Epithelial MLCK and smooth muscle MLCK may play different roles in the development of inflammatory bowel disease

Selenoprotein N Was Required for the Regulation of Selenium on the Uterine Smooth Muscle Contraction in Mice

Selenium (Se) is an essential micronutrient affecting various aspects of health. The balance of the Se concentration has an important protective and promoter effect on physiological function in inducing muscular disorders in smooth muscle. Selenoprotein N (SelN) is closely related to Ca²⁺ release. The present study aimed to determine the effects and mechanism of action of dietary Se on uterine smooth muscle contraction via SelN using a mouse model. Quantitative polymerase chain reaction (qPCR) analysis was performed to detect mRNA levels. Western blotting was performed to detect protein levels. The results of the immunohistochemical analysis showed that Se had an effect on the uterine smooth muscle. The Se-supplement increased the release of Ca²⁺, Ca²⁺-calmodulin (CaM) expression, myosin light chain kinase (MLCK) expression, and myosin light chain (MLC) phosphorylation but did not affect ROCK and RhoA in uterine smooth muscle. Furthermore, the lack of Se showed an opposite impact. The effects of Se regulation were closely related to SelN. The interference of mouse SelN was performed on the uterine smooth muscle cell. Additionally, the results displayed the regulation of Se on the release of Ca²⁺, CaM expression, MLCK expression, and MLC phosphorylation were significant inhibited, and there was no effect on ROCK and RhoA. In conclusion, Se played an important role in regulating the process of contraction in uterine smooth muscle with SelN.

Myosin Light Chain Kinase: A Potential Target for Treatment of Inflammatory Diseases

Myosin light chain kinase (MLCK) induces contraction of the perijunctional apical actomyosin ring in response to phosphorylation of the myosin light chain. Abnormal expression of MLCK has been observed in respiratory diseases, pancreatitis, cardiovascular diseases, cancer, and inflammatory bowel disease. The signaling pathways involved in MLCK activation and triggering of endothelial barrier dysfunction are discussed in this review. The pharmacological effects of regulating MLCK expression by inhibitors such as ML-9, ML-7, microbial products, naturally occurring products, and microRNAs are also discussed. The influence of MLCK in inflammatory diseases starts with endothelial barrier dysfunction. The effectiveness of anti-MLCK treatment may depend on alleviation of that primary pathological mechanism. This review summarizes evidence for the potential benefits of anti-MLCK agents in the treatment of inflammatory disease and the importance of avoiding treatment-related side effects, as MLCK is widely expressed in many different tissues.

Comparison of gene expression profiles in aortic dissection and normal human aortic tissues

The aim of the present study was to compare the gene expression profiles in aortic dissection (AD) and healthy human aortic tissue samples by DNA microarray analysis in order to screen the differential genes. In total, five AD and four healthy aortic specimens were selected; the total RNA was extracted and reverse transcribed into cDNA and in vitro transcribed into aRNA, followed by microarray hybridization for analysis. Thereafter, the transcription levels of six differential genes, myosin light chain kinase (MYLK), polycystin 1, transient receptor potential channel interacting (PKD-1), myosin heavy chain 11 (MYH11), superoxide dismutase 3, extracellular (SOD3), filamin A (FLNA), and transgelin (TAGLN), screened from the expression profiles were quantitatively verified. Compared with the healthy aortic specimens, a total of 1,661 genes in the AD group demonstrated more than 2-fold differential expression, of which 997 genes were upregulated and 664 genes were downregulated. Thereafter, six AD-associated genes that showed downregulation in the microarray assay were selected for quantitatively verifying the gene transcription level using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), which confirmed their downregulation compared with the healthy aortic tissue genes; of the six genes, the expression levels of MYLK, PKD-1, MYH11, SOD3 and TAGLN were significantly downregulated (P<0.05), while the expression of FLNA was not significantly downregulated (P>0.05). Thus, whole genome microarray may be used to screen differentially expressed genes between AD and healthy aortic tissues. When used in combination with RT-qPCR validation, this method may provide novel strategies for investigating AD.

Cholinergic receptor activation on epithelia protects against cytokine-induced barrier dysfunction

AIM

Various types of cholinergic receptors are expressed on intestinal epithelia. Their function is not completely understood. We hypothesize that cholinergic receptor activation on epithelium may serve a protective function in cytokine-induced barrier dysfunction.

METHODS

The effect of cholinergic receptor activation on cellular barrier function in epithelial cells was assessed by measuring electrical impedance, and by determining para-cellular transport in transwell experiments. Cell lysates treated with cytokine and/or cholinergic agonists were analysed for cyto- and chemokine production, and tight junction (TJ) protein rearrangement was assessed. Primary colonic epithelial cells were isolated from surgically resected colon tissue of patients with inflammatory bowel disease.

RESULTS

IL-1β induced production of chemokines (CXCL-1, CXCL-10, IL-8, CCL-7) and led to a rearrangement of TJ proteins (occludin and ZO-1). This response was inhibited by pre-treatment with muscarinic, rather than nicotinic, acetylcholine receptor agonists. Treatment with IL-1β enhanced paracellular permeability (4kD dextran) and reduced impedance across the monolayer, which was counteracted by pre-incubation with acetylcholine, or muscarinic receptor agonist bethanechol. The protective effect of acetylcholine was antagonized by atropine, underscoring muscarinic receptor involvement. IL-1β induced transcription of myosin light chain kinase and phosphorylation of myosin light chain, and this cytokine-induced phosphorylation of MLC was inhibited by muscarinic receptor agonists. Furthermore, in epithelial cells from resection material of patients with Crohn's disease and ulcerative colitis, high expression of CXCL-8 was associated with a reduced choline acetyl transferase expression, suggesting an aberrant epithelial production of ACh in inflammatory context.

CONCLUSION

Acetylcholine acts on muscarinic receptors on epithelial cells to maintain epithelial barrier function under inflammatory conditions.