Tumor necrosis factor-alpha upregulates angiotensin II type 1 receptors on cardiac fibroblasts

Validity of mental and physical stress models

Different stress models are employed to enhance our understanding of the underlying mechanisms and explore potential interventions. However, the utility of these models remains a critical concern, as their validities may be limited by the complexity of stress processes. Literature review revealed that both mental and physical stress models possess reasonable construct and criterion validities, respectively reflected in psychometrically assessed stress ratings and in activation of the sympathoadrenal system and the hypothalamic-pituitary-adrenal axis. The findings are less robust, though, in the pharmacological perturbations' domain, including such agents as adenosine or dobutamine. Likewise, stress models' convergent- and discriminant validity vary depending on the stressors' nature. Stress models share similarities, but also have important differences regarding their validities. Specific traits defined by the nature of the stressor stimulus should be taken into consideration when selecting stress models. Doing so can personalize prevention and treatment of stress-related antecedents, its acute processing, and chronic sequelae. Further work is warranted to refine stress models' validity and customize them so they commensurate diverse populations and circumstances.

Properties and Functions of Fibroblasts and Myofibroblasts in Myocardial Infarction

The adult mammalian heart contains abundant interstitial and perivascular fibroblasts that expand following injury and play a reparative role but also contribute to maladaptive fibrotic remodeling. Following myocardial infarction, cardiac fibroblasts undergo dynamic phenotypic transitions, contributing to the regulation of inflammatory, reparative, and angiogenic responses. This review manuscript discusses the mechanisms of regulation, roles and fate of fibroblasts in the infarcted heart. During the inflammatory phase of infarct healing, the release of alarmins by necrotic cells promotes a pro-inflammatory and matrix-degrading fibroblast phenotype that may contribute to leukocyte recruitment. The clearance of dead cells and matrix debris from the infarct stimulates anti-inflammatory pathways and activates transforming growth factor (TGF)-β cascades, resulting in the conversion of fibroblasts to α-smooth muscle actin (α-SMA)-expressing myofibroblasts. Activated myofibroblasts secrete large amounts of matrix proteins and form a collagen-based scar that protects the infarcted ventricle from catastrophic complications, such as cardiac rupture. Moreover, infarct fibroblasts may also contribute to cardiac repair by stimulating angiogenesis. During scar maturation, fibroblasts disassemble α-SMA+ stress fibers and convert to specialized cells that may serve in scar maintenance. The prolonged activation of fibroblasts and myofibroblasts in the infarct border zone and in the remote remodeling myocardium may contribute to adverse remodeling and to the pathogenesis of heart failure. In addition to their phenotypic plasticity, fibroblasts exhibit remarkable heterogeneity. Subsets with distinct phenotypic profiles may be responsible for the wide range of functions of fibroblast populations in infarcted and remodeling hearts.

The Role of Nrf2 in the PM-Induced Vascular Injury Under Real Ambient Particulate Matter Exposure in C57/B6 Mice

Short-and long-term exposure to particulate matter (PM) has been associated with cardiovascular disease (CVD). It is well recognized that oxidative stress is a potential major mechanism in PM-induced vascular injuries, in which the nuclear factor E2-related factor 2 (Nrf2) signaling pathway plays a critical role. In the current study, a Nrf2 knockout mouse model was used in combination with an individual ventilated cage (IVC)-based real-ambient PM exposure system to assess the potential vascular injury and the potential role of Nrf2 in the angiotensin II (Ang II)-associated vascular injury. After 6-or 11-week exposure to PM, the histopathology assay revealed that PM exposure resulted in the thickening of the walls of vascular. After 6 weeks exposure to PM, the ELISA assay revealed that PM exposure resulted in the elevated plasma concentration of Ang II. The expression levels of genes of interest were then further investigated with quantitative real-time PCR. Notably, the results showed that Angiotensinogen (AGT), Angiotensin converting enzyme (ACE) and Angiotensin type I receptor (AT1R) were involved in PM-induced pathological changes. Western blotting for ACE showed similar results. Moreover, the extent of vascular thickening and the Ang II elevation was most prominent in the Nrf2 gene knockout PM exposure group (KOE). Furthermore, the expression of Nrf2 downstream relevant genes (HO1, Nqo1, Gclc, Gsta4) were significantly enhanced in the wildtype PM exposure group (WTE), while those were remarkably suppressed in the Nrf2 gene knockout groups. The ELISA result of monocyte chemoattractant protein-1 (MCP-1) serum levels in the KOE group was significantly higher in relation to that in the Nrf2 knockout control group (KOC). In summary, PM exposure is associated with thickening of vascular wall, while Nrf2 knockout may further enhance this effect. A potential mechanistic contributor of such effects is the activation of ACE/ANGII/AT1R axis, in which Nrf2 played a regulatory role.

Inflammation in myocardial injury- Stem cells as potential immunomodulators for myocardial regeneration and restoration

The ineffective immunosuppressant's and targeted strategies to neutralize inflammatory mediators have worsened the scenario of heart failure and have opened many questions for debate. Stem cell therapy has proven to be a promising approach for treating heart following myocardial infarction (MI). Adult stem cells, induced pluripotent stem cells and embryonic stem cells are possible cell types and have successfully shown to regenerate damaged myocardial tissue in pre-clinical and clinical studies. Current implications of using mesenchymal stem cells (MSCs) owing to their immunomodulatory functions and paracrine effects could serve as an effective alternative treatment option for rejuvenating the heart post MI. The major setback associated with the use of MSCs is reduced cell retention, engraftment and decreased effectiveness. With a few reports on understanding the role of inflammation and its dual effects on the structure and function of heart, this review focuses on these missing insights and further exemplifies the role of MSCs as an alternative therapy in treating the pathological consequences in myocardial infarction (MI).

Brain-derived neurotrophic factor is related with adverse cardiac remodeling and high NTproBNP

The brain-derived neurotrophic factor (BDNF) is a neuronal growth factor essential for normal cardiac contraction and relaxation. Alterations in BDNF signaling are related to the development of cardiovascular disease. Whether BDNF is related to subclinical cardiac remodeling is unclear. We related BDNF with echocardiographic parameters and NTproBNP in a large population-based cohort (n = 2,976, median age 48 years; 45% male). Transthoracic echocardiography was performed on all subjects and BDNF was measured by ELISA. Study participants with severe kidney dysfunction, previous myocardial infarction, and LV ejection fraction <40% were excluded. Linear regression models were adjusted for age, sex, lean mass, fat mass, current smoking, systolic blood pressure and depression. Low BDNF was associated with high NTproBNP. A 10,000 pg/ml lower BDNF was related with a 2.5 g higher (95%-confidence interval [CI]: 0.2 to 4.9; p = 0.036) LV mass, 0.01 cm posterior wall thickness (0.003 to 0.022; p = 0.007) and 0.02 E/A ratio (0.003 to 0.042, p = 0.026). Here we show that low BDNF levels are related with adverse cardiac remodeling and higher levels of NTproBNP. Further research is warranted to assess if BDNF may be used to monitor neuronal-cardiac damage during CVD progression.

Anti-Apoptotic Effect of G-Protein-Coupled Receptor 40 Activation on Tumor Necrosis Factor-α-Induced Injury of Rat Proximal Tubular Cells

G-protein-coupled receptor 40 (GPR40) has an anti-apoptotic effect in pancreatic β-cells. However, its role in renal tubular cell apoptosis remains unclear. To explore the role of GPR40 in renal tubular apoptosis, a two-week unilateral ureteral obstruction (UUO) mouse model was used. The protein expression of GPR40 was decreased, while the Bax/Bcl-2 protein expression ratio, the expression of tumor necrosis factor (TNF)-α mRNA, and angiotensin II type 1 receptor (AT1R) protein were increased in mice with UUO. In vitro, pretreatment of rat proximal tubular (NRK52E) cells with GW9508, a GPR40 agonist, attenuated the decreased cell viability, increased the Bax/Bcl-2 protein expression ratio, increased protein expression of cleaved caspase-3 and activated the nuclear translocation of nuclear factor-κB (NF-κB) p65 subunit induced by TNF-α treatment. TNF-α treatment significantly increased the expression of AT1R protein and the generation of reactive oxygen species (ROS), whereas GW9508 treatment markedly reversed these effects. Pretreatment with GW1100, a GPR40 antagonist, or silencing of GPR40 in NRK52E cells promoted the increased expression of the cleaved caspase-3 protein by TNF-α treatment. Our results demonstrate that decreased expression of GPR40 is associated with apoptosis via TNF-α and AT1R in the ureteral obstructed kidney. The activation of GPR40 attenuates TNF-α-induced apoptosis by inhibiting AT1R expression and ROS generation through regulation of the NF-κB signaling pathway.

Mechanisms of cardiac collagen deposition in experimental models and human disease

The inappropriate deposition of extracellular matrix within the heart (termed cardiac fibrosis) is associated with nearly all types of heart disease, including ischemic, hypertensive, diabetic, and valvular. This alteration in the composition of the myocardium can physically limit cardiomyocyte contractility and relaxation, impede electrical conductivity, and hamper regional nutrient diffusion. Fibrosis can be grossly divided into 2 types, namely reparative (where collagen deposition replaces damaged myocardium) and reactive (where typically diffuse collagen deposition occurs without myocardial damage). Despite the widespread association of fibrosis with heart disease and general understanding of its negative impact on heart physiology, it is still not clear when collagen deposition becomes pathologic and translates into disease symptoms. In this review, we have summarized the current knowledge of cardiac fibrosis in human patients and experimental animal models, discussing the mechanisms that have been deduced from the latter in relation to the former. Because assessment of the extent of fibrosis is paramount both as a research tool to further understanding and as a clinical tool to assess patients, we have also summarized the current state of noninvasive/minimally invasive detection systems for cardiac fibrosis. Albeit not exhaustive, our aim is to provide an overview of the current understanding of cardiac fibrosis, both clinically and experimentally.

Nandrolone alter left ventricular contractility and promotes remodelling involving calcium-handling proteins and renin-angiotensin system in male SHR

AIMS

Hypertension is a highly prevalent disease that has been correlated to severe organ damage and mortality. However, the role of androgens in hypertension is controversial. The aim of this study was to evaluate the cardiac effects of the nandrolone decanoate (NDL) in male SHR.

MAIN METHODS

At 12 weeks of age, male SHR rats were separated into three groups: Control (CON), Nandrolone 10 mg/kg twice weekly (NDL), and NDL plus Enalapril 10 mg/kg/day (NDL-E) groups. The animals were treated for 4 weeks. Haemodynamic parameters were acquired through ventricular catheter implantation. The left ventricle was stained with haematoxylin/eosin or picrosirius red. Western blot analysis of TNF-α, ACE, AT₁R, β₁-AR, PLB, p-PLB^ser16 and SERCA2a was performed.

KEY FINDINGS

Nandrolone increased hypertension in SHR rats and enalapril reduced blood pressure to values below those of the control. NDL increased +dP/dt_max, -dP/dt_max and cardiac hypertrophy, which were prevented in the NDL-E group. Cardiac collagen deposition was increased in the NDL group, with this effect being attenuated by enalapril in NDL-E animals. TNF-α, ACE, AT₁R and β1-AR proteins were increased in the NDL, and enalapril decreased them, except for TNF-α. The ratio p-PLB^ser16/PLB revealed an increase after nandrolone, which was prevented in the NDL-E group. The SERCA2a expression protein and SERCA2a/PLB were increased in NDL animals, which did not occur in the NDL-E group.

SIGNIFICANCE

Nandrolone has distinct effects on cardiac function and remodelling in male SHR, altering the hypertension development process in the heart through modulation of calcium handling proteins and the renin-angiotensin system.

Serum brain-derived neurotrophic factor and risk of atrial fibrillation

Brain-derived neurotrophic factor (BDNF) is expressed by endothelial cells and can affect cardiovascular function. We examined if serum BDNF was associated with risk of incident atrial fibrillation (AF) in the Framingham Heart Study.

METHODS

We studied individuals without an AF diagnosis at baseline from the Framingham original and offspring cohorts. We used age- and sex-adjusted, and multivariable-adjusted Cox proportional hazards regression models to examine the association of serum BDNF concentrations with 10-year risk of incident AF.

RESULTS

We studied 3,457 participants (mean age 65±11years, 58% women). During follow-up, 395 participants developed AF. In unadjusted analysis, higher mean serum BDNF concentration was associated with lower incidence of AF (hazard ratio 0.89 per SD, 95% CI 0.80-0.99). In multivariable-adjusted analyses, serum BDNF concentration was not significantly associated with incident AF (hazard ratio 0.98 per SD, 95% CI 0.88-1.09). Compared with the lowest quartile, BDNF levels in the other quartiles were not associated with risk of AF in multivariable-adjusted analyses. No interactions between sex or age with serum BDNF concentrations and risk of AF were found.

CONCLUSIONS

In our prospective, community-based sample, we did not find a statistically significant association of serum BDNF levels with risk of incident AF.

Update on RAAS Modulation for the Treatment of Diabetic Cardiovascular Disease

Since the advent of insulin, the improvements in diabetes detection and the therapies to treat hyperglycemia have reduced the mortality of acute metabolic emergencies, such that today chronic complications are the major cause of morbidity and mortality among diabetic patients. More than half of the mortality that is seen in the diabetic population can be ascribed to cardiovascular disease (CVD), which includes not only myocardial infarction due to premature atherosclerosis but also diabetic cardiomyopathy. The importance of renin-angiotensin-aldosterone system (RAAS) antagonism in the prevention of diabetic CVD has demonstrated the key role that the RAAS plays in diabetic CVD onset and development. Today, ACE inhibitors and angiotensin II receptor blockers represent the first line therapy for primary and secondary CVD prevention in patients with diabetes. Recent research has uncovered new dimensions of the RAAS and, therefore, new potential therapeutic targets against diabetic CVD. Here we describe the timeline of paradigm shifts in RAAS understanding, how diabetes modifies the RAAS, and what new parts of the RAAS pathway could be targeted in order to achieve RAAS modulation against diabetic CVD.

Immune Mechanisms Linking Obesity and Preeclampsia

Preeclampsia (PE) is characterized by hypertension occurring after the twentieth week of pregnancy. It is a significant contributor to maternal and perinatal morbidity and mortality in developing countries and its pervasiveness is increasing within developed countries including the USA. However, the mechanisms mediating the pathogenesis of this maternal disorder and its rising prevalence are far from clear. A major theory with strong experimental evidence is that placental ischemia, resulting from inappropriate remodeling and widening of the maternal spiral arteries, stimulates the release of soluble factors from the ischemic placenta causing maternal endothelial dysfunction and hypertension. Aberrant maternal immune responses and inflammation have been implicated in each of these stages in the cascade leading to PE. Regarding the increased prevalence of this disease, it is becoming increasingly evident from epidemiological data that obesity, which is a state of chronic inflammation in itself, increases the risk for PE. Although the specific mechanisms whereby obesity increases the rate of PE are unclear, there are strong candidates including activated macrophages and natural killer cells within the uterus and placenta and activation in the periphery of T helper cells producing cytokines including TNF-α, IL-6 and IL-17 and the anti-angiogenic factor sFlt-1 and B cells producing the agonistic autoantibodies to the angiotensin type 1 receptor (AT1-aa). This review will focus on the immune mechanisms that have been implicated in the pathogenesis of hypertension in PE with an emphasis on the potential importance of inflammatory factors in the increased risk of developing PE in obese pregnancies.

Tumor Necrosis Factor - Alpha Is Essential for Angiotensin II-Induced Ventricular Remodeling: Role for Oxidative Stress

The functional crosstalk between angiotensin II (Ang II) and tumor necrosis factor (TNF)-α has been shown to cause adverse left ventricular remodeling and hypertrophy in hypertension. Previous studies from our lab showed that mice lacking TNF-α (TNF-α^-/-) have attenuated hypertensive response to Ang II; however, the signaling mechanisms involved are not known. In this study, we investigated the signaling pathways involved in the Ang II and TNF-α interaction. Chronic Ang II infusion (1μg/kg/min, 14 days) significantly increased cardiac collagen I, collagen III, CTGF and TGF-β mRNA and protein expression in wild-type (WT) mice, whereas these changes were decreased in TNF-α^-/- mice. TNF-α^-/- mice with Ang II infusion showed reduced myocardial perivascular and interstitial fibrosis compared to WT mice with Ang II infusion. In WT mice, Ang II infusion increased reactive oxygen species formation and the expression of NADPH oxidase subunits, indicating increased oxidative stress, but not in TNF-α^-/- mice. In addition, treatment with etanercept (8 mg/kg, every 3 days) for two weeks blunted the Ang II-induced hypertension (133±4 vs 154±3 mmHg, p<0.05) and cardiac hypertrophy (heart weight to body weight ratio, 4.8±0.2 vs 5.6±0.3, p<0.05) in WT mice. Furthermore, Ang II-induced activation of NF-κB, p38 MAPK, and JNK were reduced in both TNF-α^-/- mice and mice treated with etanercept. Together, these findings indicate that TNF-α contributes to Ang II-induced hypertension and adverse cardiac remodeling, and that these effects are associated with changes in the oxidative stress dependent MAPK/TGF-β/NF-κB pathway. These results may provide new insight into the mechanisms of Ang II and TNF-α interaction.

Acute and subchronic exposure to air particulate matter induces expression of angiotensin and bradykinin-related genes in the lungs and heart: Angiotensin-II type-I receptor as a molecular target of particulate matter exposure

Background

Particulate matter (PM) adverse effects on health include lung and heart damage. The renin-angiotensin-aldosterone (RAAS) and kallikrein-kinin (KKS) endocrine systems are involved in the pathophysiology of cardiovascular diseases and have been found to impact lung diseases. The aim of the present study was to evaluate whether PM exposure regulates elements of RAAS and KKS.

Methods

Sprague–Dawley rats were acutely (3 days) and subchronically (8 weeks) exposed to coarse (CP), fine (FP) or ultrafine (UFP) particulates using a particulate concentrator, and a control group exposed to filtered air (FA). We evaluated the mRNA of the RAAS components At1, At2r and Ace, and of the KKS components B1r, B2r and Klk-1 by RT-PCR in the lungs and heart. The ACE and AT₁R protein were evaluated by Western blot, as were HO-1 and γGCSc as indicators of the antioxidant response and IL-6 levels as an inflammation marker.

We performed a binding assay to determinate AT₁R density in the lung, also the subcellular AT₁R distribution in the lungs was evaluated. Finally, we performed a histological analysis of intramyocardial coronary arteries and the expression of markers of heart gene reprogramming (Acta1 and Col3a1).

Results

The PM fractions induced the expression of RAAS and KKS elements in the lungs and heart in a time-dependent manner. CP exposure induced Ace mRNA expression and regulated its protein in the lungs. Acute and subchronic exposure to FP and UFP induced the expression of At1r in the lungs and heart. All PM fractions increased the AT₁R protein in a size-dependent manner in the lungs and heart after subchronic exposure. The AT₁R lung protein showed a time-dependent change in subcellular distribution. In addition, the presence of AT₁R in the heart was accompanied by a decrease in HO-1, which was concomitant with the induction of Acta1 and Col3a1 and the increment of IL-6. Moreover, exposure to all PM fractions increased coronary artery wall thickness.

Conclusion

We demonstrate that exposure to PM induces the expression of RAAS and KKS elements, including AT₁R, which was the main target in the lungs and the heart.

Protective and Therapeutic Effects of Chinese Medicine Formula Jiajian Yunvjian on Experimental Cardiac Remodeling after Myocardial Infarction Induced by Coronary Artery Ligation

Introduction. This study was designed to explore the effect and mechanism of a classic Chinese medicine formula Jiajian Yunvjian (JJYNJ) on cardiac remodeling. Cardiac remodeling after myocardial infarction (MI) model was achieved by coronary artery ligation (CAL). Methodology. When dosed orally once daily, the effects of JJYNJ on hemodynamics, left ventricular weight index (LVWI), heart weight index (HWI), concentration, and gene expression of neuroendocrine factors as well as the histomorphological observation were determined. Results. After 4 weeks, mild cardiac remodeling in CAL group was characterized compared with sham group, but after 4 weeks of treatment of JJYNJ, hemodynamics improved, HWI reduced, and circulating angiotensin II (Ang II), endothelin-1 (ET-1), tumor necrosis factor-α (TNF-α), and hydroxyproline (Hyp) concentrations as well as Ang II receptor type 1 (AT₁R) mRNA, transforming growth factor β₁ (TGF-β₁) mRNA, and TNF-α mRNA levels in myocardium were lower than in CAL group. Decreased plasma aldosterone (ALD) concentration, cross-sectional area of cardiomyocyte, collagen volume fraction (CVF), collagen types I and III, perivascular collagen area (PVCA), and upregulated nitric oxide (NO) levels were observed at the same time. Conclusions. These findings suggest that JJYNJ may have a protective and therapeutic function on cardiac remodeling related to MI.

Role of tumor necrosis factor alpha in the pathogenesis of atrial fibrillation: A novel potential therapeutic target?

Atrial fibrillation (AF) is the most common sustained arrhythmia in clinical practice and a major cause of morbidity and mortality. Although the fundamental mechanisms underlying AF remain incompletely understood, atrial remodeling, including structural, electrical, contractile, and autonomic remodeling, has been demonstrated to contribute to the substrate for AF maintenance. Accumulating evidence shows that tumor necrosis factor alpha (TNF-α) plays exceedingly important roles in atrial remodeling. This article reviews recent advances in the roles of TNF-α in the pathogenesis of AF, elucidates the related mechanisms, and exploits its potential usefulness as a novel therapeutic target.

Testosterone induces apoptosis in cardiomyocytes by increasing proapoptotic signaling involving tumor necrosis factor-α and renin angiotensin system

Anabolic androgenic steroids lead to cardiac complications and have been shown to exhibit proapoptotic effects in cardiac cells; however, the mechanism involved in those effects is unclear. The aim of this study was to assess whether apoptosis and the activation of caspase-3 (Casp-3) induced by testosterone in high concentrations involves increments in tumor necrosis factor-α (TNF-α) concentrations and angiotensin-converting enzyme (ACE) activity in cardiomyocytes (H9c2) cell cultures. Cardiomyocytes were treated with testosterone (5 × 10−6 mol/L), doxorubicin (9.2 × 10−6 mol/L), testosterone + etanercept (Eta; 6.67 × 10−5 mol/L), testosterone + losartan (Los; 10−7 mol/L), and testosterone + AC-DEVD-CHO (10−5 mol/L; Casp-3 inhibitor). Apoptosis was determined by flow cytometry and by the proteolytic activity of Casp-3. We demonstrated that incubation of H9c2 cells for 48 h with testosterone causes the apoptotic death of 60–70% of the cells and co-treatments with Eta, Los, or AC-DEVD-CHO reduced this effect. Testosterone also induces apoptosis (concentration dependent) and increases the proteolytic activity of Casp-3, which were reduced by co-treatments. TNF-α and ACE activities were elevated by testosterone treatment, while co-treatment with Los and Eta reduced these effects. We concluded that an interaction between testosterone, angiotensin II, and TNF-α induced apoptosis and Casp-3 activity in cultured cardiomyocytes, which contributed to the reduced viability of these cells induced by testosterone in toxic concentrations.

Drug-Disease Interactions: Losartan Effect Is Not Downregulated by Rheumatoid Arthritis

Inflammatory conditions, such as rheumatoid arthritis, reduce response to calcium channel and beta-adrenergic antagonists but not the angiotensin II type 1 receptor (AT(1)R) antagonist valsartan. Inflammation also reduces clearance of some drugs or active metabolite, thereby reducing response. Active (n = 14) and controlled rheumatoid arthritis (n = 12) and healthy subjects (n = 12) received losartan (100 mg). Blood pressures were measured, and samples were taken for pharmacokinetic and inflammatory mediator concentration determination. Active disease significantly increased arthritic index, nitric oxide, and Creactive protein. Although no between-group difference in plasma losartan concentration-time curves was observed, concentrations of the active metabolite, EXP 3174, were significantly reduced by arthritis. This, however, was not accompanied by reduced clinical response. One subject produced no detectable concentrations of EXP 3174 likely due to insufficient CYP2C9 activity. Despite reduced concentrations of the active metabolite, AT1R antagonists potency does not appear to be reduced by inflammation.

Nandrolone decanoate determines cardiac remodelling and injury by an imbalance in cardiac inflammatory cytokines and ACE activity, blunting of the Bezold-Jarisch reflex, resulting in the development of hypertension

The aims of this study were to evaluate the effects of nandrolone (ND) on cardiac inflammatory cytokines, ACE activity, troponin I, and the sensitivity of the Bezold-Jarisch reflex (BJR). Male Wistar rats were administered either ND (20 mg/kg; DECA) or vehicle (control animals; CONT) for 4 weeks. BJR was analyzed by measuring the bradycardia and hypotension responses elicited by serotonin administration (2-32 μg/kg). Mean arterial pressure (MAP) was assessed and myocyte hypertrophy was determined by the heart weight/body weight ratio and by morphometric analysis. Matrix collagen deposition was assessed by histological analysis of the picrosirius red-stained samples. Mesenteric vascular reactivity was performed and central venous pressure (CVP) evaluated. Cardiac inflammatory cytokine levels and angiotensin-converting enzyme (ACE) activity were studied as well the biomarker of cardiac lesion, troponin I. DECA group showed enhancement of matrix type I collagen deposition (p < 0.01) and cardiac ACE activity (p < 0.01) compared with the CONT. Interleukin (IL)-10 was reduced (p < 0.01) and pro-inflammatory cytokines (TNF-α and IL-6; p < 0.01) were increased in the DECA group compared with CONT. Cardiac injury was observed in the DECA group shown by the reduction in cardiac troponin I (p < 0.01) compared with the CONT group. Animals in the DECA group also developed myocyte hypertrophy and reduction of BJR sensitivity. The MAP of animals treated with ND reached hypertensive levels (p < 0.01; compared with CONT). No changes in CVP and vascular reactivity were observed in both experimental groups. We conclude that high doses of ND elicit cardiotoxic effects with cardiac remodelling and injury. Cardiac changes reduce the BJR sensitivity. Together, these abnormalities contributed to the development of hypertension in animals in the DECA group.

Increased circulating ANG II and TNF-α represents important risk factors in obese saudi adults with hypertension irrespective of diabetic status and BMI

Central adiposity is a significant determinant of obesity-related hypertension risk, which may arise due to the pathogenic inflammatory nature of the abdominal fat depot. However, the influence of pro-inflammatory adipokines on blood pressure in the obese hypertensive phenotype has not been well established in Saudi subjects. As such, our study investigated whether inflammatory factors may represent useful biomarkers to delineate hypertension risk in a Saudi cohort with and without hypertension and/or diabetes mellitus type 2 (DMT2). Subjects were subdivided into four groups: healthy lean controls (age: 47.9±5.1 yr; BMI: 22.9±2.1 Kg/m²), non-hypertensive obese (age: 46.1±5.0 yr; BMI: 33.7±4.2 Kg/m²), hypertensive obese (age: 48.6±6.1 yr; BMI: 36.5±7.7 Kg/m²) and hypertensive obese with DMT2 (age: 50.8±6.0 yr; BMI: 35.3±6.7 Kg/m²). Anthropometric data were collected from all subjects and fasting blood samples were utilized for biochemical analysis. Serum angiotensin II (ANG II) levels were elevated in hypertensive obese (p<0.05) and hypertensive obese with DMT2 (p<0.001) compared with normotensive controls. Systolic blood pressure was positively associated with BMI (p<0.001), glucose (p<0.001), insulin (p<0.05), HOMA-IR (p<0.001), leptin (p<0.01), TNF-α (p<0.001) and ANG II (p<0.05). Associations between ANG II and TNF-α with systolic blood pressure remained significant after controlling for BMI. Additionally CRP (p<0.05), leptin (p<0.001) and leptin/adiponectin ratio (p<0.001) were also significantly associated with the hypertension phenotype. In conclusion our data suggests that circulating pro-inflammatory adipokines, particularly ANG II and, TNF-α, represent important factors associated with a hypertension phenotype and may directly contribute to predicting and exacerbating hypertension risk.

Soluble CD163 is associated with body mass index and blood pressure in hypertensive obese Saudi patients

BACKGROUND

The hallmark of vascular inflammation is the recruitment of circulating leucocytes, primarily monocytes, macrophages and T lymphocytes, into the vascular wall; however, the link between monocyte/macrophage activation and hypertension has not been established as yet. In this study, we determined how sCD163, a monocyte/macrophage soluble scavenger receptor and immunomodulator, relates to arterial blood pressure (BP) in hypertensive Saudi individuals.

MATERIALS AND METHODS

A total of 90 (30 non-hypertensive obese, 30 hypertensive obese and 30 lean normotensive controls) adult Saudi subjects, aged 40-60 years, participated in this cross-sectional study. Serum fasting blood glucose, triglycerides, total cholesterol, HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), leptin, adiponectin, resistin, insulin, tumour necrosis factor-alpha (TNF-α), PAI-1, angiotensin II, high-sensitivity C-reactive protein (hsCRP) and sCD163 were measured in all subjects studied.

RESULTS

sCD163 concentrations were significantly increased in obese hypertensive patients compared to controls (P=0.016). Positive correlations between sCD163 and body mass index (BMI) (r=0.27, P=0.01), systolic BP (r=0.25, P=0.01), diastolic BP (r=0.33, P=0.001), LDL-C (r=0.21, P=0.04), TNF-α (r=0.23, P=0.02) and hsCRP (r=0.33, P=0.008) were observed. Positive correlations between sCD163 and diastolic BP (r=0.23, P=0.04) and LDL-C (r=0.22, P=0.03) remained significant after controlling for BMI.

CONCLUSIONS

Taken together, these data demonstrate that the monocyte/macrophage activation-related sCD163 is positively associated with BMI and increased arterial BP with the elevation in diastolic BP being independent of the BMI.

Soluble CD163 is associated with body mass index and blood pressure in hypertensive obese Saudi patients

Eur J Clin Invest 2012; 42 (11): 1221–1226

Abstract

Background  The hallmark of vascular inflammation is the recruitment of circulating leucocytes, primarily monocytes, macrophages and T lymphocytes, into the vascular wall; however, the link between monocyte/macrophage activation and hypertension has not been established as yet. In this study, we determined how sCD163, a monocyte/macrophage soluble scavenger receptor and immunomodulator, relates to arterial blood pressure (BP) in hypertensive Saudi individuals.

Materials and methods  A total of 90 (30 non‐hypertensive obese, 30 hypertensive obese and 30 lean normotensive controls) adult Saudi subjects, aged 40–60 years, participated in this cross‐sectional study. Serum fasting blood glucose, triglycerides, total cholesterol, HDL‐cholesterol (HDL‐C), LDL‐cholesterol (LDL‐C), leptin, adiponectin, resistin, insulin, tumour necrosis factor‐alpha (TNF‐α), PAI‐1, angiotensin II, high‐sensitivity C‐reactive protein (hsCRP) and sCD163 were measured in all subjects studied.

Results  sCD163 concentrations were significantly increased in obese hypertensive patients compared to controls (P = 0·016). Positive correlations between sCD163 and body mass index (BMI) (r = 0·27, P = 0·01), systolic BP (r = 0·25, P = 0·01), diastolic BP (r = 0·33, P = 0·001), LDL‐C (r = 0·21, P = 0·04), TNF‐α (r = 0·23, P = 0·02) and hsCRP (r = 0·33, P = 0·008) were observed. Positive correlations between sCD163 and diastolic BP (r = 0·23, P = 0·04) and LDL‐C (r = 0·22, P = 0·03) remained significant after controlling for BMI.

Conclusions  Taken together, these data demonstrate that the monocyte/macrophage activation‐related sCD163 is positively associated with BMI and increased arterial BP with the elevation in diastolic BP being independent of the BMI.

Total Flavonoids of Fructus Chorspondiatis inhibits collagen synthesis of cultured rat cardiac fibroblasts induced by angiotensin II: correlated with NO/cGMP signaling pathway

AIM

To investigate the molecular mechanism of Total Flavonoids of Fructus Chorspondiatis (TFFC) on preventing cardiac fibroblasts collagen synthesis induced by angiotensin II.

METHODS

Collagen synthesis was determined by measuring (3)H-proline incorporation cardiac fibroblasts and hydroxyproline content in the culture mediums. The expression of collagen types I and III mRNA and protein was measured by RT-PCR and western blot, respectively. NO level in the culture medium was measured by the Griess reagent. NOS level in the culture medium was measured by chemical colorimetric method. The cellular concentration of cyclic GMP (cGMP) was measured by radioimmunoassay.

RESULTS

TFFC (25, 50, and 100mg/L) inhibited collagen synthesis in cardiac fibroblasts in a dose-dependent manner compared with angiotensin II group (P<0.01), and the inhibitory effects were blocked by pretreatment with NG-nitro-L-arginine methyl ester (L-NAME) and 1H-[1,2,4]-oxadiazole-[4,3-a]-quinoxalin-1-one (ODQ). TFFC increased nitric oxide (NO) and nitric oxide synthase (NOS) levels in the culture medium, increased intracellular cGMP level in cardiac fibroblasts, decreased collagen types I and III protein level in cardiac fibroblasts. The mRNA expression of collagen type I and III was suppressed by TFFC.

CONCLUSIONS

These results suggested that TFFC inhibited collagen synthesis induced by angiotensin II in cardiac fibroblasts, and the inhibitory effect might associate with the activation of the NO/cGMP signaling pathway.

Drug therapy of heart failure: an immunologic view

Heart failure (HF) is a clinical syndrome manifested by signs and symptoms of low cardiac output, pulmonary, and/or systemic congestion. Immunologically, HF is defined as a state of immune activation and persistent inflammation, especially the circulatory levels of inflammatory cytokines have been found to increase. Traditional drugs used in HF have expressed immunomodulatory and/or anticytokine activities that may participate in their therapeutic efficacy in the disease. The angiotensin-converting enzyme inhibitors like captopril and enalapril as well as the angiotensin II receptor antagonist losartan indicated in HF exerted reducing effects on the inflammatory cytokines such as tumor necrosis factor-alpha and interleukin-6 at experimental and clinical levels. Aldosterone antagonists like spironolactone when administered concomitantly with losartan can attenuate angiotensin II-enhanced cytokine production in HF. Carvedilol beta-adrenergic blockers showed a wider spectrum of anti-inflammatory/anticytokine activity that proved to be associated with improvement of cardiac function and ejection fraction in patients with HF. The poor prognosis in HF despite the long experience with its treatment necessitated thinking about new drugs to be added to the traditional ones. Methotrexate and statins are examples of these drugs, especially because they exert immunologic effects. A low dose of methotrexate has been considered as a hopeful adjunct therapy in chronic HF, but large long-term clinical trials are required. Statins showed conflicting results, although they might be useful early after acute ischemic events associated with left ventricular dysfunction or failure, especially in younger patients with less advanced HF.

Low doses of simvastatin therapy ameliorate cardiac inflammatory remodeling in Trypanosoma cruzi-infected dogs

Chagas cardiomyopathy remodeling is based on the presence of Trypanosoma cruzi in heart tissue and on the complex inflammatory response leading to a myocardium fibrosis and alterations in conductive and functional heart parameters. This study aims to evaluate Simvastatin on the inflammatory response and heart functionality using dogs infected with Y strain of T. cruzi. Animals were treated daily with Simvastatin (20 mg) for 6 months and submitted to clinical and immunopathological evaluations. Simvastatin reduced heart expression and serum levels of interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) but not interleukin-10 (IL-10), possibly favoring blood parasitism but reducing inflammation and fibrosis in the left ventricle and right atrium. Simvastatin also ameliorated ejection fraction, diastolic diameter, and mass index of the left ventricle 6 months after infection. This study suggests that more investigation should be performed on the use of statins as a prophylactic therapy against cardiac remodeling because of their effects on modifying immune response and benefiting functional parameters in dogs with T. cruzi-induced ventricular dysfunctions.

Proinflammatory cytokines in heart failure: double-edged swords

Increased circulating and intracardiac levels of proinflammatory cytokines have been associated with chronic heart failure. Following an initial insult, the increased production of proinflammatory cytokines, including TNF-α, IL-6, IL-1, and IL-18, jeopardizes the surrounding tissue through propagation of the inflammatory response and direct effects on the cardiac myocyte structure and function. Cardiac myocyte hypertrophy, contractile dysfunction, cardiac myocyte apoptosis, and extracellular matrix remodeling contribute enormously to the development and progression of chronic heart failure. Despite the identification of efficacious pharmacological regimens and introduction of mechanical interventions, chronic heart failure remains among the leading causes of mortality worldwide. To introduce novel therapeutic strategies that modulate the inflammatory response in the context of the failing heart, it is of prime importance to determine the contributions of TNF-α, IL-6, IL-1, and IL-18 in mediating cardiac adaptive and maladaptive responses, as well as delineating their downstream intracellular signaling pathways and their potential therapeutic implications.

Interplay between miR-155, AT1R A1166C polymorphism, and AT1R expression in young untreated hypertensives

BACKGROUND

A silent polymorphism (+1166 A/C single-nucleotide polymorphism) localized in the 3'-UTR (untranslated region) of the human angiotensin II type-1 receptor (AT1R) has been associated with hypertension and cardiovascular complications. The +1166 A/C is recognized by a specific microRNA-155 (miR-155), which is base-pairing complementary with the +1166 A-allele but not with the mutant +1166 C allele. Aim of our study was to investigate the interplay between miR-155 and AT1R protein expression.

METHODS

Sixty-four subjects were selected for the +1166 A/C from the cohort of hypertensives (n = 573) of the Hypertension and Ambulatory Recording Venetia Study (HARVEST): 25 were homozygous for the 1166 A allele, 20 heterozygous, and 19 homozygous for the 1166 C allele.

RESULTS

miR-155 expression was significantly decreased in subjects with CC genotype in comparison to AA and AC genotype. AT1R protein expression was significantly increased in the CC group in comparison to AA and AC (P < 0.01) although AT1R mRNA expression was not significantly different in the three groups. AT1R protein expression was positively correlated with systolic and diastolic blood pressure and negatively correlated with miR-155 expression level. Plasma transforming growth factor-β1 (TGF-β1) may have a modulator role in the interplay between miR-155 and AT1R protein expression as it was correlated negatively with miR-155 expression and positively with AT1R protein expression in subjects with CC genotype.

CONCLUSION

The interplay between miR-155 expression, +1166C polymorphism, and AT1R protein expression may have a role in the regulation of blood pressure.

Role of adipokines in obesity-associated hypertension

It has been well documented that obesity is a major risk factor for the development of the hypertensive state. The correlation between body mass index and blood pressure level is well established. Nevertheless, the exact mechanisms which contribute to obesity-related hypertension remain poorly understood. In the last years, we have realized that the white adipose tissue is not just an inert organ for nutrient storage and isolation but rather depending on the body mass index the biggest endocrinological organ. Thus, the possible contribution of adipokines to the blood pressure elevation becomes an attractive hypothesis to explain the hypertensive state that often occurs in obesity. In this review, we consider direct and indirect effects of main adipokines on structural and functional changes in the cardiovascular system.

Aliskiren, a renin inhibitor, downregulates TNF-α-induced tissue factor expression in HUVECS

Angiotensin (Ang)II, the effector arm of the locally active renin—angiotensin system (RAS), modulates Tissue Factor (TF), the principal initiator of blood coagulation and a key promoter of atherothrombotic events. Consistent with that knowledge, previous data showed inhibitory properties of angiotensin-converting enzyme inhibitor (ACEI)s and angiotensin II type-1 receptor blocker (ARB)s, but no data are available about the effect of renin inhibition. We aimed to evaluate whether aliskiren, a direct renin inhibitor (DRI), modulates TNF-α-stimulated TF expression in cultured human umbilical vein endothelial cells (HUVECs). Zofenopril, an ACEI, and olmesartan, an ARB, were the controls. HUVECs were incubated with experimental drugs (1 nM) 30 min prior to TNF-α stimulation (0.1 ng/ml × 4 h). Main evaluation variables were procoagulant activity (single-stage clotting assay), TF antigen (ELISA) and mRNA expression (real-time polymerase chain reaction) in cell lysates. TNF-α stimulated procoagulant activity and increased TF antigen and mRNA expression. Aliskiren inhibited TNF-α-mediated TF stimulation; zofenopril and olmesartan exerted a comparable effect. We conclude that aliskiren, a DRI, downregulates TNF-α-stimulated TF expression in HUVECs, possibly as a reflection of endothelial renin activation by the cytokine.

Cardiac fibroblasts: at the heart of myocardial remodeling

Cardiac fibroblasts are the most prevalent cell type in the heart and play a key role in regulating normal myocardial function and in the adverse myocardial remodeling that occurs with hypertension, myocardial infarction and heart failure. Many of the functional effects of cardiac fibroblasts are mediated through differentiation to a myofibroblast phenotype that expresses contractile proteins and exhibits increased migratory, proliferative and secretory properties. Cardiac myofibroblasts respond to proinflammatory cytokines (e.g. TNFalpha, IL-1, IL-6, TGF-beta), vasoactive peptides (e.g. angiotensin II, endothelin-1, natriuretic peptides) and hormones (e.g. noradrenaline), the levels of which are increased in the remodeling heart. Their function is also modulated by mechanical stretch and changes in oxygen availability (e.g. ischaemia-reperfusion). Myofibroblast responses to such stimuli include changes in cell proliferation, cell migration, extracellular matrix metabolism and secretion of various bioactive molecules including cytokines, vasoactive peptides and growth factors. Several classes of commonly prescribed therapeutic agents for cardiovascular disease also exert pleiotropic effects on cardiac fibroblasts that may explain some of their beneficial outcomes on the remodeling heart. These include drugs for reducing hypertension (ACE inhibitors, angiotensin receptor blockers, beta-blockers), cholesterol levels (statins, fibrates) and insulin resistance (thiazolidinediones). In this review, we provide insight into the properties of cardiac fibroblasts that underscores their importance in the remodeling heart, including their origin, electrophysiological properties, role in matrix metabolism, functional responses to environmental stimuli and ability to secrete bioactive molecules. We also review the evidence suggesting that certain cardiovascular drugs can reduce myocardial remodeling specifically via modulatory effects on cardiac fibroblasts.

Chronic etanercept treatment prevents the development of hypertension in fructose-fed rats

The purpose of this study was to investigate the effect of chronic treatment with etanercept (a soluble recombinant fusion protein consisting of the extracellular ligand-binding domain of tumor necrosis factor receptor type 2) on the development of hypertension in fructose-fed rats (FFR). High fructose feeding and treatment with etanercept (0.3 mg/kg, three times per week) was initiated simultaneously in male Wistar rats. Systolic blood pressure, fasted plasma parameters, insulin sensitivity, vascular reactivity, plasma angiotensin II (Ang II), and norepinephrine were determined following 9 weeks of treatment. FFR exhibited insulin resistance, hyperinsulinemia, hypertriglyceridemia, endothelial dysfunction, and hypertension. Treatment with etanercept prevented the rise in blood pressure without affecting insulin levels, insulin sensitivity, triglycerides, or Ang II levels in FFR. Etanercept treatment improved acetylcholine-induced relaxation and normalized endothelial nitric oxide synthase expression in aortas from FFR. The results of this study suggest that treatment with etanercept prevented the development of hypertension by improving vascular function and restoring endothelial nitric oxide synthase expression in FFR.

Ameliorative effect of Captopril and Valsartan on an animal model of diabetic cardiomyopathy

The objective of this study was to clarify the relationship between angiotensin II and the pathogenesis of diabetic cardiomyopathy by observing the effects of related drugs on diabetic cardiomyopathy in rats. Captopril and Valsartan, an automatic biochemical analyzer, and radioimmunoassay technology were used to an experimental rat model of diabetic cardiomyopathy to dynamically measure the levels of creatine kinase-MB, lactate dehydrogenase-1 in the serum, and angiotensin I and II in the plasma, and to observe changes in the myocardial ultrastructure. The content of angiotensin I and II was increased and the renin-angiotensin system was in a hyperfunctional state in experimental rats with myocardial damage. Angiotensin-converting enzyme inhibitors and angiotensin II receptor 1 antagonists improved the myocardial structure and cardiac function. It is concluded that hyperfunction of the renin-angiotensin system is involved in the pathogenesis of diabetic cardiomyopathy, with an increase in angiotensin being a key factor. Preventing the increase in angiotensin II or the action of angiotensin II on its receptor can prevent the occurrence and development of diabetic cardiomyopathy.

Macrophage roles following myocardial infarction

Following myocardial infarction (MI), circulating blood monocytes respond to chemotactic factors, migrate into the infarcted myocardium, and differentiate into macrophages. At the injury site, macrophages remove necrotic cardiac myocytes and apoptotic neutrophils; secrete cytokines, chemokines, and growth factors; and modulate phases of the angiogenic response. As such, the macrophage is a primary responder cell type that is involved in the regulation of post-MI wound healing at multiple levels. This review summarizes what is currently known about macrophage functions post-MI and borrows literature from other injury and inflammatory models to speculate on additional roles. Basic science and clinical avenues that remain to be explored are also discussed.

Involvement of tumor necrosis factor-alpha in angiotensin II-mediated effects on salt appetite, hypertension, and cardiac hypertrophy

Hypertension is considered a low-grade inflammatory condition induced by various proinflammatory cytokines, including tumor necrosis factor (TNF)-alpha. Recent studies have implicated an involvement of TNF-alpha in the development of salt-sensitive hypertension induced by angiotensin II (Ang II). To understand further the relationship between TNF-alpha and Ang II, we examined the responses to Ang II in TNF-alpha knockout (TNF-alpha(-/-)) mice in the present study. A continuous infusion of Ang II (1 microg/kg per minute) for 2 weeks was given to both TNF-alpha(-/-) and wild-type (WT) mice with implanted osmotic minipumps. Daily measurement of water intake, salt intake, and urine output were performed using metabolic cages. Blood pressure was monitored continuously with implanted radiotelemetry. Ang II administration for 2 weeks caused increases in salt (0.2+/-0.07 to 5.6+/-0.95 mL/d) and water (5.4+/-0.34 to 11.5+/-1.2 mL/d) intake and in mean arterial pressure (115+/-1 to 151+/-3 mm Hg) in wild-type mice, but these responses were absent in TNF-alpha(-/-) mice (0.2+/-0.04 to 0.3+/-0.09 mL/d, 5.5+/-0.2 to 6.1+/-0.07 mL/d, and 113+/-2 to 123+/-3 mm Hg, respectively). Cardiac hypertrophy induced by Ang II was significantly attenuated in TNF-alpha(-/-) mice compared with wild-type mice. In a group of TNF-alpha(-/-) mice, when replacement therapy was made with recombinant TNF-alpha, Ang II induced similar responses in salt appetite, mean arterial pressure, and cardiac hypertrophy, as observed in wild-type mice. These results suggest that TNF-alpha plays a mechanistic role in mediating chronic Ang II-induced effects on salt appetite and blood pressure, as well as on cardiac hypertrophy.

Angiotensin II receptor blocker inhibits tumour necrosis factor-alpha-induced cell damage in human renal proximal tubular epithelial cells

AIM

We investigated the effect of angiotensin II (AII) type 1 (AT1) and angiotensin II type 2 (AT2) receptor blockers on tumour necrosis factor alpha (TNF-alpha)-induced cell damage in human renal proximal tubular epithelial cells (RPTEC).

METHODS

The lactate dehydrogenase (LDH) and N-acetyl-beta-glucosaminidase (NAG) release into the medium after TNF-alpha treatment in RPTEC were determined using modified commercial procedures. In addition, the levels of caspase 3/7 activity in RPTEC were measured after TNF-alpha treatment with AlphaTau1 or AT2 receptor blockers. Finally we investigated the change of p22phox protein levels after TNF-alpha with AlphaTau1 or AT2 receptor blockers in RPTEC.

RESULTS

Tumour necrosis factor alpha (10(-8) mol/L) significantly increased LDH and NAG release into the medium from RPTEC. AlphaTau1 receptor blockers, olmesartan and valsartan (10(-9)-10(-6) mol/L) showed a significant reduction on TNF-alpha-induced LDH and NAG release in RPTEC. AT2 receptor blocker, PD123319 (10(-7)-10(-5) mol/L) also decreased TNF-alpha-induced LDH and NAG release in RPTEC. Blockade of both AlphaTau1 and AT2 receptor indicated additional reduction on TNF-alpha-induced LDH and NAG release. TNF-alpha (10(-8) mol/L) treatment showed small but significant increases of caspase 3/7 activity in RPTEC, and AT1 and AT2 receptor blockers (10(-8) mol/L) comparably decreased TNF-alpha-induced caspase 3/7 activity. Significant increases of p22phox protein levels were observed in TNF-alpha-treated group in RPTEC. However, only AlphaTau1 (10(-8) mol/L) but not AT2 (10(-5) mol/L) receptor blocker significantly decreased TNF-alpha-induced p22phox protein levels.

CONCLUSION

The present study demonstrates that TNF-alpha induces renal tubular cell damage in RPTEC and AT1/AT2 receptor blockers showed cytoprotective effects probably via at least partly different mechanism.

Cytokines, interstitial collagen and ventricular remodelling in dilated cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) is associated with myocardial fibrosis, and proinflammatory cytokines may play a role in this.

METHODS

N-terminal type I and III procollagen propeptides (PINP, PIIINP) and cross-linked telopeptide of type I collagen (ICTP) were measured from serum samples of 73 patients with DCM and 56 age and sex matched controls. Circulating cytokine levels were determined in DCM patients.

RESULTS

Serum levels of PINP and PIIINP were lower in patients than in controls (p<0.05 and p=0.001). In patients with DCM, the levels of PIIINP and ICTP correlated significantly with each other (p<0.01), and the proinflammatory cytokines, tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6), correlated positively with ICTP (p<0.001, p<0.05), PIIINP/PINP ratio (p<0.05, p<0.01) and left atrial size (p<0.01, p<0.05). Presence of atrial fibrillation was associated with lower serum PINP level and higher PIIINP/PINP ratio (p<0.05).

CONCLUSIONS

Our results suggest that interstitial myocardial collagen metabolism is altered in DCM patients and regulated by proinflammatory cytokines. These changes in collagen metabolism are associated with presence of atrial fibrillation, but do not reflect left ventricular remodelling. Treatment with beta-blockers and inhibitors of the renin angiotensin aldosterone system seem to effectively inhibit overall type I and III collagen syntheses.

Transforming growth factor-beta receptor antagonism attenuates myocardial fibrosis in mice with cardiac-restricted overexpression of tumor necrosis factor

The mechanisms that are responsible for the development of myocardial fibrosis in inflammatory cardiomyopathy are unknown. We have previously generated lines of transgenic mice with cardiac-restricted overexpression of tumor necrosis factor (MHCsTNF mice), a pro-inflammatory cytokine. The MHCsTNF mice develop a heart failure phenotype that is characterized by progressive myocardial fibrosis, as well as increased levels transforming growth factor-beta (TGF-beta)(mRNA and protein. In order to determine whether TGF-beta-mediated signaling was responsible for the myocardial fibrosis observed in the MHCsTNF mice, we treated MHCsTNF and littermate control mice from 4 to 12 weeks of age with a novel orally available TGF-beta receptor antagonist (NP-40208). At the time of terminal study, myocardial collagen content was determined using the picrosirius red technique, and left ventricular (LV) systolic and diastolic function were determined using the Langendorff method. Treatment with NP-40208 resulted in a significant (P < 0.05) 65% decrease in nuclear translocation of Smad 2/3, a significant (P < 0.05), decrease in the heart-weight to body-weight ratio from 6.5 to 5.7, a approximately 37% decrease in fibrillar collagen content (P < 0.01) and a significant (P < 0.05) decrease in the LV chamber stiffness by approximately 25% in the MHCsTNF mice when compared to diluent-treated controls. Treatment with NP-40208 had no discernable effect on LV systolic function, nor any effect on cardiac myocyte size or fetal gene expression in the MHCsTNF mice. Taken together, these observations suggest that sustained pro-inflammatory signaling in the adult heart is associated with a pro-fibrotic phenotype that arises, at least in part, from TGF-beta-mediated signaling, with resultant activation of Smad 2/3, leading to increased myocardial fibrosis and increased LV diastolic chamber stiffness.

Urotensin II accelerates cardiac fibrosis and hypertrophy of rats induced by isoproterenol

AIM

To study whether urotensin II (UII), a potent vasoconstrictive peptide, is involved in the development of cardiac hypertrophy and fibrogenesis of rats induced by isoproterenol (ISO).

METHODS

Thirty male Wistar rats were randomly divided into 3 groups. Group 1 was the healthy control group, group 2 was the ISO group, and group 3 was the ISO+UII group. In groups 2 and 3, ISO (5 mg x kg(-1) x d(-1)) was given (sc) once daily for 7 d. Group 3 was also given UII in the first day [3 nmol/kg (5 microg/kg), iv], followed by sc (1.5 microg/kg) twice daily. Group 1 received 0.9% saline. UII receptor (UT) mRNA expression was determined by RT-PCR. The contents of UII and angiotensin II (Ang II) were determined by radioimmunoassay. In vitro, the effects of UII on DNA/collagen synthesis of cardiac fibroblasts were determined by [3H]thymidine/[3H]proline incorporation.

RESULTS

The ratio of heart weight/body weight, plasma lactate dehydrogenase activity, myocardial malondialdehyde and hydroxyproline concentration increased significantly in the ISO group, as well as UT mRNA expression, plasma and cardiac UII and ventricular Ang II, compared with the control group (P< 0.01). ISO induced significant myocardial fibrogenesis. Moreover, UII+ISO co-treatment significantly increased the changes of biochemical markers of injury and the degree of cardiac hypertrophy and fibrosis. In vitro, 5 x 10(-9 )-5 x 10(-7 ) mol/L UII stimulated [3H]thymidine/[3H] proline incorporation into cardiac fibroblasts in a dose-dependent manner (P< 0.01).

CONCLUSION

These results suggest that UII was involved in the development of cardiac fibrosis and hypertrophy by synergistic effects with ISO.

The mechanistic basis of infarct healing

Myocardial infarction triggers an inflammatory cascade that results in healing and replacement of the damaged tissue with scar. Cardiomyocyte necrosis triggers innate immune mechanisms eliciting Toll-like receptor- mediated responses, activating the complement cascade and generating reactive oxygen species. Subsequent activation of NF-kappaB is a critical element in the regulation of cytokine, chemokine, and adhesion molecule expression in the ischemic myocardium. Chemokine induction mediates leukocyte recruitment in the myocardium. Pleiotropic proinflammatory cytokines, such as TNF-alpha, IL-1, and IL-6, are also upregulated in the infarct and exert a wide range of effects on a variety of cell types. Timely repression of proinflammatory gene synthesis is crucial for optimal healing; IL-10 and TGF-beta-mediated pathways may be important for suppression of chemokine and cytokine expression and for resolution of the leukocytic infiltrate. In addition, TGF-beta may be critically involved in inducing myofibroblast differentiation and activation, promoting extracellular matrix protein deposition in the infarcted area. The composition of the extracellular matrix plays an important role in regulating cell behavior. Both structural and matricellular proteins modulate cell signaling through interactions with specific surface receptors. The molecular and cellular changes associated with infarct healing directly influence ventricular remodeling and affect prognosis in patients with myocardial infarction.

AT1 Receptor Blockade Prevents Cardiac Dysfunction after Myocardial Infarction in Rats

Myocardial infarction (MI) can induce severe alterations of contractile function that can, in turn, lead to heart failure. In a previous study, we have demonstrated that TNF-alpha was involved in cardiac contractile dysfunction 7 days after coronary artery ligation in rats. Since Angiotensin II type 1 (AT1) receptor can be involved in TNF-alpha production, we have investigated whether early short-term treatment with irbesartan, an AT1 receptor blocker, is able to limit TNF-alpha production within the heart and to improve cardiac function and geometry following MI in rats. Male Wistar rats were subjected to permanent coronary artery ligation and received either a placebo or irbesartan (50 mg/kg/day) per os daily from day 3 to day 6 after surgery. On day 7, cardiac TNF-alpha was significantly reduced in MI rats receiving irbesartan (p < 0.05). Moreover, irbesartan improved residual LV end-diastolic pressure under both basal conditions and after volume overload (p < 0.01). In addition, a significant leftward shift of the pressure-volume curve in the irbesartan-treated group was found versus placebo. Finally, infarct expansion index was also significantly improved by irbesartan (p < 0.01). In conclusion, early, short-term AT1 receptor blockade limits post-infarct cardiac TNF-alpha production and diminishes myocardial alterations observed 7 days after MI in the rat.

Angiotensin-(1-7) binds to specific receptors on cardiac fibroblasts to initiate antifibrotic and antitrophic effects

ANG-(1-7) improves the function of the remodeling heart. Although this peptide is generated directly within the myocardium, the effects of ANG-(1-7) on cardiac fibroblasts that play a critical role in cardiac remodeling are largely unknown. We tested the hypothesis that specific binding of ANG-(1-7) to cardiac fibroblasts regulates cellular functions that are involved in cardiac remodeling. 125I-labeled ANG-(1-7) binding assays identified specific binding sites of ANG-(1-7) on adult rat cardiac fibroblasts (ARCFs) with an affinity of 11.3 nM and a density of 131 fmol/mg protein. At nanomolar concentrations, ANG-(1-7) interacted with specific sites that were distinct from ANG II type 1 and type 2 receptors without increasing cytosolic Ca2+ concentration. At these concentrations, ANG-(1-7) had inhibitory effects on collagen synthesis as assessed by [3H]proline incorporation and decreased mRNA expression of growth factors in ARCFs. These effects of ANG-(1-7) contrasted with effects of ANG II. Pretreatment of ARCFs with ANG-(1-7) inhibited ANG II-induced increases in collagen synthesis and in mRNA expression of growth factors, including endothelin-1 and leukemia inhibitory factor. ANG-(1-7) pretreatment also inhibited the stimulatory effects of conditioned medium from ANG II-treated ARCFs on [3H]leucine incorporation and atrial natriuretic factor mRNA expression, markers of hypertrophy, in cardiomyocytes. Thus ANG-(1-7) interacted with specific receptors on ARCFs to exert potential antifibrotic and antitrophic effects that could reverse ANG II effects. These results suggest that ANG-(1-7) may play an important role in the heart in regulating cardiac remodeling.

Effects of cytokine treatment on angiotensin II type 1A receptor transcription and splicing in rat cardiac fibroblasts

Angiotensin II (ANG II) plays important roles in cardiac extracellular matrix remodeling via its type 1A (AT(1A)) receptor. The cytokines tumor necrosis factor-alpha and interleukin-1beta (IL-1beta) were shown previously to upregulate AT(1A) receptor mRNA and protein, thereby increasing the profibrotic response to ANG II in cardiac fibroblasts. The present experiments implicate increased nuclear factor-kappaB (NF-kappaB)-dependent transcription and also, to a lesser extent, altered mRNA splicing in the mechanism of receptor upregulation. Cytokine stimulation was found to increase AT(1A) heterogeneous nuclear RNA levels, which strongly suggests that mRNA upregulation occurs transcriptionally. The transcription factor NF-kappaB was previously deemed necessary for cytokine-induced AT(1A) receptor mRNA upregulation. Computer analysis of upstream DNA sequences revealed putative NF-kappaB elements at -365 and -2540 bp. Both isolated elements were shown to bind NF-kappaB (using gel-shift assays) and to transactivate a minimal promoter (using reporter assays), although the element at -365 bp appeared stronger. Three splice variants of AT(1A) receptor mRNA that have different 5' untranslated regions were detected in rat tissues, namely, exons 1-2-3 (predominant), 1-2-3+6, and 1-3. Cytokine treatment of fibroblasts upregulated all splice variants, but exon 1-3 increased more than the others. This differential upregulation, albeit of modest magnitude, was statistically significant with IL-1beta treatment. Exon 2 contains an inhibitory minicistron and a predicted inhibitory hairpin structure. Luciferase reporter assays indicated that each splice variant translates at a different efficiency, with exon 1-2-3+6 (both minicistron and hairpin) < exon 1-2-3 (minicistron only) < exon 1-3 (neither minicistron or hairpin). These results provide evidence that cytokines increase AT(1) protein levels by altering both transcription and splicing.

The interaction of coronary tone and cardiac fibrosis

Regulation of coronary vascular tone is critical for proper perfusion and function of the myocardium. Many disease processes result in compromised regulation of coronary vascular tone and impaired myocardial perfusion. A common result of coronary vascular dysfunction is the development of areas of replacement fibrosis within the myocardium and surrounding the vasculature. Both intravascular processes, such as coronary atherosclerosis and endothelial dysfunction, and extravascular processes, including compromised myocardial metabolism, hormone excesses, and altered local signaling, may result in coronary vascular dysregulation. Coronary occlusion events, in turn, lead to myocardial damage and the activation of inflammatory cells and fibroblasts. The role of fibroblasts in regulating myocardial fibrosis and the contribution of myofibroblasts, cells that have limited contractile potential while retaining many of the extracellular matrix regulating processes of the fibroblast, may also contribute to the development of myocardial disease. In this review we examine the recent literature on myocardial fibrosis and myofibroblast activity, highlighting the effects of several classes of cardiovascular agents on the remodeling process.

Profibrotic influence of high glucose concentration on cardiac fibroblast functions: effects of losartan and vitamin E

Long-standing diabetes can result in the development of cardiomyopathy, which can be accompanied by myocardial fibrosis. Although exposure of cultured kidney and skin fibroblasts to high glucose (HG) concentration is known to increase collagen synthesis, little is known about cardiac fibroblasts (CFs). Therefore, we determined the influence of HG conditions on CF functions and the effects of losartan and vitamin E in these responses. We cultured rat CFs in either normal glucose (NG; 5.5 mM) or HG (25 mM) media and assessed changes in protein and collagen synthesis, matrix metalloproteinase (MMP) activity, and levels of mRNA for ANG II type 1 (AT1) receptors. Results indicate that HG-level CFs synthesized more protein and collagen, and these effects were not due to changes in osmotic pressure. The addition of ANG II stimulated protein and collagen synthesis in NG-concentration but not HG-concentration CFs. Interestingly, losartan pretreatment blocked the HG- or ANG II-induced increases in both protein and collagen synthesis. HG or ANG II decreased total MMP activity. Decreases in MMP activity were blocked by losartan. AT1 mRNA levels were upregulated with HG concentration. Vitamin E pretreatment blocked the effects of HG on total protein synthesis and stimulated MMP activity. Results suggest that HG levels may promote fibrosis by increasing CF protein and collagen synthesis and decreasing MMP activity. HG levels may cause these effects via the upregulation of AT1 receptors, which can be blocked by losartan. However, vitamin E can alter HG concentration-induced changes in CF functions independently of AT1 mRNA levels.