Citations

Abstract Chronic nasal and skin colonization with superantigen (SAg)-producing Staphylococcus aureus is well documented in humans. Given that trans-mucosal and trans-cutaneous absorption of SAgs can occur, we determined whether chronic exposure to small amounts of SAg per se could activate autoreactive CD4+ and CD8+ T cells and precipitate any autoimmune disease without further external autoantigenic stimulation. Because HLA class II molecules present SAg more efficiently than do mouse MHC class II molecules, HLA-DQ8 transgenic mice were implanted s.c. with mini-osmotic pumps capable of continuously delivering the SAg, staphylococcal enterotoxin B (total of 10 μg/mouse), or PBS over 4 wk. Chronic exposure to staphylococcal enterotoxin B resulted in a multisystem autoimmune inflammatory disease with features similar to systemic lupus erythematosus. The disease was characterized by mononuclear cell infiltration of lungs, liver, and kidneys, accompanied by the production of anti-nuclear Abs and deposition of immune complexes in the renal glomeruli. The inflammatory infiltrates in various organs predominantly consisted of CD4+ T cells bearing TCR Vβ8. The extent of immunopathology was markedly reduced in mice lacking CD4+ T cells and CD28, indicating that the disease is CD4+ T cell mediated and CD28 dependent. The absence of disease in STAT4-deficient, as well as IFN-γ–deficient, HLA-DQ8 mice suggested the pathogenic role of Th1-type cytokines, IL-12 and IFN-γ. In conclusion, our study suggests that chronic exposure to extremely small amounts of bacterial SAg could be an etiological factor for systemic lupus erythematosus.

Background — The role of load versus angiotensin II (Ang II) and endothelin-1 (ET) in the pathogenesis of hypertensive heart disease is controversial. We sought to determine whether alterations in cardiac structure and function due to hypertension (HTN) were dependent on Ang II or ET activation. Methods and Results — Bilateral renal wrapping to produce HTN (n=12) or sham surgery (n=6) was performed in adult dogs. Weekly blood pressure, plasma renin activity, Ang II, ET, and catecholamines were measured. Systolic (end-systolic elastance, Ees) and diastolic (τ) function were assessed in sham and HTN dogs at 5 (HTN-5wk) or 12 (HTN-12wk) weeks. Ang II and ET were assayed in the left ventricle (LV) and kidney. Mean arterial pressure was higher in renal wrap dogs at week 1 (* P <0.05 versus controls: 139±4* versus 123±4 mm Hg), week 5 (174±7* versus 124±4 mm Hg), and week 12 (181±12* versus 124±4 mm Hg). LV mass index was increased in HTN-5wk (22%*) and HTN-12wk (39%*). LV fibrosis was increased in HTN-12wk. Ees was preserved in HTN-5wk and HTN-12wk. τ was increased in HTN-5wk (50±3* ms) and HTN-12wk (62±10* ms) dogs compared with sham (41±2 ms). Plasma Ang II, ET, catecholamines, and plasma renin activity were unchanged during the progressive HTN. Ang II and ET in LV and kidney were not different from controls. Conclusions — Systemic HTN induces LV hypertrophy, myocardial fibrosis, and isolated diastolic dysfunction in the absence of local or systemic activation of Ang II or ET. These findings suggest that load is the prevailing stimulus for the structural and functional changes associated with early hypertensive heart disease.

Abstract Intermittent caloric restriction (ICR) provides greater prevention of mammary tumor (MT) development than chronic caloric restriction (CCR). Here we assessed the impact of a high-fat diet on this protective effect in relation to serum IGF-I, leptin and adiponectin. At 10 wk of age MMTV-TGF-α female mice were assigned to AL (ad libitum 23% fat calories), ICR (3-wk of 50% caloric restriction with 2× protein, fat, vitamins and minerals followed by 3-wk of 100%AL mice's consumption) and CCR (calorie/nutrient intake matched to ICR for each 6-wk cycle) groups (n=45/group). Food intakes were determined daily. Body weights, MT palpation and MT measurements were done weekly. Mice were followed until MT burden necessitated euthanasia or they reached 79 (end of restriction) or 82 (end of refeeding) weeks of age. Serum samples were obtained at baseline, euthanasia and cycles 5, 8, and 11 during restriction and refeeding for ICR mice. Food intakes for ICR and CCR mice were 24.2% and 24.3% lower than AL mice (p&lt;0.05). Body weights of ICR mice fluctuated in response to their calorie intake resulting in a significant difference among the groups. Final body, mammary and internal fat pad weights of AL mice were heaviest, followed by CCR and ICR-refed mice. ICR-restricted mice weights were the lowest. 66.7% of AL mice developed 1–5 MTs/mouse (grade 1–4). 52.3% of CCR mice had 1–3 MTs/mouse (grade 1–4). Only 4.4% of ICR mice developed 1 MT/mouse (grade 2). ICR-Restricted mice had significantly higher terminal serum IGFBP-3 and lower IGF-I and IGF-1/IGFBP-3 ratio than AL mice. There were no differences for CCR and ICR-Refed mice compared to either AL or ICR-Restricted groups. ICR-Restricted mice had significantly lower serum leptin and significantly higher terminal adiponectin and adiponectin/leptin ratio compared to AL, CCR and ICR-Refed mice. There were no differences in terminal serum measurements between mice with MTs versus those without MTs. IGF-I of AL and CCR mice did not change with age whereas for ICR mice IGF-1 was reduced during restriction periods. AL mice had the highest leptin levels across the study follow by CCR. For ICR mice leptin fluctuated in response to calorie intake, higher in refeeding vs restriction. Adiponectin levels for AL and CCR mice over time were similar. ICR mice had higher adiponectin levels when restricted vs refed. The adiponectin/leptin ratio of AL, CCR and ICR-refed mice was dramatically lower across the study compared with baseline but for ICR-restricted mice it was similar. These results indicate that ICR provides greater protection compared to CCR to prevent MT development even when a high fat diet is fed during refeeding. This was reflected by decreased MT incidence and MT burden and aggressiveness. Serum IGF-I, adiponectin and leptin were significantly affected by periods of 50% restriction providing a milieu conducive to reduced MT development. Citation Information: Cancer Prev Res 2010;3(1 Suppl):A110.

Although the two-kidney, one-clip (2K1C) model is widely used as a model of human renovascular hypertension, mechanisms leading to the development of fibrosis and atrophy in the cuffed kidney and compensatory hyperplasia in the contralateral kidney have not been defined. Based on the well-established role of the transforming growth factor (TGF)-β signaling pathway in renal fibrosis, we tested the hypothesis that abrogation of TGF-β/Smad3 signaling would prevent fibrosis in the cuffed kidney. Renal artery stenosis (RAS) was established in mice with a targeted disruption of exon 2 of the Smad3 gene (Smad3 KO) and wild-type (WT) controls by placement of a polytetrafluoroethylene cuff on the right renal artery. Serial pulse-wave Doppler ultrasound assessments verified that blood flow through the cuffed renal artery was decreased to a similar extent in Smad3 KO and WT mice. Two weeks after surgery, systolic blood pressure and plasma renin activity were significantly elevated in both the Smad3 KO and WT mice. The cuffed kidney of WT mice developed renal atrophy (50% reduction in weight after 6 wk, P < 0.0001), which was associated with the development of interstitial fibrosis, tubular atrophy, and interstitial inflammation. Remarkably, despite a similar reduction of renal blood flow, the cuffed kidney of the Smad3 KO mice showed minimal atrophy (9% reduction in weight, P = not significant), with no significant histopathological alterations (interstitial fibrosis, tubular atrophy, and interstitial inflammation). We conclude that abrogation of TGF-β/Smad3 signaling confers protection against the development of fibrosis and atrophy in RAS.

Atherosclerotic renal artery stenosis has a range of manifestations depending on the severity of vascular occlusion. The aim of this study was to examine whether exceeding the limits of adaptation to reduced blood flow ultimately leads to tissue hypoxia, as determined by blood oxygen level dependent MRI. We compared 3 groups of hypertensive patients, 24 with essential hypertension, 13 with “moderate” (Doppler velocities 200–384 cm/s), and 17 with “severe” atherosclerotic renal artery stenosis (ARAS; velocities >384 cm/s and loss of functional renal tissue). Cortical and medullary blood flows and volumes were determined by multidetector computed tomography. Poststenotic kidney size and blood flow were reduced with ARAS, and tissue perfusion fell in the most severe lesions. Tissue medullary deoxyhemoglobin, as reflected by R2* values, was higher as compared with the cortex for all of the groups and did not differ between subjects with renal artery lesions and essential hypertension. By contrast, cortical R2* levels were elevated for severe ARAS (21.6±9.4 per second) as compared with either essential hypertension (17.8±2.3 per second; P <0.01) or moderate ARAS (15.7±2.1 per second; P <0.01). Changes in medullary R2* after furosemide administration tended to be blunted in severe ARAS as compared with unaffected (contralateral) kidneys. These results demonstrate that severe vascular occlusion overwhelms the capacity of the kidney to adapt to reduced blood flow, manifest as overt cortical hypoxia as measured by blood oxygen level–dependent MRI. The level of cortical hypoxia is out of proportion to the medulla and may provide a marker to identify irreversible parenchymal injury.