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CD14 as a Novel Negative Modulator of Immune System‐Dependent Renal Damage and Salt‐Sensitive Hypertension

Hypertension affects one‐third of Americans of which approximately half are termed salt‐sensitive. Previous work in our laboratory has implicated a significant role for the immune system in potentiating the hypertensive and kidney damage phenotypes which occur in the Dahl Salt‐Sensitive (SS) rat. A previously performed RNA‐Seq based transcriptomic experiment on medullary tissue from SS rats fed either a low (0.4% NaCl) or high salt (4.0% NaCl) diet demonstrated an upregulation of molecules involved in the innate immune response including Cluster of Differentiation 14 (CD14). CD14 has been associated with hypertension in various human and animal studies, but mechanistic studies have not been previously performed. The present study tests the hypothesis that CD14 influences the extent of high‐salt diet induced renal damage and hypertension in the Dahl SS rat, by modulating activation of the innate immune system. Using CRISPR‐Cas9 technology, we generated a targeted mutation in the CD14 gene on the Dahl SS rat background, creating a 7‐bp frameshift deletion of bases 248–254 resulting in a predicted premature stop codon (SSCD14−/−). As CD14 is involved in macrophage activation, Interleukin‐1β production, a stereotypical pro‐inflammatory activation response by macrophages, was assessed. SSCD14−/− peritoneal macrophages demonstrated an increased ability to produce IL‐1β (307.8±31.3pg/ml) in response to Lipopolysaccharide + ATP stimulation compared to SSCD14+/+ littermates (142.9±31.5pg/ml, p=0.0099). We then assessed salt‐sensitive hypertension and renal damage phenotypes in these animals. SSCD14+/+ and SSCD14−/− female littermates, maintained on 0.4% NaCl chow, underwent a carotid artery telemetry implantation surgery at 7 weeks of age. After recovery and six days of baseline mean arterial pressure (MAP) recording (day 0: MAP SSCD14+/+=117.2±1.5mmhg, SSCD14−/−=132±11.0mmhg) animals were switched to a 4.0% NaCl diet for three weeks. Overnight urine collections occurred during the low salt period and throughout the high salt diet period. At 21 days, SSCD14−/− had a significantly greater MAP (172.0±11.4mmhg) than SSCD14+/+ animals (148.2±3.5mmhg), p<0.001. Urinary albumin excretion, though not different at baseline (SSCD14+/+=5.6±0.7, SSCD14−/−=21.9±10.5, p>0.05), was significantly greater in SSCD14−/− compared to SSCD14+/+ littermates at days 14 (SSCD14+/+=47.4±8.7, SSCD14−/−=139.8±51.7mg/day, p=0.011) and 21 (SSCD14+/+=79.8±15.9, SSCD14−/−=164.8±36.4mg/day, p=0.017) of the high salt diet. Together these data indicate that CD14 may modulate the full extent of the immune response in the macrophage during the induction and potentiation of salt‐sensitive hypertension and renal disease.