Project Summary
The podocyte has become a crucial focus of research and clinical efforts as a target for kidney disease
interventions due to its vital role in regulating glomerular permeability and maintaining glomerular structure.
Podocyte injury is pathogenetically and prognostically important in diabetic kidney disease (DKD). One of the
main factors determining pathological changes in glomerular morphology and permeability is the elevation of
basal intracellular calcium ([Ca2+]i) levels in podocytes, which can occur due to activation of various signaling
cascades. Protease-activated receptors (PARs) are emerging as proteins of interest for their potential to
modulate podocyte [Ca2+]i levels, especially under pathological conditions, such as DKD. Clinical studies have
demonstrated that circulating concentrations of PAR-activating proteases are associated with DKD.
Furthermore, the recent prospective OPTIMUS-5 study revealed several beneficial effects of the FDA-approved
PAR1 antagonist Vorapaxar in type 2 diabetes mellitus. However, despite crucial evidence for the importance of
PAR signaling pathways in podocytes in DKD, this area is still understudied. Our preliminary data demonstrate
the functional presence of a PAR-GPCR-TRPC6 signaling pathway in rat and human podocytes that is increased
under diabetic conditions. Consistent with these findings, we found that serine proteases promote activation of
PAR1-TRPC6 cascade in podocytes from freshly isolated rat glomeruli, which triggers a rapid elevation of [Ca2+]i.
Furthermore, our pilot studies have revealed that these signaling pathways are highly upregulated in a rat model
of type 2 Diabetic Nephropathy (T2DN rats), similar to clinical observations in human patients. The central
hypothesis of this proposal is that during the development of DKD in type 2 diabetes, when urinary thrombin and
urokinase concentrations increase rapidly, overstimulation of PAR1 promotes excessive [Ca2+]i levels in
podocytes through activation of TRPC6 channels, ultimately leading to cell apoptosis, development of
albuminuria and glomerular damage. Thus, inhibition of PAR1 activity will mitigate podocyte damage and may
be of therapeutic benefit in DKD. Several innovative approaches and unique rat models will be utilized to test
the following Specific Aims: Aim 1 will test the hypothesis that PAR1 expression and its activity increase during
the progression of DKD in type 2 diabetes and that this pathway contributes to the alterations in Ca2+ homeostasis
in podocytes and glomerular damage; and Aim 2 will provide mechanistic insight into the activation of PAR-1
mediated signaling in podocytes and associated glomerular structure and function changes. In addition, the
correlation of PAR signaling in podocytes and sex difference in the development of DKD in T2DN rats will be
explored.