CONTROL OF HYALURONAN (HA) GENERATION IN RENAL PROXIMAL TUBULAR EPITHELIAL CELLS

ABSTRACT Progression of renal disease is correlated to the degree of renal interstitial fibrosis. Proximal tubular cells (PTC) contribute to these pathological changes by the generation of cytokines and alterations in the composition of the extracellular matrix. Hyaluroanan (HA) is a ubiquitous connective tissue polysaccharide which regulates cell function and may therefore contribute to, and regulate, tissue remodelling. In the context of diabetic nephropathy, increased renal hyaluronan production, has been implicated in the glomerular hypercellularity in the streptozotocin model of diabetes. Recent studies have also implicated macrophage infiltration in the pathogenesis of diabetic nephropathy. In the current study we investigated PTC production of HA in response to alterations in glucose concentration and the macrophage derived cytokine IL-1β. The results demonstrate a time dependent increase in HA concentration in the culture supernatant in response to both 25mM D-glucose and IL-1β. Hyaluronan synthases (HAS) mRNA expression was examined by RT-PCR. HAS2 mRNA induction was seen following either 25mM D-glucose or IL-1β stimulation. HAS3 mRNA was constitutively expressed by PTC and was not influenced by the addition of either 25mM D-glucose or IL-1β. In contrast HAS1 mRNA expression was not detected in either unstimulated or stimulated cells. Stimulation of HA generation by either IL-1 or 25 mM D-glucose, was abrogated by inhibition of I-kappa B kinase (IKKβ) using Sulindac, and by the use of the proteosome inhibitor PSI, thus implicating activation of NF-κB in transcriptional activation of HAS2.