Role of the immune system during the development of acute and chronic renal disease

Abstract

The purpose of this thesis was to investigate the contribution of the inflammatory mediators Nuclear factor κB and complement during the progression of renal diseases. The first two results chapters in this thesis demonstrated a novel role for complement component 3 (C3) during the progression of chronic renal disease in the murine model of unilateral ureteric obstruction (UUO) C3 gene up-regulation and complement activation persisted throughout the course of UUO in wild type (WT) mice. In situ hybridisation showed that renal tubular epithelial cells were the primary site of C3 gene expression during early ureteric obstruction in the renal cortices of WT mice. Gene expression for transforming growth factor-beta (TGF-β) and collagen I in obstructed C3 deficient (C3-/-) mouse kidneys was significantly reduced compared with obstructed kidneys from WT mice. The decrease in TGF-β and collagen I also coincided with a significant reduction in mRNA expression for alpha-smooth muscle actin (α-SMA) as well as a significant decrease in interstitial collagen deposition. In addition to these observations, the number of infiltrating CD8+ T cells and F4/80+ macrophages counted within the cortical tubulointerstitial compartment, was significantly higher in C3-/- mice. Gene expression for the membrane-bound complement regulatory proteins complement receptor-related protein-y (crry), CD59a and decay accelerating factor 1 (DAF1) decreased in WT and C3-/- mice during the course of UUO. In particular, crry, CD59a and DAF1 mRNA expression was found to be much lower in C3-/- mice. A transition from membrane to cytoplasmic expression of crry protein was also demonstrated in tubular epithelial cells of obstructed WT mouse kidneys. In contrast to this, factor H gene expression was markedly elevated in WT mice, but not in C3-/- mice. 13 In vitro stimulation of mouse proximal tubular cells using lipopolysaccharide (LPS) resulted in complement activation, C3 gene up-regulation and production of C3 protein, providing an in vitro model to use for future targeting of proximal tubular epithelial cell C3 gene expression. The final results chapter of this thesis demonstrated an important role for nuclear factor kappa-B (NF-κB) subunit nfκb1 during the progression of renal inflammation in the nephrotoxic serum nephritis model of acute renal injury. nfκb1 deficient mice developed significantly worse glomerular injury and proteinuria and displayed sustained up-regulation of interleukin-6 and S100 calcium binding proteins A8 and A9. Finally, in contrast to observations in the nephrotoxic serum model, fibrosis, immune cell infiltration and cytokine mRNA expression were all unchanged in nfκb1 deficient mice compared with WT mice after ten days of ureteric obstruction.