Down-regulation of FKBP12.6 and SERCA2a contributes to acute heart failure in septic shock and is related to an up-regulated endothelin signalling pathway

Research progress on Cornus officinalis and its active compounds in the treatment of diabetic nephropathy

Diabetic nephropathy (DN) is a kidney disorder secondary to diabetes and is one of the main diabetic microvascular complications. As the number of diabetic patients grows, DN has become the leading cause of chronic kidney disease in China. Unfortunately, no definitive cure currently exists for DN. Cornus officinalis (CO), frequently utilized in clinical settings for diabetes mellitus treatment, has proven vital in both preventing and treating DN. This article explores the pathogenesis of DN and how CO and its active compounds regulate glucose and lipid metabolism, exhibit anti-inflammatory properties, inhibit oxidative stress, regulate podocytes, and manage autophagy. The mechanism and role of and its active compounds in the treatment of DN are discussed.

Heart Dysfunction in Sepsis

Cardiac involvement during sepsis frequently occurs. A series of molecules induces a set of changes at the cellular level that result in the malfunction of the myocardium. The understanding of these molecular alterations has simultaneously promoted the implementation of diagnostic strategies that are much more precise and allowed the advance of the therapeutics. The heart is a vital organ for survival. Its well-being ensures the adequate supply of essential elements for organs and tissues.

Role of complement C5a and histones in septic cardiomyopathy

Polymicrobial sepsis (after cecal ligation and puncture, CLP) causes robust complement activation with release of C5a. Many adverse events develop thereafter and will be discussed in this review article. Activation of complement system results in generation of C5a which interacts with its receptors (C5aR1, C5aR2). This leads to a series of harmful events, some of which are connected to the cardiomyopathy of sepsis, resulting in defective action potentials in cardiomyocytes (CMs), activation of the NLRP3 inflammasome in CMs and the appearance of extracellular histones, likely arising from activated neutrophils which form neutrophil extracellular traps (NETs). These events are associated with activation of mitogen-activated protein kinases (MAPKs) in CMs. The ensuing release of histones results in defective action potentials in CMs and reduced levels of [Ca²⁺]i-regulatory enzymes including sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA2) and Na⁺/Ca²⁺ exchanger (NCX) as well as Na⁺/K⁺-ATPase in CMs. There is also evidence that CLP causes release of IL-1β via activation of the NLRP3 inflammasome in CMs of septic hearts or in CMs incubated in vitro with C5a. Many of these events occur after in vivo or in vitro contact of CMs with histones. Together, these data emphasize the role of complement (C5a) and C5a receptors (C5aR1, C5aR2), as well as extracellular histones in events that lead to cardiac dysfunction of sepsis (septic cardiomyopathy).

Interleukin-18 gene deletion protects against sepsis-induced cardiac dysfunction by inhibiting PP2A activity

BACKGROUND

Interleukin-18 (IL-18) neutralization protects against lipopolysaccharide (LPS)-induced injuries, including myocardial dysfunction. However, the mechanism is yet to be fully elucidated. The aim of the present study was to determine whether IL-18 gene deletion prevents sepsis-induced cardiac dysfunction and to elucidate the potential mechanisms underlying IL-18-mediated cardiotoxicity by LPS.

METHODS AND RESULTS

Ten-week-old male wild-type (WT) and IL-18 knockout (IL-18 KO) mice were intraperitoneally administered LPS. Serial echocardiography showed better systolic pump function and less left ventricular (LV) dilatation in LPS-treated IL-18 KO mice compared with those in LPS-treated WT mice. LPS treatment significantly decreased the levels of phospholamban (PLN) and Akt phosphorylation in WT mice compared with those in saline-treated WT mice, while the LPS-induced decrease in the phosphorylation levels was attenuated in IL-18 KO mice compared with that in WT mice. IL-18 gene deletion also attenuated an LPS-induced increase of type 2 protein phosphatase 2A (PP2A) activity, a molecule that dephosphorylates PLN and Akt. There was no difference in type 1 protein phosphatase (PP1) activity. To address whether IL-18 affects PLN and Akt phosphorylation via PP2A activation in cardiomyocytes, rat neonatal cardiac myocytes were cultured and stimulated using 100ng/ml of recombinant rat IL-18. Exogenous IL-18 decreased the level of PLN and Akt phosphorylation in cardiomyocytes. PP2A activity but not PP1 activity was increased by IL-18 stimulation in cardiomyocytes.

CONCLUSIONS

IL-18 plays a pivotal role in advancing sepsis-induced cardiac dysfunction, and the mechanisms underlying IL-18-mediated cardiotoxicity potentially involve the regulation of PLN and Akt phosphorylation through PP2A activity.

Complement and sepsis-induced heart dysfunction

It is well known that cardiac dysfunction develops during sepsis in both humans and in rodents (rats, mice). These defects appear to be reversible, since after "recovery" from sepsis, cardiac dysfunction disappears and the heart returns to its function that was present before the onset of sepsis. Our studies, using in vivo and in vitro models, have demonstrated that C5a and its receptors (C5aR1 and C5aR2) play key roles in cardiac dysfunction developing during sepsis. Use of a neutralizing antibody to C5a largely attenuates cardiac dysfunction and other adverse events developing during sepsis. The molecular basis for cardiac dysfunctions is linked to generation of C5a and its interaction with C5a receptors present on surfaces of cardiomyocytes (CMs). It is established that C5a interactions with C5a receptors leads to significant reductions involving faulty contractility and relaxation in CMs. In addition, C5a interactions with C5a receptors on CMs results in reductions in Na⁺/K⁺-ATPase in CMs. This ATPase is essential for intact action potentials in CMs. The enzymatic activity and protein for this ATPase were strikingly reduced in CMs during sepsis by unknown mechanisms. In addition, C5a interactions with C5aRs also caused reductions in CM homeostatic proteins that regulate cytosolic [Ca²⁺]i in CMs: sarco/endoplasmic reticulum Ca²⁺-ATPase2 (SERCA2) and Na⁺/Ca²⁺ exchanger (NCX). In the absence of C5a receptors, defects in SERCA2 and NCX in CMs after sepsis are strikingly attenuated. These observations suggest new strategies to protect the heart from dysfunction developing during sepsis.

Impact of endotoxin challenge in obese pigs

Studies exploring the influence of obesity on septic shock remain limited and controversial. Pigs were chosen as a clinically relevant species, resembling to humans in various functions. We hypothesize obesity may impair porcine acute endotoxic shock. Four groups of five "Yucatan" minipigs were studied: lean and obese control groups, lean lipopolysaccharide (LPS) group receiving Escherichia coli endotoxin (LPS) and obese LPS group receiving the same endotoxin dose. We measured hemodynamic and oxygenation parameters, skin microvascular blood flow at rest and during reactive hyperemia, von Willebrand factor, tumor necrosis factor α, and interleukin 6. All measurements were performed at baseline and at 30, 60, 90, 150, and 300 min. Results were given as median with 25th to 75th interquartile range. Control groups remained stable during the study period. In LPS groups, administration of endotoxin resulted in a typical hypokinetic shock. In obese LPS group at 300 min, we observed a significant impairment of cardiac index (1.2 [1.06-1.45] vs. 1.7 [1.57-1.97] L/min per m, P = 0.008) compared with the lean LPS group; moreover, pulmonary hypertension (mean arterial pressure: 42 [39-47] vs. 32 [28-34] mmHg, P = 0.008), hypoxemia (partial pressure of oxygen: 216 [178-262] vs. 325 [285-414] mmHg, P = 0.02), and lactate levels (5.8 [4.2-6.8] vs. 3.9 [2.2-5.5] mmol/L, P = 0.04) were significantly higher compared with the lean LPS group. Throughout the study, rest flow and peak flow during reactive hyperemia were more decreased in the obese LPS group. Compared with the lean LPS group, tumor necrosis factor α levels at 60 min (269 [178-428] vs. 126 [105-166] ng/mL, P = 0.03) and interleukin 6 levels at 300 min (101 [61-142] vs. 52 [36-64] ng/mL, P = 0.03) were significantly higher in the obese LPS group. In our model of endotoxic shock, obese pigs developed a more severe hemodynamic failure with pronounced microcirculatory dysfunction and proinflammatory response.

Exendin-4 improves cardiac function in mice overexpressing monocyte chemoattractant protein-1 in cardiomyocytes

The incretin hormone glucagon-like peptide-1 (Glp1) is cardioprotective in models of ischemia-reperfusion injury, myocardial infarction and gluco/lipotoxicity. Inflammation is a factor in these models, yet it is unknown whether Glp1 receptor (Glp1r) agonists are protective against cardiac inflammation. We tested the hypothesis that the Glp1r agonist Exendin-4 (Ex4) is cardioprotective in mice with cardiac-specific monocyte chemoattractant protein-1 overexpression. These MHC-MCP1 mice exhibit increased cardiac monocyte infiltration, endoplasmic reticulum (ER) stress, apoptosis, fibrosis and left ventricular dysfunction. Ex4 treatment for 8 weeks improved cardiac function and reduced monocyte infiltration, fibrosis and apoptosis in MHC-MCP1 mice. Ex4 enhanced expression of the ER chaperone glucose-regulated protein-78 (GRP78), decreased expression of the pro-apoptotic ER stress marker CCAAT/-enhancer-binding protein homologous protein (CHOP) and increased expression of the ER calcium regulator Sarco/Endoplasmic Reticulum Calcium ATPase-2a (SERCA2a). These findings suggest that the Glp1r is a viable target for treating cardiomyopathies associated with stimulation of pro-inflammatory factors.

Significant reversal of cardiac upregulated endothelin-1 system in a rat model of sepsis by landiolol hydrochloride

AIMS

Landiolol hydrochloride, an ultra-short-acting highly cardio-selective β-1 blocker, has become useful for various medical problems. Recent studies have demonstrated that co-treatment with landiolol protects against acute lung injury and cardiac dysfunction in rats of lipopolysaccharide (LPS)-induced systemic inflammation, and was also associated with a significant reduction in serum levels of the inflammation mediator HMGB-1 and histological lung damage. Endothelin (ET)-1, a potent vasoconstrictor, has been implicated in pathogenesis of sepsis and sepsis-induced multiple organ dysfunction syndrome. Here, we investigated whether landiolol hydrochloride can play important roles in ameliorating LPS-induced alterations in cardiac ET system of septic rats.

MAIN METHODS

Eight-week-old male Wistar rats were administered LPS only for 3 h and the rest were treated with LPS as well as with landiolol non-stop for 3 h.

KEY FINDINGS

At 3 h after LPS (only) administration, circulatory tumor necrosis factor (TNF)-α level, blood lactate concentration and percentage of fractional shortening of heart were significantly increased. In addition, LPS induced a significant expression of various components of cardiac ET-1 system compared to control. Finally, treatment of LPS-administered rats with landiolol for 3 h normalized LPS-induced blood lactate levels and cardiac functional compensatory events, without altering levels of plasma TNF-α and ET-1. Most strikingly, landiolol treatment significantly normalized various components of cardiac ET-1 signaling system in septic rat.

SIGNIFICANCE

Taken together, these data led us to conclude that landiolol may be cardio-protective in septic rats by normalizing the expression of cardiac vasoactive peptide such as ET, without altering the circulatory levels of inflammatory cytokines.

Caspase-dependent protein phosphatase 2A activation contributes to endotoxin-induced cardiomyocyte contractile dysfunction

OBJECTIVE

Several studies report calcium mishandling, sarcomere disarray, and caspase activation during heart failure. Although active caspases have been shown to cleave myofibrillar proteins, little is known regarding their effects on calcium handling proteins. Therefore, we aimed to explore how endotoxin-induced caspase activation disrupts intracellular calcium regulation.

DESIGN

Randomized controlled trial.

SETTING

Small animal research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

Sepsis was induced by injection of endotoxin (10 mg/kg, intravenously). Caspase inhibition was achieved by coinjection with zVAD.fmk (3 mg/kg, intravenously). We first isolated adult rat ventricular myocytes from control, endotoxin, and (endotoxin + zVAD)-treated rats to characterize contractile parameters and cellular calcium homeostasis. Underlying molecular mechanisms responsible for calcium mishandling were explored on sarcoplasmic reticulum vesicles and mitochondria prepared from treated animals. All experiments were performed 4 hrs postendotoxin treatment.

MEASUREMENTS AND MAIN RESULTS

zVAD normalized reductions in fractional cell shortening and relaxation rate triggered by endotoxin treatment. Both sarco-/endoplasmic reticulum Ca-ATPase and mitochondria-dependent calcium uptakes were impaired after endotoxin treatment and prevented when myocytes were isolated from zVAD-treated endotoxinic rat hearts. zVAD blocked endotoxin-induced phospholamban dephosphorylation, protein phosphatase 2A activation, and mitochondrial calcium retention capacity reduction. To strengthen these results, control sarcoplasmic reticulum vesicles and mitochondria were incubated with active recombinant caspase-3. Although no effects were observed on mitochondria, caspase-3 directly exerts detrimental effects on sarcoplasmic reticulum calcium uptake capacity by activating protein phosphatase 2A, leading to phospholamban dephosphorylation.

CONCLUSIONS

Caspase inhibition protects from endotoxin-induced sarcoplasmic reticulum calcium uptake capacity reduction and mitochondrial dysfunction.

Total triterpene acids, active ingredients from Fructus Corni, attenuate diabetic cardiomyopathy by normalizing ET pathway and expression of FKBP12.6 and SERCA2a in streptozotocin-rats

Total triterpene acids (TTAs) isolated from Cornus officinalis Sieb., one of the herbs contained in Liuwei Dihuang decoction, were aimed at alleviating diabetic cardiomyopathy. We hypothesized that the benefits of TTAs may result from suppressing the endothelin-reactive oxidative species (ET-ROS) pathway in the myocardium. Diabetes was produced by a single injection of streptozotocin (STZ, 60 mg kg−1, i.p.) in rats. Assessment of cardiac function, calcium handling proteins, endothelin-1 (ET-1) and redox system was conducted 8 weeks after STZ injection. Medication with TTAs (50 mg kg−1, i.g.) was installed in the last 4 weeks. The compromised cardiac function was characterized by depressed contractility (LVSP and LV+dp/dtmax) and relaxation (LVEDP and -LVdp/dtmin) in association with hyperglycaemia (30.2 ± 2.6 mmol L−1) in STZ-injected rats. Down-regulated expression of FKBP12.6 (calstabin 2), sarcoplasmic reticulum Ca2+-ATPase 2a (SERCA2a) and phospholamban (PLB) were also found. These changes occurred in connection with an increased ET-1, up-regulated mRNA of propreET-1 and endothelin converting enzyme (ECE), and a state of oxidant stress was found by increased malondialdehyde (MDA), decreased superoxide dismutase (SOD) and glutathione peroxidase (GSH-px) activity, and an enhanced activity and expression of inducible nitric oxide synthase (iNOS) in the diabetic myocardium. After 4 weeks of treatment with TTAs, these changes were alleviated dramatically despite a mild reduction in hyperglycaemia (26.9 ± 3.4 mmol L−1). In conclusion, TTAs, as active ingredients of Liuwei Dihuang decoction, alleviated diabetic cardiomyopathy by normalizing the abnormality of FKBP12.6 and SERCA2a and ET-ROS pathway in the myocardium rather than by hypoglycaemic activity.

Protective effect of the endothelin antagonist CPU0213 against isoprenaline-induced heart failure by suppressing abnormal expression of leptin, calcineurin and SERCA2a in rats

Heart failure (HF) may be produced by sustained β-adrenoceptor stimulation by causing changes in the expression of endothelin-1 (ET-1), the leptin system, calcineurin and sarcoplasmic reticulum Ca2+ ATPase 2a (SERCA2a) underlying cardiac dysfunction. The aim of this study was to verify whether isoprenaline (ISO)-induced HF is attributed to changes in the above molecular markers, and whether the dual ET-receptor antagonist CPU0213 could reverse the cardiac dysfunction caused by ISO treatment, focusing on these molecular markers. HF was induced in rats by administration of ISO (2 mgkg−1 s.c.) for 10 days. CPU0213 (30 mgkg−1 s.c.) and propranolol (4 mgkg−1 s.c.) were administered on days 7–10. HF developed after 10 days' ISO administration and was manifest as impaired cardiac performance, increased heart weight index, oxidative stress, elevated serum enzymes, and disordered expression of the endothelin system, leptin system, calcineurin and SERCA2a. All these abnormalities were significantly reversed by CPU0213, and the effectiveness of this ET-receptor antagonist was comparable to that of propranolol. Thus, antagonism of ET receptors by CPU0213 normalizes these changes in molecular markers, alleviating HF.

Decreased FKBP12.6 expression and enhanced endothelin receptor signaling associated with arrhymogenesis in myocardial infarction rats

An increased propensity towards cardiac arrhythmias and aggravated heart function is observed in myocardial infarction (MI), the development of which is associated with the calcium handling system in the myocardium. It was hypothesized that the abnormal changes in the MI model may be a consequence of the abnormal expression and function of the RyR2-FKBP12.6 channel complex and that these abnormalities may be related to an over-activated endothelin (ET) system. Salvianolic acid B is expected to suppress life-threatening arrhythmias and to restore the abnormality of the RyR2-FKBP12.6 complex in rats. MI was produced by ligating the coronary artery for 4 weeks. Salvianolic acid B (100 mg/kg/day, p.o. for 4 weeks) was administered to rats 0.5 h before surgery. Measurements of cardiac arrhythmias, cardiac function, calcium transient, cardiac calcium release channel handling proteins and the endothelin system were conducted. The aggravated arrhythmia and compromised cardiac function in MI rats was accompanied by elevated diastolic Ca(2+) levels in the cytosol and a significant down-regulation of expression of RyR2-FKBP12.6. These were closely linked with an over-activated ET pathway in the myocardium. After a 4-week treatment with salvianolic acid B, all abnormalities were reversed significantly. Salvianolic acid B was capable of normalizing FKBP12.6 expression levels and decreasing the propensity towards arrhythmias by attenuating the up-regulated ET pathway.

Downregulated FKBP12.6 expression and upregulated endothelin signaling contribute to elevated diastolic calcium and arrhythmogenesis in rat cardiomyopathy produced by l-thyroxin

BACKGROUND

Dissociation of FKBP12.6 from RyR2 is considered as an important molecular event resulting in calcium leak and an increased risk in arrhythmogenesis. We hypothesized that augmented ventricular fibrillation (VF) on reperfusion of rat cardiomyopathy induced by l-thyroxin may result from elevated diastolic Ca(2+) levels due to dissociation (downregulation) of FKBP12.6 and upregulation of endothelin (ET-1) signaling pathway.

METHODS

Rats were treated with l-thyroxin (0.4 mg/kg, s.c.) for 10 days. Dajisentan (CPU0213), a dual endothelin receptor antagonist (100 mg/kg p.o.), or propranolol was administered on day 6 to 10. Susceptibility to VF was evaluated on ischemia/reperfusion episode. mRNA expression of FKBP12.6, and ET-1 levels were determined. Calcium transients and FKBP12.6 immunohistochemistry were measured by confocal microscopy in isolated cardiomyocytes from cardiomyopathy.

RESULTS

Cardiomyopathy induced by l-thyroxin resulted in an increased susceptibility to VF on ischemia/reperfusion. Upregulated mRNA expression of RyR2 and PKA in association with downregulated FKBP12.6 expression was found in l-thyroxin-treated rats compared to controls. Calcium transients evoked by field electrical stimulation showed an increase in Ca(2+) by +75% during diastole. An increase in ET-1 (ng/mg protein) (+36.6%) and mRNA abundance of preproET-1 were found in the left ventricle. A decreased mRNA ratio of FKBP12.6 to RyR2 likely reflected dissociation of FKBP12.6 in cardiomyopathy. These changes were normalized by Dajisentan, comparable to propranolol.

CONCLUSION

Increased susceptibility to VF in l-thyroxin-induced cardiomyopathy is related to increase in diastolic Ca(2+) levels, resulting from downregulated FKBP12.6 and upregulated ET system. ET antagonism might be useful in settings of FKBP12.6 dissociation.

Endothelin receptor antagonist CPU0213 and vitamin E reverse downregulation of FKBP12.6 and SERCA2a: a role of hyperphosphorylation of PKCepsilon

Downregulation of FKBP12.6 and sarcoplasmic reticulum Ca(2+) ATPase (SERCA2a) contributes to sudden cardiac death and heart failure. We aimed to test the hypothesis that (i) downregulation of FKBP12.6 and SERCA2a can be taken as molecular markers for drug interventions and (ii) such downregulation is produced by crosstalk between endothelin-reactive oxygen species and beta-adrenoceptors stimulation, mediated by hyperphosphorylation of protein kinase Cvarepsilon (PKCvarepsilon). Rat cardiomyocytes were incubated with isoproterenol (1 microM), endothelin-1 (0.1 microM) or hydrogen peroxide (10 microM) for 18 h, resulting in downregulation of mRNA and protein of FKBP12.6 and SERCA2a, as well as upregulation of PKCvarepsilon mRNA and phosphorylated PKCvarepsilon protein. These changes were reversed by an application of either propranolol (1 microM), endothelin receptor antagonist CPU0213 (1 microM) or vitamin E (1 microM). As indicated by the fluorescent dye Fluo3, diastolic [Ca(2+)](i) in rat ventricular myocytes was increased after incubation with isoproterenol (0.1 microM). The increased [Ca(2+)](i) in diastole was dramatically decreased by CPU0213. Thus, the downregulation of FKBP12.6 and SERCA2a, and hyperphosphorylation of PKCvarepsilon, appear to be related to crosstalk between over-activated endothelin-reactive oxygen species and a beta-adrenoceptor pathway. CPU0213 is beneficial in treating cardiac insufficiency and preventing cardiac arrhythmias possibly by normalizing hyperphosphorylation of PKCvarepsilon and abnormal FKBP12.6 and SERCA2a. The antioxidant activity of vitamin E was sufficient to normalize the levels of FKBP12.6 and SERCA2a and phosphorylation of PKCvarepsilon. Thus by testing with biomarkers FKBP12.6 and SERCA2a, we have shown that the endothelin receptor antagonist CPU0213 and the antioxidant vitamin E may relieve risk of lethal arrhythmias and heart failure by suppressing PKCvarepsilon.

Comparison of cardioprotective effects using salvianolic acid B and benazepril for the treatment of chronic myocardial infarction in rats

The aim of this study was to compare the cardioprotective effects of salvianolic acid B (Sal B) and the angiotension-converting enzyme inhibitor, benazepril, in rats with chronic myocardial infarction (MI) that resulted from a coronary artery ligation for 4 weeks. The rats were divided into four groups: those undergoing a sham operation; a MI group; a MI+SalB group (100 mg/kg by a gavage, once a day for 4 weeks); a MI+benazepril group (10 mg/kg by a gavage, once a day for 4 weeks). The following parameters were measured: echocardiographic, hemodynamic and hemorheological changes, angiogenesis, infarct size and cardiac remodeling and the messenger ribonucleic acid (mRNA) of vascular endothelium growth factor (VEGF). Rats treated with SalB or benazepril manifested the following: (1) marked improvements in echocardiographic, hemodynamic and hemorheological parameters; (2) significant reduction of infarct size; (3) significantly attenuated heart, kidney and lung hypertrophies, left ventricular (LV) dilatation and fibrosis. The unique effects of SalB were angiogenesis and augmented VEGF expression in the border and remote noninfarcted left ventricular area. These results suggest that both SalB and benazepril exerted beneficial cardioprotective effects in our experimental system, but that the modality of Sal B was different from that of benazepril. The additional beneficial effects of Sal B relative to benazpril, augmenting VEGF expression and promoting angiogenesis, may result in improved myocardial microcirculation.