Reflecting the pro inflammatory functions of nephritis, genes such as JAK3, STAT3 and MAPK1 involved in signalling path ways are expressed at higher levels in the disease state. Also SOCS3, a negative regulator of JAKs and PTPN1 and CDKN1A, a negative regulator of STATs, are also elevated in the disease state. Although activation of these signalling path ways occurs through phosphorylation dephosphorylation events of pathway components, it can be noted here that this pathway is also dysregulated at the transcriptional level in lupus nephritis. This complex dysregulation of the JAKSTAT pathway, which drives production of multiple cytokines and other inflammatory mediators, is returned to asymptomatic lev els on sirolimus treatment.
PTPN1, a negative regulator of STATs, is a notable exception, selleckchem suggesting a link between the quiescence of this pathway with amelioration of disease. Con sistent with the activation of this signalling pathway, genes involved in immune system cascades, such the IFN regulated genes, and sig nalling by IL2 subfamily of type 1 cytokines were also up regulated in the disease state and are down regulated by sirolimus. Genes of the complement pathway known to be involved in renal damage, such as C3, C4, C1QA, CCL13 and FCGR2a, are also expressed at higher levels than in the untreated group. C3, C4 and C1QA play a role in antigen clearance. Using sig Pathway, an algorithm that identifies differentially expressed gene sets, additional components of the complement pathway are transcriptionally elevated in the dis eased renal tissue.
Our results suggest that the complement components in the early parts PI3K delta inhibitor of both the classical and alter nate pathways are elevated in nephritis, while one component of the membrane attack complex, further downstream in the complement pathway, is down regulated. C1q and C3, but not C4, were normalised by treatment. Complement pathway components are known to be significant contributors to renal damage. C3 deposition in the kidney has been observed in both human lupus nephritis and in murine models. The elevated levels of C4 during disease amelioration is consistent with the concept that the early members of the classical path way may be important in reducing disease pathology by clear ing immune complexes and apoptotic cells.
Our profiling analysis also identified a large number of immu noglobulin transcripts elevated in the kidney tissue consistent with the role of autoantibodies and immune complex deposi tion in pathology. To understand the mechanism by which sirolimus normalised such a wide range of biological processes, networks were built around the nephritis genes and the rapalog mTOR path way. Using curated findings from the literature, the shortest path for about one sixth of the 387 nephritis genes was defined to be either 0 or one step downstream of the rapalog mTOR pathway.