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Thick Ascending Limb‐derived TNF production regulates the blood pressure response to high NaCl intake
Author(s) -
Ferreri Nicholas R,
Hao Shoujin
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.855.7
Subject(s) - tumor necrosis factor alpha , endocrinology , medicine , kidney , chemistry , blood pressure , messenger rna , urine , cytokine , endogeny , urinary system , biochemistry , gene
We previously showed that the thick ascending limb (TAL) produces tumor necrosis factor‐alpha (TNF) in response to diverse stimuli and acts as an endogenous inhibitor of NKCC2 expression and activity. In this study we determined the effect of TNF derived from the TAL on the renal adaptation to high NaCl (HS) intake. TNF levels were higher in urine (40±4 vs 18±5 pg/24 h) of mice that ingested 1% NaCl in the drinking water for three days compared with tap water. The increase in urinary TNF levels was associated with a 4‐four fold increase (p<0.05) in TNF mRNA abundance in mTAL tubules isolated from mice given HS. In contrast, plasma levels of TNF remained unchanged in these mice (HS: 20±3 vs tap water: 18±3pg/ml). The increase in renal TNF mRNA levels induced by HS intake decreased by more than 80% (p<0.05) in mice given an intrarenal injection of a lentivirus construct that silences TNF in the kidney. Neither injection of a control lentivirus (U6) nor EGFP‐TNF‐ex4 altered baseline blood pressure in mice ingesting a normal salt diet and tap water. However, renal‐specific silencing of TNF rapidly increased blood pressure in mice drinking 1% NaCl (U6: 110±4 vs shTNF: 136±6mmHg; p<0.05), an effect that was sustained for 11 days. Baseline blood pressure was rapidly restored when mice were switched to tap water (days 12–16), and rapidly increased when they were switched back to HS (days 17–21). Renal outer medullary NKCC2A mRNA accumulation increased approximately 3‐fold (p<0.05) after injection of EGFP‐TNF‐ex4 followed by ingestion of HS for 3 days compared with U6 control groups. The Cre/loxP recombination system was then used to generate TAL‐specific TNF knockout mice (TAL‐TNF KO). Specific recombination in the TAL was validated by PCR of microdissected nephron segments. The recombined allele product (0.45kb) was present in TAL tubules but not PT, IMCD, or spleen. Baseline blood pressure was similar in TNF‐TAL KO mice and littermate controls but increased when TNF‐TAL KO mice were given HS for three days. Food, water intake, and body weight were not different between groups in either model of TNF deletion and the increases in blood pressure were not associated with damage to glomeruli, blood vessels, or tubules. The increase in renal TNF levels in response to HS intake without a concomitant increase in blood pressure or an inflammatory component, and the increase in blood pressure in response to HS when TNF is silenced in the TAL suggests deficiency of TAL‐derived TNF is sufficient to render normotensive healthy mice salt‐sensitive.