Spontaneously Hypertensive Heart Failure Research Articles

Characterization of cardiac fibrosis in older lean vs. obese male ZSF1 rats

The ZSF1 rat is a novel strain produced by crossing a ZDF (Zucker diabetic fatty) female and SHHF (Spontaneously Hypertensive Heart Failure) male rat. Offspring of this hybrid have two phenotypes: healthy lean or obese prone to diabetes and heart failure. The metabolic syndrome and hypertension displayed by the obese ZSF1 rat mimics that seen in individuals who are predisposed to heart failure with preserved ejection fraction (HFpEF). Historically, HFpEF is a diffcult disease to accurately model with rodents and the ZSF1 rat is a promising model for the spontaneous progression to HFpEF. In recent studies, the oldest age at which ZSF1 rats were studied was 32 weeks and these obese rats displayed diastolic dysfunction, cardiac fibrosis, and hypertrophy. Since the prevalence of HFpEF increases with advanced age, the aim of the current study is to evaluate the extent of fibrosis in older ZSF1 rats (40-42 weeks) and determine whether this age group is more appropriate for the study of fibrotic cardiac remodeling related to HFpEF. We hypothesize that left ventricular (LV) fibrosis and collagen gene expression will be increased in obese compared to lean counterparts. Furthermore, we expect that the extent of fibrosis in this age group will exceed that reported in 32-week-old rats; thus, providing an improved model for the study of fibrotic heart disease. Lean and obese male ZSF1 rats (n=8/group) were aged to 40-42 weeks. Rats were anesthetized with a ketamine/xylazine cocktail and cardiac function was evaluated by invasive hemodynamics. The heart was removed, and the LV was trimmed and weighed. A mid-myocardial section from the LV was fixed and embedded in paraffn for histology. Remaining LV tissue was frozen for extraction of RNA and protein for biochemical analysis. LV collagen was assessed by Sirius red stain and collagen I ( Col1a1) and III ( Col3a1) gene expression were assessed by RTqPCR. With no significant difference in heart rate, obese ZSF1 rats had higher LV developed pressure compared to lean (191.1 vs. 122.0 mmHg, p<0.05) and increased maximum and minimum dP/dT (p<0.05). Obese ZSF1 rats exhibited cardiac hypertrophy as measured by LV weight normalized to tibial length (30.21 vs. 23.61 mg/mm, p<0.05, n=7/group) and increased fibrosis (Sirius red) compared to lean counterparts. Furthermore, the fibrosis in obese ZSF1 rats was concentrated in the endocardial and perivascular regions, and qualitatively more than previously published in the 32-week-old ZSF1. Preliminarily, obese ZSF1 rats exhibit a 3.5-fold increase in Col1a1 (p=0.02) and a 19-fold increase in C ol3a1 (p=0.06) gene expression compared to lean (n=3/group). Interestingly, not only is this a larger increase than that reported in 32-week-old old ZSF1s, but the relative increase in Col3a1 vs. Col1a1 is larger. Taken together, these data suggest a progression of cardiac fibrosis beyond what has been reported in the 32-week-old ZSF1 rats. Use of aged ZSF1 rats may be valuable for the study of fibrogenic mediators in HFpEF for the elucidation of therapeutic agents to reduce or reverse cardiac fibrosis. Future studies will include female rats to evaluate sex-specific progression of fibrosis. North Carolina Biotechnology Center Flash Grant (JH) and ECU REDE startup program (AG). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The redox-active defensive Selenoprotein T as a novel stress sensor protein playing a key role in the pathophysiology of heart failure

Maladaptive cardiac hypertrophy contributes to the development of heart failure (HF). The oxidoreductase Selenoprotein T (SELENOT) emerged as a key regulator during rat cardiogenesis and acute cardiac protection. However, its action in chronic settings of cardiac dysfunction is not understood. Here, we investigated the role of SELENOT in the pathophysiology of HF: (i) by designing a small peptide (PSELT), recapitulating SELENOT activity via the redox site, and assessed its beneficial action in a preclinical model of HF [aged spontaneously hypertensive heart failure (SHHF) rats] and against isoproterenol (ISO)-induced hypertrophy in rat ventricular H9c2 and adult human AC16 cardiomyocytes; (ii) by evaluating the SELENOT intra-cardiomyocyte production and secretion under hypertrophied stimulation. Results showed that PSELT attenuated systemic inflammation, lipopolysaccharide (LPS)-induced macrophage M1 polarization, myocardial injury, and the severe ultrastructural alterations, while counteracting key mediators of cardiac fibrosis, aging, and DNA damage and restoring desmin downregulation and SELENOT upregulation in the failing hearts. In the hemodynamic assessment, PSELT improved the contractile impairment at baseline and following ischemia/reperfusion injury, and reduced infarct size in normal and failing hearts. At cellular level, PSELT counteracted ISO-mediated hypertrophy and ultrastructural alterations through its redox motif, while mitigating ISO-triggered SELENOT intracellular production and secretion, a phenomenon that presumably reflects the extent of cell damage. Altogether, these results indicate that SELENOT could represent a novel sensor of hypertrophied cardiomyocytes and a potential PSELT-based new therapeutic approach in myocardial hypertrophy and HF.Graphical

Analysis of the gut microbiota profile targeted to multiple hypervariable regions of 16S rRNA in a hypertensive heart failure rat model.

The gut microbiota, comprising a diverse community of microorganisms, significantly influences various aspects of health. Changes in the composition of the gut microbiota are implicated in adverse effects on host physiology, contributing to the pathogenesis of cardiovascular diseases, among others pathological conditions. Understanding the role of the gut microbiota in the context of heart failure is particularly important. In this regard, the spontaneously hypertensive heart failure (SHHF) rat is an adequate experimental model since exhibits many features in common with heart failure (HF) in humans. Recent advancements in next-generation sequencing (NGS) have greatly improved microbiome analysis. However, standardization and the adoption of best practices are essential to mitigate experimental variations across studies. This manuscript outlines a straightforward methodology for analyzing gut microbiota composition in SHHF rat fecal samples using 16S rRNA sequencing, emphasizing the relevance of gut microbiota in heart failure.

Paradoxically reduced pulmonary vascular resistance and abnormal vascular remodeling in the obese spontaneously hypertensive heart failure ZSF1 rats

Pulmonary arterial dysfunction and remodeling often develop secondary to left heart disease and systemic hypertension. Excessive body weight is a well-established independent risk factor for the development of cardiovascular disease. However, data have emerged that for heart failure associated pulmonary complications obesity displays a lower long-term mortality. The impact of obesity on hypertension-related heart failure in affecting pulmonary vascular changes is incompletely understood. Here, we examined pulmonary vascular resistance and pulmonary artery function and remodeling in obese diabetic Zucker fatty/spontaneously hypertensive heart failure F1 hybrid (ZSF1) rats. 20-week-old male obese ZSF1 rats display increased left ventricle (LV) hypertrophy and diastolic dysfunction, when compared to age-matched lean spontaneously hypertensive heart failure (SHHR). Pulmonary vascular resistance, pulmonary arterial function and vascular wall remodeling were examined in isolated and perfused, ventilated lung preparations and isolated small pulmonary artery pressure and wire myography, respectively. We found that the pulmonary vascular resistance (normalized to lung weight) was significantly reduced in obese ZSF1 rats compared to SHHR (ZSF1: 0.2±0.02 mmHg·mL -1 ·min·g-1 vs SHHR: 0.29±0.018 mmHg·mL -1 ·min·g-1, p=0.01). In isolated pulmonary arteries the acetylcholine-induced relaxation was maintained, whereas the nitric oxide donor, sodium nitroprusside-induced relaxation was reduced in obese ZSF1 rats (SNP -log(IC50) ZSF1: 4.185±0.166 vs SHHR: 4.96±0.136, p=0.005). The wall thickness and wall-to-lumen ratio of pulmonary arteries were higher in the obese ZSF1 rats when compared to SHHR. Collectively, we found that obesity is associated with a reduced pulmonary vascular resistance and abnormal pulmonary artery remodeling in rats with systemic hypertension and diastolic heart failure, which may have implications in the clinically observed obesity paradox. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Protective Role of the Long Pentraxin PTX3 in Spontaneously Hypertensive Rats with Heart Failure.

Pentraxin 3 (PTX3) is synthesized locally and released into the circulation, reflecting local inflammation in the cardiovascular system. Therefore, we conducted a study to explore the effect of PTX3 in spontaneously hypertensive heart failure (SHHF) rats. Sprague Dawley (SD) and SHHF rats were treated with recombinant PTX3 protein, and the blood pressure (BP) and echocardiographic parameters were collected. Radioimmunoassay, enzyme immunoassay and enzyme-linked immunosorbent assay (ELISA) were applied to detect plasma levels of atrial/B-type natriuretic peptide (ANP/BNP) and PTX3. The pathological changes in the myocardial tissues were observed by hematoxylin and eosin (HE) and Masson stainings. The mRNA and protein expressions were detected by quantitative real-time reverse-transcription polymerase chain reaction (qPCR) and western blotting. Cardiomyocyte apoptosis was evaluated by TUNEL staining and DNA fragmentation test. Increased plasma concentrations of PTX3 were found in SHHF rats compared with SD rats, which was further enhanced by recombinant PTX3 protein. After injection with recombinant PTX3 protein, the heart function was improved in SHHF rats with the decreased systolic and diastolic BP, and the reduced plasma levels of ANP and BNP. Moreover, PTX3 improved the myocardial damage and interstitial fibrosis in SHHF rats with reduced cardiomyocyte apoptosis and decreased mRNA expressions of pro-inflammatory factors in myocardial tissues. PTX3 could decrease the BP and plasma levels of ANP and BNP in SHHF rats, as well as improve the inflammation, cardiomyocyte apoptosis, and pathological changes of myocardial tissues, suggesting it may be a useful intervention in the treatment of SHHF.

TMAO, a seafood-derived molecule, produces diuresis and reduces mortality in heart failure rats.

Trimethylamine-oxide (TMAO) is present in seafood which is considered to be beneficial for health. Deep-water animals accumulate TMAO to protect proteins, such as lactate dehydrogenase (LDH), against hydrostatic pressure stress (HPS). We hypothesized that TMAO exerts beneficial effects on the circulatory system and protects cardiac LDH exposed to HPS produced by the contracting heart. Male, Sprague-Dawley and Spontaneously-Hypertensive-Heart-Failure (SHHF) rats were treated orally with either water (control) or TMAO. In vitro, LDH with or without TMAO was exposed to HPS and was evaluated using fluorescence correlation spectroscopy. TMAO-treated rats showed higher diuresis and natriuresis, lower arterial pressure and plasma NT-proBNP. Survival in SHHF-control was 66% vs 100% in SHHF-TMAO. In vitro, exposure of LDH to HPS with or without TMAO did not affect protein structure. In conclusion, TMAO reduced mortality in SHHF, which was associated with diuretic, natriuretic and hypotensive effects. HPS and TMAO did not affect LDH protein structure.

Linoleic acid improves assembly of the CII subunit and CIII2/CIV complex of the mitochondrial oxidative phosphorylation system in heart failure

BackgroundLinoleic acid is the major fatty acid moiety of cardiolipin, which is central to the assembly of components involved in mitochondrial oxidative phosphorylation (OXPHOS). Although linoleic acid is an essential nutrient, its excess intake is harmful to health. On the other hand, linoleic acid has been shown to prevent the reduction in cardiolipin content and to improve mitochondrial function in aged rats with spontaneous hypertensive heart failure (HF). In this study, we found that lower dietary intake of linoleic acid in HF patients statistically correlates with greater severity of HF, and we investigated the mechanisms therein involved.MethodsHF patients, who were classified as New York Heart Association (NYHA) functional class I (n = 45), II (n = 93), and III (n = 15), were analyzed regarding their dietary intakes of different fatty acids during the one month prior to the study. Then, using a mouse model of HF, we confirmed reduced cardiolipin levels in their cardiac myocytes, and then analyzed the mechanisms by which dietary supplementation of linoleic acid improves cardiac malfunction of mitochondria.ResultsThe dietary intake of linoleic acid was significantly lower in NYHA III patients, as compared to NYHA II patients. In HF model mice, both CI-based and CII-based OXPHOS activities were affected together with reduced cardiolipin levels. Silencing of CRLS1, which encodes cardiolipin synthetase, in cultured cardiomyocytes phenocopied these events. Feeding HF mice with linoleic acid improved both CI-based and CII-based respiration as well as left ventricular function, together with an increase in cardiolipin levels. However, although assembly of the respirasome (i.e., CI/CIII2/CIV complex), as well as assembly of CII subunits and the CIII2/CIV complex statistically correlated with cardiolipin levels in cultured cardiomyocytes, respirasome assembly was not notably restored by dietary linoleic acid in HF mice. Therefore, although linoleic acid may significantly improve both CI-based and CII-based respiration of cardiomyocytes, respirasomes impaired by HF were not easily repaired by the dietary intake of linoleic acid.ConclusionsDietary supplement of linoleic acid is beneficial for improving cardiac malfunction in HF, but is unable to completely cure HF.

Abstract P3021: Trimethylamine but Not Trimethylamine N-Oxide Increases Blood Pressure in Rats, Affects Viability of Vascular Smooth Muscle Cells and Degrades Protein Structure

Increased plasma level of trimethylamine N-oxide (TMAO), a liver metabolite of gut bacteria-produced trimethylamine (TMA), has been suggested to increase cardiovascular risk. Mechanisms of TMAO increase in plasma and biological effects of TMAO are obscure. We evaluated the impact of heart failure (HF) on plasma levels of TMA and TMAO, and biological effects of the molecules. Gut permeability was evaluated in male, 58-week-old Spontaneously Hypertensive Heart Failure (SHHF) and Wistar-Kyoto (WKY) rats. TMA and TMAO levels were assessed using LC-MS. Mean arterial blood pressure (MABP) was measured in anaesthetized, male, 16-week-old WKY treated intravenously with either 0.9% NaCl (vehicle), TMA or TMAO. The cytotoxicity of TMA and TMAO in human vascular smooth muscle cells (hVSMCs) was evaluated using MTT assay. The effect of TMA and TMAO on protein structure of bovine albumin was assessed by fluorescence correlation spectroscopy. WKY showed no pathological changes in the circulatory system. SHHF showed HF with reduced ejection fraction. In comparison to WKY, SHHF had a significantly higher plasma level (μM) of TMA (99.05±6.40 vs 149.30±21.87) and TMAO (5.22±0.61 vs 6.69±0.67). SHHF had a significantly higher plasma-to-stool ratio of TMA, decreased intestinal blood flow and morphological alterations in the colon indicating the increased gut-to-blood penetration of TMA due to HF-induced leaky gut. In WKY treatment with the vehicle and TMAO did not affect MABP. In contrast, TMA (at equimolar doses to TMAO) significantly increased MABP by 5-40 mmHg in a dose dependent manner. In vitro, TMA at a concentration of 500μM reduced hVSMCs viability. TMAO at a concentration of 100mM was not cytotoxic whereas TMA at the same concentration killed cells within 24h. Finally, the incubation of albumin with TMA but not with TMAO resulted in the degradation of the protein structure. In conclusion, HF rats show increased plasma TMA and TMAO, which results from increased gut-to-blood penetration of TMA, a TMAO precursor. TMA but not TMAO affects hemodynamics in rats, reduces viability of cells and degrades protein structure. Therefore, TMA but not TMAO may exert deleterious effects on the circulatory system. Further clinical studies should evaluate not only TMAO but also TMA.

Empagliflozin reduces myocardial ketone utilization while preserving glucose utilization in diabetic hypertensive heart disease: A hyperpolarized 13 C magnetic resonance spectroscopy study.

AimTo investigate the effects of the sodium‐glucose co‐transporter‐2 inhibitor empagliflozin on myocardial ketone body utilization in diabetic, obese rats with spontaneously hypertensive heart failure (SHHF), after 6 months of treatment.Materials and MethodsMyocardial ketone body utilization was measured in vivo real time using a novel ketone probe (hyperpolarized [3‐13C]acetoacetate) and magnetic resonance spectroscopy (MRS). Myocardial glucose utilization and cardiac function were also determined in vivo using hyperpolarized [1‐13C]pyruvate MRS and magnetic resonance imaging (MRI), respectively. Myocardial fatty acid uptake and liver ketogenesis were assessed via protein expression.ResultsAt baseline, myocardial ketone and glucose utilization were both higher in SHHF compared with control rats. Six months of empagliflozin treatment in SHHF rats was associated with less obesity, lower blood pressure, reduced blood glucose and insulin levels, and increased fasting blood β‐hydroxybutyrate levels, as expected. Contrary to the hypothesis, myocardial ketone body utilization was lower in empagliflozin‐treated SHHF rats, while glucose utilization and cardiac function were unaltered and hepatic congestion was reduced, compared with vehicle‐treated SHHF rats.ConclusionsIn diabetic hypertensive heart disease, empagliflozin reduces afterload without altering myocardial function and glucose utilization in the face of falling blood glucose levels, but does not enhance myocardial ketone utilization despite increased circulating levels.

In Silico Analysis of Differential Gene Expression in Three Common Rat Models of Diastolic Dysfunction.

Standard therapies for heart failure with preserved ejection fraction (HFpEF) have been unsuccessful, demonstrating that the contribution of the underlying diastolic dysfunction pathophysiology differs from that of systolic dysfunction in heart failure and currently is far from being understood. Complicating the investigation of HFpEF is the contribution of several comorbidities. Here, we selected three established rat models of diastolic dysfunction defined by three major risk factors associated with HFpEF and researched their commonalities and differences. The top differentially expressed genes in the left ventricle of Dahl salt sensitive (Dahl/SS), spontaneous hypertensive heart failure (SHHF), and diabetes 1 induced HFpEF models were derived from published data in Gene Expression Omnibus and used for a comprehensive interpretation of the underlying pathophysiological context of each model. The diversity of the underlying transcriptomic of the heart of each model is clearly observed by the different panel of top regulated genes: the diabetic model has 20 genes in common with the Dahl/SS and 15 with the SHHF models. Advanced analytics performed in Ingenuity Pathway Analysis (IPA®) revealed that Dahl/SS heart tissue transcripts triggered by upstream regulators lead to dilated cardiomyopathy, hypertrophy of heart, arrhythmia, and failure of heart. In the heart of SHHF, a total of 26 genes were closely linked to cardiovascular disease including cardiotoxicity, pericarditis, ST-elevated myocardial infarction, and dilated cardiomyopathy. IPA Upstream Regulator analyses revealed that protection of cardiomyocytes is hampered by inhibition of the ERBB2 plasma membrane-bound receptor tyrosine kinases. Cardioprotective markers such as natriuretic peptide A (NPPA), heat shock 27 kDa protein 1 (HSPB1), and angiogenin (ANG) were upregulated in the diabetes 1 induced model; however, the model showed a different underlying mechanism with a majority of the regulated genes involved in metabolic disorders. In conclusion, our findings suggest that multiple mechanisms may contribute to diastolic dysfunction and HFpEF, and thus drug therapies may need to be guided more by phenotypic characteristics of the cardiac remodeling events than by the underlying molecular processes.

Cardiac myofibrillar contractile properties during the progression from hypertension to decompensated heart failure.

Heart failure arises, in part, from a constellation of changes in cardiac myocytes including remodeling, energetics, Ca2+ handling, and myofibrillar function. However, little is known about the changes in myofibrillar contractile properties during the progression from hypertension to decompensated heart failure. The aim of the present study was to provide a comprehensive assessment of myofibrillar functional properties from health to heart disease. A rodent model of uncontrolled hypertension was used to test the hypothesis that myocytes in compensated hearts exhibit increased force, higher rates of force development, faster loaded shortening, and greater power output; however, with progression to overt heart failure, we predicted marked depression in these contractile properties. We assessed contractile properties in skinned cardiac myocyte preparations from left ventricles of Wistar-Kyoto control rats and spontaneous hypertensive heart failure (SHHF) rats at ~3, ~12, and >20 mo of age to evaluate the time course of myofilament properties associated with normal aging processes compared with myofilaments from rats with a predisposition to heart failure. In control rats, the myofilament contractile properties were virtually unchanged throughout the aging process. Conversely, in SHHF rats, the rate of force development, loaded shortening velocity, and power all increased at ~12 mo and then significantly fell at the >20-mo time point, which coincided with a decrease in left ventricular fractional shortening. Furthermore, these changes occurred independent of changes in β-myosin heavy chain but were associated with depressed phosphorylation of myofibrillar proteins, and the fall in loaded shortening and peak power output corresponded with the onset of clinical signs of heart failure.NEW & NOTEWORTHY This novel study systematically examined the power-generating capacity of cardiac myofilaments during the progression from hypertension to heart disease. Previously undiscovered changes in myofibrillar power output were found and were associated with alterations in myofilament proteins, providing potential new targets to exploit for improved ventricular pump function in heart failure.

Peripheral and Cerebral Resistance Arteries in the Spontaneously Hypertensive Heart Failure Rat: Effects of Stilbenoid Polyphenols

Hypertension is associated with aberrant structure and mechanical properties of resistance arteries. We determined the effects of resveratrol, a non-flavonoid polyphenol found in foods such as red grapes, and structurally-similar analogues (pterostilbene and gnetol) on systolic blood pressure (SBP) and resistance arteries from the spontaneously hypertensive heart failure (SHHF) rat. SBP was elevated in 17-week-old SHHF vs. Sprague-Dawley rats (normotensive control; 194 ± 3 vs. 142 ± 6 mmHg, p < 0.01) and was unaffected by resveratrol, pterostilbene, or gnetol (2.5 mg/kg/d). Geometry and mechanical properties of pressurized mesenteric resistance arteries and middle cerebral arteries were calculated from media and lumen dimensions measured at incremental intraluminal pressures. SHHF arteries exhibited remodeling which consisted of augmented media-to-lumen ratios, and this was attenuated by stilbenoid treatment. Compliance was significantly reduced in SHHF middle cerebral arteries but not mesenteric arteries vis-à-vis increased wall component stiffness; stilbenoid treatment failed to normalize compliance and wall component stiffness. Our data suggest that neither AMPK nor ERK mediate stilbenoid effects. In conclusion, we observed arterial bed-specific abnormalities, where mesenteric resistance arteries exhibited remodeling and cerebral arteries exhibited remodeling and stiffening. Resveratrol, pterostilbene, and gnetol exhibited similar abilities to attenuate vascular alterations.

Disparate Effects of Stilbenoid Polyphenols on Hypertrophic Cardiomyocytes In Vitro vs. in the Spontaneously Hypertensive Heart Failure Rat.

Stilbenoids are bioactive polyphenols, and resveratrol (trans-3,5,4′-trihydroxystilbene) is a representative stilbenoid that reportedly exerts cardioprotective actions. As resveratrol exhibits low oral bioavailability, we turned our attention to other stilbenoid compounds with a history of medicinal use and/or improved bioavailability. We determined the effects of gnetol (trans-3,5,2′,6′-tetrahydroxystilbene) and pterostilbene (trans-3,5-dimethoxy-4′-hydroxystilbene) on cardiac hypertrophy. In vitro, gnetol and pterostilbene prevented endothelin-1-induced indicators of cardiomyocyte hypertrophy including cell enlargement and protein synthesis. Gnetol and pterostilbene stimulated AMP-activated protein kinase (AMPK), and inhibition of AMPK, using compound C or shRNA knockdown, abolished these anti-hypertrophic effects. In contrast, resveratrol, gnetol, nor pterostilbene reduced blood pressure or hypertrophy in the spontaneously hypertensive heart failure (SHHF) rat. In fact, AMPK levels were similar between Sprague-Dawley and SHHF rats whether treated by stilbenoids or not. These data suggest that the anti-hypertrophic actions of resveratrol (and other stilbenoids?) do not extend to the SHHF rat, which models heart failure superimposed on hypertension. Notably, SHHF rat hearts exhibited prolonged isovolumic relaxation time (an indicator of diastolic dysfunction), and this was improved by stilbenoid treatment. In conclusion, stilbenoid-based treatment as a viable strategy to prevent pathological cardiac hypertrophy, a major risk factor for heart failure, may be context-dependent and requires further study.

The interplay between genetic background and sexual dimorphism of doxorubicin-induced cardiotoxicity.

BackgroundDoxorubicin (DOX) is a very effective anticancer medication that is commonly used to treat hematological malignancies and solid tumors. Nevertheless, DOX is known to have cardiotoxic effects that may lead to cardiac dysfunction and failure. In experimental studies, female animals have been shown to be protected against DOX-induced cardiotoxicity; however, the evidence of this sexual dimorphism is inconclusive in clinical studies. Therefore, we sought to investigate whether genetic background could influence the sexual dimorphism of DOX-induced cardiotoxicity.MethodsMale and female Wistar Kyoto (WKY) and Spontaneous Hypertensive Heart Failure (SHHF) rats were used. DOX was administered in eight doses of 2 mg/kg/week and the rats were followed for an additional 12 weeks. Cardiac function was assessed by trans-thoracic echocardiography, systolic blood pressure was measured by the tail cuff method, and heart and kidney tissues were collected for histopathology.ResultsFemale sex protected against DOX-induced weight loss and increase in blood pressure in the WKY rats, whereas it protected against DOX-induced cardiac dysfunction and the elevation of cardiac troponin in SHHF rats. In both strains, female sex was protective against DOX-induced nephrotoxicity. There was a strong correlation between DOX-induced renal pathology and DOX-induced cardiac dysfunction.ConclusionsThis study highlights the importance of studying the interaction between sex and genetic background to determine the risk of DOX-induced cardiotoxicity. In addition, our findings suggest that DOX-induced nephrotoxicity may play a role in DOX-induced cardiac dysfunction in rodent models.

Time-Course of Cardiac Myofibrillar Contractile Properties during the Progression of Rat Hypertensive Heart Failure

Heart failure arises, at least in part, from a constellation of changes in cardiac myocytes including remodeling, energetics, calcium handling, and myofibrillar function. The aim of this study was to determine the time-course of changes in myofibrillar functional properties during the progression of heart failure. The rodent spontaneously hypertensive heart failure (SHHF) model was used to test the hypothesis that myocytes in compensated hearts exhibit increased force, higher rates of force development, faster loaded shortening, and greater power output; however, with progression to overt clinical signs of heart failure we predicted a marked depression in all these properties. We assessed contractile properties in skinned cardiac myocyte preparations from left ventricles of Wistar-Kyoto control rats and SHHF rats at 3-months, 12-months and 22-months of age. The Wistar-Kyoto control rats were studied to evaluate the time-course myofilament properties associated with normal aging processes compared to myofilaments from rats with a pre-disposition to heart failure. In the control group, force, rates of force development, loaded shortening, and power were unchanged throughout the time-course. Conversely, in the SHHF group, force, force development rates, loaded shortening, and power all tended to increase at 12-months and markedly fell at the 22-month time point, as did the fractional shortening of left ventricles in vivo. Interestingly, the fall in loaded shortening and normalized peak power output corresponded with the onset of clinical signs of heart failure (e.g., labored breathing, ascites, edema). This study indicates that depressed myofibrillar loaded shortening and power output coincides with symptomatic end-stage heart failure.

Long-term physiological T3 supplementation in hypertensive heart disease in rats.

Animal studies suggest that hypertension leads to cardiac tissue hypothyroidism, a condition that can by itself lead to heart failure. We have previously shown that short-term thyroid hormone treatment in Spontaneously Hypertensive Heart Failure (SHHF) rats near heart failure is beneficial. This study tested the hypothesis that therapeutic, long-term T3 treatment in SHHF rats can prevent or attenuate cardiac dysfunction. Female SHHF rats were treated orally with a physiological T3 dose (0.04 μg/ml) from 12 to 24 mo of age. Age-matched female SHHF and Wistar-Kyoto rats served as hypertensive and normotensive controls, respectively. SHHF rats had reduced serum free thyroid hormone levels and cardiac tissue T3 levels, LV dysfunction, and elevated LV collagen content compared with normotensive controls. Restoration of serum and cardiac tissue thyroid hormone levels in T3-treated rats was associated with no change in heart rate, but strong trends for improvement in LV systolic function and collagen levels. For instance, end-systolic diameter, fractional shortening, systolic wall stress, and LV collagen levels were no longer significantly different from controls. In conclusion, longstanding hypertension in rats led to chronic low serum and cardiac tissue thyroid hormone levels. Long-term treatment with low-dose T3 was safe. While cardiac dysfunction could not be completely prevented in the absence of antihypertensive treatment, T3 may offer additional benefits as an adjunct therapy with possible improvement in diastolic function.

Left ventricular gene expression profile of healthy and cardiovascular compromised rat models used in air pollution studies

The link between pollutant exposure and cardiovascular disease (CVD) has prompted mechanistic research with animal models of CVD. We hypothesized that the cardiac gene expression patterns of healthy and genetically compromised, CVD-prone rat models, with or without metabolic impairment, will reveal underlying disease processes that facilitate understanding of the mechanisms of air pollution susceptibility differences. Left ventricular gene expression was examined using Affymetrix rat 230A-gene arrays in male, age-matched (12–14 weeks old) healthy Wistar Kyoto (WKY) and CV-compromised spontaneously hypertensive (SH), stroke-prone SH (SHSP), obese SH heart failure (SHHF) and obese insulin-resistant (JCR) rats. Principle component analysis separated strains in three clusters: (1) WKY, (2) JCR and (3) SH, SHSP and SHHF. Gene expression pattern in JCR differed from all other CVD strains. Both SHHF and JCR strains presented the most differentially expressed genes from WKY, but generally with opposing directional pattern suggesting that the CVD in these strains arise through different mechanisms. Hierarchical clustering of nuclear factor-kappaB target genes indicated varying degrees of, but similar directional changes, in SH, SHSP and SHHF relative to WKY rats, which may relate to the severity of their CVD. The JCR strain had less pronounced expressions of these genes suggesting milder cardiac disease. No unique expression pattern could be identified for genes implicated in stroke and heart failure in SHSP and SHHF rats, respectively. The data show that the CVD pathophysiological mechanisms differ in models with different genetic backgrounds, and therefore, the mechanisms by which air pollutants affect the cardiopulmonary system are likely to vary.

Pulmonary transcriptional response to ozone in healthy and cardiovascular compromised rat models

The genetic cardiovascular disease (CVD) and associated metabolic impairments can influence the lung injury from inhaled pollutants. We hypothesized that comparative assessment of global pulmonary expression profile of healthy and CVD-prone rat models will provide mechanistic insights into susceptibility differences to ozone. The lung expression profiles of healthy Wistar Kyoto (WKY) and CVD-compromised spontaneously hypertensive (SH), stroke-prone SH (SHSP), obese SH heart failure (SHHF) and obese, atherosclerosis-prone JCR rats were analyzed using Affymetrix platform immediately after 4-h air or 1 ppm ozone exposure. At baseline, the JCR exhibited the largest difference in the number of genes among all strains when compared with WKY. Interestingly, the number of genes affected by ozone was inversely correlated with genes different at baseline relative to WKY. A cluster of NFkB target genes involved in cell-adhesion, antioxidant response, inflammation and apoptosis was induced in all strains, albeit at different levels (JCR < WKY < SHHF < SH < SHSP). The lung metabolic syndrome gene cluster indicated expressions in opposite directions for SHHF and JCR suggesting different mechanisms for common disease phenotype and perhaps obesity-independent contribution to exacerbated lung disease. The differences in expression of adrenergic receptors and ion-channel genes suggested distinct mechanisms by which ozone might induce protein leakage in CVD models, especially SHHF and JCR. Thus, the pulmonary response to ozone in CVD strains was likely linked to the defining gene expression profiles. Differential transcriptional patterns between healthy and CVD rat strains at baseline, and after ozone suggests that lung inflammation and injury might be influenced by multiple biological pathways affecting inflammation gene signatures.

Clinical and pathological manifestations of cardiovascular disease in rat models: the influence of acute ozone exposure

Rodent models of cardiovascular diseases (CVD) and metabolic disorders are used for examining susceptibility variations to environmental exposures. However, cross-model organ pathologies and clinical manifestations are often not compared. We hypothesized that genetic CVD rat models will exhibit baseline pathologies and will thus express varied lung response to acute ozone exposure. Male 12–14-week-old healthy Wistar Kyoto (WKY), Wistar (WIS), and Sprague–Dawley (SD) rats and CVD-compromised spontaneously hypertensive (SH), fawn-hooded hypertensive (FHH), stroke-prone SH (SHSP), obese SH heart-failure (SHHF), obese diabetic JCR (JCR) rats were exposed to 0.0, 0.25, 0.5, or 1.0 ppm ozone for 4 h and clinical biomarkers, and lung, heart and kidney pathologies were compared immediately following (0–h) or 20-h later. Strain differences were observed between air-exposed CVD-prone and WKY rats in clinical biomarkers and in kidney and heart pathology. Serum cholesterol was higher in air-exposed obese SHHF and JCR compared to other air-exposed strains. Ozone did not produce lesions in the heart or kidney. CVD-prone and SD rats demonstrated glomerulopathy and kidney inflammation (WKY = WIS = SH < SD = SHSP < SHHF < JCR = FHH) regardless of ozone. Cardiac myofiber degeneration was evident in SH, SHHF, and JCR, while only JCR tends to have inflammation in coronaries. Lung pathology in air-exposed rats was minimal in all strains except JCR. Ozone induced variable alveolar histiocytosis and bronchiolar inflammation; JCR and SHHF were less affected. This study provides a comparative account of the clinical manifestations of disease and early-life organ pathologies in several rat models of CVD and their differential susceptibility to lung injury from air pollutant exposure.

Variability in ozone-induced pulmonary injury and inflammation in healthy and cardiovascular-compromised rat models

The molecular bases for variability in air pollutant-induced pulmonary injury due to underlying cardiovascular (CVD) and/or metabolic diseases are unknown. We hypothesized that healthy and genetic CVD-prone rat models will exhibit exacerbated response to acute ozone exposure dependent on the type and severity of disease. Healthy male 12–14-week-old Wistar Kyoto (WKY), Wistar (WS) and Sprague Dawley (SD); and CVD-compromised spontaneously hypertensive (SH), Fawn-Hooded hypertensive (FHH), stroke-prone spontaneously hypertensive (SHSP), obese spontaneously hypertensive heart failure (SHHF) and obese JCR (JCR) rats were exposed to 0.0, 0.25, 0.5, or 1.0 ppm ozone for 4 h; pulmonary injury and inflammation were analyzed immediately following (0-h) or 20-h later. Baseline bronchoalveolar lavage fluid (BALF) protein was higher in CVD strains except for FHH when compared to healthy. Ozone-induced increases in protein and inflammation were concentration-dependent within each strain but the degree of response varied from strain to strain and with time. Among healthy rats, SD were least affected. Among CVD strains, lean rats were more susceptible to protein leakage from ozone than obese rats. Ozone caused least neutrophilic inflammation in SH and SHHF while SHSP and FHH were most affected. BALF neutrophils and protein were poorly correlated when considering the entire dataset (r = 0.55). The baseline and ozone-induced increases in cytokine mRNA varied markedly between strains and did not correlate with inflammation. These data illustrate that the degree of ozone-induced lung injury/inflammation response is likely influenced by both genetic and physiological factors that govern the nature of cardiovascular compromise in CVD models.