TGFbeta1 expression in colonic mucosa: modulation by dietary lipids

Molecular mechanisms by which casein glycomacropeptide maintains internal homeostasis in mice with experimental ulcerative colitis

OBJECTIVES

The aim of this study was to elucidate the molecular mechanisms by which food-derived casein glycomacropeptide (CGMP) maintains internal homeostasis in the intestinal mucosa and to investigate the effects of CGMP on the intestinal mucosal immunological barrier and related signal transduction pathways.

METHODS

In this study, a famoxadone (OXZ)-induced mouse experimental ulcerative colitis (UC) model was built. The experimental UC mice were intragastrically administered milk-derived CGMP for four consecutive days. The molecular mechanisms by which milk-derived CGMP improved and restored the inflammatory status in UC symptoms were elucidated by H&E staining, immunohistochemical staining and western blotting.

RESULTS

The results indicated that CGMP (50 mg/(kg bw·d)) could significantly improve morphological injury to intestinal mucosa in OXZ-induced UC mice to the same extent that did sulfasalazine (SASP, 40 mg/(kg bw·d)), a medicine used to treat UC, in the control group. The study found that CGMP could significantly reduce the expression of Human mucosal addressin cell adhesion molecule-1 (MAdCAM-1), Cluster of differentiation 4 (CD4) and Cluster of differentiation 8 (CD8) in the lamina propria of the intestinal mucosa and significantly stimulate the secretion of sIgA to increase intestinal immunity. Furthermore, CGMP was found to be directly involved in inhibiting the MAPK pathway and activating the TGF-β1/Smad signal transduction cascade, which could maintain immunological regulation of the intestinal mucosa and protect the functions of the intestinal mucosal barrier.

CONCLUSIONS

This study elucidated the molecular mechanisms by which CGMP maintained homeostasis of the intestinal mucosa and further confirmed its pharmaceutical value as a food-derived functional component with promising potential for further exploration/utilization.

Formation of malondialdehyde (MDA), 4-hydroxy-2-hexenal (HHE) and 4-hydroxy-2-nonenal (HNE) in fish and fish oil during dynamic gastrointestinal in vitro digestion

Reactive lipid peroxidation products (MDA, HHE and HNE) are formed during dynamic gastrointestinalin vitrodigestion of fish and fish oil.

Mechanisms of oxysterol-induced carcinogenesis

Oxysterols are oxidation products of cholesterol that are generated by enzymatic reactions mediated by cytochrome P450 family enzymes or by non-enzymatic reactions involving reactive oxygen and nitrogen species. Oxysterols play various regulatory roles in normal cellular processes such as cholesterol homeostasis by acting as intermediates in cholesterol catabolism. Pathological effects of oxysterols have also been described, and various reports have implicated oxysterols in several disease states, including atherosclerosis, neurological disease, and cancer. Numerous studies show that oxysterols are associated with various types of cancer, including cancers of the colon, lung, skin, breast and bile ducts. The molecular mechanisms whereby oxysterols contribute to the initiation and progression of cancer are an area of active investigation. This review focuses on the current state of knowledge regarding the role of oxysterols in carcinogenesis. Mutagenicity of oxysterols has been described in both nuclear and mitochondrial DNA. Certain oxysterols such as cholesterol-epoxide and cholestanetriol have been shown to be mutagenic and genotoxic. Oxysterols possess pro-oxidative and pro-inflammatory properties that can contribute to carcinogenesis. Oxysterols can induce the production of inflammatory cytokines such as interleukin-8 and interleukin-1β. Certain oxysterols are also involved in the induction of cyclo-oxygenase-2 expression. Inflammatory effects can also be mediated through the activation of liver-X-receptor, a nuclear receptor for oxysterols. Thus, several distinct molecular mechanisms have been described showing that oxysterols contribute to the initiation and progression of cancers arising in various organ systems.

Inhibition of transforming growth factor-beta/Smad signaling improves regeneration of small-for-size rat liver grafts

Transforming growth factor-beta (TGF-beta) is a potent inhibitor of cell proliferation. This study investigated whether overexpression of Smad7, which blocks TGF-beta-induced activation of Smad2/3, could prevent the suppression of regeneration of small-for-size liver grafts. Rats were intravenously given adenoviruses (2 x 10(10) pfu/rat) carrying the LacZ gene or the Smad7 gene (Ad-Smad7) 3 days prior to liver harvesting. Half-size livers were implanted into recipients of the same weight or twice the donor weight, and this resulted in half-size or quarter-size liver grafts. Cell proliferation, detected by 5-bromo-2'-deoxyuridine (BrdU) incorporation, increased to 23% in half-size grafts at 38 hours after implantation but was only 4% in quarter-size grafts. Graft weight did not increase after 38 hours in full-size and quarter-size grafts but increased 28% in half-size grafts. Ad-Smad7 restored BrdU labeling to 32%, and the graft weight increased to 43% in quarter-size grafts. Serum total bilirubin increased approximately 30-fold after the implantation of quarter-size grafts. Ad-Smad7 blunted hyperbilirubinemia by 80%. The basal hepatic TGF-beta(1) level was 7 ng/g of liver wet weight, and this increased to 30 ng/g at 1.5 hours after the transplantation of full-size grafts but decreased rapidly afterwards. After the transplantation of quarter-size grafts, however, TGF-beta(1) progressively increased to 159 ng/g in 38 hours. Nuclear phosphorylated Smad2/3 was barely detectable, and p21Cip1 expression was negligible in full-size grafts but increased markedly in quarter-size grafts. Ad-Smad7 blocked Smad2/3 activation and expression of p21Cip1. Together, these data show that TGF-beta is responsible, at least in part, for the defective liver regeneration in small-for-size grafts by activating the Smad signaling pathway.

4-hydroxynonenal, a lipid peroxidation product of dietary polyunsaturated fatty acids, has anticarcinogenic properties in colon carcinoma cell lines through the inhibition of telomerase activity

The effects of polyunsaturated fatty acids (PUFAs) obtained from the diet on colorectal cancer have been widely explored. However, controversial results have been obtained about the role played by the lipid peroxidation products of PUFAs, such as 4-hydroxy-nonenal (HNE), in the control of colon cancer growth. This aldehyde, indeed, showed both procarcinogenic and protective effects. In an attempt to verify the action of HNE, we studied the effects of a low dose of HNE (1 microM), similar to those "physiologically" found in normal cells and plasma, on telomerase activity, a key parameter of malignant transformation. Caco-2 cells were exposed to HNE and, paralleling cell growth inhibition, we observed the down-regulation of telomerase activity and hTERT expression. Similar effects have also been observed in HT-29 cells, in which HNE inhibited cell proliferation, telomerase activity and hTERT expression, suggesting that the inhibition of telomerase activity could be a general mechanism involved in the antiproliferative effect exerted by this aldehyde. Finally, we elucidated the mechanism of hTERT inhibition by HNE. A reduction of GSH content preceded the decrease of telomerase activity, but this only partially explained the telomerase activity inhibition. The major mechanism of HNE action seems to be the modulation of expression and activity of transcription factors belonging to the Myc/Mad/Max network. Since the presence of PUFAs in the diet exposes epithelial colon cells to HNE, this aldehyde could contribute to cell growth control through the inhibitory action on telomerase activity and hTERT expression, suggesting a protective effect on colon mucosa.