However, preconditioning with tacrolimus has a clear anti-apoptotic effect, as it has been shown that tacrolimus diminishes the levels of Fas, Fas-ligand and caspases 1 and 3, which occur with I/R injury [16]. The decrease in apoptosis observed in immunosuppressive treatment groups
could be explained partially by the decreased in-situ expression of TNF-α, a known inflammatory mediator related to extrinsic pathway of apoptosis inducing apoptosis in renal epithelial cells [45,46]. Similarly, the observed decrease in C3 systemic and local levels could be another reason to explain why preconditioning improves clinical outcomes, as a relationship between apoptosis and complement SB431542 concentration generation in I/R injury is well established [47,48]. In a warm ischaemia model, Thurman et al. have shown even higher systemic levels of C3 than in our results, although the measurement was taken in a different time-frame (8 h
post-I/R injury) [49]. An up-regulated in-situ expression of C3 and caspase 3 can be seen as soon as 2 h following I/R injury [50]. In our work, with a 3-h cold ischaemia model, the reduction in plasmatic levels of C3 in immunosuppressive treatment groups could be related to lower expression of C3 observed in situ. Once again, the combined treatment BKM120 price with rapamycin and tacrolimus presented the lowest levels of plasma C3 and local C3 expression. One of the most important approaches to administer immunosuppressive drugs to the donor begins with the study carried out by Farrar et al., showing that C3-deficient kidneys are protected from ischaemic damage after post-transplantation into syngeneic recipient mice with normal serum complement activity; i.e. kidney-derived C3, not serum C3, drives the expression of I/R injury [6]. C3 is synthesized by tubular,
mesangial and endothelial cells and contributes to the inflammatory process in kidney transplantation and is up-regulated rapidly after I/R [51]. VAV2 Complement damaging effects depend mainly on the cleavage of C3, which is the central component on which all activation pathways converge. This activation may occur via the mannose-binding lectin pathway as well as through the alternative pathway in kidney transplant [52]. C3 cleavage is an essential part of the process ending in the membrane attack complex synthesis which, in turn, could lead to TNF-α and IL-6 production promoting injury [53]. The mechanism by which both drugs attenuate local and systemic C3 expression is still unknown and needs to be explained. In our exploratory study, the combination of a calcineurin inhibitor and inhibitors of mTOR diminishes the in-situ generation of proinflammatory mediators; in addition, this combination up-regulates cytoprotective genes.