Hydrogen Sulfide Metabolizing Enzymes in the Intestinal Mucosa in Pediatric and Adult Inflammatory Bowel Disease

Cystathionine Gamma-Lyase Regulates TNF-α-Mediated Injury Response in Human Colonic Epithelial Cells and Colonoids

Cystathionine gamma-lyase (CSE) and TNF-α are now recognized as key regulators of intestinal homeostasis, inflammation, and wound healing. In colonic epithelial cells, both molecules have been shown to influence a variety of biological processes, but the specific interactions between intracellular signaling pathways regulated by CSE and TNF-α are poorly understood. In the present study, we investigated these interactions in normal colonocytes and an organoid model of the healthy human colon using CSE-specific pharmacological inhibitors and siRNA-mediated transient gene silencing in analytical and functional assays in vitro. We demonstrated that CSE and TNF-α mutually regulated each other's functions in colonic epithelial cells. TNF-α treatment stimulated CSE activity within minutes and upregulated CSE expression after 24 h, increasing endogenous CSE-derived H2S production. In turn, CSE activity promoted TNF-α-induced NF-ĸB and ERK1/2 activation but did not affect the p38 MAPK signaling pathway. Inhibition of CSE activity completely abolished the TNF-α-induced increase in transepithelial permeability and wound healing. Our data suggest that CSE activity may be essential for effective TNF-α-mediated intestinal injury response. Furthermore, CSE regulation of TNF-α-controlled intracellular signaling pathways could provide new therapeutic targets in diseases of the colon associated with impaired epithelial wound healing.

Update of gut gas metabolism in ulcerative colitis

INTRODUCTION

Ulcerative colitis (UC) is a chronic, nonspecific inflammatory disease of the intestine. The intestinal microbiota is essential in the occurrence and development of UC. Gut gases are produced via bacterial fermentation or chemical interactions, which can reveal altered intestinal microbiota, abnormal cellular metabolism, and inflammation responses. Recent studies have demonstrated that UC patients have an altered gut gas metabolism.

AREAS COVERED

In this review, we integrate gut gas metabolism advances in UC and discuss intestinal gases' clinical values as new biomarkers or therapeutic targets for UC, providing the foundation for further research. Literature regarding gut gas metabolism and its significance in UC from inception to October 2023 was searched on the MEDLINE database and references from relevant articles were investigated.

EXPERT OPINION

Depending on their type, concentration, and volume, gut gases can induce or alleviate clinical symptoms and regulate intestinal motility, inflammatory responses, immune function, and oxidative stress, significantly impacting UC. Gut gases may function as new biomarkers and provide potential diagnostic or therapeutic targets for UC.

Role of Hydrogen Sulfide in Inflammatory Bowel Disease

Hydrogen sulfide (H2S), originally known as toxic gas, has now attracted attention as one of the gasotransmitters involved in many reactions in the human body. H2S has been assumed to play a role in the pathogenesis of many chronic diseases, of which the exact pathogenesis remains unknown. One of them is inflammatory bowel disease (IBD), a chronic intestinal disease subclassified as Crohn's disease (CD) and ulcerative colitis (UC). Any change in the amount of H2S seems to be linked to inflammation in this illness. These changes can be brought about by alterations in the microbiota, in the endogenous metabolism of H2S and in the diet. As both too little and too much H2S drive inflammation, a balanced level is needed for intestinal health. The aim of this review is to summarize the available literature published until June 2023 in order to provide an overview of the current knowledge of the connection between H2S and IBD.

Galanin System in the Human Bile Duct and Perihilar Cholangiocarcinoma

BACKGROUND

Perihilar cholangiocarcinoma (pCCA) is characterised by poor outcomes. Early diagnosis is essential for patient survival. The peptide galanin (GAL) and its receptors GAL1-3 are expressed in various tumours. Detailed characterisation of the GAL system in pCCA is lacking. Our study sought to characterise GAL and GAL1-3 receptor (GAL1-3-R) expression in the healthy human bile duct, in cholestasis and pCCA.

METHODS

Immunohistochemical staining was performed in healthy controls (n = 5) and in the peritumoural tissues (with and without cholestasis) (n = 20) and tumour tissues of pCCA patients (n = 33) using validated antibodies. The score values of GAL and GAL1-3-R expression were calculated and statistically evaluated.

RESULTS

GAL and GAL1-R were expressed in various bile duct cell types. GAL2-R was only slightly but still expressed in almost all the examined tissues, and GAL3-R specifically in cholangiocytes and capillaries. In a small pCCA patient cohort (n = 18), high GAL expression correlated with good survival, whereas high GAL3-R correlated with poor survival.

CONCLUSIONS

Our in-depth characterisation of the GAL system in the healthy human biliary duct and pCCA in a small patient cohort revealed that GAL and GAL3-R expression in tumour cells of pCCA patients could potentially represent suitable biomarkers for survival.

Study of hydrogen sulfide biosynthesis in synovial tissue from diabetes-associated osteoarthritis and its influence on macrophage phenotype and abundance

Type 2 diabetes (DB) is an independent risk factor for osteoarthritis (OA). However, the mechanisms underlying the connection between both diseases remain unclear. Synovial macrophages from OA patients with DB present a marked pro-inflammatory phenotype. Since hydrogen sulphide (H₂S) has been previously described to be involved in macrophage polarization, in this study we examined H₂S biosynthesis in synovial tissue from OA patients with DB, observing a reduction of H₂S-synthetizing enzymes in this subset of individuals. To elucidate these findings, we detected that differentiated TPH-1 cells to macrophages exposed to high levels of glucose presented a lower expression of H₂S-synthetizing enzymes and an increased inflammatory response to LPS, showing upregulated expression of markers associated with M1 phenotype (i.e., CD11c, CD86, iNOS, and IL-6) and reduced levels of those related to M2 fate (CD206 and CD163). The co-treatment of the cells with a slow-releasing H₂S donor, GYY-4137, attenuated the expression of M1 markers, but failed to modulate the levels of M2 indicators. GYY-4137 also reduced HIF-1α expression and upregulated the protein levels of HO-1, suggesting their involvement in the anti-inflammatory effects of H₂S induction. In addition, we observed that intraarticular administration of H₂S donor attenuated synovial abundance of CD68⁺ cells, mainly macrophages, in an in vivo model of OA. Taken together, the findings of this study seem to reinforce the key role of H₂S in the M1-like polarization of synovial macrophages associated to OA and specifically its metabolic phenotype, opening new therapeutic perspectives in the management of this pathology.

Differential Roles of Cystathionine Gamma-Lyase and Mercaptopyruvate Sulfurtransferase in Hapten-Induced Colitis and Contact Dermatitis in Mice

Hydrogen sulfide (H₂S) has been shown to act as both anti-inflammatory and pro-inflammatory mediators. Application of H₂S donors generally protects against inflammation; however, experimental results using mice lacking endogenous H₂S-producing enzymes, such as cystathionine γ-lyase (CTH) and mercaptopyruvate sulfurtransferase (MPST), are often contradictory. We herein examined two types of model hapten-induced inflammation models, colitis (an inflammatory bowel disease model of mucosal immunity) and contact dermatitis (a type IV allergic model of systemic immunity), in CTH-deficient (Cth^-/-) and MPST-deficient (Mpst^-/-) mice. Both mice exhibited no significant alteration from wild-type mice in trinitrobenzene sulfonic acid (Th1-type hapten)-induced colitis (a Crohn's disease model) and oxazolone (Th1/Th2 mix-type; Th2 dominant)-induced colitis (an ulcerative colitis model). However, Cth^-/- (not Mpst^-/-) mice displayed more exacerbated phenotypes in trinitrochlorobenzene (TNCB; Th1-type)-induced contact dermatitis, but not oxazolone, at the delayed phase (24 h post-administration) of inflammation. CTH mRNA expression was upregulated in the TNCB-treated ears of both wild-type and Mpst^-/- mice. Although mRNA expression of pro-inflammatory cytokines (IL-1β and IL-6) was upregulated in both early (2 h) and delayed phases of TNCB-triggered dermatitis in all genotypes, that of Th2 (IL-4) and Treg cytokines (IL-10) was upregulated only in Cth^-/- mice, when that of Th1 cytokines (IFNγ and IL-2) was upregulated in wild-type and Mpst^-/- mice at the delayed phase. These results suggest that (upregulated) CTH or H₂S produced by it helps maintain Th1/Th2 balance to protect against contact dermatitis.