Infiltrating immune cells in the kidney in salt-sensitive hypertension and renal injury

Abstract

The importance of the immune system in hypertension, vascular disease, and renal disease has been appreciated for over 50 years. Recent experimental advances have led to a greater appreciation of the mechanisms whereby inflammation and immunity participate in cardiovascular disease. In addition to the experimental data, multiple studies in patients have demonstrated a strong correlation between the observations made in animals and humans. Of great interest is the development of salt-sensitive hypertension in humans with the concurrent increase in albumin excretion rate. Experiments in our laboratory have demonstrated that feeding a high-NaCl diet to Dahl salt-sensitive (SS) rats results in a significant infiltration of T lymphocytes into the kidney that is accompanied by the development of hypertension and renal disease. The development of disease in the Dahl SS closely resembles observations made in patients; studies were therefore performed to investigate the pathological role of infiltrating immune cells in the kidney in hypertension and renal disease. Pharmacological and genetic studies indicate that immune cell infiltration into the kidney amplifies the disease process. Further experiments demonstrated that infiltrating T cells may accentuate the Dahl SS phenotype by increasing intrarenal ANG II and oxidative stress. From these and other data, we hypothesize that infiltrating immune cells, which surround the blood vessels and tubules, can serve as a local source of bioactive molecules which mediate vascular constriction, increase tubular sodium reabsorption, and mediate the retention of sodium and water to amplify sodium-sensitive hypertension. Multiple experiments remain to be performed to refine and clarify this hypothesis.

Keywords: hypertension; infiltrating immune cells.

Fig. 1.

Mean arterial blood pressure (MAP; A), renal cortical fibrosis (B), glomerulosclerosis (C), and infiltrating macrophages in the kidneys (D) of normotensive (n = 34) and hypertensive (n = 46) African-Americans. *P < 0.05 vs. normotensive group. Data are presented as the median with the 25th and 75th percentile. Redrawn with permission from Hughson et al. (29).

Fig. 2.

Development of hypertension (A) and albuminuria (B) in Dahl salt-sensitive (SS) rats when switched from a 0.4 to a 4.0% NaCl diet. Representative histological images of trichrome-stained sections of the renal cortex (C) and outer medulla (D) obtained from Dahl SS after 3 wk of 4.0% NaCl diet. Immunohistochemical images of CD3-positive T lymphocytes in the renal interstitial spaces in the renal cortex (E) and outer medulla (F) of Dahl SS rats fed the 4.0% NaCl diet for 3 wk. Data replotted with permission from De Miguel et al. (13).

Fig. 3.

Representative flow cytometric demonstration of T-lymphocytes (CD-3) and B-lymphocytes (CD-45R) in the blood of Dahl SS (A) and Rag1 mutant rats (B). Development of hypertension (C) and albuminuria (D) in Dahl SS and Rag1 mutant rats when switched from a 0.4 to a 4.0% NaCl diet. Representative histological images of trichrome-stained kidneys (1× original magnification) obtained from Dahl SS (E) and Rag1 mutant rats (F) after 3 wk of 4.0% NaCl diet. Data replotted with permission from Mattson et al. (49).

Fig. 4.

Block diagram depicting proposed mechanism whereby infiltrating immune cells amplify sodium-sensitive hypertension and renal damage.