Interplay between Senescence and Macrophages in Diabetic Cardiomyopathy: A Review of the Potential Role of GDF-15 and Klotho.

Type 2 diabetes mellitus (T2DM) is a critical health problem, with 700 million diagnoses expected worldwide by 2045. Uncontrolled high blood glucose levels can lead to serious complications, including diabetic cardiomyopathy (DCM). Diabetes induces cardiovascular aging and inflammation, increasing cardiomyopathy risk. DCM is characterized by structural and functional abnormalities in the heart. Growing evidence suggests that cellular senescence and macrophage-mediated inflammation participate in the pathogenesis and progression of DCM. Evidence indicates that growth differentiation factor-15 (GDF-15), a protein that belongs to the transforming growth factor-beta (TGF-ß) superfamily, is associated with age-related diseases and exerts an anti-inflammatory role in various disease models. Although further evidence suggests that GDF-15 can preserve Klotho, a transmembrane antiaging protein, emerging research has elucidated the potential involvement of GDF-15 and Klotho in the interplay between macrophages-induced inflammation and cellular senescence in the context of DCM. This review explores the intricate relationship between senescence and macrophages in DCM while highlighting the possible contributions of GDF-15 and Klotho.

Liraglutide Attenuates Diabetic Cardiomyopathy via the ILK/PI3K/AKT/PTEN Signaling Pathway in Rats with Streptozotocin-Induced Type 2 Diabetes Mellitus.

One of the possible candidates for the treatment of diabetic cardiomyopathy is liraglutide, a glucagon-like peptide-1 receptor (GLP1R) agonist. In this study, the impacts of liraglutide on the integrin-linked kinase (ILK)-related PI3K/AKT axis in rats with type 2 diabetes induced via streptozotocin were examined. Twenty-four Wistar albino rats were distributed in four different groups, and a high-fat diet and streptozotocin were used to induce type 2 in two groups. Rats in the untreated control groups were administered 0.9% NaCl solution over a 6-week period, and those in the treatment groups were administered 0.9% NaCl for 3 weeks, followed by subcutaneous injection of liraglutide (150 µg/kg) for an additional 3 weeks. In the liraglutide-treated diabetic group, the heart-to-body weight ratio was significantly reduced, levels of cardiac biomarkers, troponin I and creatine-kinase-MB, were improved; activities of antioxidant enzymes, glutathione peroxidase and superoxide dismutase, were increased; and levels of malondialdehyde were decreased. Western blotting and immunohistochemical studies revealed increased levels of ILK, P-PI3K, P-AKT, and BCL2, as well as those of caspase 3, BAX, and P-PTEN, indicating mitigation of cardiomyocyte apoptosis. Our results show that liraglutide, by targeting GLP1Rs, enhances the expression of proteins in the ILK/PI3K/AKT/PTEN pathway and thereby exerts its cardioprotective effects in rats with DCM.

Role of the integrin-linked kinase/TGF-ß/SMAD pathway in sitagliptin-mediated cardioprotective effects in a rat model of diabetic cardiomyopathy.

OBJECTIVES: Diabetic cardiomyopathy is a known complication of diabetes mellitus. Herein, we aimed to determine whether glycemic control mediated by sitagliptin, a dipeptidyl peptidase-4 inhibitor, can ameliorate diabetic myocardial abnormalities by modulating TGF-ß signaling via the SMAD and integrin-linked kinase (ILK) pathways. METHODS: Four groups of male Wistar albino rats were used, with six rats in each group. Two nondiabetic and two diabetic (produced by a single intraperitoneal dose of streptozotocin (55 mg/kg)) groups were administered either normal saline or sitagliptin (100 mg/kg) orally for 6 weeks. Subsequently, HW/BW ratios and cardiac enzymes were assessed, along with a histological examination of cardiac tissues. Levels of TGF-ß, collagen I, p-SMAD2/3, TNF-α, MMP-9, and ILK were detected. RESULTS: Compared with the diabetic control group, sitagliptin-treated diabetic rats exhibited considerably reduced HW/BW ratios and troponin I and creatine kinase-MB levels, with improvements in histopathological changes in cardiac tissues. TGF-ß, collagen I, p-SMAD2/3, TNF-α, and MMP-9 levels were significantly decreased in the sitagliptin-treated diabetic group, whereas ILK was elevated following sitagliptin treatment. CONCLUSION: Sitagliptin could afford cardioprotective effects for the first time by altering ILK-associated TGF-ß/SMAD signaling pathways. Thus, sitagliptin may be a promising therapeutic target for the prevention of diabetic cardiomyopathy.

Cardioprotective Effects of the GRK2 Inhibitor Paroxetine on Isoproterenol-Induced Cardiac Remodeling by Modulating NF-κB Mediated Prohypertrophic and Profibrotic Gene Expression.

Pathological cardiac remodeling is associated with cardiovascular disease and can lead to heart failure. Nuclear factor-kappa B (NF-κB) is upregulated in the hypertrophic heart. Moreover, the expression of the G-protein-coupled receptor kinase 2 (GRK2) is increased and linked to the progression of heart failure. The inhibitory effects of paroxetine on GRK2 have been established. However, its protective effect on IκBα/NFκB signaling has not been elucidated. This study investigated the cardioprotective effect of paroxetine in an animal model of cardiac hypertrophy (CH), focusing on its effect on GRK2-mediated NF-κB-regulated expression of prohypertrophic and profibrotic genes. Wistar albino rats were administered normal saline, paroxetine, or fluoxetine, followed by isoproterenol to induce CH. The cardioprotective effects of the treatments were determined by assessing cardiac injury, inflammatory biomarker levels, histopathological changes, and hypertrophic and fibrotic genes in cardiomyocytes. Paroxetine pre-treatment significantly decreased the HW/BW ratio (p < 0.001), and the expression of prohypertrophic and profibrotic genes Troponin-I (p < 0.001), BNP (p < 0.01), ANP (p < 0.001), hydroxyproline (p < 0.05), TGF-ß1 (p < 0.05), and αSMA (p < 0.01) as well as inflammatory markers. It also markedly decreased pIκBα, NFκB(p105) subunit expression (p < 0.05) and phosphorylation. The findings suggest that paroxetine prevents pathological cardiac remodeling by inhibiting the GRK2-mediated IκBα/NF-κB signaling pathway.

Sitagliptin Mitigates Diabetic Nephropathy in a Rat Model of Streptozotocin-Induced Type 2 Diabetes: Possible Role of PTP1B/JAK-STAT Pathway.

Diabetic nephropathy (DN) is a microvascular complication of diabetes mellitus. This study examined the therapeutic effects of sitagliptin, a dipeptidyl peptidase inhibitor, on DN and explored the underlying mechanism. Male Wistar albino rats (n = 12) were intraperitoneally administered a single dose of streptozotocin (30 mg/kg) to induce diabetes. Streptozotocin-treated and untreated rats (n = 12) were further divided into normal control, normal sitagliptin-treated control, diabetic control, and sitagliptin-treated diabetic groups (n = 6 in each). The normal and diabetic control groups received normal saline, whereas the sitagliptin-treated control and diabetic groups received sitagliptin (100 mg/kg, p.o.). We assessed the serum levels of DN and inflammatory biomarkers. Protein tyrosine phosphatase 1 B (PTP1B), phosphorylated Janus kinase 2 (P-JAK2), and phosphorylated signal transducer activator of transcription (P-STAT3) levels in kidney tissues were assessed using Western blotting, and kidney sections were examined histologically. Sitagliptin reduced DN and inflammatory biomarkers and the expression of PTP1B, p-JAK2, and p-STAT3 (p < 0.001) and improved streptozotocin-induced histological changes in the kidney. These results demonstrate that sitagliptin ameliorates inflammation by inhibiting DPP-4 and consequently modulating the PTP1B-related JAK/STAT axis, leading to the alleviation of DN.

α1A Adrenoreceptor blockade attenuates myocardial infarction by modulating the integrin-linked kinase/TGF-ß/Smad signaling pathways.

BACKGROUND: Myocardial infarction (MI) is considered a public health problem. According to the World Health Organization, MI is a leading cause of death and comorbidities worldwide. Activation of the α1A adrenergic receptor is a contributing factor to the development of MI. Tamsulosin, an α1A adrenergic blocker, has gained wide popularity as a medication for the treatment of benign prostatic hyperplasia. Limited evidence from previous studies has revealed the potential cardioprotective effects of tamsulosin, as its inhibitory effect on the α1A adrenoceptor protects the heart by acting on the smooth muscle of blood vessels, which results in hypotension; however, its effect on the infarcted heart is still unclear. The mechanisms of the expected cardioprotective effects mediated by tamsulosin are not yet understood. Transforming growth factor-beta (TGF-ß), a mediator of fibrosis, is considered an attractive therapeutic target for remodeling after MI. The role of α1A adrenoceptor inhibition or its relationships with integrin-linked kinase (ILK) and TGF-ß/small mothers against decapentaplegic (Smad) signaling pathways in attenuating MI are unclear. The present study was designed to investigate whether tamsulosin attenuates MI by modulating an ILK-related TGF-ß/Smad pathway. METHODS: Twenty-four adult male Wistar rats were randomly divided into 4 groups: control, ISO, TAM, and ISO + TAM. ISO (150 mg/kg, intraperitoneally) was injected on Days 20 and 21 to induce MI. Tamsulosin (0.8 mg/kg, orally) was administered for 21 days, prior to ISO injection for 2 consecutive days. Heart-to-body weight ratios and cardiac and fibrotic biomarker levels were subsequently determined. ILK, TGF-ß1, p-Smad2/3, and collagen III protein expression levels were determined using biomolecular methods. RESULTS: Tamsulosin significantly attenuated the relative heart-to-body weight index (p < 0.5) and creatine kinase-MB level (p < 0.01) compared with those in the ISO control group. While ISO resulted in superoxide anion production and enhanced oxidative damage, tamsulosin significantly prevented this damage through antioxidant defense mechanisms, increasing glutathione and superoxide dismutase levels (p < 0.05) and decreasing lipid peroxide oxidation levels (p < 0.01). The present data revealed that tamsulosin reduced TGF-ß/p-Smad2/3 expression and enhanced ILK expression. CONCLUSION: Tamsulosin may exert a cardioprotective effect by modulating the ILK-related TGF-ß/Smad signaling pathway. Thus, tamsulosin may be a useful therapeutic approach for preventing MI.

P2X7 purinergic receptor: A potential target in heart diseases (Review).

The P2X7 purinergic receptor (P2X7R) is a non­selective cation channel activated by high levels of adenosine triphosphate that are commonly present in serious conditions. Activation of this purinergic receptor is closely related to the development of various disease states including inflammatory and neurodegenerative disorders, orthopedic diseases and types of cancer. Accumulating evidence has shown that the P2X7R plays a crucial role in the development of various heart diseases. For example, activation of P2X7Rs may alleviate myocardial ischemia­reperfusion injury by releasing endogenous cardiac protective substances. In contrast to these findings, activation of P2X7Rs can promote the development of acute myocardial infarction and myocarditis by inducing inflammatory responses. Activation of these receptors can also contribute to the development of different types of cardiomyopathies including diabetic cardiomyopathy, dilated cardiomyopathy and hypertrophic cardiomyopathy by inducing cardiac hypertrophy, fibrosis and apoptosis. Notably, inhibition of P2X7Rs can improve cardiac structure and function abnormalities following acute myocardial infarction, reduction of inflammatory responses following myocarditis and attenuation of the cardiomyopathy process. Furthermore, recent evidence has demonstrated that P2X7Rs are highly active in patients infected with coronavirus disease­2019 (COVID­19). Hyperactivation of P2X7Rs in COVID­19 may induce severe myocardial injury through the activation of several signaling pathways. The present study reviewed the important role of the P2X7R in cardiac dysfunctions and discusses its use as a possible new therapeutic approach for the prevention and treatment of several myocardial diseases.

Inflammation and Treatment-Resistant Depression from Clinical to Animal Study: A Possible Link?

The aim of this study was to investigate the relationship between treatment-resistant depression (TRD) and inflammation in humans and experimental models. For the human study, a retrospective cohort study was conducted with 206 participants; half were on antidepressants for major depressive disorder. The patients were divided into healthy and depressed groups. Inflammation was assessed based on the values of the main inflammatory biomarkers (CRP, WBC and ESR). For the animal experiments, 35 adult male Wistar rats were assigned to stressed and non-stressed groups. Inflammation and stress were induced using lipopolysaccharide and chronic unpredictable mild stress. A 10 mg/kg intraperitoneal injection of fluoxetine (FLX), a known antidepressant, was simultaneously administered daily for 4 weeks. Behavioral tests were performed. The plasma levels of inflammatory and stress biomarkers were measured and were significantly higher in the stressed and non-responsive groups in both studies. This study provides evidence of the link between inflammation and TRD. We further observed a possible link via the Phosphorylated Janus Kinase 2 and Phosphorylated Signal Transducer and Activator of Transcription 3 (P-JAK2/P-STAT3) signaling pathway and found that chronic stress and high inflammation hinder the antidepressant effects of FLX. Thus, non-response to antidepressants could be mitigated by treating inflammation to improve the antidepressant effect in patients with TRD.

Examining Anxiety, Sleep Quality, and Physical Activity as Predictors of Depression among University Students from Saudi Arabia during the Second Wave of the COVID-19 Pandemic.

Conducted during the second wave of the pandemic, this cross-sectional study examined the link between sleep quality, physical activity, exposure, and the impact of COVID-19 as predictors of mental health in Saudi undergraduate students. A convenience sample of 207 participants were recruited, 89% of whom were females and 94% were single. The measures included questionnaires on the level of exposure and the perceived impact of COVID-19, a physical activity measure, GAD-7, PHQ-9, and PSQI. The results indicated that approximately 43% of participants exhibited moderate anxiety, and 50% were at risk of depression. Overall, 63.93% of students exposed to strict quarantine for at least 14 days (n = 39) exhibited a high risk of developing depression (χ2(1) = 6.49, p < 0.05, ϕ = 0.18). A higher risk of depression was also found in students whose loved ones lost their jobs (χ2(1) = 4.24, p < 0.05, ϕ = 0.14). Moreover, there was also a strong association between depression and anxiety (ß = 0.33, p < 0.01), sleep quality (ß = 0.32, p < 0.01), and the perceived negative impact of COVID-19 on socio-economic status (ß = 0.26, p < 0.05), explaining 66.67% of depression variance. Our study highlights the socio-economic impact of this pandemic and the overwhelming prevalence of depression.

G protein-coupled receptor kinase 2 is essential to enable vasoconstrictor-mediated arterial smooth muscle proliferation.

Hypertension is associated with increased production and circulation of vasoconstrictors, resulting in enhanced signalling through their cognate G protein-coupled receptors (GPCR). Prolonged vasoconstrictor GPCR signalling increases arterial contraction and stimulates signalling pathways that promote vascular smooth muscle cell (VSMC) proliferation, contributing to the development of atherosclerotic plaques, re-stenosis lesions and vascular remodelling. GPCR signalling through phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) promotes VSMC proliferation. In VSMC, G protein-coupled receptor kinase 2 (GRK2) is known to regulate numerous vasoconstrictor GPCRs and their downstream signalling pathways. As GRK2 is implicated in controlling various aspects of cellular growth, we examined whether GRK2 could affect VSMC proliferation. Using two indices of cell growth, we show that PI3K inhibition and depletion of GRK2 expression produced a similar ablation of pro-proliferative vasoconstrictor-stimulated VSMC growth. Furthermore, GRK2-knockdown ablated the sustained phase of endothelin-1 and angiotensin-II-stimulated Akt phosphorylation, whilst the peak (5 min) phase was unaffected. Conversely, the GRK2 inhibitor compound 101 did not affect vasoconstrictor-driven Akt phosphorylation. Vasoconstrictor-stimulated phosphorylation of the Akt substrates GSK3α and GSK3ß was ablated following RNAi-mediated GRK2 depletion, or after PI3K inhibition. Moreover, GRK2 knockdown prevented endothelin-1 and angiotensin-II from increasing cyclin D1 expression. These data suggest GRK2 expression is essential to facilitate vasoconstrictor-driven VSMC proliferation through its ability to promote efficient prolonged PI3K-Akt signalling, and thus relieve the GSK3-mediated block on cell cycling. Considering VSMC GRK2 expression increases early in the development of hypertension, this highlights the potential for GRK2 to promote VSMC growth and exacerbate hypertensive pathophysiological vascular remodelling.

A novel form of glycolytic metabolism-dependent cardioprotection revealed by PKCα and ß inhibition.

KEY POINTS: Acute hyperglycaemia at the time of a heart attack worsens the outcome for the patient. Acute hyperglycaemia is not limited to diabetic patients and can be due to a stress response in non-diabetics. This study suggests that the damaging cardiac effects of hyperglycaemia can be reversed by selective PKC inhibition. If PKCα/ß isoforms are inhibited, then high glucose itself becomes protective against ischaemic damage. Selective PKC inhibition may therefore be a useful therapeutic tool to limit the damage that can occur during a heart attack by stress-induced hyperglycaemia. ABSTRACT: Hyperglycaemia has a powerful association with adverse prognosis for patients with acute coronary syndromes (ACS). Previous work shows that high glucose prevents ischaemic preconditioning and causes electrical and mechanical disruption via protein kinase C α/ß (PKCα/ß) activation. The present study aimed to: (i) determine whether the adverse clinical association of hyperglycaemia in ACS can be replicated in preclinical cellular models of ACS and (ii) determine the importance of PKCα/ß activation to the deleterious effect of glucose. Freshly isolated rat, guinea pig or rabbit cardiomyocytes were exposed to simulated ischaemia after incubation in the presence of normal (5 mm) or high (20 mm) glucose in the absence or presence of small molecule or tat-peptide-linked PKCαß inhibitors. In each of the four conditions, the following hallmarks of cardioprotection were recorded using electrophysiology or fluorescence imaging: cardiomyocyte contraction and survival, action potential stability and time to failure, intracellular calcium and ATP, mitochondrial depolarization, ischaemia-sensitive leak current, and time to Kir 6.2 opening. High glucose alone resulted in decreased cardiomyocyte contraction and survival; however, it also imparted cardioprotection in the presence of PKCα/ß inhibitors. This cardioprotective phenotype displayed improvements in all of the measured parameters and decreased myocardium damage during whole heart coronary ligation experiments. High glucose is deleterious to cellular and whole-heart models of simulated ischaemia, in keeping with the clinical association of hyperglycaemia with an adverse outcome in ACS. PKCαß inhibition revealed high glucose to show a cardioprotective phenotype in this setting. The results of the present study suggest the potential for the therapeutic application of PKCαß inhibition in ACS associated with hyperglycaemia.