Quantitative expression of RIG-like helicase, NOD-like receptor and inflammasome-related mRNAs in humans and mice.

The cell-type-, organ- and species-specific expression of the surface and endosomally located Toll-like receptors are well described but little is known about the respective expression profiles of cytosolic pattern recognition molecules. We therefore determined the mRNA expression levels of 15 cytosolic pattern recognition molecules in 11 solid organs of human and mice. Human organs revealed lower mRNA levels of most molecules as in spleen but at least 2-fold higher were inflammasome-related NOD, leucine-rich repeat and pyrin domain-containing protein 1-3 (NLRP1-3) and -12 in brain, LGP2, retinoic acid-inducible gene I (RIG-I) and NLRP10 in liver, NLRP10 in small intestine, LGP2, RIG-I, NAIP, NLRP2 and -3 in testis and RIG-I, NLRP2 and -10 in muscle. In mice, most organs also expressed lower mRNA levels compared with spleen. Only NLRP6 in liver, NAIP and NLRP6 in small intestine, LGP2, nucleotide-binding oligomerization domain 1 (NOD1), NLRP1, -2, -6, -10 and -12 in colon and MDA5, RIG-I, NLRC4, NOD1, -2, NLRP1, -2, -6, -10 and -12 mRNA levels in kidney were higher. Resting human and mouse monocytes and T cells expressed most molecules and produced IL-1 beta and CCL5/RANTES upon activation. However, murine monocytes strongly up-regulated, whereas human monocytes down-regulated receptor expression upon activation. These data suggest that the cell-type-, organ- and species-specific expression and regulation need to be considered in the design and interpretation of related studies.

Resident dendritic cells prevent postischemic acute renal failure by help of single Ig IL-1 receptor-related protein.

Ischemia-reperfusion (IR) triggers tissue injury by activating innate immunity, for example, via TLR2 and TLR4. Surprisingly, TLR signaling in intrinsic renal cells predominates in comparison to intrarenal myeloid cells in the postischemic kidney. We hypothesized that immune cell activation is specifically suppressed in the postischemic kidney, for example, by single Ig IL-1-related receptor (SIGIRR). SIGIRR deficiency aggravated postischemic acute renal failure in association with increased renal CXCL2/MIP2, CCL2/MCP-1, and IL-6 mRNA expression 24 h after IR. Consistent with this finding interstitial neutrophil and macrophage counts were increased and tubular cell necrosis was aggravated in Sigirr-deficient vs wild-type IR kidneys. In vivo microscopy revealed increased leukocyte transmigration in the postischemic microvasculature of Sigirr-deficient mice. IL-6 and CXCL2/MIP2 release was much higher in Sigirr-deficient renal myeloid cells but not in Sigirr-deficient tubular epithelial cells after transient hypoxic culture conditions. Renal IR studies with chimeric mice confirmed this finding, as lack of SIGIRR in myeloid cells largely reproduced the phenotype of renal IR injury seen in Sigirr(-/-) mice. Additionally, clodronate depletion of dendritic cells prevented the aggravated renal failure in Sigirr(-/-) mice. Thus, loss of function mutations in the SIGIRR gene predispose to acute renal failure because SIGIRR prevents overshooting tissue injury by suppressing the postischemic activation of intrarenal myeloid cells.

Ccl2/Mcp-1 blockade reduces glomerular and interstitial macrophages but does not ameliorate renal pathology in collagen4A3-deficient mice with autosomal recessive Alport nephropathy.

Lack of the alpha3 or alpha4 chain of type IV collagen (COL4) causes autosomal recessive Alport nephropathy in humans and mice that is characterized by progressive glomerulosclerosis and tubulointerstitial disease. Renal pathology is associated with chemokine-mediated macrophage infiltrates but their contribution to the progression of Alport nephropathy is unclear. We found Ccl2 to be expressed in increasing amounts during the progression of nephropathy in Col4a3-deficient mice; hence, we blocked Ccl2 with anti-Ccl2 Spiegelmers, biostable L-enantiomeric RNA aptamers suitable for in vivo applications. Ccl2 blockade reduced the recruitment of ex vivo-labelled macrophages into kidneys of Col4a3-deficient mice. We therefore hypothesized that a prolonged course of Ccl2 blockade would reduce renal macrophage counts and prevent renal pathology in Col4a3-deficient mice. Groups of Col4a3-deficient mice received subcutaneous injections of either an anti-mCcl2 Spiegelmer or non-functional control Spiegelmer on alternate days, starting from day 21 or 42 of age. Glomerular and interstitial macrophage counts were found to be reduced with Ccl2 blockade by 50% and 30%, respectively. However, this was not associated with an improvement of glomerular pathology, interstitial pathology, or of overall survival of Col4a3-deficient mice. We conclude that Ccl2 mediates the recruitment of glomerular and interstitial macrophages but this mechanism does not contribute to the progression of Alport nephropathy in Col4a3-deficient mice.