Aviptadil: Class Effect of a Synthetic Vasoactive Intestinal Peptide as a Treatment Option in Patients with COVID-19 with Severe Respiratory Failure

Despite dynamic drug and vaccine development processes to reduce the disease burden of COVID-19, the treatment options are still very limited. Vasoactive intestinal peptide (VIP) has a diversified physiological action with specific features of lung protection-related activities. VIP inhibits severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) gene replication in human monocytes and the viral replication in Calu-3 cells, thus further reducing the generation of proinflammatory mediators. Aviptadil, a synthetic form of VIP, is the only pulmonary therapeutic agent to have been granted ‘fast track’ status by the U.S. Food and Drug Administration (FDA) and to be allowed into both Phase II and III clinical trials. Initial binding of Aviptadil with non-structural protein (nsp) 10 and nsp16, which may inhibit the 2’-O-methyltransferase activity of the SARS-CoV-2 nsp10 and nsp16 complex. Aviptadil has already proved to be an effective option in the treatment of severe respiratory failures due to sepsis and other related lung injuries. Interim analysis results of this drug used in respiratory failure caused by SARS-CoV-2 has evolved a new hope in regard to safety and efficacy. The final results from a recently completed trial, as well as all currently ongoing trials, will clarify the class effect of this drug in the treatment of COVID-19 in future days.

Vasoactive intestinal peptide indirectly elicits pituitary LH secretion independent of GnRH in female zebrafish

Vasoactive intestinal peptide (Vip) regulates luteinizing hormone (LH) release through the direct regulation of gonadotropin-releasing hormone (GnRH) neurons at the level of the brain in female rodents. However, little is known regarding the roles of Vip in teleost reproduction. Although GnRH is critical for fertility through the regulation of LH secretion in vertebrates, the exact role of the hypophysiotropic GnRH (GnRH3) in zebrafish is unclear since GnRH3 null fish are reproductively fertile. This phenomenon raises the possibility of a redundant regulatory pathway(s) for LH secretion in zebrafish. Here, we demonstrate that VipA (homologues of mammalian Vip) both inhibits and induces LH secretion in zebrafish. Despite the observation that VipA axons may reach the pituitary proximal pars distalis including LH cells, pituitary incubation with VipA in vitro, and intraperitoneal injection of VipA, did not induce LH secretion and lhβ mRNA expression in sexually mature females, respectively. On the other hand, intracerebroventricular administration of VipA augmented plasma LH levels in both wild type and gnrh3-/- females at 1 hour post-treatment, with no observed changes in pituitary GnRH2 and GnRH3 contents and gnrh3 mRNA levels in the brains. While VipA’s manner of inhibition of LH secretion has yet to be explored, the stimulation seems to occur via a different pathway than GnRH3, dopamine, and E2 in regulating LH secretion. The results indicate that VipA induces LH release possibly by acting with or through a non-GnRH factor(s), providing proof for the existence of functional redundancy of LH release in sexually mature female zebrafish.

The Role of Vasoactive Intestinal Peptide and Mast Cells in the Regulatory Effect of Lactobacillus casei ATCC 393 on Intestinal Mucosal Immune Barrier

Vasoactive intestinal peptide (VIP) plays an important role in the neuro-endocrine-immune system. Mast cells (MCs) are important immune effector cells. This study was conducted to investigate the protective effect of L. casei ATCC 393 on Enterotoxigenic Escherichia coli (ETEC) K88-induced intestinal mucosal immune barrier injury and its association with VIP/MC signaling by in vitro experiments in cultures of porcine mucosal mast cells (PMMCs) and in vivo experiments using VIP receptor antagonist (aVIP) drug. The results showed that compared with the ETEC K88 and lipopolysaccharides (LPS)-induced model groups, VIP pretreatment significantly inhibited the activation of MCs and the release of β-hexosaminidase (β-hex), histamine and tryptase. Pretreatment with aVIP abolished the protective effect of L. casei ATCC 393 on ETEC K88-induced intestinal mucosal immune barrier dysfunction in C57BL/6 mice. Also, with the blocking of VIP signal transduction, the ETEC K88 infection increased serum inflammatory cytokines, and the numbers of degranulated MCs in ileum, which were decreased by administration of L. casei ATCC 393. In addition, VIP mediated the regulatory effect of L. casei ATCC 393 on intestinal microbiota in mice. These findings suggested that VIP may mediate the protective effect of L.casei ATCC 393 on intestinal mucosal immune barrier dysfunction via MCs.