Vasoactive intestinal peptide prevents PKCε-induced intestinal epithelial barrier disruption during EPEC infection

Abstract

We previously showed that vasoactive intestinal peptide (VIP) protects against bacterial pathogen-induced epithelial barrier disruption and colitis, although the mechanisms remain poorly defined. The aim of the current study was to identify cellular pathways of VIP-mediated protection with use of pharmacological inhibitors during enteropathogenic Escherichia coli (EPEC) infection of Caco-2 cell monolayers and during Citrobacter rodentium-induced colitis. EPEC-induced epithelial barrier disruption involved the PKC pathway but was independent of functional cAMP, Rho, and NF-κB pathways. VIP mediated its protective effects by inhibiting EPEC-induced PKC activity and increasing expression of the junctional protein claudin-4. Short-term treatment with TPA, which is known to activate PKC, was inhibited by VIP pretreatment, while PKC degradation via long-term treatment with TPA mimicked the protective actions of VIP. Immunostaining for specific PKC isotypes showed upregulated expression of PKCθ and PKCε during EPEC infection. Treatment with specific inhibitors revealed a critical role for PKCε in EPEC-induced barrier disruption. Furthermore, activation of PKCε and loss of barrier integrity correlated with claudin-4 degradation. In contrast, inhibition of PKCε by VIP pretreatment or the PKCε inhibitor maintained membrane-bound claudin-4 levels, along with barrier function. Finally, in vivo treatment with the PKCε inhibitor protected mice from C. rodentium-induced colitis. In conclusion, EPEC infection increases intracellular PKCε levels, leading to decreased claudin-4 levels and compromising epithelial barrier integrity. VIP inhibits PKCε activation, thereby attenuating EPEC-induced barrier disruption.

Recombinant expressed vasoactive intestinal peptide analogue ameliorates TNBS-induced colitis in rats

“…VIP restores immune tolerance by down-regulation of the inflammatory response and by induction of regulatory T cells[ 15 ]. VIP protects against bacterial pathogen EPEC-induced epithelial barrier disruption and colitis, which may be associated with the inhibition of PKCε activation by VIP[ 24 ]. Previous research indicate that exogenous VIP alleviates symptoms of histopathology of TNBS-induced colitis, which may be related to the decrease of the inflammatory and T helper cell type 1 (Th1)-driven autoimmune components[ 25 ].…”

Vasoactive Intestinal Polypeptide (VIP) in the Intestinal Mucosal Nerve Fibers in Dogs with Inflammatory Bowel Disease

“…Namely, it is known that the administration of VIP (especially using sterically stabilized micelles) is capable of alleviating colitis in mice and showing anti-inflammatory and antidiarrheal effects [ 49 ]. Therapeutic effects of VIP may result from VIP-induced stabilization of the intestinal immune homeostasis [ 50 ], protection of the epithelial mitochondria [ 51 ], roles in the maintenance of an appropriate intestinal barrier integrity [ 52 , 53 ] and blockage of the inflammatory cascade [ 54 ]. However, it should be underlined that the therapeutic roles of VIP in experimentally induced colitis in rodents are controversial, because other studies (contrary to the above-mentioned) strongly suggest proinflammatory and pathogenic roles of VIP and suggest the use of VIP antagonists and VIP receptor blockades in the treatment of intestinal inflammatory processes [ 55 ].…”

Here, there, and everywhere: How pathogenicEscherichia colisense and respond to gastrointestinal biogeography

“…Cell chirality is modulated by protein kinase C (PKC) enzymes. Given that PKC enzymes are activated in response to infection, it will be interesting to determine whether AE pathogens unsettle intestinal barrier integrity through the disruption of cell chirality (Malladi, Shankar, Williams, & Balakrishnan, ; Morampudi et al, ).…”

“…However, AE pathogens cause hyperproliferation of the crypt stem cells leading to epithelial oxygenation which favours aerobic pathogen expansion. The microbiota also pose a substantial barrier, as they resist the colonisation of enteric pathogens through nutrient competition and contact-dependent inhibition via the T6SS unsettle intestinal barrier integrity through the disruption of cell chirality (Malladi, Shankar, Williams, & Balakrishnan, 2004;Morampudi et al, 2015).…”