Corticosteroids Augment Cyclosporine Nephrotoxicity in Pediatric Nephrotic Syndrome: Potential Role of CD163+ M2-type Macrophage

Background: Cyclosporin A (CsA) is an effective steroid-sparing agent for patients with steroid-dependent nephrotic syndrome (SDNS), however, it can cause chronic interstitial damage. We previously reported that alternativley-activated (M2) macrophages (MQ) are intimately involved in interstitial fibrosis pathogenesis in chronic progressive kidney disease. In this study, we investigated the possible involvement of M2 MQ in CsA nephrotoxicity in SDNS. Methods: A total of 33 children diagnosed with SDNS who were treated with CsA for more than 2 years were investigated. Thirteen biopsy specimens from age-matched SDNS children who had not received CsA treatment were used as the control. Renal fibrosis was assessed by Masson chrome staining of biopsy sections. Sections were also stained for α-smooth muscle actin (α-SMA), type I collagen, CD68 (total MQ) and CD163 (M2 marker). Urine levels of CCL2 were measured by ELISA. Cultured human monocyte-derived MQ were stimulated with dexamethasone (Dex) for 48hr and RNA levels compared to control cells. Results: The CsA-treated group showed a significant increase in interstitial fibrosis (10.8 vs 6.7%, P<0.001) with accumulation of interstitial CD163+CD68+ MQ (10.8 vs 7.9/HPF, P<0.001) compared with SDNS control patients. There was a significant correlation between the degree of interstitial fibrosis and the number of interstitial CD163+ cells (p<0.001), and between interstitial fibrosis and the dose of steroid used during CsA treatment (p<0.001), while no correlation was found between the dose of steroid used before CsA treatment and histological changes. Stimulation of MQ with Dex induced up-regulation of CD163 and cytokines and growth factors associated with inflammation and fibrosis (CCL2, NOS1, NOS2, FGF-8, FGF-21 and CTGF). Immunostaining revealed significant expression of CTGF and CCL2 in biopsies from CsA group which co-localized with CD163+MQ. In addition, the urine CCL2/creatinine ratio was increased 4-fold in CsA group vs control group (940.0 vs 204.1, P=0.012) Conclusion: Our findings suggest that CD163+ M2-type MQ may participate in the development of interstitial fibrosis induced by CsA. Steroid treatment during CsA treatment might contribute to augment CsA nephrotoxicity through the production of pro-fibrotic and pro-inflammatory factors. Funding: Government Support – Non-U.S.