Increase in Interleukin‐16, a Pro‐inflammatory Cytokine, and Other Distinct Markers of Lymphocytic Activation, in Kidney Tissue of Cats with Renal Dysfunction

Abstract

Inflammation plays an important role in the initiation and subsequent progression of chronic kidney disease. An increase in inflammatory markers including cytokines as well as markers of oxidative stress is associated with reduced kidney function. Inflammatory markers and the underlying mechanisms that contribute to the pathophysiology of kidney disease are not clear and likely are multifactorial. Another feature associated with renal dysfunction and inflammatory response is the formation of calcium oxalate stones formed from the crystal deposits in the tubular epithelial cells. The aim of the present study was to investigate changes in gene expression in the renal cortex obtained from cats with kidney disease or calcium oxalate stone formers (CaOx) at necropsy in order to identify novel inflammatory biomarkers associated with renal dysfunction. At the time of death the circulating levels of creatinine as well as symmetric dimethyl arginine (SDMA), both markers of kidney decline in cats, were significantly higher in cats with renal disease (n=11) or stone‐forming cats (CaOx, n=12) when compared to controls (n=19). Using RNAseq in kidney tissue, we found a significant increase in the expression of IL‐16, a T‐cell chemoattractant, in both cats with kidney disease (6.72 fold) and stone formers (7.03 fold) compared to controls (both p<0.0001). There was also a significant increase in caspase recruitment domain family member 11 (CARD11), an activator of T and B‐lymphocytes and NFkB, in cats with kidney disease (9.2 fold) and stone formers (10 fold) compared to controls (p<0001). However, some differences between the kidney disease and CaOx groups were also observed. In cats with kidney disease there was an increased expression of LY9 (CD299), found in T and B‐cells and thymocytes, IL2Rg, a marker of lymphocyte activation, and SPP1 (Osteopontin), expressed in activated T and B‐cells (all >6‐fold) when compared to controls (p<0.0001) but such increased expression was not seen in CaOx cats. In summary, while IL‐16 was increased in both groups, our results indicate important molecular differences in the pathogenesis of kidney dysfunction in cats with kidney disease and stone formers, and that distinct lymphocyte markers may be involved in the persistent decline of kidney function. Our studies suggest that the optimal nutritional therapy to slow the progression of kidney dysfunction may be different for cats with kidney disease or stone formers. Support or Funding Information This study was funded by Hill’s Pet Nutrition, Inc