Deleterious effects of social isolation on neuroendocrine-immune status, and cancer progression in rats.

Accumulating evidence indicates that social isolation (SI) in humans and rodents is associated with increased cancer incidence and mortality, yet mediating mechanisms remain elusive. Here, we examine the neuroendocrine and immunological consequences of SI and its short- and long-term physiological impacts in naïve and cancer-bearing rats. Findings indicate that isolated animals experienced a significant decrease in weight compared to controls. Specifically, females showed a marked weight decrease during the first week of isolation. Isolated rats had significantly higher numbers of MADB106 experimental pulmonary metastases. Although mortality rates were higher in isolated tumor-bearing rats, unexpectedly, they exhibited a reduced growth rate of orthotopically implanted MADB106 tumors. Transcriptomic analyses of these excised tumors indicated a major downregulation in the expression of various genes, including those associated with pro-metastatic processes (e.g., EMT). In naïve rats (no cancer), levels of IL-6 increased, and total IgG levels decreased under SI conditions. A mixed effect was found for TNFα, which increased in females and decreased in males. In the central nervous system, isolated rats showed altered gene expression in key brain regions associated with stress responses and social behavior. The paraventricular nucleus of the thalamus emerged as a significantly affected region, along with the bed nucleus of the stria terminalis. Changes were observed in the expression of oxytocin, serotonin, and dopamine receptors. Isolated rats also exhibited greater alterations in hypothalamic-pituitary-adrenal (HPA) axis-related regulation and an increase in plasma CORT levels. Our study highlights the profound impact of SI on metastatic processes. Additionally, the potential detrimental effects of SI on thermoregulation were discussed, emphasizing the importance of social thermoregulation in maintaining physiological stability and highlighting the need to avoid single-caging practices in research. We report neuro-immune interactions and changes in brain gene expression, highlighting the need for further research into these underlying processes to improve outcomes in animal models and potential interventions for cancer patients through increased social support.

Downregulated Expression of TRPV2 in Peripheral Blood Cells following Acute Myocardial Infarction Is Inversely Correlated with Serum Levels of CRP and Troponin I.

OBJECTIVES: We have recently shown that the transient receptor potential vanilloid 2 (TRPV2) channel is exclusively upregulated in rat/murine peri-infarct monocytes/macrophages following an acute myocardial infarction (AMI), and that this overexpression might be detrimental for cardiac recovery. We aimed to characterize the expression levels of TRPV2 in peripheral blood mononuclear cells (PBMCs) of AMI patients relative to individuals with normal coronaries, and to analyze potential associations with inflammatory and cardiac ischemic markers. METHODS: Patients who underwent coronary angiography due to AMI or chest pain were prospectively included. PBMCs were isolated from whole blood by Ficoll gradient centrifugation. TRPV2 expression was analyzed by real-time PCR. C-reactive protein (CRP) and troponin I (TpI) levels were determined at the central chemistry laboratory; interleukin 6 and insulin-like growth factor (IGF)-1 levels were tested by ELISA. RESULTS: Following AMI, the number of TRPV2-expressing PBMCs was reduced when compared to in patients with normal coronaries. An inverse correlation was documented between the numbers of circulating macrophages and TRPV2 expression. Additionally, TRPV2 expression was inversely correlated with CRP and TpI and directly correlated with serum IGF-1. CONCLUSIONS: We assume that peripheral TRPV2 downregulation occurs concomitantly with the accumulation of TRPV2-white blood cells in the peri-infarct zone. TRPV2 may thus represent a novel target for treatment in the acute phase after MI.

Differential Effects of Colchicine on Cardiac Cell Viability in an in vitro Model Simulating Myocardial Infarction.

OBJECTIVES: We aimed to examine the effects of colchicine, currently in clinical trials for acute myocardial infarction (AMI), on the viability of cardiac cells using a cell line model of AMI. METHODS: HL-1, a murine cardiomyocyte cell line, and H9C2, a rat cardiomyoblast cell line, were incubated with TNFα or sera derived from rats that underwent AMI or sham operation followed by addition of colchicine. In another experiment, HL-1/H9C2 cells were exposed to anoxia with or without subsequent addition of colchicine. Cell morphology and viability were assessed by light microscopy, flow cytometry and Western blot analyses for apoptotic markers. RESULTS: Cellular viability was similar in both sera; however, exposing both cell lines to anoxia reduced their viability. Adding colchicine to anoxic H9C2, but not to anoxic HL-1, further increased their mortality, at least in part via enhanced apoptosis. Under any condition, colchicine induced detachment of H9C2 cells from their culture plates. This phenomenon did not apply to HL-1 cells. CONCLUSIONS: Colchicine enhanced cardiomyoblast mortality under in vitro conditions mimicking AMI and reduced their adherence capability. HL-1 was not affected by colchicine; nevertheless, no salvage effect was observed. We thus conclude that colchicine may not inhibit myocardial apoptosis following AMI.

Down-Regulation of Cardiac Erythropoietin Receptor and its Downstream Activated Signal Transducer Phospho-STAT-5 in a Rat Model of Chronic Kidney Disease.

BACKGROUND: Chronic kidney disease (CKD) is often accompanied by impairment of cardiac function that may lead to major cardiac events. Erythropoietin (EPO), a kidney-produced protein, was shown to be beneficial to heart function. It was suggested that reduced EPO secretion in CKD may play a role in the initiation of heart damage. OBJECTIVES: To investigate molecular changes in the EPO/ erythropoietin receptor (EPO-R) axis in rat cardiomyocytes using a rat model for CKD. METHODS: We established a rat model for CKD by kidney resection. Cardiac tissue sections were stained with Masson's trichrome to assess interstitial fibrosis indicating cardiac damage. To evaluate changes in the EPO/EPO-R signaling cascade in the myocardium we measured cardiac EPO and EPO-R as well as the phosphorylation levels of STAT-5, a downstream element in this cascade. RESULTS: At 11 weeks after resection, animals presented severe renal failure reflected by reduced creatinine clearance, elevated blood urea nitrogen and presence of anemia. Histological analysis revealed enhanced fibrosis in cardiac sections of CKD animals compared to the sham controls. Parallel to these changes, we found that although cardiac EPO levels were similar in both groups, the expression of EPO-R and the activated form of its downstream protein STAT-5 were significantly lower in CKD animals. CONCLUSIONS: CKD results in molecular changes in the EPO/EPO-R axis. These changes may play a role in early cardiac damage observed in the cardiorenal syndrome.

Cardiac Hypertrophy and Cardiac Cell Death in Chronic Kidney Disease.

BACKGROUND: Chronic kidney disease (CKD) is a prevalent clinical condition affecting 15% of the general population. Cardiorenal syndrome (CRS) type 4 is characterized by an underlying CKD condition leading to impairment of cardiac function and increased risk for major cardiovascular events. To date, the mechanisms leading from CKD to CRS are not completely understood. In particular, it is unclear whether the pathological changes that occur in the heart in the setting of CKD involve enhanced cell death of cardiac cells. OBJECTIVES: To assess whether CKD may mediate loss of cardiac cells by apoptosis. METHODS: We established rat models for CKD, acute myocardial infarction (acute MI), left ventricular dysfunction (LVD), and sham. We measured the cardiac-to-body weight as well as kidney-to-body weight ratios to validate that renal and cardiac hypertrophy occur as part of disease progression to CRS. Cardiac cells were then isolated and the percent of cell death was determined by flow cytometry following staining with annexin-FITC and propidium iodide. In addition, the levels of caspase-3-dependent apoptosis were determined by Western blot analysis using an anti-cleaved caspase-3 antibody. RESULTS: CKD, as well as acute MI and LVD, resulted in significant cardiac hypertrophy. Nevertheless, unlike the increased levels of cell death observed in the acute MI group, in the CKD group, cardiac hypertrophy was not associated with induction of cell death of cardiac cells. Caspase-3 activity was even slightly reduced compared to sham-operated controls. CONCLUSIONS: Our data show that while CKD induces pathological changes in the heart, it does not induce cardiac cell death.

Kynurenic acid, a key L-tryptophan-derived metabolite, protects the heart from an ischemic damage.

BACKGROUND: Renal injury induces major changes in plasma and cardiac metabolites. Using a small- animal in vivo model, we sought to identify a key metabolite whose levels are significantly modified following an acute kidney injury (AKI) and to analyze whether this agent could offer cardiac protection once an ischemic event has occurred. METHODS AND RESULTS: Metabolomics profiling of cardiac lysates and plasma samples derived from rats that underwent AKI 1 or 7 days earlier by 5/6 nephrectomy versus sham-operated controls was performed. We detected 26 differential metabolites in both heart and plasma samples at the two selected time points, relative to sham. Out of which, kynurenic acid (kynurenate, KYNA) seemed most relevant. Interestingly, KYNA given at 10 mM concentration significantly rescued the viability of H9C2 cardiac myoblast cells grown under anoxic conditions and largely increased their mitochondrial content and activity as determined by flow cytometry and cell staining with MitoTracker dyes. Moreover, KYNA diluted in the drinking water of animals induced with an acute myocardial infarction, highly enhanced their cardiac recovery according to echocardiography and histopathology. CONCLUSION: KYNA may represent a key metabolite absorbed by the heart following AKI as part of a compensatory mechanism aiming at preserving the cardiac function. KYNA preserves the in vitro myocyte viability following exposure to anoxia in a mechanism that is mediated, at least in part, by protection of the cardiac mitochondria. A short-term administration of KYNA may be highly beneficial in the treatment of the acute phase of kidney disease in order to attenuate progression to reno-cardiac syndrom and to reduce the ischemic myocardial damage following an ischemic event.

Cardiac remodeling secondary to chronic volume overload is attenuated by a novel MMP9/2 blocking antibody.

OBJECTIVE: Monoclonal antibody derivatives are promising drugs for the treatment of various diseases due to their high matrix metalloproteinases (MMP) active site specificity. We studied the effects of a novel antibody, SDS3, which specifically recognizes the mature active site of MMP9/2 during ventricular remodeling progression in a mouse model of chronic volume overload (VO). METHODS: VO was induced by creating an aortocaval fistula (ACF) in 10- to 12-week-old C57BL male mice. The VO-induced mice were treated with either vehicle control (PBS) or with SDS3 twice weekly by intraperitoneal (ip) injection. The relative changes in cardiac parameters between baseline (day 1) and end-point (day 30), were evaluated by echocardiography. The effects of SDS3 treatment on cardiac fibrosis, cardiomyocyte volume, and cardiac inflammation were tested by cardiac staining with Masson's trichrome, wheat Germ Agglutinin (WGA), and CD45, respectively. Serum levels of TNFα and IL-6 with and without SDS3 treatment were tested by ELISA. RESULTS: SDS3 significantly reduced cardiac dilatation, left ventricular (LV) mass, and cardiomyocyte hypertrophy compared to the vehicle treated animals. The antibody also reduced the heart-to-body weight ratio of the ACF animals to values comparable to those of the controls. Interestingly, the SDS3 group underwent significant reduction of cardiac inflammation and pro-inflammatory cytokine production, indicating a regulatory role for MMP9/2 in tissue remodeling, possibly by tumor necrosis factor alpha (TNFα) activation. In addition, significant changes in the expression of proteins related to mitochondrial function were observed in ACF animals, these changes were reversed following treatment with SDS3. CONCLUSION: The data suggest that MMP9/2 blockage with SDS3 attenuates myocardial remodeling associated with chronic VO by three potential pathways: downregulating the extracellular matrix proteolytic cleavage, reducing the cardiac inflammatory responses, and preserving the cardiac mitochondrial structure and function.

Correction: Cardiac remodeling secondary to chronic volume overload is attenuated by a novel MMP9/2 blocking antibody.

[This corrects the article DOI: 10.1371/journal.pone.0231202.].

Pathological presentation of cardiac mitochondria in a rat model for chronic kidney disease.

BACKGROUND: Mitochondria hold crucial importance in organs with high energy demand especially the heart. We investigated whether chronic kidney disease (CKD), which eventually culminates in cardiorenal syndrome, could affect cardiac mitochondria and assessed the potential involvement of angiotensin II (AngII) in the process. METHODS: Male Lewis rats underwent 5/6 nephrectomy allowing CKD development for eight months or for eleven weeks. Short-term CKD rats were administered with AngII receptor blocker (ARB). Cardiac function was assessed by echocardiography and cardiac sections were evaluated for interstitial fibrosis and cardiomyocytes' hypertrophy. Electron microscopy was used to explore the spatial organization of the cardiomyocytes. Expression levels of mitochondrial content and activity markers were tested in order to delineate the underlying mechanisms for mitochondrial pathology in the CKD setting with or without ARB administration. RESULTS: CKD per-se resulted in induced cardiac interstitial fibrosis and cardiomyocytes' hypertrophy combined with a marked disruption of the mitochondrial structure. Moreover, CKD led to enhanced cytochrome C leakage to the cytosol and to enhanced PARP-1 cleavage which are associated with cellular apoptosis. ARB treatment did not improve kidney function but markedly reduced left ventricular mass, cardiomyocytes' hypertrophy and interstitial fibrosis. Interestingly, ARB administration improved the spatial organization of cardiac mitochondria and reduced their increased volume compared to untreated CKD animals. Nevertheless, ARB did not improve mitochondrial content, mitochondrial biogenesis or the respiratory enzyme activity. ARB mildly upregulated protein levels of mitochondrial fusion-related proteins. CONCLUSIONS: CKD results in cardiac pathological changes combined with mitochondrial damage and elevated apoptotic markers. We anticipate that the increased mitochondrial volume mainly represents mitochondrial swelling that occurs during the pathological process of cardiac hypertrophy. Chronic administration of ARB may improve the pathological appearance of the heart. Further recognition of the molecular pathways leading to mitochondrial insult and appropriate intervention is of crucial importance.

TRPV2 knockout mice demonstrate an improved cardiac performance following myocardial infarction due to attenuated activity of peri-infarct macrophages.

BACKGROUND: We have recently shown that the expression of the transient receptor potential vanilloid 2 channel, TRPV2, is upregulated in the peri-infarct zone 3-5 days following an acute myocardial infarction (AMI). Further analysis has demonstrated that invading monocytes maturing to macrophages merely harbor the documented elevated expression of this channel. PURPOSE: Assess cardiac function in TRPV2-KO mice compared to TRPV2-WT following AMI and analyze the potential involvement of TRPV2-expressing macrophages in the recovery process. METHODS: TRPV2-KO or WT mice were induced with AMI by ligation of the left anterior descending artery (LAD). In another set of experiments, TRPV2-KO mice induced with AMI, were intravenously (IV) injected with WT or TRPV2-KO peritoneal macrophages in order to directly assess the potential contribution of TRPV2-expressing macrophages to cardiac healing. Cardiac parameters were obtained by echocardiography 1 day and 30 days post infarction. The relative changes in the ejection fraction (EF) and additional cardiac parameters between baseline (day 1) and day 30 were calculated and statistical significance was determined (SPSS). RESULTS: The in vivo study showed that while EF was significantly decreased in the WT animals between baseline and day 30, EF was only slightly and insignificantly reduced in the KO animals. Likewise LVESD and LVESA were significantly modified exclusively in the WT animals. Moreover, intravenous administration of peritoneal WT macrophages, but not KO macrophages, significantly reduced survival of post-MI TRPV2-KO mice. CONCLUSION: The data suggest that knockout of the TRPV2 channel may attenuate macrophage-dependent pro-inflammatory processes and result in better cardiac recovery. TRPV2 may thus represent a novel therapeutic target for treatment of patients undergoing an acute MI.