RACK1 In The Regulation Of Liver Fibrosis And The Mechanism Of PQQ Intervention In The Development Of Liver Fibrosis

Part I Study on the role of RACKl in liver fibrosisLiver fibrosis is characterized by the excessive accumulation of ECM in the liver. Also, it represents the consequences of imbalance of ECM production and degradation. The activation of quiescent hepatic stellate cells (HSCs) into a myofibroblast-like phenotype is considered as the central event of liver fibrosis. The activation of HSCs always accompanied with the loss of Vitamin A droplet, the morphological alteration, the ECM production, a-SMA expression and contractility acquisition. It is reported that various cellular regulation and signal pathways have involved in the activation of apoptosis of HSCs. TGF-β1play important role in stimulating HSCs differentiate into myofibroblasts and product collagen I. It is secreted by HSCs or Kupffer cell in autocrine and paracrine manner. RACKl, the receptor for activated C-kinase1, is a classical scaffold protein implicated in numerous signaling pathways and cellular processes; however, the role of RACK1in liver fibrosis is little defined.In our study, we investigate the relation between liver fibrosis and RACKl. We report that RACK1is up-regulated in activated HSCs in transforming growth factor beta1(TGF-β1)-dndependent manner both in vitro and in vivo. And TGF-β1stimulates the expression of RACK1through NF-κB signaling. Moreover, the overexpression of RACK1promote the activation and migration of HSCs induced by TGF-β1, meanwhile, it promotes platelet-derived growth factor (PDGF)-mediated activation of pro-fibrogenic pathways as well as the proliferation and migration of HSOs. Depletion of RACK1suppresses the progression of TAA-induced liver fibrosis in vivo. In addition, the expression of RACKl in fibrogenic cells also positively correlates well with the stage of liver fibrosis in clinical cases.Our results suggest RACKl as a downstream target gene of TGF-β1involved in the modulation of liver fibrosis progression in vitro and in vivo, and propose a strategy to target RACK1for liver fibrosis treatment. Part II Study of the role of PQQ on liver fibroLiver fibrosis represents the consequences of a sustained wound healing response to various chronic liver injuries including viral, autoimmune, drug induced, cholestatic and metabolic diseases, and is characterized by the progressive replacement of functional hepatic tissue with highly cross-linked collagen-rich extracellular matrix. Activation of HSCs into myofibroblasts is considered to be the central event of liver fibrosis. In liver injury, activated kupffer cells release a large amount of cytokines, such as PDGF, TGF-β1and reactive oxygen species (ROS). In the normal liver, the antioxidant system including SOD, CAT, GSH-Px could get rid of the excessive ROS and maintain the homoiostasis. However, in the injury, the excessive ROS damage lipid, protein, DNA and induce cell apoptosis and necrosis, as well as deteriorate inflammation. On the other hand, ROS maintain continuous activation state and high proliferative state of HSCs. Therefore, ROS play a critical role in liver injury and liver fibrosis.Pyrroloquinoline-quinone (PQQ), was first identified in methylotrophic bacteria as a coenzyme for methanol dehydrogenase, also a large number of other enzymes have also been found to require PQQ as a cofactor. Additionally, PQQ is widely reported to have a strong superoxide scavenging activity, Oxidative stress may is involved in many aspects of liver fibrosis. Hence, we demonstrated whether PQQ may attenuate the progression of liver fibrosis by scavenging ROS. Our data support that in the mouse model of liver fibrosis induced by TAA and BDL, PQQ effectively suppress the level of serum enzyme and attenuate the antioxidant enzyme activity, such as GSH-Px, CAT, SOD and reduce the MDA level. Also it decrease the expression of a-SMA and Col I. Moreover, we demonstrated that PQQ reduce the activation of Kupffer cells and production of inflammatory cytokines. And it suggested that PQQ reduce ROS may partly due to the inhibition effect on expression of Nox2and Duoxl. Additionally, in primary HSCs, PQQ inhibit ROS level induced by TGF-β1and PDGF. Also, we found that PQQ inhibit the TGF-β1-induced HSCs activation through p38MAPK and Smad2/3pathway; meanwhile, the PDGF-induced HSCs proliferation was inhibited through AKT and ERK pathway.PQQ is water solubility, a safe natural element of the food and a nutrient for supporting the growth and protection of living cells under stress, which make it a potential application of PQQ in the prevention, therapy support or maybe treatment of liver fibrosis.