Infiltrating T lymphocytes in the kidney increase oxidative stress and participate in the development of hypertension and renal disease

Abstract

The present studies examined the role and mechanism of action of infiltrating T lymphocytes in the kidney during salt-sensitive hypertension. Infiltrating T lymphocytes in the Dahl salt-sensitive (SS) kidney significantly increased from 7.2 Ϯ 1.8 ϫ 10 5 cells/2 kidneys to 18.2 Ϯ 3.9 ϫ 10 5 cells/2 kidneys (n ϭ 6/group) when dietary NaCl was increased from 0.4 to 4.0%. Furthermore, the expression of immunoreactive p67 phox , gp91 phox , and p47 phox subunits of NADPH oxidase was increased in T cells isolated from the kidneys of rats fed 4.0% NaCl. The urinary excretion of thiobarbituric acid-reactive substances (TBARS; an index of oxidative stress) also increased from 367 Ϯ 49 to 688 Ϯ 92 nmol/day (n ϭ 8/group) when NaCl intake was increased in Dahl SS rats. Studies were then performed on rats treated with a daily injection of vehicle (5% dextrose) or tacrolimus (0.25 mg · kg Ϫ1 · day Ϫ1 ip), a calcineurin inhibitor that suppresses immune function, during the period of high-NaCl intake (n ϭ 5/group). In contrast to the immune cell infiltration, increased NADPH oxidase expression, and elevated urine TBARS excretion in vehicle-treated Dahl SS fed high salt, these parameters were unaltered as NaCl intake was increased in Dahl SS rats administered tacrolimus. Moreover, tacrolimus treatment blunted high-salt mean arterial blood pressure and albumin excretion rate (152 Ϯ 3 mmHg and 20 Ϯ 9 mg/day, respectively) compared with values in dextrose-treated Dahl SS rats (171 Ϯ 8 mmHg and 74 Ϯ 28 mg/day). These experiments indicate that blockade of infiltrating immune cells is associated with decreased oxidative stress, an attenuation of hypertension, and a reduction of renal damage in Dahl SS rats fed high salt. reactive oxygen species generation; chronic renal insufficiency OXIDATIVE STRESS, DEFINED as a persistent imbalance between the production of highly reactive molecular species (mainly oxygen and nitrogen) and antioxidant defenses, has been implicated in pathophysiological conditions that affect the cardiovascular system (12,28,35). Increased levels of oxidative stress have been described in experimental models of hypertension (2, 6, 20) and hypertensive patients (22,35).A number of studies in animal models of hypertension demonstrated elevations of blood pressure by stimulation of reactive oxygen species (ROS) generation (24,44,47). Moreover, treatment with a variety of antioxidants reduces blood pressure in several genetic and experimental models of hypertension (4,7,30,40,48). One of the most important biological mechanisms for the production of ROS results from the generation of superoxide (O 2 ·Ϫ ) from O 2 by the enzyme NADPH oxidase (14). Stimulation of NADPH oxidase appears to be the primary source of oxidants in systemic arterial vessels in renovascular hypertension (16), ANG II-induced hypertension (8, 34), DOCA-salt hypertension (42, 49), chronic renal insufficiency (47), and the spontaneously hypertensive rat (49). In humans, NADPH oxidase is the principal source of O 2 ·Ϫ in vascular smooth muscle cells (1...

Genetic mutation of recombination activating gene 1 in Dahl salt-sensitive rats attenuates hypertension and renal damage

“…The experimental methods for phenotyping (isolation of infiltrating mononuclear cells from the kidney, histology, immunohistochemistry, flow cytometry, Western blotting, and surgical preparation of the animals) were all performed using methods previously described (3,4,5,17).…”

“…Immune cells were isolated from the kidney, spleen, and blood using methods that we previously described (3,4,5). Rats were anesthetized with pentobarbital sodium (50 mg/kg ip); the kidneys were flushed with heparinized saline, minced with a razor blade, and incubated in a PBS solution containing collagenase.…”

“…Kidneys were obtained for histological and immunohistochemical analysis using methods previously described (3,4,5). Tissue was fixed in 10% formaldehyde, paraffin embedded (Microm HMP 300), cut in 3-m sections (Microm HM355S), mounted, and stained with Gomori's one-step trichrome.…”

“…Experiments in our laboratory have examined the influence of two mechanistically dissimilar immunosuppressive agents on the development of salt-induced hypertension and kidney damage in the Dahl salt-sensitive rat (3,4), a genetic model of hypertension and renal disease that exhibits many phenotypic characteristics in common with human hypertension (1,2,6,10,14). A major concern related to the studies that have used pharmacological agents to suppress the immune system, are the potential nonspecific effects of these agents.…”

The inextricable role of the kidney in hypertension

“…Similarly, preventing infiltration of immune cells into the kidney reduces oxidative stress and lowers blood pressure in rat models of salt-sensitive hypertension (82). Various cytokines prominent in inflammatory responses have direct effects on kidney function.…”