41,42 Nevertheless, a direct connection involving ANG II and Epac1 from the pathogenesis of diabetic nephropathy is unknown. The only details readily available within the literature relates for the transgenic mice over expressing inducible cAMP re pressor.These mice have sustained large lev els of glucose thanks to minimal synthesis of insulin through the pancreatic cells. Even though, accentuated glomerular changes had been noted in these mice following streptozoto cin administration, tubular hypertrophy was not ob served. 43 Other conceivable mechanisms which have been implicated in selleck chemicals the pathogenesis of tubular hypertrophy consist of perturbation inside the intracellular calcium and acti vation of TGF one. 44,45 Apart from ANG II, the activation of TGF one has been recognized to take place by PKC iota,46 reactive oxygen species,47 and thrombospondin.
48 Here, it can be worth mentioning here that Epac1 interactions with TGF one receptor are acknowledged, selleck but they are independent of cAMP binding domain of Epac1, and hence it is actually possible that Epac1 utilizes a unique pathway within the induction of tubular hypertrophy. 49 In line with these above observa tions, studies were performed to assess if high glucose ambience could directly exert its effect through the cAMP stimulated GEF, Epac1, and thereon modulate the down stream events leading to tubular hypertrophy. The higher glucose induced a hypertrophic response in HK 2 cells also, along with prominence of cytoskeletal organiza tion, boosting of de novo protein synthesis, as assessed by confocal microscopy, and improved 3H leucine incor poration and protein DNA ratio.The hypertro phic response was substantially blunted with all the trans fection of Epac1 siRNA or Epac1 mutants lacking cAMP binding and GEF domains.
Related blunting effects of Epac1 siRNA have been reported in adrenergic recep tor induced hypertrophy in cardiomyocytes,24 suggesting that Epac1 may possibly also play a role inside the tubular hypertrophy at the same time. To straight assess the hypertrophic effect of Epac1 the cells were both taken care of with cAMP analog, eight CPT two O Me cAMP or transfected with Epac1 cDNA. Even underneath minimal glucose ambience this yielded a substantial hypertrophic response. Interestingly, transfection of cells with full length Epac1 cDNA beneath higher glucose ambience led to a marked hypertrophic response that was insensitive to PKA inhibitor, H89, therefore confirming the role of cAMP responsive Epac1 in cellular hypertrophy at the very least below in vitro substantial glucose problems.Other mechanisms by which substantial glucose could induce cellular hypertrophy which have been re ported from the literature include the activation of a prohy pertrophic signaling pathway, which requires the Ca2 delicate phosphatase, calcineurin, its key down stream effector,22 and ANG II induced phosphorylation of cAMP responsive el ement binding protein.