Comparison of in vitro cardiovascular function with in vivo echocardiographic assessment after long-term administration of cyclosporine to rats

Cardiovascular toxicities by calcineurin inhibitors: Cellular mechanisms behind clinical manifestations

Calcineurin inhibitors (CNI), including cyclosporine A (CsA) and tacrolimus (TAC), are cornerstones of immunosuppressive therapy in solid organ transplant recipients. While extensively recognized for their capacity to induce nephrotoxicity, hypertension, and dyslipidemia, emerging reports suggest potential direct cardiovascular toxicities associated with CNI. Evidence from both in vitro and in vivo studies has demonstrated direct cardiotoxic impact of CNI, manifesting itself as induction of cardiomyocyte apoptosis, enhanced oxidative stress, inflammatory cell infiltration, and cardiac fibrosis. CNI enhances cellular apoptosis through CaSR via activation of the p38 MAPK pathway and deactivation of the ERK pathway, and enhancement of miR-377 axis. Although CNI could attenuate cardiac hypertrophy in certain animal models, CNI concurrently impaired systolic function, enhanced cardiac fibrosis, and increased the risk of heart failure. Evidence from in vivo studies demonstrated that CNI prolong the duration of action potentials through a decrease in potassium current. CNI also exerted direct effects on endothelial cell injury, inducing apoptosis and enhancing oxidative stress. CNI may induce vascular inflammation through TLR4 via MyD88 and TRIF pathways. In addition, CNI affects vascular function by impairing endothelial-dependent vasodilation and promoting vasoconstriction. Clinical studies in transplant patients also revealed an increased incidence of cardiac remodeling. However, the evidence is constrained by the limited number of participants and potential confounding factors. Several studies indicate differing cardiovascular toxicity profiles between CsA and TAC, and these could be potentially due to their different interactions with calcineurin subunits and calcineurin-independent effects. Further studies are needed to clarify these mechanisms to improve cardiovascular outcomes for transplant patients with CNI.

Protective effect of 3-deazaadenosine in a rat model of lipopolysaccharide-induced myocardial dysfunction

Severe sepsis is accompanied by a profound depression of myocardial contractility. Leukocyte adhesion with subsequent local excess nitric oxide and reactive oxygen species production play major roles for this deleterious effect. We hypothesized that 3-deazaadenosine (c3Ado), an adenosine analogue with anti-inflammatory properties, prevents endotoxin-induced myocardial dysfunction. Wistar rats (8 per group) were treated with Escherichia coli lipopoly-saccharide (LPS, 1 mg/kg, i.p., strain 0111:B4) +/- c3Ado (10 mg/kg, i.p.) 8 h before their hearts were harvested for isolated perfusion, histochemical analysis, or electrophoretic mobility shift assay. LPS induced a marked depression of left ventricular contractility. Immunohistochemistry revealed an upregulation of the adhesion molecules VCAM-1, ICAM-1, and P-selectin within the postcapillary venules. c3Ado inhibited VCAM-1 and ICAM-1 upregulation, but not P-selectin, and prevented cardiodepression. Electrophoretic mobility shift assay revealed inactivation of the transcription factor nuclear factor-kappaB and immunohistochemical staining for gp91phox, ED1, and CD11b demonstrated that c3Ado prevented local recruitment of monocytes and polymorph nuclear neutrophils to the myocardium. Accordingly, significantly fewer leukocytes producing nitric oxide or reactive oxygen species accumulated within the myocardium. Intravital microscopy of intestinal venules confirmed that LPS-induced adhesion of leukocytes was prevented by c3Ado. Additionally, c3Ado prevented LPS-induced elevation of serum tumor necrosis factor-alpha levels. Our results imply that c3Ado may prove to have clinical relevance for inflammatory disease processes.

Cyclosporin A inhibits cardiac hypertrophy and enhances cardiac dysfunction during postinfarction failure in rats

Calcineurin has recently been implicated as a mediator in the signaling pathways that transform intracellular calcium signals to the phenotype of myocardial hypertrophy. The present study was conducted to examine the effects of cyclosporin A (CsA), an inhibitor of calcineurin, on myocardial hypertrophy and remodeling during congestive heart failure (CHF) in rats. After ligation of the left coronary artery, rats were randomized to treatment with CsA or vehicle for 14 days. Compared with vehicle, CsA substantially attenuated myocardial hypertrophy in the CHF rats as assessed by alterations in ventricular weight-to-tibial length ratios (P < 0.05). Myocardial gene expression of skeletal alpha-actin was also reduced in the failing left ventricle (LV) after treatment with CsA (P < 0. 05), although the mRNA levels were still substantially elevated relative to those of sham rats. CsA-induced inhibition of compensatory myocardial hypertrophy in the CHF rats led to increased dilatation of the LV cavity and reduced fractional shortening and peak positive and negative first derivatives of LV pressure (P < 0. 05). Plasma renin and endothelin-1 levels were increased in the CHF-CsA rats, providing humoral cues of aggravated cardiac function. Thus this study supports a crucial role of calcineurin-dependent pathways in the mechanisms of compensatory myocardial hypertrophy during CHF. In addition, our data indicate that inhibition of compensatory myocardial hypertrophy exerts detrimental effects on cardiac remodeling and function after myocardial infarction.