The role of anticytokine therapy in heart failure: recent lessons from preclinical and clinical trials?

Tumor necrosis factor-α confers cardioprotection through ectopic expression of keratins K8 and K18

Tumor necrosis factor-α (TNF-α), one of the major stress-induced proinflammatory cytokines, is upregulated in the heart after tissue injury, and its sustained expression can contribute to the development of heart failure. Whether TNF-α also exerts cytoprotective effects in heart failure is not known. Here we provide evidence for a cardioprotective function of TNF-α in a genetic heart failure model, desmin-deficient mice. The cardioprotective effects of TNF-α are a consequence of nuclear factor-κB (NF-κB)-mediated ectopic expression in cardiomyocytes of keratin 8 (K8) and keratin 18 (K18), two epithelial-specific intermediate filament proteins. In cardiomyocytes, K8 and K18 (K8/K18) formed an alternative cytoskeletal network that localized mainly at intercalated discs (IDs) and conferred cardioprotection by maintaining normal ID structure and mitochondrial integrity and function. Ectopic induction of K8/K18 expression in cardiomyocytes also occurred in other genetic and experimental models of heart failure. Loss of the K8/K18 network resulted in a maladaptive cardiac phenotype following transverse aortic constriction. In human failing myocardium, where TNF-α expression is upregulated, K8/K18 were also ectopically expressed and localized primarily at IDs, which did not contain detectable amounts of desmin. Thus, TNF-α- and NF-κB-mediated formation of an alternative, stress-induced intermediate filament cytoskeleton has cardioprotective function in mice and potentially in humans.

Emerging concepts in cardiac matrix biologyThis article is one of a selection of papers published in a special issue on Advances in Cardiovascular Research

The cardiac extracellular matrix, far from being merely a static support structure for the heart, is now recognized to play central roles in cardiac development, morphology, and cell signaling. Recent studies have better shaped our understanding of the tremendous complexity of this active and dynamic network. By activating intracellular signal cascades, the matrix transduces myocardial physical forces into responses by myocytes and fibroblasts, affecting their function and behavior. In turn, cardiac fibroblasts and myocytes play active roles in remodeling the matrix. Coupled with the ability of the matrix to act as a dynamic reservoir for growth factors and cytokines, this interplay between the support structure and embedded cells has the potential to exert dramatic effects on cardiac structure and function. One of the clearest examples of this occurs when cell–matrix interactions are altered inappropriately, contributing to pathological fibrosis and heart failure. This review will examine some of the recent concepts that have emerged regarding exactly how the cardiac matrix mediates these effects, how our collective vision of the matrix has changed as a result, and the current state of attempts to pharmacologically treat fibrosis.

Protection from adverse myocardial remodeling secondary to chronic volume overload in mast cell deficient rats

Mast cells have diverse roles throughout the body as evidenced by their heterogeneous nature. In the heart, cardiac mast cells have been implicated in left ventricular (LV) remodeling in response to elevated myocardial stress. Accordingly, the purpose of this study was to use mast cell deficient rats (Ws/Ws) to delineate the interaction between cardiac mast cell activation and LV remodeling. LV matrix metalloproteinase (MMP) activity, fibrillar collagen, TNF-alpha levels, and LV diameter were compared in Ws/Ws and wild type (WT) rats subjected to 5 d (n=3/group) and 8 weeks (n=4/group) of aortocaval fistula-induced volume overload. In contrast to attenuation of myocardial remodeling in the Ws/Ws group: 1) MMP-2 activity was significantly increased in the WT group at 5 days; 2) there was marked degradation of the extracellular collagen matrix in WT at 5 days and 8 weeks; 3) the percent increase in LV diameter from baseline was significantly greater in WT at 2, 4, 6, and 8 weeks post-fistula; and 4) myocardial TNF-alpha levels were markedly elevated in the WT group at 5 days post-fistula. These results underscore the importance of cardiac mast cells in mediating MMP activation, collagen degradation and LV dilatation and suggest that mast cell-derived TNF-alpha plays a role in early myocardial remodeling.

Inflammatory factors in age-related muscle wasting

PURPOSE OF REVIEW

This review focuses on recent evidence pointing to the importance of inflammatory factors in the onset and progression of age-related muscle wasting, also known as sarcopenia, and discusses critical areas of uncertainty within the literature that require further development in order to identify novel therapeutics.

RECENT FINDINGS

The research performed in recent years has only strengthened the evidence that inflammatory factors are important in the progression of a catabolic state in muscle wasting. Interactions among various inflammatory cytokines and anabolic factors have been observed, with the balance skewed in favor of catabolism in sarcopenia. Adiposity appears to play an important role in the inflammatory process and possibly the onset of sarcopenia. Inflammatory factors are likely to play an important role in the increased activity of the ubiquitin proteasome, which we argue should be a primary target for the development of molecular therapeutics.

SUMMARY

Future research will need to delve into the molecular interactions that link inflammatory factors and the imbalance between muscle anabolism and catabolism that develops with aging. Identification of specific pathways of importance to sarcopenia will have relevance to a wide range of wasting disorders.

The cardiac fibroblast: therapeutic target in myocardial remodeling and failure

Cardiac fibroblasts play a central role in the maintenance of extracellular matrix in the normal heart and as mediators of inflammatory and fibrotic myocardial remodeling in the injured and failing heart. In this review, we evaluate the cardiac fibroblast as a therapeutic target in heart disease. Unique features of cardiac fibroblast cell biology are discussed in relation to normal and pathophysiological cardiac function. The contribution of cardiac fibrosis as an independent risk factor in the outcome of heart failure is considered. Candidate drug therapies that derive benefit from actions on cardiac fibroblasts are summarized, including inhibitors of angiotensin-aldosterone systems, endothelin receptor antagonists, statins, anticytokine therapies, matrix metalloproteinase inhibitors, and novel antifibrotic/anti-inflammatory agents. These findings point the way to future challenges in cardiac fibroblast biology and pharmacotherapy.

Memories of virus-specific CD8+ T cells

This brief review focuses on the way that our understanding of virus-specific CD8(+) T-cell-mediated immunity evolved, giving particular attention to the early impact of the program at the Australian National University. The story developed through a sequence of distinct eras, each of which can be defined in the context of the technologies available at that time. The progress has been enormous, but there is a great deal still to be learned. A particular challenge is to use what we know for human benefit.