Role of inflammation in the pathogenesis of heart failure with preserved ejection fraction and its potential as a therapeutic target.

Heart failure (HF) with preserved ejection fraction (HFPEF) is an increasingly prevalent clinical syndrome with many unresolved issues regarding diagnosis, pathophysiology, and treatment. The major pathophysiological mechanisms underlying HFPEF are known to be fibrosis and reduced ventricular compliance, and hypertension (HTN) is perhaps the most significant risk factor for the development of left ventricular diastolic dysfunction (LVDD). Inflammation is one of the earliest events in cardiac stress situations such as pressure and/or volume overload and involves elevated levels of endothelial adhesion molecules as well as increased production and release of inflammatory cytokines and chemokines in the tissue. The latter promotes the infiltration of activated inflammatory cells, particularly monocytes, into the cardiac tissue. Increased monocyte infiltration is seen in the early and late stages of HTN and HFPEF. Once inside the tissue, monocytes differentiate into macrophages and promote cardiac inflammation, tissue injury, and myocardial fibrosis. This review focuses on inflammation as the initial and primary trigger of ventricular remodelling in HTN and LVDD, affecting progression to HFPEF. The link between inflammation and b-type natriuretic peptide (BNP), a clinical marker of cardiac pressure overload which is positively associated with cardiac dysfunction and HF, is also described. Finally, current and prospective therapeutic approaches for HFPEF based on modification of the inflammatory response are reviewed.

Getting to the heart of cardiac remodeling; how collagen subtypes may contribute to phenotype.

The objective of this study was to investigate the nature and biomechanical properties of collagen fibers within the human myocardium. Targeting cardiac interstitial abnormalities will likely become a major focus of future preventative strategies with regard to the management of cardiac dysfunction. Current knowledge regarding the component structures of myocardial collagen networks is limited, further delineation of which will require application of more innovative technologies. We applied a novel methodology involving combined confocal laser scanning and atomic force microscopy to investigate myocardial collagen within ex-vivo right atrial tissue from 10 patients undergoing elective coronary bypass surgery. Immuno-fluorescent co-staining revealed discrete collagen I and III fibers. During single fiber deformation, overall median values of stiffness recorded in collagen III were 37±16% lower than in collagen I [p<0.001]. On fiber retraction, collagen I exhibited greater degrees of elastic recoil [p<0.001; relative percentage increase in elastic recoil 7±3%] and less energy dissipation than collagen III [p<0.001; relative percentage increase in work recovered 7±2%]. In atrial biopsies taken from patients in permanent atrial fibrillation (n=5) versus sinus rhythm (n=5), stiffness of both collagen fiber subtypes was augmented (p<0.008). Myocardial fibrillar collagen fibers organize in a discrete manner and possess distinct biomechanical differences; specifically, collagen I fibers exhibit relatively higher stiffness, contrasting with higher susceptibility to plastic deformation and less energy efficiency on deformation with collagen III fibers. Augmented stiffness of both collagen fiber subtypes in tissue samples from patients with atrial fibrillation compared to those in sinus rhythm are consistent with recent published findings of increased collagen cross-linking in this setting.

Mechanisms for modulating TNF alpha in immune and inflammatory disease.

The development of tumor necrosis factor-alpha (TNF alpha) inhibitors has been one of the most active areas of drug development over the last ten years for the treatment of inflammatory diseases. Following the definition of TNF alpha as a key mediator of inflammatory disease and the success demonstrated by various anti-TNF alpha strategies in the treatment of rheumatoid arthritis and inflammatory bowel disease, many investigators have sought to refine mechanisms by which to modulate TNF alpha in vivo. Many advances are presently being made in the understanding of how TNF alpha production is regulated, and with this knowledge comes the identification of new targets and pathways for therapeutic intervention. Here, we review the development of the currently available therapeutics and the progressive steps that are being made to improve clinical efficacy of anti-TNF alpha strategies.

Macrophage migration inhibitory factor: a neuroendocrine modulator of chronic inflammation.

The diverse actions of macrophage migration inhibitory factor (MIF) within the immuno-neuroendocrine system are yet to be fully understood, but it is clear that MIF plays a pivotal role in the regulation of both the innate and adaptive immune response. An emerging body of data presently indicates that MIF's position within the cytokine cascade is to act in concert with glucocorticoids to control the 'set point' and magnitude of the immune and inflammatory response. In this article we will review the actions of MIF within the immune system and discuss the overlapping and contrasting aspects of MIF and glucocorticoid biology. In particular we will focus on the role of MIF within the immuno-neuroendocrine interface and suggest molecular mechanisms by which MIF may counter-regulate glucocorticoid function. Finally we will discuss emerging evidence that functional MIF gene-promoter polymorphisms render one susceptible to elevated MIF expression, and the development of an exaggerated immune/inflammatory response that potentiates the progression to chronic inflammatory disease.

Sarcoidosis and MIF gene polymorphism: a case-control study in an Irish population.

Macrophage migration inhibitory factor is a key pro-inflammatory mediator. A 5-CATT repeat functional polymorphism within the promoter of the gene was previously associated with the lowest promoter activity. It was hypothesised that patients exhibiting a 5-CATT allele would have a less aggressive inflammatory response with an associated less severe clinical phenotype in sarcoidosis. Irish Caucasian sarcoidosis patients (n = 173) followed up for 1-39 yrs and a control group (n = 166) were genotyped for the CATT repeat polymorphism. Disease severity at the time of diagnosis and at the time of elaboration of the present study was assessed by the presence of thoracic and extrathoracic symptoms, erythema nodosum, radiographic interstitial changes (chest radiograph score equal to stage II or greater, or high-resolution computed tomography confirmed), pulmonary function tests, steroid use, erythrocyte sedimentation rate, C-reactive protein and angiotensin-converting enzyme levels. In the Irish population studied, no evidence was found of a significant association between either sarcoidosis susceptibility and disease severity and the 5-CATT repeat functional polymorphism in the macrophage migration inhibitory gene. The present study found no significant association between the 5-CATT repeat macrophage migration inhibitory factor gene polymorphism and sarcoidosis, and did not support the overriding role for macrophage migration inhibitory factor in driving sarcoidosis pathogenesis.

A functional promoter polymorphism in the macrophage migration inhibitory factor (MIF) gene associated with disease severity in rheumatoid arthritis.

The macrophage migration inhibitory factor (MIF) is a potent pro-inflammatory cytokine and regulates the anti-inflammator effects of glucocorticoids. An important role for MIF within the cytokine cascade is to act in concert with endogenous glucocorticoids to control the set-point and magnitude of the inflammatory response. Elevated expression of MIF in the circulation and in the synovial joint has been documented in rheumatoid arthritis. MIF also has been linked to the development of joint damage and disease pathology in experimental animal models. We describe herein a novel CATT-tetranucleotide repeat polymorphism at position -794 of the human Mif gene and show that it functionally affects the activity of the MIF promoter in gene reporter assays. We describe four genotypes which comprise 5, 6, 7, or 8-CATT repeat units and show that the 5-CATT allele has the lowest level of basal and stimulated MIF promoter activity in vitro. The presence of the low expressing, 5-CATT repeat allele correlated with low disease severity in a cohort of rheumatoid arthritis patients.