Bilirubin Attenuates ER Stress-Mediated Inflammation, Escalates Apoptosis and Reduces Proliferation in the LS174T Colonic Epithelial Cell Line

Abstract

Mildly elevated serum unconjugated bilirubin (UCB) concentrations are associated with protection against disease conditions underpinned by cellular and metabolic stress. To determine the potential therapeutic efficacy of UCB we tested it in an in vitro model of gut inflammation. Tunicamycin TUN (10 µg/mL) was used to induce endoplasmic reticular stress (ERS) affecting N-glycosylation in LS174T cells. Cultured cells were investigated with addition of UCB at doses 0.1, 1 and 10µM (resulting in bilirubin:albumin ratios of 0.325-0.003)against ER stress-mediated effects including inflammation, cell survival (determined by apoptosis) and proliferation. Gene expression of ER stress markers (Grp78, Perk, XBP1 and ATF6) were evaluated in addition to cytokine concentrations in media after six hours of treatment. We then verified the potential role of UCB in executing programmed cell death via PARP, Caspase3 and Annexin V assays and further explored cell proliferation using the Click-iT EdU assay. A dose of 10µM UCB most potently reduced tunicamycin-mediated effects on enhanced UPR markers, inflammatory cytokines and proliferation; however all the doses (i.e.0.1-10µM) reduced the expression of ER stress and inflammatory markers Grp78, NLRP3, IL1-b, XBP1, PERK and ATF6. Furthermore, media concentrations of pro-inflammatory cytokines IL-8, IL-4 and TNFα decreased and the anti-inflammatory cytokine IL-10 increased (P<0.05). A dose of 10µM UCB initiated intrinsic apoptosis via Caspase 3 and in addition reduced cellular proliferation. Collectively, these data indicate that co treatment with UCB resulted in reducing ER stress response to TUN in gastrointestinal epithelial cells, reduced the subsequent inflammatory response, induced cancer cell death and decreased cellular proliferation. These data suggest that mildly elevated circulating or enteric UCB might protect against gastrointestinal inflammatory disorders.

Mitofusin-2 regulates inflammation-mediated mouse neuroblastoma N2a cells dysfunction and endoplasmic reticulum stress via the Yap-Hippo pathway

“…These results indicate that ER stress could be regarded as a primary downstream effector of inflammation injury, and they are in accordance with previously reported results [51,52]. For example, in a colonic epithelial cell line, inhibition of ER stress attenuated inflammation injury [53]. ER stress has also been observed to modulate the viability of pancreatic β-cells [54], human monocytic leukemia cell [55], alveolar epithelium [56] and bronchial epithelial cells [57] in the context of an inflammation-induced microenvironment.…”

Human Milk Oligosaccharides Differently Modulate Goblet Cells Under Homeostatic, Proinflammatory Conditions and ER Stress

“…Mucin biosynthesis involves C‐terminal dimerization and N‐glycosylation in the ER, followed by O ‐glycosylation in the Golgi and N‐terminal oligomerization. Tm‐induced ER‐stress affects N‐glycosylation and disrupts mucus synthesis in goblet cells . We observed that LNT2 rather than 2′‐FL and 3‐FL impact mucus function‐related gene expression.…”

Celastrol ameliorates endoplasmic stress-mediated apoptosis of osteoarthritis via regulating ATF-6/CHOP signalling pathway

“…[ 24 ] It was reported to have a strong pharmacological activity on regulating miR‐223 and SDF‐1/CXCR4 signalling pathway in OA. [ 25,26 ] We used a Tm‐exposed chondrocyte OA model, and we confirmed the protective effects of celastrol on Tm‐exposed chondrocytes, which occurred through two mechanisms, namely, enhancement of cell viability and reduction in cell apoptosis. Celastrol suppressed the apoptosis rate and down‐regulated the expressions of caspase‐3, caspase‐6 and caspase‐9 in supernatant and intracellular of Tm‐exposed chondrocytes.…”