Background: Macrophages play diverse roles in tissue injury. We evaluated their role in cyclosporine (CsA)-induced renal injury by depletion with liposomal clodronate (CL).
Methods: Male Sprague Dawley rats were treated with CsA with or without CL treatment for 28 days. We assessed responses from the pathology and by measuring renal functions and levels of a proinflammatory cytokine (osteopontin), a profibrotic cytokine (betaig-h3), innate immune response markers (toll-like receptor 2 and MHC class II molecules), apoptotic cell death (deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labelling staining and caspase-3 expression) and oxidative stress (8-hydroxy-2'-deoxyguanosine, 8-OHdG).
Results: Macrophage depletion with CL improved not only renal function but also histopathology compared with the CsA-treated rats. Osteopontin and betaig-h3 levels increased significantly in CsA-treated rat kidneys, but CL treatment decreased both markers. Enhanced innate immune response and apoptotic cell death in CsA-treated rat kidney were decreased with CL. The increased rates of urinary 8-OHdG excretion and the tubular expression of 8-OHdG produced by CsA treatment were reversed with CL treatment.
Conclusions: Thus, infiltrating macrophages were involved in both nonimmunologic and immunologic injury and led to apoptotic cell death in this rat model of chronic CsA nephropathy.