Macrophages mediate adverse effects of cholesterol feeding in experimental nephrosis

Inflammatory Stress Exacerbated Mesangial Foam Cell Formation and Renal Injury via Disrupting Cellular Cholesterol Homeostasis

Inflammation and lipids play significant roles in the progression of chronic kidney disease. This study was designed to investigate whether inflammation disrupts cellular cholesterol homeostasis and causes the lipid nephrotoxicity in vitro and in vivo, and explored its underlying mechanisms. Inflammatory stress was induced by cytokines (interleukin-1β (IL-1β); tumor necrosis factor α (TNF-α)) to human mesangial cells (HMCs) in vitro and by subcutaneous casein injection in C57BL/6J mice in vivo. The data showed that inflammatory stress exacerbated renal cholesterol ester accumulation in vitro and in vivo. Inflammation increased cellular cholesterol uptake and synthesis via upregulating the expression of low-density lipoprotein receptor (LDLr) and 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCoA-R), while it decreased cholesterol efflux via downregulating the expression of liver X receptor alpha and ATP-binding cassette transporter A1. The increased lipid accumulation by inflammatory stress induced reactive oxygen species (ROS) and increased levels of endoplasmic reticulum (ER) stress markers (inositol-requiring protein 1 and activating transcription factor 6) in HMCs and kidneys of C57BL/6J mice. This study implied that inflammation promoted renal lipid accumulation and foam cell formation by disrupting cellular cholesterol homeostasis. Increased intracellular lipids under inflammatory stress caused oxidative stress and ER stress in vitro and in vivo which may contribute to renal injury and progression of chronic kidney disease.

Tubular cell and HIV-1 gp120 interaction products promote migration of monocytes

Renal interstitial accumulation of monocytes is an important feature of HIV-associated nephropathy. We studied the effects of proximal tubular cell products (TCP) and proximal tubular cell-gp120 interaction products (TC-120IP) on the migration of monocytes across a modified Boyden chamber. TC-120IP promoted (P < 0.001) the migration of monocytes when compared with TCP (TCP, 45.0 +/- 5.9 vs. TC-120IP, 192.3 +/- 39.5 migrated monocytes/field). This effect of TC-120IP on monocyte migration was dose dependent. Anti-MCP-1 (TCP, 24.7 +/- 2.6; TC-120IP, 82.3 +/- 5.5; TC120-IP + anti-MCP-1 antibody, 46.5 +/- 3.5 migrated monocytes/field) as well as anti-TGF-beta antibodies (TCP, 25.8 +/- 3.4; TC120-IP, 80.3 +/- 6.9; TC-120IP + anti-TGF-beta antibody, 43.8 +/- 5.6 migrated monocytes/field) partly attenuated TC-120IP-induced migration of monocytes across a filter. Moreover, anti-MCP-1 and anti-TGF antibodies showed an additive inhibitory effect on TC-120IP-induced migration of monocytes across a filter. These results suggest that TC-120IP-induced migration of monocytes may be mediated through the generation of MCP-1 and TGF-beta by tubular cells. The present study provides the basis for a hypothesis that HIV-1 gp120 protein may be contributing to the infiltration of monocytes in the renal interstitium of patients with HIV-associated nephropathy.