed that sevoflurane significantly increased urinary leukotriene excretion and 5-lipoxygenase mRNA expression in the spleen, but not hypothalamus. These results suggest that the production of leukotriene may lead to the development of sevoflurane-induced pica in rats, and that inhibition of the leukotriene pathway could be potentially useful for the treatment of PONV.

The lead optimization of the polyamine conjugate of flavonoid with a naphthalene motif: Synthesis and biological evaluation

Polyamine conjugated flavonoid with a naphthalene moiety (ZYY14) displayed excellent therapeutic activity against hepatocellular carcinoma. In this study, three different series of novel flavonoid-polyamine conjugates were designed and screened against tumor cell lines. The structure-activity relationship study demonstrated the importance of the naphthalene moiety (as the B-ring), the basic side chains in the A-ring, and the methoxy group linked to the C-ring. The optimized compound 9b displayed better antitumor potency in vitro and in vivo than the lead compound ZYY14. Fluorescent assays revealed that 9b could enter cancer cells via polyamine transporter (PAT) and locate in mitochondria and endoplasmic reticulum. Compound 9b and ZYY14 demonstrated similar apoptotic mechanism in the cytotoxicity studies and stimulated the expression of apoptosis-related proteins, such as p-p38, p-JNK, p53 and Bax. In addition, 9b can initiate autophagy which inhibited the occurrence of apoptosis. Thus, 9b can be used as a valuable lead for the future development of antitumor agents.