Role and mechanism of phosphate myosin light chain in chronic allograft nephropathy of rats

Objective To investigate role and mechanism of phosphate myosin light chain ( pMLC) in rat kidney of chronic allograft nephropathy ( CAN) model. Methods Left donor kidneys from Fisher ( F344) rats were ortho-topically transplanted into Lewis recipients,Meanwhile, F344 rats and LEW rats with resection of right

The sphingosine-1-phosphate/RhoA/Rho associated kinases/myosin light chain pathway in detrusor of female rats is down-regulated in response to ovariectomy

Background:Dysuria is one of the main symptoms of genitourinary syndrome of menopause,which causes serious disruption to the normal life of peri-menopausal women.Studies have shown that it is related to decrease of detrusor contractile function,but the exact mechanism is still poorly understood.Previous results have suggested that the sphingosine-1-phosphate(S1P)pathway can regulate detrusor contraction,and this pathway is affected by estrogen in various tissues.However,how estrogen affects this pathway in the detrusor has not been investigated.In this study,we detected changes of the S1P/RhoA/Rho associated kinases(ROCK)/myosin light chain(MLC)pathway in the detrusor of ovariectomized rats in order to explore the underlying mechanism of dysuria during peri-menopause.Methods::Thirty-six female Sprague-Dawley rats were randomly divided into SHAM(sham operation),OVX(ovariectomy),and E groups(ovariectomy+estrogen),with 12 rats in each group.We obtained bladder detrusor tissues from each group and examined the mRNA and protein levels of the major components of the S1P/RhoA/ROCK/MLC pathway using quantitative real-time polymerase chain reaction and Western blotting,respectively.We also quantified the content of S1P in the detrusor using an enzyme linked immunosorbent assay.Finally,we compared results between the groups with one-way analysis of variance.Results::The components of the S1P pathway and the RhoA/ROCK/MLC pathway of the OVX group were significantly decreased,as compared with SHAM group.The percent decreases of the components in the S1P pathway were as follows:sphingosine kinase 1(mRNA:39%,protein:45%)(both P<0.05),S1P(21.73±1.09 nmol/g vs.18.86±0.69 nmol/g)(P<0.05),and S1P receptor 2/3(S1PR2/3)(mRNA:25%,27%,respectively)(P<0.05).However,the protein expression levels of S1PR2/3 and the protein and mRNA levels of SphK2 and S1PR1 did not show significant differences between groups(P>0.05).The percent decreases of the components in the RhoA/ROCK/MLC pathway were as follows:ROCK2(protein:41%,mRNA:36%)(both P<0.05),p-MYPT1(protein:54%)(P<0.05),and p-MLC20(protein:47%)(P<0.05),but there were no significant differences in the mRNA and protein levels of RhoA,ROCK1,MYPT1,and MLC20(all P>0.05).In addition,all of the above-mentioned decreases could be reversed after estrogen supplementation(E group vs.SHAM group)(all P>0.05).Conclusion::In this study,we confirmed that ovariectomy is closely associated with the down-regulation of the S1P/RhoA/ROCK/MLC pathway in the rat detrusor,which may be one mechanism of dysuria caused by decreased contractile function of the female detrusor during peri-menopause.

Acanthopanax senticosus polysaccharides-induced intestinal tight junction injury alleviation via inhibition of NF-κB/MLCK pathway in a mouse endotoxemia model

AIM To examine the effects of Acanthopanax senticosus polysaccharides(ASPS) on intestinal tight junction(TJ) disruption and nuclear factor-kappa B(NF-κB)/myosin light chain kinase(MLCK) activation in endotoxemia.METHODS BALB/C mice(6-8-weeks-old) received continuous intragastric gavage of ASPS for 7 d before injection of lipopolysaccharide(LPS), or received ASPS once after LPS injection. Blood and intestinal mucosal samples were collected 6 h after LPS challenge. Clinical symptoms, histological injury, intestinal permeability,TJ ultrastructure, and TJ protein expression were determined.RESULTS Compared with mice in the LPS group, pretreatment with ASPS improved clinical and histological scores by 390.9%(P < 0.05) and 57.89%(P < 0.05), respectively, and gut permeability change in endotoxemic mice was shown by a 61.93% reduction in reduced leakage of fluorescein isothiocyanate-dextran 6 h after LPS injection(P < 0.05). ASPS pretreatment also prevented LPS-induced TJ ultrastructure breakdown supported by increased electron dense materials between adjoining cells, sustained redistribution and expression of occludin(0.597 ± 0.027 vs 0.103 ± 0.009, P < 0.05) and zonula occludens-1(0.507 ± 0.032 vs 0.125 ± 0.019, P < 0.05), and suppressed activation of the NF-κB/MLCK pathway indicated by reduced expression of NF-κB, phospho-inhibitor kappa B-alpha, MLCK and phospho-myosin light-chain-2 by 16.06%(P < 0.05), 54.31%(P < 0.05), 66.10%(P < 0.05) and 64.82%(P < 0.05), respectively. CONCLUSION ASPS pretreatment may be associated with inhibition of the NF-κB/MLCK pathway and concomitant amelioration of LPS-induced TJ dysfunction of intestinal epithelium in endotoxemia.

Recombinant angiopoietin-like protein 4 attenuates intestinal barrier structure and function injury after ischemia/reperfusion

BACKGROUND Intestinal barrier breakdown,a frequent complication of intestinal ischemiareperfusion(I/R)including dysfunction and the structure changes of the intestine,is characterized by a loss of tight junction and enhanced permeability of the intestinal barrier and increased mortality.To develop effective and novel therapeutics is important for the improvement of outcome of patients with intestinal barrier deterioration.Recombinant human angiopoietin-like protein 4(rhANGPTL4)is reported to protect the blood-brain barrier when administered exogenously,and endogenous ANGPTL4 deficiency deteriorates radiationinduced intestinal injury.AIM To identify whether rhANGPTL4 may protect intestinal barrier breakdown induced by I/R.METHODS Intestinal I/R injury was elicited through clamping the superior mesenteric artery for 60 min followed by 240 min reperfusion.Intestinal epithelial(Caco-2)cells and human umbilical vein endothelial cells were challenged by hypoxia/reoxygenation to mimic I/R in vitro.RESULTS Indicators including fluorescein isothiocyanate-conjugated dextran(4 kilodaltons;FD-4)clearance,ratio of phosphorylated myosin light chain/total myosin light chain,myosin light chain kinase and loss of zonula occludens-1,claudin-2 and VE-cadherin were significantly increased after intestinal I/R or cell hypoxia/reoxygenation.rhANGPTL4 treatment significantly reversed these indicators,which were associated with inhibiting the inflammatory and oxidative cascade,excessive activation of cellular autophagy and apoptosis and improvement of survival rate.Similar results were observed in vitro when cells were challenged by hypoxia/reoxygenation,whereas rhANGPTL4 reversed the indicators close to normal level in Caco-2 cells and human umbilical vein endothelial cells significantly.CONCLUSION rhANGPTL4 can function as a protective agent against intestinal injury induced by intestinal I/R and improve survival via maintenance of intestinal barrier structure and functions.

Intestinal barrier dysfunction in severe burn injury

Severe burn injury is often accompanied by intestinal barrier dysfunction,which is closely associated with post-burn shock,bacterial translocation,systemic inflammatory response syndrome,hypercatabolism,sepsis,multiple organ dysfunction syndrome,and other complications.The intestinal epithelium forms a physical barrier that separates the intestinal lumen from the internal milieu,in which the tight junction plays a principal role.It has been well documented that after severe burn injury,many factors such as stress,ischemia/hypoxia,proinflammatory cytokines,and endotoxins can induce intestinal barrier dysfunction via multiple signaling pathways.Recent advances have provided new insights into the mechanisms and the therapeutic strategies of intestinal epithelial barrier dysfunction associated with severe burn injury.In this review,we will describe the current knowledge of the mechanisms involved in intestinal barrier dysfunction in response to severe burn injury and the emerging therapies for treating intestinal barrier dysfunction following severe burn injury.

Chang'an Ⅱ Decoction(肠安Ⅱ号方)-Containing Serum Ameliorates Tumor Necrosis Factor-α-Induced Intestinal Epithelial Barrier Dysfunction via MLCK-MLC Signaling Pathway in Rats

Objective To investigate the effect of Chang’an Ⅱ Decoction(肠安Ⅱ号方))-containing serum on intestinal epithelial barrier dysfunction in rats.Methods Tumor necrosis factor(TNF)-α-induced injury of Caco-2 monolayers were established as an inflammatory model of human intestinal epithelium.Caco-2 monolayers were treated with blank serum and Chang’an Ⅱ Decoction-containing serum that obtained from the rats which were treated with distilled water and Chang’an Ⅱ Decoction intragastrically at doses of 0.49,0.98,1.96 g/(kg·d)for 1 week,respectively.After preparation of containing serum,cells were divided into the normal group,the model group,the Chang’an Ⅱ-H,M,and L groups(treated with 30 ng/mL TNF-αand medium plus 10%high,middle-,and low-doses Chang’an Ⅱ serum,respectively).Epithelial barrier function was assessed by transepithelial electrical resistance(TER)and permeability of fluorescein isothiocyanate(FITC)-labeled dextran.Transmission electron microscopy was used to observe the ultrastructure of tight junctions(TJs).Immunofluorescence of zonula occludens-1(ZO-1),claudin-1 and nuclear transcription factor-kappa p65(NF-κBp65)were measured to determine the protein distribution.The mRNA expression of myosin light chain kinase(MLCK)was measured by real-time polymerase chain reaction.The expression levels of MLCK,myosin light chain(MLC)and p-MLC were determined by Western blot.Results Chang’an Ⅱ Decoction-containing serum significantly attenuated the TER and paracellular permeability induced by TNF-α.It alleviated TNF-α-induced morphological alterations in TJ proteins.The increases in MLCK mRNA and MLCK,MLC and p-MLC protein expressions induced by TNF-αwere significantly inhibited in the Chang’an Ⅱ-H group.Additionally,Chang’an Ⅱ Decoction significantly attenuated translocation of NF-κBp65 into the nucleus.Conclusion High-dose Chang’an Ⅱ-containing serum attenuates TNF-α-induced intestinal barrier dysfunction.The underlying mechanism may be involved in inhibiting the MLCK-MLC phosphorylation signaling pathway mediated by NF-κBp65.

ERK signaling mediates enhanced angiotensin II-induced rat aortic constriction following chronic intermittent hypoxia

Background Obstructive sleep apnea （OSA） has been recognized as an independent risk factor for systemic hypertension. The study investigated the functional consequences of chronic intermittent hypoxia （CIH） on aortic constriction induced by angiotensin II （Ang II） and the possible signaling involving ERK1/2 and contractile proteins such as myosin light chain kinase （MLCK）, myosin phosphatase targeting subunit （MYPT1） and myosin light chain （MLC）. Methods Male Wistar rats were randomly divided into CIH group and normoxia group and exposed to either CIH procedure or air-air cycles. Phosphorylation of ERK1/2, MYPT1 and MLC was assessed by Western blotting following constrictor studies in the presence or absence of PD98059 （10 μmol/L）. Results CIH-exposure resulted in more body weight gain and elevated blood pressure, which could be attenuated by pretreatment with PD98059. Endothelium-removed aortic rings from CIH rats exhibited higher constrictor sensitivity to Ang II （Emax： （138.56±5.78）% versus （98.45±5.31）% of KCI; pD2：7.98±0.14 versus 8.14±0.05, respectively）. CIH procedure exerted complex effects on ERK expressions （total ERK1/2 decreased whereas the ratio of phosphorylated to total ERK1/2 increased）. CIH aortas had higher MLCK mRNA and basal phosphorylation of MYPT1 and MLC. In parallel to greater increases in phosphorylation of ERK1/2, MYPT1 and MLC, Ang II-induced aortic constriction was significantly enhanced in CIH rats, which was largely reversed by PD98059. However vascular constriction of normoxia rats remained unchanged despite similar but smaller changing tendency of proteins phosphorylation. Conclusion These data suggest that CIH exposure results in aortic hyperresponsiveness to Ang II, presumably owing to more activated ERK1/2 signaling pathway.