Ethanol Upregulates iNOS Expression in Colon Through Activation of Nuclear Factor‐kappa B in Rats

Abstract

Background: Alcohol inhibits colonic motility but the mechanism is unknown. The goal of this study was to test the possibility that nuclear factor-kappa B (NF-jB) is involved in the upregulation of inducible nitric oxide synthase (iNOS) expression induced by ethanol in colon.Methods: The isometric contraction of longitudinal muscle strips of proximal colon (LP) was monitored by polygraph. Western blot analysis was used to measure the amount of iNOS and I-jB in the cytoplasm and P65 in the nucleus. Immunohistochemistry was applied to locate iNOS in colon.Results: Ethanol (87mM) inhibited the contraction of LP. Pretreatment of S-methylisothioure (SMT) (1 mM), a specific iNOS inhibitor, Pyrrolidine dithiocarbamate (PDTC) (10 mM) and BAY11-7082(10 mM), specific inhibitors of NF-jB significantly reversed the inhibitory effect of ethanol on LP contraction. Ethanol increased the amount of iNOS and content of NO in colon, and these effects were attenuated by pretreatment of PDTC. Following ethanol administration, the amount of I-jB in the cytoplasm decreased, but that of P65, the subunit of NF-jB in the nucleus, increased. The iNOS was located in the cell body of myenteric plexus in colon.Conclusion: Ethanol inhibited the contraction of LP in colon mainly through activation of NF-jB, the subsequent upregulation of iNOS expression and increase of NO release in myenteric plexus.

Mitochondrial ROS induced by chronic ethanol exposure promote hyper-activation of the NLRP3 inflammasome

“…Protracted treatment with ethanol increases the expression of iNOS and promotes NO production in vitro and in vivo [24], [25]. Similarly, CE cells stimulated with LPS display higher Nos2 and lower Arg1 expression, and produce significantly more NO than UT cells (Fig.…”

“…Long-term treatment with ethanol in vivo and in vitro promotes iNOS activation and aberrant NO production [24], [62]. To examine whether CE cells display a similar phenotype, Nos2 and Arg1 expression were measured by RT-qPCR using cDNA generated from mRNA extracted from the lysates of UT and CE cells with or without 4 h of LPS stimulation.…”

“…Ethanol metabolism by CYP2E1 and alcohol dehydrogenase (ADH) results in the generation of acetaldehyde, which induces oxidative stress and the formation of DNA and protein adducts [21], [22], [23]. Ethanol exposure has also been shown to promote inducible nitric oxide synthase (iNOS) expression and the subsequent production of NO [24], [25]. Together, the ROS, reactive nitrogen species (RNS), and acetaldehyde produced during chronic ethanol exposure can induce nuclear and mitochondrial DNA damage and initiate ER stress via the accumulation of misfolded proteins [25], [26], [27].…”

Molecular Basis of Alcohol-Related Gastric and Colon Cancer

“…Following ethanol administration to rats, the amount of its inhibitor, IκB in the cytoplasm decreased in colon, but the localization of p65, the functionally active subunit of NF-κB in the nucleus, increased [72]. As a consequence, the expression of iNOS and content of its product nitric oxide were elevated, leading to inhibition of colonic contraction in rats [72]. Ethanol treatment enhanced production of both interferon γ and IL-4 in the cells from cecal lymph node [73].…”

Protein Kinase R Mediates the Inflammatory Response Induced by Hyperosmotic Stress

“…The transcription factor nuclear factor B (NF-B) induces transcription of the iNOS gene under conditions such as ethanol treatment (25), Toll-like receptor (TLR) activation (26), and hyperosmotic stress (27). NF-B is a dimeric transcription factor that is held inactive in the cytoplasm but is released upon signal-induced phosphorylation and degradation of the inhibitory binding partner (IB␣) to enter the nucleus (28).…”