Search

Background: Abnormalities in cardiac energy metabolism occur in heart failure (HF) and contribute to contractile dysfunction, but their role, if any, in HF-related pathologic remodeling is much less established. CK (creatine kinase), the primary muscle energy reserve reaction which rapidly provides ATP at the myofibrils and regenerates mitochondrial ADP, is down-regulated in experimental and human HF. We tested the hypotheses that pathologic remodeling in human HF is related to impaired cardiac CK energy metabolism and that rescuing CK attenuates maladaptive hypertrophy in experimental HF., Methods: First, in 27 HF patients and 14 healthy subjects, we measured cardiac energetics and left ventricular remodeling using noninvasive magnetic resonance 31 P spectroscopy and magnetic resonance imaging, respectively. Second, we tested the impact of metabolic rescue with cardiac-specific overexpression of either Ckmyofib (myofibrillar CK) or Ckmito (mitochondrial CK) on HF-related maladaptive hypertrophy in mice., Results: In people, pathologic left ventricular hypertrophy and dilatation correlate closely with reduced myocardial ATP levels and rates of ATP synthesis through CK. In mice, transverse aortic constriction-induced left ventricular hypertrophy and dilatation are attenuated by overexpression of CKmito, but not by overexpression of CKmyofib. CKmito overexpression also attenuates hypertrophy after chronic isoproterenol stimulation. CKmito lowers mitochondrial reactive oxygen species, tissue reactive oxygen species levels, and upregulates antioxidants and their promoters. When the CK capacity of CKmito-overexpressing mice is limited by creatine substrate depletion, the protection against pathologic remodeling is lost, suggesting the ADP regenerating capacity of the CKmito reaction rather than CK protein per se is critical in limiting adverse HF remodeling., Conclusions: In the failing human heart, pathologic hypertrophy and adverse remodeling are closely related to deficits in ATP levels and in the CK energy reserve reaction. CKmito, sitting at the intersection of cardiac energetics and redox balance, plays a crucial role in attenuating pathologic remodeling in HF. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT00181259.

Objective: To evaluate the performance of Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine, cystatin C, and creatinine-cystatin C estimating equations in HIV-positive patients., Methods: We evaluated the performance of the Modification of Diet in Renal Disease (MDRD) Study and CKD-EPI creatinine 2009, CKD-EPI cystatin C 2012, and CKD-EPI creatinine-cystatin C 2012 glomerular filtration rate (GFR) estimating equations compared with GFR measured using plasma clearance of iohexol in 200 HIV-positive patients on stable antiretroviral therapy. Creatinine and cystatin C assays were standardized to certified reference materials., Results: Of the 200 participants, median (IQR) CD4 count was 536 (421) and 61% had an undetectable HIV viral load. Mean (SD) measured GFR (mGFR) was 87 (26) mL/min per 1.73 m. All CKD-EPI equations performed better than the MDRD Study equation. All 3 CKD-EPI equations had similar bias and precision. The cystatin C equation was not more accurate than the creatinine equation. The creatinine-cystatin C equation was significantly more accurate than the cystatin C equation, and there was a trend toward greater accuracy than the creatinine equation. Accuracy was equal or better in most subgroups with the combined equation compared to either alone., Conclusions: The CKD-EPI cystatin C equation does not seem to be more accurate than the CKD-EPI creatinine equation in patients who are HIV-positive, supporting the use of the CKD-EPI creatinine equation for routine clinical care for use in North American populations with HIV. The use of both filtration markers together as a confirmatory test for decreased estimated GFR based on creatinine in individuals who are HIV-positive requires further study.

Adriamycin (ADR) is an established, life-saving antineoplastic agent, the use of which is often limited by cardiotoxicity. ADR-induced cardiomyopathy is often accompanied by depressed myocardial high-energy phosphate (HEP) metabolism. Impaired HEP metabolism has been suggested as a potential mechanism of ADR cardiomyopathy, in which case the bioenergetic decline should precede left ventricular (LV) dysfunction. We tested the hypothesis that murine cardiac energetics decrease before LV dysfunction following ADR (5 mg/kg ip, weekly, 5 injections) in the mouse. As a result, the mean myocardial phosphocreatine-to-ATP ratio (PCr/ATP) by spatially localized (31)P magnetic resonance spectroscopy decreased at 6 wk after first ADR injection (1.79 + or - 0.18 vs. 1.39 + or - 0.30, means + or - SD, control vs. ADR, respectively, P < 0.05) when indices of systolic and diastolic function by magnetic resonance imaging were unchanged from control values. At 8 wk, lower PCr/ATP was accompanied by a reduction in ejection fraction (67.3 + or - 3.9 vs. 55.9 + or - 4.2%, control vs. ADR, respectively, P < 0.002) and peak filling rate (0.56 + or - 0.12 vs. 0.30 + or - 0.13 microl/ms, control vs. ADR, respectively, P < 0.01). PCr/ATP correlated with peak filling rate and ejection fraction, suggesting a relationship between cardiac energetics and both LV systolic and diastolic dysfunction. In conclusion, myocardial in vivo HEP metabolism is impaired following ADR administration, occurring before systolic or diastolic abnormalities and in proportion to the extent of eventual contractile abnormalities. These observations are consistent with the hypothesis that impaired HEP metabolism contributes to ADR-induced myocardial dysfunction.

This paper concerns the role of nitric oxide (NO) in controlling metamorphosis in the marine gastropod Crepidula fornicata. Metamorphosis was stimulated by the nitric oxide synthase (NOS) inhibitors AGH (aminoguanidine hemisulfate) and SMIS (S-methylisothiourea sulfate) at concentrations of about 100-1000 micromol l(-1) and 50-200 micromol l(-1), respectively. Metamorphosis was not, however, induced by the NOS inhibitor l-NAME (l-N(G)-nitroarginine methyl ester) at even the highest concentration tested, 500 micromol l(-1). Moreover, pre-incubation with l-NAME at 20 and 80 micromol l(-1) did not increase the sensitivity of competent larvae to excess K(+), a potent inducer of metamorphosis in this species; we suggest that either l-NAME is ineffective in suppressing NO production in larvae of C. fornicata, or that it works only on the constitutive isoform of the enzyme. In contrast, metamorphosis was potentiated by the guanylate cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3, -a]quinoxalin-1-one) in response to a natural metamorphic inducer derived from conspecific adults. Because NO typically stimulates cGMP production through the activation of soluble guanylate cyclase, this result supports the hypothesis that NO acts as an endogenous inhibitor of metamorphosis in C. fornicata. The expression of NOS, shown by immunohistochemical techniques, was detected in the apical ganglion of young larvae but not in older larvae, further supporting the hypothesis that metamorphosis in C. fornicata is made possible by declines in the endogenous concentration of NO during development.

ST elevation is a classical hallmark of acute transmural myocardial ischemia. Indeed, ST elevation is the major clinical criterion for committing patients with chest pain to emergent coronary revascularization. Despite its clinical importance, the mechanism of ST elevation remains unclear. Various studies have suggested that activation of sarcolemmal ATP-sensitive potassium (K(ATP)) channels by ischemic ATP depletion may play a role, but little direct evidence is available. We studied mice with homozygous knockout (KO) of the Kir6.2 gene, which encodes the pore-forming subunit of cardiac surface K(ATP) channels. Patch-clamp studies in cardiomyocytes confirmed that surface K(ATP) current was indeed absent in KO, but robust in cells from wild-type mice (WT). We then measured continuous electrocardiograms in anesthetized adult mice before and after open-chest ligation of the left anterior descending artery (LAD). Whereas ST elevation was readily evident in WT after LAD ligation, it was markedly suppressed in KO. Such qualitative differences persisted for the rest of the 60-minute observation period of ischemia. In support of the concept that K(ATP) channels are responsible for ST elevation, the surface K(ATP)channel blocker HMR1098 (5 mg/kg IP) suppressed early ST elevation in WT. Thus, the opening of sarcolemmal K(ATP)channels underlies ST elevation during ischemia. These data are the first to link a specific gene product with a common electrocardiographic phenomenon.

Coxsackievirus infection causes myocarditis and pancreatitis in humans. In certain strains of mice, Coxsackievirus causes a severe pancreatitis. We explored the role of NO in the host immune response to viral pancreatitis. Coxsackievirus replicates to higher titers in mice lacking NO synthase 2 (NOS2) than in wild-type mice, with particularly high viral titers and viral RNA levels in the pancreas. Mice lacking NOS have a severe, necrotizing pancreatitis, with elevated pancreatic enzymes in the blood and necrotic acinar cells. Lack of NOS2 leads to a rapid increase in the mortality of infected mice. Thus, NOS2 is a critical component in the immune response to Coxsackievirus infection.

The host response to Coxsackievirus infection is complex, including T lymphocytes, B lymphocytes, natural killer cells, and macrophages. Although Coxsackievirus infection induces expression of inducible nitric oxide synthase (NOS2; EC 1.14.13.39) in macrophages, the precise role of NOS2 in the host response to Coxsackievirus myocarditis has been unclear. We show, by using mice homozygous for a disrupted NOS2 allele, that Coxsackievirus replicates to higher titers in NOS2(-/-) mice, that the host lacking NOS2 clears virus more slowly than the wild-type host, and that myocarditis is much more severe in infected NOS2(-/-) mice. These data show that NOS2 is crucial for the host response to Coxsackievirus in the mouse.

Patients with myocarditis often develop dilated cardiomyopathy and congestive heart failure. Histologically, myocarditis is manifested by rare foci of myocyte necrosis with interstitial inflammation, while cardiomyopathy is characterized by diffuse interstitial fibrosis, myocyte hypertrophy, and an absence of active interstitial inflammation. The relationship between myocardial inflammation and interstitial fibrosis is poorly understood. This relationship was examined in mice that developed a diffuse interstitial inflammation of the heart over a period of 21 days following infection with encephalomyocarditis virus. Typical early lesions (day 7) included focal zones of myocytolysis containing mononuclear and polymorphonuclear inflammatory cells that were associated with the focal loss of reticular fibers. Later pathology (days 14-21) was characterized by a sparse, diffuse interstitial myocarditis with little ongoing necrosis. Changes within the myocardial interstitium remote from healing necrotic foci were marked by reticular fiber thickening and disorganization, often associated with pleomorphic fibroblasts. Reticulin fiber deposition was quantitatively increased in sparsely inflamed regions of hearts from infected animals as compared to noninflamed regions from the same hearts (p < 0.005) or hearts of control animals (p < 0.001). Scanning electron microscopy revealed interstitial changes that were more extensive than indicated by routine staining with hematoxylin and eosin for Masson's trichrome. The progressive changes within the cardiac interstitium during the development of postmyocarditic cardiomyopathy suggest that direct viral infection of fibroblasts or an interaction between the interstitium and inflammatory cells and their secreted products may contribute to pathologic changes within the interstitial collagen matrix., (Copyright © 1993. Published by Elsevier Inc.)

The complement system is an important mediator of the acute inflammatory response, and an effective inhibitor would suppress tissue damage in many autoimmune and inflammatory diseases. Such an inhibitor might be found among the endogenous regulatory proteins of complement that block the enzymes that activate C3 and C5. Of these proteins, complement receptor type 1 (CR1; CD35) has the most inhibitory potential, but its restriction to a few cell types limits its function in vivo. This limitation was overcome by the recombinant, soluble human CR1, sCR1, which lacks the transmembrane and cytoplasmic domains. The sCR1 bivalently bound dimeric forms of its ligands, C3b and methylamine-treated C4 (C4-ma), and promoted their inactivation by factor I. In nanomolar concentrations, sCR1 blocked complement activation in human serum by the two pathways. The sCR1 had complement inhibitory and anti-inflammatory activities in a rat model of reperfusion injury of ischemic myocardium, reducing myocardial infarction size by 44 percent. These findings identify sCR1 as a potential agent for the suppression of complement-dependent tissue injury in autoimmune and inflammatory diseases.

In summary, conversion of wild-type CR1 to a soluble form (sCR1) creates a potent inhibitor of complement activation by both the classical and alternative pathways by inhibiting the C3/C5 convertases. In the rat reperfusion infarct model, sCR1 significantly suppresses complement activation at the endothelial surface of capillaries and venules. This suppression of complement activation is accompanied by reduced accumulation of leukocytes within the infarct zone, perhaps because of reduction of the generation of C5a, which promotes expression of leukocyte adhesion receptors and leukocyte chemotaxis. In addition, formation of the C5b-9 attack complex, which may contribute to direct endothelial injury, was suppressed by sCR1. The inhibition of complement activation and leukocyte infiltration by sCR1 explains the observed significant reduction in myocardial necrosis after ischemia and reperfusion. These studies have identified sCR1 as a potential agent for therapeutic intervention in diseases associated with complement-dependent tissue injury.