Expression of midkine and receptor-like protein tyrosine phosphatase (RPTP)-beta genes in the rat stomach and the influence of rebamipide

Role of vacuolating cytotoxin A in Helicobacter pylori infection and its impact on gastric pathogenesis

Introduction Helicobacter pylori causes, via the influence of several virulence factors, persistent infection of the stomach, which leads to severe complications. Vacuolating cytotoxin A (VacA) is observed in almost all clinical strains of H. pylori; however, only some strains produce the toxigenic and pathogenic VacA, which is influenced by the gene sequence variations. VacA exerts its action by causing cell vacuolation and apoptosis. We performed a PubMed search to review the latest literatures published in English language. Areas covered Articles regarding H. pylori VacA and its genotypes, architecture, internalization, and role in gastric infection and pathogenicity are reviewed. We included the search for recently published literature until January 2020. Expert opinion H. pylori VacA plays a crucial role in severe gastric pathogenicity. In addition, VacA mediated in vivo bacterial survival leads to persistent infection and an enhanced bacterial evasion from the action of antibiotics and the innate host defense system, which leads to drug evasion. VacA as a co-stimulator for the CagA phosphorylation may exert a synergistic effect playing an important role in the CagA-mediated pathogenicity.

The Expression, Functions, Interactions and Prognostic Values of PTPRZ1: A Review and Bioinformatic Analysis

Available studies demonstrate that receptor-type tyrosine-protein phosphatase zeta (PTPRZ1) is expressed in different tumor tissues, and functions in cell proliferation, cell adhesion and migration, epithelial-to-mesenchymal transition, cancer stem cells and treatment resistance by interacting with or binding to several molecules. These included pleiotrophin (PTN), midkine, interleukin-34, β-catenin, VEGF, NF-κB, HIF-2, PSD-95, MAGI-3, contactin and ErbB4. PTPRZ1 was involved in survival signaling and could predict the prognosis of several tumors. This review discusses: the current knowledge about PTPRZ1, its expression, co-receptors, ligands, functions, signaling pathway, prognostic values and therapeutic agents that target PTPRZ1.

New Insights into VacA Intoxication Mediated through Its Cell Surface Receptors

Helicobacter pylori (H. pylori), a major cause of gastroduodenal diseases, produces VacA, a vacuolating cytotoxin associated with gastric inflammation and ulceration. The C-terminal domain of VacA plays a crucial role in receptor recognition on target cells. We have previously identified three proteins (i.e., RPTPα, RPTPβ, and LRP1) that serve as VacA receptors. These receptors contribute to the internalization of VacA into epithelial cells, activate signal transduction pathways, and contribute to cell death and gastric ulceration. In addition, other factors (e.g., CD18, sphingomyelin) have also been identified as cell-surface, VacA-binding proteins. Since we believe that, following interactions with its host cell receptors, VacA participates in events leading to disease, a better understanding of the cellular function of VacA receptors may provide valuable information regarding the mechanisms underlying the pleiotropic actions of VacA and the pathogenesis of H. pylori-mediated disease. In this review, we focus on VacA receptors and their role in events leading to cell damage.

Midkine is a NF-kappaB-inducible gene that supports prostate cancer cell survival

Background

Midkine is a heparin-binding growth factor that is over-expressed in various human cancers and plays important roles in cell transformation, growth, survival, migration, and angiogenesis. However, little is known about the upstream factors and signaling mechanisms that regulate midkine gene expression.

Methods

Two prostate cancer cell lines LNCaP and PC3 were studied for their expression of midkine. Induction of midkine expression in LNCaP cells by serum, growth factors and cytokines was determined by Western blot analysis and/or real-time quantitative reverse-transcription – polymerase chain reaction (RT-PCR). The cell viability was determined by the trypan blue exclusion assay when the LNCaP cells were treated with tumor necrosis factor alpha (TNFα) and/or recombinant midkine. When the LNCaP cells were treated with recombinant midkine, activation of intracellular signalling pathways was determined by Western blot analysis. Prostate tissue microarray slides containing 129 cases (18 normal prostate tissues, 40 early stage cancers, and 71 late stage cancers) were assessed for midkine expression by immunohistochemical staining.

Results

We identified that fetal bovine serum, some growth factors (epidermal growth factor, androgen, insulin-like growth factor-I, and hepatocyte growth factor) and cytokines (TNFα and interleukin-1beta) induced midkine expression in a human prostate cancer cell line LNCaP cells. TNFα also induced midkine expression in PC3 cells. TNFα was the strongest inducer of midkine expression via nuclear factor-kappa B pathway. Midkine partially inhibited TNFα-induced apoptosis in LNCaP cells. Knockdown of endogenous midkine expression by small interfering RNA enhanced TNFα-induced apoptosis in LNCaP cells. Midkine activated extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase pathways in LNCaP cells. Furthermore, midkine expression was significantly increased in late stage prostate cancer, which coincides with previously reported high serum levels of TNFα in advanced prostate cancer.

Conclusion

These findings provide the first demonstration that midkine expression is induced by certain growth factors and cytokines, particularly TNFα, which offers new insight into understanding how midkine expression is increased in the late stage prostate cancer.

Increased expression of midkine in the rat colon during healing of experimental colitis

Midkine (MK) is a unique growth and differentiation factor that modulates the proliferation and migration of various cells; however, little is known regarding its relationship to intestinal diseases. The aim of this study was to investigate MK expression and its role in dextran sulfate sodium (DSS)-induced colitis in rats. The expressions of MK, receptor-like protein-tyrosine phosphatase (RPTP)-beta, and proinflammatory cytokines were examined in rat colonic tissues after the development of DSS-induced colitis using Northern blotting, immunohistochemistry, and laser-capture microdissection (LCM) coupled with RT-PCR. The effects of MK on the migration of intestinal epithelial cells (IEC-6) were also evaluated in vitro using an intestinal wound repair model. MK expression was significantly increased in damaged colonic mucosa, mainly from day 3 to day 5 after the end of DSS administration, with abundant MK immunoreactive signals detected in submucosal fibroblasts. Expressions of proinflammatory cytokines were most strongly induced on day 1, which preceded the augmentation of MK expression. Results of LCM coupled with RT-PCR clearly indicated RPTP-beta expression in colonic epithelial cells. The migration assay showed that wound repair in the MK-treated groups was accelerated dose dependently. The present results showed for the first time that intestinal inflammation upregulates the MK-RPTP-beta system, which may stimulate mucosal regeneration during the process of healing of colitis. Additional investigations regarding the role of MK may contribute to the development of new options for the treatment of inflammatory bowel diseases.

Epithelial toll-like receptor 5 is constitutively localized in the mouse cecum and exhibits distinctive down-regulation during experimental colitis

We recently demonstrated that the pattern recognition receptors (PRRs) toll-like receptor 2 (TLR2), TLR4, and CD14 are expressed in mouse colonic epithelium in a compartmentalized manner. Here we report the localization of TLR5, the receptor for bacterial flagellin, and its distinctive down-regulation during experimental colitis. Guts from normal BALB/c mice and those with dextran sodium sulfate (DSS)-induced colitis were compared. Each gut was divided into seven segments (stomach, small intestine [three parts], and colon [three parts]), and epithelial cells and crypt units were collected by scraping and EDTA treatment, respectively. Northern blotting showed that TLR5 mRNA was preferentially expressed in the epithelium of the proximal colon in normal mice. Laser capture microdissection coupled to reverse transcriptase PCR confirmed this localization. TLR5 protein expression reflected mRNA expression, as evidenced by Western blotting. In mice with acute colitis, inflammation occurred mainly in the distal colon. Interestingly, while TLR2, TLR4, and CD14 were up-regulated in the inflamed colon, TLR5 was down-regulated at both the mRNA and protein levels. Decreased TLR5 expression was more evident during chronic colitis. Additional in vitro studies using a mouse cell line, Colon-26, showed that gamma interferon (IFN-gamma) time- and dose-dependently down-regulates TLR5. In conclusion, epithelial cells, mainly in the proximal colon, constitutively express TLR5. TLR5 expression is down-regulated in vivo during acute and chronic DSS-induced colitis, in contrast to the expression of TLR2, TLR4, and CD14. The mechanism governing TLR5 regulation may therefore differ from that controlling other PRRs. Finally, IFN-gamma may be involved in down-regulating TLR5 expression.