Does indoxyl sulfate, a uraemic toxin, have direct effects on cardiac fibroblasts and myocytes?

AIMS: Indoxyl sulfate (IS) is a uraemic toxin found at high concentration in patients with chronic kidney disease (CKD) co-morbid with chronic heart failure (CHF). The aim of this study was to determine direct effects of IS on cardiac cells as well as the pro-inflammatory effect of IS. METHODS AND RESULTS: Indoxyl sulfate significantly increased neonatal rat cardiac fibroblast collagen synthesis (by 145.7% vs. control, P < 0.05) and myocyte hypertrophy (by 134.5% vs. control, P < 0.001) as determined by (3)H-proline or (3)H-leucine incorporation, respectively. Indoxyl sulfate stimulated tumour necrosis factor-alpha, interleukin-6 (IL-6), and IL-1beta mRNA expression in THP-1 cells as quantified by RT-PCR. Both p38 (RWJ-67657) and MEK1/2 (U0126) inhibitors suppressed all these effects by IS. Furthermore, western blot analysis showed that IS activated mitogen-activated protein kinase (MAPK) (p38, p42/44) and nuclear factor-kappa B (NFkappaB) pathways. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed that IS exerted its effects without affecting cell viability. CONCLUSION: This study has, for the first time, demonstrated that IS has pro-fibrotic, pro-hypertrophic, and pro-inflammatory effects, indicating that IS might play an important role in adverse cardiac remodelling mediated via activation of the p38 MAPK, p42/44 MAPK, and NFkappaB pathways. Targeting reduction of IS and/or the pathways it activates may represent a novel therapeutic approach to the management of CHF with concomitant CKD.

Celecoxib, but not rofecoxib or naproxen, attenuates cardiac hypertrophy and fibrosis induced in vitro by angiotensin and aldosterone.

1. Cyclo-oxygenase (COX)-2 inhibitors and other non-steroidal anti-inflammatory drugs (NSAIDs) have been implicated in increased cardiovascular events. However, the direct effects of these drugs on cardiac function have not been explored extensively. Given the important role of the renin-angiotensin-aldosterone system (RAAS) in cardiac remodelling, we sought to determine the effect of COX-2 inhibitors and non-specific (NS-) NSAIDs on RAAS-induced cardiac hypertrophy and fibrosis in neonatal rat cardiac myocytes (NCM) and fibroblasts (NCF) isolated from 1-2-day-old Sprague-Dawley rat pups. 2. The NCM were pretreated for 2 h with COX-2 inhibitors (celecoxib or rofecoxib) or NS-NSAIDs (naproxen; all at 0.1-10 micromol/L) before being stimulated with 10 micromol/L aldosterone for 72 h or with 0.1 micromol/L angiotensin (Ang) II for 60 h. Hypertrophy of NCM was assessed by [3H]-leucine incorporation. 3. The NCF were pretreated with COX-2 inhibitors or naproxen as described for NCM before being stimulated with 0.1 micromol/L AngII for 48 h. Collagen synthesis was subsequently assayed by [3H]-proline incorporation. 4. Pooled cryopreserved male and female rat hepatocytes were treated with or without COX-2 inhibitors for 1 h before 1 nmol/L aldosterone ( approximately 540 pg/mL) was added to all wells. Cells were incubated for a further 60 min and culture media harvested by centrifugation. Human hepatic HepG2 cells were treated with compounds with or without serum starvation for 48 h. All cells were pretreated with COX-2 inhibitors for 2 h before the addition of aldosterone. Cell culture media were harvested after a further 3, 18, 24 or 48 h incubation. Aldosterone concentrations in the culture media were determined by enzyme immunoassay. 5. Aldosterone- and AngII-stimulated NCM hypertrophy was inhibited by celecoxib, but not by rofecoxib or naproxen. In NCF, AngII-stimulated collagen synthesis was inhibited by celecoxib and, to a lesser extent, by rofecoxib, whereas naproxen had no effect. The COX-2 inhibitors inhibited aldosterone uptake and/or metabolism by rat hepatocytes, but had no effect in human hepatic HepG2 cells. 6. These results demonstrate a potential antiremodelling effect of selective COX-2 inhibitors in the setting of RAAS stimulation in cardiac cells, whereas naproxen has no effect.

Effects of a Rho kinase inhibitor on pressure overload induced cardiac hypertrophy and associated diastolic dysfunction.

The RhoA-Rho kinase (ROCK) signaling pathway has an important role in cardiovascular diseases. However, the effect of Rho kinase inhibition on pressure overload-induced cardiac hypertrophy (POH) and associated diastolic dysfunction has not been evaluated. This study examined the effect of a selective ROCK inhibitor (GSK-576371) in a POH model, induced by suprarenal abdominal aortic constriction. POH rats were divided into the following four groups: 1 (GSK 1, n = 9) or 3 (GSK 3, n = 10) mg/kg bid GSK-576371, 1 mg.kg(-1).day(-1) ramipril (n = 10) or vehicle (n = 11) treatment for 4 wk. Sham animals (n = 11) underwent surgery without banding. Echocardiograms were performed before surgery and posttreatment, and hemodynamic data were obtained at completion of the study. Echocardiography showed an increase in relative wall thickness of the left ventricle (LV) following POH + vehicle treatment compared with sham animals. This was attenuated by both doses of GSK-576371 and ramipril. Vehicle treatment demonstrated abnormal diastolic parameters, including mitral valve (MV) inflow E wave deceleration time, isovolumic relaxation time, and MV annular velocity, which were dose dependently restored toward sham values by GSK-576371. LV end diastolic pressure was increased following POH + vehicle treatment compared with sham (6.9 +/- 0.7 vs. 3.2 +/- 0.7 mmHg, P = 0.008) and was reduced with GSK 3 and ramipril treatment (1.7 +/- 0.7, P < 0.01 and 2.9 +/- 0.6 mmHg, P < 0.01, respectively). Collagen I deposition in the LV was increased following POH + vehicle treatment (32.2%; P < 0.01) compared with sham animals and was significantly attenuated with GSK 1 (21.7%; P < 0.05), GSK 3 (23.8%; P < 0.01), and ramipril (35.5%; P < 0.01) treatment. These results suggest that ROCK inhibition improves LV geometry and reduces collagen deposition accompanied by improved diastolic function in POH.