p38 MAPK inhibitors suppress biomarkers of hypertension end-organ damage, osteopontin and plasminogen activator inhibitor-1

Abstract

The assessment of target organ damage is important in defining the optimal treatment of hypertension and blood pressure-related cardiovascular disease. The aims of the present study were (1) to investigate candidate biomarkers of target organ damage, osteopontin (OPN) and plasminogen activator inhibitor-1 (PAI-1), in models of malignant hypertension with well characterized end-organ pathology; and (2) to evaluate the effects of chronic treatment with a p38 MAPK inhibitor. Gene expression, plasma concentrations, and renal immunohistochemical localization of OPN and PAI-1 were measured in stroke-prone spontaneously hypertensive rats on a salt–fat diet (SFD SHR-SP) and in spontaneously hypertensive rats receiving N^ω-nitro-L-arginine methyl ester (L-NAME SHR). Plasma concentrations of OPN and PAI-1 increased significantly in SFD SHR-SP and L-NAME SHR as compared with controls, (2.5–4.5-fold for OPN and 2.0–9.0-fold for PAI-1). The plasma levels of OPN and PAI-1 were significantly correlated with the urinary excretion of albumin (p<0.0001). Elevations in urinary albumin, plasma OPN and PAI-1 were abolished by chronic treatment (4–8 weeks) with a specific p38 MAPK inhibitor, SB-239063AN. OPN immunoreactivity was localized predominantly in the apical portion of tubule epithelium, while PAI-1 immunoreactivity was robust in glomeruli, tubules and renal artery endothelium. Treatment with the p38 MAPK inhibitor significantly reduced OPN and PAI-1 protein expression in target organs. Kidney gene expression was increased for OPN (4.9- and 7.9-fold) and PAI-1 (2.8- and 11.5-fold) in SFD SHR-SP and L-NAME SHR, respectively. In-silico pathway analysis revealed that activation of p38 MAPK was linked to OPN and PAI-1 via SP1, c-fos and c-jun; suggesting that these pathways may play an important role in p38 MAPK-dependent hypertensive renal dysfunction. The results suggest that enhanced OPN and PAI-1 expression reflects end-organ damage in hypertension and that suppression correlates with end-organ protection regardless of overt antihypertensive action.

Keywords: :

• Osteopontin
• plasminogen activator inhibitor-1
• hypertension
• biomarkers

Acknowledgements

The authors would like to thank Thomas Covatta for the photomicrographs.