| Renal interstitial fibrosis ( RIF) , a common finding in patients with progressive chronic renal disease of all types, arises because of a complex interplay between factors in the tubular lumen, tubular epithelial cells, peritubular capillaries, resident and infiltrating interstitial cells and extracellular matrix. Several factors: macrophages, growth factors, hypoxia, cytokines are involved in the pathogenesis of interstitial fibrosis. All these changes result in excessive matrix deposition that leads to tissue destruction and impairment of renal function . It is evident that the process of renal fibrosis is a complicated one with several cellular and molecular mediators interacting in concert, however, the mechanisms of initiation and maintenance of renal fibrosis remain obscure. Studies concerning the complex signal transduction and their interplay may contribute to the illustration of the mechanism of RIF and the prevention of RIF progression.Great inportance has been attached to the contribution of Rho/Rock signaling to chronic inflammatory fibrosis of several organs, such as lung, heart and liver. Evidence accumulated that this signaling had protective effects on renal function, however, the mechanisms underlying are to be elucidated.During the progression of RIF, fibroblast and tubular epithelial cell undergo a phenotipic change into myofibroblast, the major source of ECM. Recently, it was reported that Rho/Rock signaling may play a key role in the transformation and maintainence of myofibroblast. So it was suggested the fibrogenic effect of Rho/Rock signaling may result from the induction of myofibroblast transformation.The aim of our invo and in vitro experiments was to illustrate the significance of Rho/Rock signaling in the pathogenesis of RIF, and toclarify the mechanism underlying.Part I: the contribution of Rho/Rock signaling in the development of Renal interstitial in UUO ratObjective To observe the expression law of Rock-I , a key effector of Rho, and its functional activation in renal tissue from UUO kidneys, and to elucidate the role of Rho/Rock signaling in the progression of renal interstitial fibrosis.Methods Expression of Rock-I mRNA and protein were measured by RT-PCR and Western blotting, respectively. The phosphorylation of MBS(binding subunit of myosin phosphatase)--a substrate of Rock-I wasdetected by Western blotting, as the mark of functional activation of the kinase. And the relationship between the activation of Rho/Rock signaling and the development of RIF was clarified as well.Results ( 1) The expression of Rockl mRNA was elevated before the onset of RIF(the 3rd day after the experiment) (F=47.73, P<0.01). The expression peak of Rock-I mRNA was prior to that of ct-SMA, and there was a positive correlation between them ( r= 0.61, P<0.01) . (2) The expression of Rock-I protein was significantly enhanced in the UUO group than in the Vehicle control (F=43.39, .P<0.01) , and its increase accompanied the the fibrostic index ( r=0.82, P<0.01 ) . ( 3 ) The phosphorylation of MBS was significantly upregulated in the UUO group ( F=33.32, P<0.01) , and it was positive correlated with the fibrostic index (r=0.63, P<0.05) .Conclusions (1 ) We found the enhanced expression and functional activation of Rock-I in renal tissue from UUO rats . Rho/Rock signaling may play an important role in the progression of RIF. ( 2) Rock-I may be an useful marker and a potential target for therapeutic intervention with a view to slowing, preventing, and in some senses even reversing theprogression of renal diseases.Part II: the contribution of Rho/Rock signaling in the transformation and maintainence of myofibroblastObjective To evaluate whether the activation of Rho/Rock signalingmodulates the expression of a characteristic marker of myofibroblast--a-SMA in a fibroblastic clone of normal rat kidney cells (NRK cell lines).Methods The rat kidney fibroblast cell line NRK was treated with a selective inhibitor of Rock, Y-27632. Immunofluorescence was applied to display the polyme... |
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