Local IGF-1 isoform protects cardiomyocytes from hypertrophic and oxidative stresses via SirT1 activity

Vascular smooth muscle cell-specific Igf1r deficiency exacerbates the development of hypertension-induced cerebral microhemorrhages and gait defects

Cerebrovascular fragility and cerebral microhemorrhages (CMH) contribute to age-related cognitive impairment, mobility defects, and vascular cognitive impairment and dementia, impairing healthspan and reducing quality of life in the elderly. Insulin-like growth factor 1 (IGF-1) is a key vasoprotective growth factor that is reduced during aging. Circulating IGF-1 deficiency leads to the development of CMH and other signs of cerebrovascular dysfunction. Here our goal was to understand the contribution of IGF-1 signaling on vascular smooth muscle cells (VSMCs) to the development of CMH and associated gait defects. We used an inducible VSMC-specific promoter and an IGF-1 receptor (Igf1r) floxed mouse line (Myh11-CreERT2 Igf1rf/f) to knockdown Igf1r. Angiotensin II in combination with L-NAME-induced hypertension was used to elicit CMH. We observed that VSMC-specific Igf1r knockdown mice had accelerated development of CMH, and subsequent associated gait irregularities. These phenotypes were accompanied by upregulation of a cluster of pro-inflammatory genes associated with VSMC maladaptation. Collectively our findings support an essential role for VSMCs as a target for the vasoprotective effects of IGF-1, and suggest that VSMC dysfunction in aging may contribute to the development of CMH.

Hydrogels for Cardio and Vascular Tissue Repair and Regeneration

Cardiovascular disease (CVD), the leading cause of death globally, affects the heart and arteries with a variety of clinical manifestations, the most dramatic of which are myocardial infarction (MI), abdominal aortic aneurysm (AAA), and intracranial aneurysm (IA) rupture. In MI, necrosis of the myocardium, scar formation, and loss of cardiomyocytes result from insufficient blood supply due to coronary artery occlusion. Beyond stenosis, the arteries that are structurally and functionally connected to the cardiac tissue can undergo pathological dilation, i.e., aneurysmal dilation, with high risk of rupture. Aneurysms of the intracranial arteries (IAs) are more commonly seen in young adults, whereas those of the abdominal aorta (AAA) are predominantly seen in the elderly. IAs, unpredictably, can undergo rupture and cause life-threatening hemorrhage, while AAAs can result in rupture, internal bleeding and high mortality rate. In this clinical context, hydrogels, three-dimensional networks of water-seizing polymers, have emerged as promising biomaterials for cardiovascular tissue repair or protection due to their biocompatibility, tunable properties, and ability to encapsulate and release bioactive molecules. This review provides an overview of the current state of research on the use of hydrogels as an innovative platform to promote cardiovascular-specific tissue repair in MI and functional recovery or protection in aneurysmal dilation.

Insulin-like growth factor 1 and its prognostic value in the course of acute ischemic cerebrovascular events

Introduction

The aim of the study was to evaluate insulin-like growth factor 1 (IGF-1) as a predictor of the course of an acute cerebral ischemic event (AICE). This polypeptide, by activating receptors that are present in most tissues, including the brain, mediates the anabolic activity of growth hormone (GH) and its impact on growth and maturation processes, as well as organisms' survival time. AICE can occur in the form of a transient ischemic attack (TIA) or an ischemic stroke (IS).

Material and methods

The study included 86 participants. The correlation between serum IGF-1 concentration and the clinical status of 56 patients on days 1 and 9 of AICE, as well as risk factors and the course of the disease, were prospectively analyzed. The control group consisted of 30 healthy volunteers.

Results

Patients with a minor baseline neurological syndrome had higher serum IGF-1 concentrations than patients with severe baseline neurological dysfunctions. Multidimensional analyses showed that high IGF-1 values independently determined the worse course of the disease, especially in patients with a severe neurological deficit present on the first day of AICE.

Conclusions

Our results indicate that the high level of circulating IGF-1 on the first day of AICE is an independent factor determining the unfavorable course of the stroke, and this relationship is proportional to the severity of the baseline neurological deficit. The study also revealed a positive correlation between the decreased plasma IGF-1 concentration on the first day of AICE and the severity of neurological symptoms.

Detergent-Based Decellularization for Anisotropic Cardiac-Specific Extracellular Matrix Scaffold Generation

Cell-derived extracellular matrix (ECM) has become increasingly popular in tissue engineering applications due to its ability to provide tailored signals for desirable cellular responses. Anisotropic cardiac-specific ECM scaffold decellularized from human induced pluripotent stem cell (hiPSC)-derived cardiac fibroblasts (hiPSC-CFs) mimics the native cardiac microenvironment and provides essential biochemical and signaling cues to hiPSC-derived cardiomyocytes (hiPSC-CMs). The objective of this study was to assess the efficacy of two detergent-based decellularization methods: (1) a combination of ethylenediaminetetraacetic acid and sodium dodecyl sulfate (EDTA + SDS) and (2) a combination of sodium deoxycholate and deoxyribonuclease (SD + DNase), in preserving the composition and bioactive substances within the aligned ECM scaffold while maximumly removing cellular components. The decellularization effects were evaluated by characterizing the ECM morphology, quantifying key structural biomacromolecules, and measuring preserved growth factors. Results showed that both treatments met the standard of cell removal (less than 50 ng/mg ECM dry weight) and substantially preserved major ECM biomacromolecules and growth factors. The EDTA + SDS treatment was more time-efficient and has been determined to be a more efficient method for generating an anisotropic ECM scaffold from aligned hiPSC-CFs. Moreover, this cardiac-specific ECM has demonstrated effectiveness in supporting the alignment of hiPSC-CMs and their expression of mature structural and functional proteins in in vitro cultures, which is crucial for cardiac tissue engineering.

Cardioprotective effects of calorie restriction against inflammation and apoptosis in ovariectomized obese rats: Role of classical estrogen receptors and SIRT1

AIM

Obesity is a metabolic complication linked with bad eating habits and a sedentary lifestyle, and the heart is one of the target organs damaged by it. Estrogen deficiency during menopause worsens the situation. Calorie restriction (CR) can contribute to reducing cardiovascular disease (CVD) in postmenopausal conditions. Thus, the effects of CR on inflammation and apoptosis in ovariectomized rats' hearts with obesity were studied.

METHOD

Female Wistar rats were categorized into Sham and OVX (ovariectomized) groups and received a standard diet (SD) or high-fat diet (60%HFD) or calorie restriction (30% CR) for 16 weeks. The real-time PCR method was used to evaluate the inflammatory markers and estrogen receptors gene expression. Western-blot and ELISA methods were respectively used for the measurement of apoptosis and SIRT1 protein expression.

RESULTS

HFD led to the elevation of body weight, IL-6 (interleukin-6) and TNF-α (tumor necrosis factor-α) and reduction of IL-10 (interleukin-10) gene expressions, and also an increment in protein levels of cleaved caspase-3, Bax and Bax/Bcl2 ratio and decrement in Bcl-2 in OVX rats (P < 0.001). Additionally, HFD reduced SIRT1 (sirtuin1) protein levels, ERα (estrogen receptor α), and ERβ (estrogen receptor β) gene expressions (P < 0.001). In contrast, CR declined body weight, IL-6 and TNF-α (P < 0.001), increased IL-10 expressions (P < 0.05), decreased cleaved caspase-3 (P < 0.001), Bax (P < 0.01), and Bax/Bcl2 ratio (P < 0.05), enhanced Bcl-2 (P < 0.001), increased SIRT1 (P < 0.05) and ERα (P < 0.001) and ERβ (P < 0.01) expressions.

CONCLUSION

CR through the SIRT1 regulation and estrogen receptors attenuate obesity-induced-cardiac inflammation and apoptosis. CR can be a cardioprotective candidate in postmenopausal conditions.

Moringa oleifera leaf supplementation relieves oxidative stress and regulates intestinal flora to ameliorate polycystic ovary syndrome in letrozole-induced rats

This study investigated the effects of supplementation Moringa oleifera leaf (MOL) on relieving oxidative stress, anti-inflammation, changed the relative abundance of multiple intestinal flora and blood biochemical indices during letrozole-induced polycystic ovary syndrome (PCOS). Previous studies have shown that MOL has anti-inflammatory, anti-oxidation, insulin-sensitizing effects. However, whether MOL has beneficial effects on PCOS remains to be elucidated. In the current study, 10-week-old female Sprague-Dawley rats received letrozole to induce PCOS-like rats, and subsequently were treated with a MOL diet. Then, the body weight and estrus cycles were measured regularly in this period. Finally, the ovarian morphology, blood biochemical indices, anti-oxidative, intestinal flora, and anti-inflammation were observed at the end of the experiment. We found that MOL supplementation markedly decreased the body weight, significantly upregulated the expression of Sirt1, FoxO1, PGC-1α, IGF1, and substantially modulated the sex hormone level and improved insulin resistance, which may be associated with the relieves oxidative stress. Moreover, the supplementation of MOL changed the relative abundance of multiple intestinal flora, the relative abundance of Fusobacterium, Prevotella were decreased, and Blautia and Parabacteroides were increased. These results indicate that MOL is potentially a supplementary medication for the management of PCOS.

Metabolic landscape in cardiac aging: insights into molecular biology and therapeutic implications

Cardiac aging is evident by a reduction in function which subsequently contributes to heart failure. The metabolic microenvironment has been identified as a hallmark of malignancy, but recent studies have shed light on its role in cardiovascular diseases (CVDs). Various metabolic pathways in cardiomyocytes and noncardiomyocytes determine cellular senescence in the aging heart. Metabolic alteration is a common process throughout cardiac degeneration. Importantly, the involvement of cellular senescence in cardiac injuries, including heart failure and myocardial ischemia and infarction, has been reported. However, metabolic complexity among human aging hearts hinders the development of strategies that targets metabolic susceptibility. Advances over the past decade have linked cellular senescence and function with their metabolic reprogramming pathway in cardiac aging, including autophagy, oxidative stress, epigenetic modifications, chronic inflammation, and myocyte systolic phenotype regulation. In addition, metabolic status is involved in crucial aspects of myocardial biology, from fibrosis to hypertrophy and chronic inflammation. However, further elucidation of the metabolism involvement in cardiac degeneration is still needed. Thus, deciphering the mechanisms underlying how metabolic reprogramming impacts cardiac aging is thought to contribute to the novel interventions to protect or even restore cardiac function in aging hearts. Here, we summarize emerging concepts about metabolic landscapes of cardiac aging, with specific focuses on why metabolic profile alters during cardiac degeneration and how we could utilize the current knowledge to improve the management of cardiac aging.

Transplantation of Skeletal Muscle-Derived Sca-1+/PW1+/Pax7- Interstitial Cells (PICs) Improves Cardiac Function and Attenuates Remodeling in Mice Subjected to Myocardial Infarction

We have previously shown that skeletal muscle-derived Sca-1⁺/PW1⁺/Pax7^- interstitial cells (PICs) are multi-potent and enhance endogenous repair and regeneration. Here, we investigated the regenerative potential of PICs following intramyocardial transplantation in mice subjected to an acute myocardial infarction (MI). MI was induced through the ligation of the left anterior descending coronary artery in 8-week old male C57BL/6 mice. 5 × 10⁵ eGFP-labelled PICs (MI + PICs; n = 7) or PBS (MI-PBS; n = 7) were injected intramyocardially into the border zone. Sham mice (n = 8) were not subjected to MI, or the transplantation of PICs or PBS. BrdU was administered via osmotic mini-pump for 14 days. Echocardiography was performed prior to surgery (baseline), and 1-, 3- and 6-weeks post-MI and PICs transplantation. Mice were sacrificed at 6 weeks post-MI + PICs transplantation, and heart sections were analysed for fibrosis, hypertrophy, engraftment, proliferation, and differentiation of PICs. A significant (p < 0.05) improvement in ejection fraction (EF) and fractional shortening was observed in the MI-PICs group, compared to MI + PBS group at 6-weeks post MI + PICs transplantation. Infarct size/fibrosis of the left ventricle significantly (p < 0.05) decreased in the MI-PICs group (14.0 ± 2.5%), compared to the MI-PBS group (32.8 ± 2.2%). Cardiomyocyte hypertrophy in the border zone significantly (p < 0.05) decreased in the MI-PICs group compared to the MI-PBS group (330.0 ± 28.5 µM² vs. 543.5 ± 26.6 µm²), as did cardiomyocyte apoptosis (0.6 ± 0.9% MI-PICs vs. 2.8 ± 0.8% MI-PBS). The number of BrdU+ cardiomyocytes was significantly (p < 0.05) increased in the infarct/border zone of the MI-PICs group (7.0 ± 3.3%), compared to the MI-PBS group (1.7 ± 0.5%). The proliferation index (total BrdU+ cells) was significantly increased in the MI-PICs group compared to the MI-PBS group (27.0 ± 3.4% vs. 7.6 ± 1.0%). PICs expressed and secreted pro-survival and reparative growth factors, supporting a paracrine effect of PICs during recovery/remodeling. Skeletal muscle-derived PICs show significant reparative potential, attenuating cardiac remodelling following transplantation into the infarcted myocardium. PICs can be easily sourced from skeletal muscle and therefore show promise as a potential cell candidate for supporting the reparative and regenerative effects of cell therapies.

Testosterone protects cardiomyocytes against hydrogen peroxide-induced aging by upregulating IGF1 and SIRT1 pathways

Objective

To investigate the role of IGF1 and SIRT1 pathways in protection of hydrogen peroxide (H2O2)-induced aging in H9c2 rat cardiomyocyte cells by testosterone.

Methods

The cells were treated with testosterone or up- or down-regulated for the IGF1 and SIRT1 genes and assessed for apoptosis, aging and expression of relevant genes.

Results

Aging was induced and the expression of SIRT1 and IGF1 was down-regulated after H2O2 treatment in H9c2 cells. The aging was attenuated in a dose-dependent manner after the cells were exposed to testosterone. Down-regulation of SIRT1 and IGF1expression was offset in the H2O2-treated cells co-treated with testosterone. Up- or down-regulation of IGF1 significantly reduced or increased senescence-associated beta-galactosidase (SA-β-gal) cells and the ROS level, respectively. In addition, SIRT1 expression was regulated by IGF1 expression. Down- or up-regulation of SIRT1 significantly decreased or increased the IGF1 levels, respectively. Furthermore, after IGF1 and SIRT1 knockdown, testosterone did not protect the cells from senescence. Testosterone, and overexpression of IGF1 and SIRT1 also up-regulated the expression of the fetal genes SERCA2 and MYH6 and down-regulated the expression of the ACTA1 and MYH7 genes.

Conclusions

Our data indicate that testosterone can attenuate cardiomyocyte aging induced by H2O2 and up-regulate SIRT1 and IGF1. The IGF1and SIRT1 pathway may be new targets to treat heart aging and heart failure.

Late plasma exosome microRNA-21-5p depicts magnitude of reverse ventricular remodeling after early surgical repair of primary mitral valve regurgitation

Introduction

Primary mitral valve regurgitation (MR) results from degeneration of mitral valve apparatus. Mechanisms leading to incomplete postoperative left ventricular (LV) reverse remodeling (Rev-Rem) despite timely and successful surgical mitral valve repair (MVR) remain unknown. Plasma exosomes (pEXOs) are smallest nanovesicles exerting early postoperative cardioprotection. We hypothesized that late plasma exosomal microRNAs (miRs) contribute to Rev-Rem during the late postoperative period.

Methods

Primary MR patients (n = 19; age, 45-71 years) underwent cardiac magnetic resonance imaging and blood sampling before (T0) and 6 months after (T1) MVR. The postoperative LV Rev-Rem was assessed in terms of a decrease in LV end-diastolic volume and patients were stratified into high (HiR-REM) and low (LoR-REM) LV Rev-Rem subgroups. Isolated pEXOs were quantified by nanoparticle tracking analysis. Exosomal microRNA (miR)-1, -21-5p, -133a, and -208a levels were measured by RT-qPCR. Anti-hypertrophic effects of pEXOs were tested in HL-1 cardiomyocytes cultured with angiotensin II (AngII, 1 μM for 48 h).

Results

Surgery zeroed out volume regurgitation in all patients. Although preoperative pEXOs were similar in both groups, pEXO levels increased after MVR in HiR-REM patients (+0.75-fold, p = 0.016), who showed lower cardiac mass index (-11%, p = 0.032). Postoperative exosomal miR-21-5p values of HiR-REM patients were higher than other groups (p < 0.05). In vitro, T1-pEXOs isolated from LoR-REM patients boosted the AngII-induced cardiomyocyte hypertrophy, but not postoperative exosomes of HiR-REM. This adaptive effect was counteracted by miR-21-5p inhibition.

Summary/Conclusion

High levels of miR-21-5p-enriched pEXOs during the late postoperative period depict higher LV Rev-Rem after MVR. miR-21-5p-enriched pEXOs may be helpful to predict and to treat incomplete LV Rev-Rem after successful early surgical MVR.

Association between IGF-1 levels ranges and all-cause mortality: A meta-analysis

The association between IGF‐1 levels and mortality in humans is complex with low levels being associated with both low and high mortality. The present meta‐analysis investigates this complex relationship between IGF‐1 and all‐cause mortality in prospective cohort studies. A systematic literature search was conducted in PubMed/MEDLINE, Scopus, and Cochrane Library up to September 2019. Published studies were eligible for the meta‐analysis if they had a prospective cohort design, a hazard ratio (HR) and 95% confidence interval (CI) for two or more categories of IGF‐1 and were conducted among adults. A random‐effects model with a restricted maximum likelihood heterogeneity variance estimator was used to find combined HRs for all‐cause mortality. Nineteen studies involving 30,876 participants were included. Meta‐analysis of the 19 eligible studies showed that with respect to the low IGF‐1 category, higher IGF‐1 was not associated with increased risk of all‐cause mortality (HR = 0.84, 95% CI = 0.68–1.05). Dose–response analysis revealed a U‐shaped relation between IGF‐1 and mortality HR. Pooled results comparing low vs. middle IGF‐1 showed a significant increase of all‐cause mortality (HR = 1.33, 95% CI = 1.14–1.57), as well as comparing high vs. middle IGF‐1 categories (HR = 1.23, 95% CI = 1.06–1.44). Finally, we provide data on the association between IGF‐1 levels and the intake of proteins, carbohydrates, certain vitamins/minerals, and specific foods. Both high and low levels of IGF‐1 increase mortality risk, with a specific 120–160 ng/ml range being associated with the lowest mortality. These findings can explain the apparent controversy related to the association between IGF‐1 levels and mortality.

The Effects of Mechanical Loading Variations on the Hypertrophic, Anti-Apoptotic, and Anti-Inflammatory Responses of Differentiated Cardiomyocyte-like H9C2 Cells

Cardiomyocytes possess the ability to respond to mechanical stimuli by adapting their biological functions. This study investigated cellular and molecular events in cardiomyocyte-like H9C2 cells during differentiation as well as the signalling and gene expression responses of the differentiated cells under various mechanical stretching protocols in vitro. Immunofluorescence was used to monitor MyHC expression and structural changes during cardiomyoblast differentiation. Moreover, alterations in the expression of cardiac-specific markers, cell cycle regulatory factors, MRFs, hypertrophic, apoptotic, atrophy and inflammatory factors, as well as the activation of major intracellular signalling pathways were evaluated during differentiation and under mechanical stretching of the differentiated H9C2 cells. Compared to undifferentiated cells, advanced-differentiation cardiomyoblasts exhibited increased expression of cardiac-specific markers, MyHC, MRFs, and IGF-1 isoforms. Moreover, differentiated cells that underwent a low strain/frequency mechanical loading protocol of intermediate duration showed enhanced expression of MRFs and hypertrophic factors, along with a decreased expression of apoptotic, atrophy, and inflammatory factors compared to both high-strain/frequency loading protocols and to unloaded cells. These findings suggest that altering the strain and frequency of mechanical loading applied on differentiated H9C2 cardiomyoblasts can regulate their anabolic/survival program, with a low-strain/frequency stretching being, overall, most effective at inducing beneficial responses.

IGFBP-4 Proteolysis by PAPP-A in a Primary Culture of Rat Neonatal Cardiomyocytes under Normal and Hypertrophic Conditions

Cardiovascular diseases (CVD) are among the leading causes of death and disability worldwide. Pregnancy-associated plasma protein-A (PAPP-A) is a matrix metalloprotease localized on the cell surface. One of the substrates that PAPP-A cleaves is the insulin-like growth factor binding protein-4 (IGFBP-4), a member of the family of proteins that bind insulin-like growth factor (IGF). Proteolysis of IGFBP-4 by PAPP-A occurs at a specific site resulting in formation of two proteolytic fragments - N-terminal IGFBP-4 (NT-IGFBP-4) and C-terminal IGFBP-4 (CT-IGFBP-4), and leads to the release of IGF activating various cellular processes including migration, proliferation, and cell growth. Increased levels of the proteolytic IGFBP-4 fragments correlate with the development of CVD complications and increased risk of death in patients with the coronary heart disease, acute coronary syndrome, and heart failure. However, there is no direct evidence that PAPP-A specifically cleaves IGFBP-4 in the cardiac tissue under normal and pathological conditions. In the present study, using a primary culture of rat neonatal cardiomyocytes as a model, we have demonstrated that: 1) proteolysis of IGFBP-4 by PAPP-A occurs in the conditioned medium of cardiomyocytes, 2) PAPP-A-specific IGFBP-4 proteolysis is increased when cardiomyocytes are transformed to a hypertrophic state. Thus, it can be assumed that the enhancement of IGFBP-4 cleavage by PAPP-A and hypertrophic changes in cardiomyocytes accompanying CVD are interrelated, and PAPP-A appears to be one of the activators of the IGF-dependent processes in normal and hypertrophic-state cardiomyocytes.

The protective effects of 17-β estradiol and SIRT1 against cardiac hypertrophy: a review

One of the major causes of morbidity and mortality worldwide is cardiac hypertrophy (CH), which leads to heart failure. Sex differences in CH can be caused by sex hormones or their receptors. The incidence of CH increases in postmenopausal women due to the decrease in female sex hormone 17-β estradiol (E2) during menopause. E2 and its receptors inhibit CH in humans and animal models. Silent information regulator 1 (SIRT1) is a NAD⁺-dependent HDAC (histone deacetylase) and plays a major role in biological processes, such as inflammation, apoptosis, and oxidative stress responses. Probably SIRT1 because of these effects, is one of the main suppressors of CH and has a cardioprotective effect. On the other hand, estrogen and its agonists are highly efficient in modulating SIRT1 expression. In the present study, we review the protective effects of E2 and SIRT1 against CH.

The roles of signaling pathways in cardiac regeneration

In recent years, knowledge of cardiac regeneration mechanisms has dramatically expanded. Regeneration can replace lost parts of organs, common among animal species. The heart is commonly considered an organ with terminal development, which has no reparability potential during post-natal life; however, some intrinsic regeneration capacity has been reported for cardiac muscle, which opens novel avenues in cardiovascular disease treatment. Different endogenous mechanisms were studied for cardiac repairing and regeneration in recent decades. Survival, proliferation, inflammation, angiogenesis, cell-cell communication, cardiomyogenesis, and anti-aging pathways are the most important mechanisms that have been studied in this regard. Several in vitro and animal model studies focused on proliferation induction for cardiac regeneration reported promising results. These studies have mainly focused on promoting proliferation signaling pathways and demonstrated various signaling pathways such as Wnt, PI3K/Akt, IGF-1, TGF-β, Hippo, and VEGF signaling cardiac regeneration. Therefore, in this review, we intended to discuss the connection between different critical signaling pathways in cardiac repair and regeneration.

Optimizing mechanical stretching protocols for hypertrophic and anti-apoptotic responses in cardiomyocyte-like H9C2 cells

Cardiomyocytes possess the ability to respond to mechanical stimuli by reprogramming their gene expression. This study investigated the effects of different loading protocols on signaling and expression responses of myogenic, anabolic, inflammatory, atrophy and pro-apoptotic genes in cardiomyocyte-like H9C2 cells. Differentiated H9C2 cells underwent various stretching protocols by altering their elongation, frequency and duration, utilizing an in vitro cell tension system. The loading-induced expression changes of MyoD, Myogenin, MRF4, IGF-1 isoforms, Atrogin-1, Foxo1, Fuca and IL-6 were measured by Real Time-PCR. The stretching-induced activation of Akt and Erk 1/2 was also evaluated by Western blot analysis. Low strain (2.7% elongation), low frequency (0.25 Hz) and intermediate duration (12 h) stretching protocol was overall the most effective in inducing beneficial responses, i.e., protein synthesis along with the suppression of apoptosis, inflammation and atrophy, in the differentiated cardiomyocytes. These findings demonstrated that varying the characteristics of mechanical loading applied on H9C2 cells in vitro can regulate their anabolic/survival program.

Modulatory Effect of Myokines on Reactive Oxygen Species in Ischemia/Reperfusion

There is a growing body of evidence showing the importance of physical activity against acute ischemic events in various organs. Ischemia/reperfusion injury (I/R) is characterized by tissue damage as a result of restriction and subsequent restoration of blood supply to an organ. Oxidative stress due to increased reactive oxygen species formation and/or insufficient antioxidant defense is considered to play an important role in I/R. Physical activity not only decreases the general risk factors for ischemia but also confers direct anti-ischemic protection via myokine production. Myokines are skeletal muscle-derived cytokines, representing multifunctional communication channels between the contracting skeletal muscle and other organs through an endocrine manner. In this review, we discuss the most prominent members of the myokines (i.e., brain-derived neurotrophic factor (BDNF), cathepsin B, decorin, fibroblast growth factors-2 and -21, follistatin, follistatin-like, insulin-like growth factor-1; interleukin-6, interleukin-7, interleukin-15, irisin, leukemia inhibitory factor, meteorin-like, myonectin, musclin, myostatin, and osteoglycin) with a particular interest in their potential influence on reactive oxygen and nitrogen species formation or antioxidant capacity. A better understanding of the mechanism of action of myokines and particularly their participation in the regulation of oxidative stress may widen their possible therapeutic use and, thereby, may support the fight against I/R.

Protective role of ErbB3 signaling in myeloid cells during adaptation to cardiac pressure overload

BACKGROUND

Myeloid cells play an important role in a wide variety of cardiovascular disorders, including both ischemic and non-ischemic cardiomyopathies. Neuregulin-1 (NRG-1)/ErbB signaling has recently emerged as an important factor contributing to the control of inflammatory activation of myeloid cells after an ischemic injury. However, the role of ErbB signaling in myeloid cells in non-ischemic cardiomyopathy is not fully understood. This study investigated the role of ErbB3 receptors in the regulation of early adaptive response using a mouse model of transverse aortic constriction (TAC) for non-ischemic cardiomyopathy.

METHODS AND RESULTS

TAC surgery was performed in groups of age- and sex-matched myeloid cell-specific ErbB3-deficient mice (ErbB3^MyeKO) and control animals (ErbB3^MyeWT). The number of cardiac CD45 immune cells, CD11b myeloid cells, Ly6G neutrophils, and Ly6C monocytes was determined using flow cytometric analysis. Five days after TAC, survival was dramatically reduced in male but not female ErbB3^MyeKO mice or control animals. The examination of lung weight to body weight ratio suggested that acute pulmonary edema was present in ErbB3^MyeKO male mice after TAC. To determine the cellular and molecular mechanisms involved in the increased mortality in ErbB3^MyeKO male mice, cardiac cell populations were examined at day 3 post-TAC using flow cytometry. Myeloid cells accumulated in control but not in ErbB3^MyeKO male mouse hearts. This was accompanied by increased proliferation of Sca-1 positive non-immune cells (endothelial cells and fibroblasts) in control but not ErbB3^MyeKO male mice. No significant differences in intramyocardial accumulation of myeloid cells or proliferation of Sca-1 cells were found between the groups of ErbB3^MyeKO and ErbB3^MyeWT female mice. An antibody-based protein array analysis revealed that IGF-1 expression was significantly downregulated only in ErbB3^MyeKO mice hearts compared to control animals after TAC.

CONCLUSION

Our data demonstrate the crucial role of myeloid cell-specific ErbB3 signaling in the cardiac accumulation of myeloid cells, which contributes to the activation of cardiac endothelial cells and fibroblasts and development of an early adaptive response to cardiac pressure overload in male mice.

The intracellular renin-angiotensin system: Friend or foe. Some light from the dopaminergic neurons

The renin-angiotensin system (RAS) is one of the oldest hormone systems in vertebrate phylogeny. RAS was initially related to regulation of blood pressure and sodium and water homeostasis. However, local or paracrine RAS were later identified in many tissues, including brain, and play a major role in their physiology and pathophysiology. In addition, a major component, ACE2, is the entry receptor for SARS-CoV-2. Overactivation of tissue RAS leads several oxidative stress and inflammatory processes involved in aging-related degenerative changes. In addition, a third level of RAS, the intracellular or intracrine RAS (iRAS), with still unclear functions, has been observed. The possible interaction between the intracellular and extracellular RAS, and particularly the possible deleterious or beneficial effects of the iRAS activation are controversial. The dopaminergic system is particularly interesting to investigate the RAS as important functional interactions between dopamine and RAS have been observed in the brain and several peripheral tissues. Our recent observations in mitochondria and nucleus of dopaminergic neurons may clarify the role of the iRAS. This may be important for the developing of new therapeutic strategies, since the effects on both extracellular and intracellular RAS must be taken into account, and perhaps better understanding of COVID-19 cell mechanisms.

Role of Alternatively Spliced Messenger RNA (mRNA) Isoforms of the Insulin-Like Growth Factor 1 (IGF1) in Selected Human Tumors

Insulin-like growth factor 1 (IGF1) is a key regulator of tissue growth and development that is also implicated in the initiation and progression of various cancers. The human IGF1 gene contains six exons and five long introns, the transcription of which is controlled by two promoters (P1 and P2). Alternate promoter usage, as well as alternative splicing (AS) of IGF1, results in the expression of six various variants (isoforms) of mRNA, i.e., IA, IB, IC, IIA, IIB, and IIC. A mature 70-kDa IGF1 protein is coded only by exons 3 and 4, while exons 5 and 6 are alternatively spliced code for the three C-terminal E peptides: Ea (exon 6), Eb (exon 5), and Ec (fragments of exons 5 and 6). The most abundant of those transcripts is IGF1Ea, followed by IGF1Eb and IGF1Ec (also known as mechano-growth factor, MGF). The presence of different IGF1 transcripts suggests tissue-specific auto- and/or paracrine action, as well as separate regulation of both of these gene promoters. In physiology, the role of different IGF1 mRNA isoforms and pro-peptides is best recognized in skeletal muscle tissue. Their functions include the development and regeneration of muscles, as well as maintenance of proper muscle mass. In turn, in nervous tissue, a neuroprotective function of short peptides, produced as a result of IGF1 expression and characterized by significant blood-brain barrier penetrance, has been described and could be a potential therapeutic target. When it comes to the regulation of carcinogenesis, the potential biological role of different var iants of IGF1 mRNAs and pro-peptides is also intensively studied. This review highlights the role of IGF1 isoform expression (mRNAs, proteins) in physiology and different types of human tumors (e.g., breast cancer, cervical cancer, colorectal cancer, osteosarcoma, prostate and thyroid cancers), as well as mechanisms of IGF1 spliced variants involvement in tumor biology.

The protein Deleted in Breast Cancer-1 (DBC1) regulates vascular response and formation of aortic dissection during Angiotensin II infusion

Cardiovascular diseases are among the main causes of morbimortality in the adult population. Among them, hypertension is a leading cause for stroke, heart disease and kidney failure. Also, as a result of arterial wall weakness, hypertension can lead to the development of dissecting aortic aneurysms, a rare but often fatal condition if not readily treated. In this work, we investigated the role of DBC1 in the regulation of vascular function in an ANGII-induced hypertension mouse model. We found that WT and DBC1 KO mice developed hypertension in response to ANGII infusion. However, DBC1 KO mice showed increased susceptibility to develop aortic dissections. The effect was accompanied by upregulation of vascular remodeling factors, including MMP9 and also VEGF. Consistent with this, we found decreased collagen deposition and elastic fiber fragmentation, suggesting that increased expression of MMPs in DBC1 KO mice weakens the arterial wall, promoting the formation of aortic dissections during treatment with ANGII. Finally, DBC1 KO mice had reduced cell proliferation in the intima-media layer in response to ANGII, paralleled with an impairment to increase wall thickness in response to hypertension. Furthermore, VSMC purified from DBC1 KO mice showed impaired capacity to leave quiescence, confirming the in vivo results. Altogether, our results show for the first time that DBC1 regulates vascular response and function during hypertension and protects against vascular injury. This work also brings novel insights into the molecular mechanisms of the development of aortic dissections.

Cellular and Molecular Differences between HFpEF and HFrEF: A Step Ahead in an Improved Pathological Understanding

Heart failure (HF) is the most rapidly growing cardiovascular health burden worldwide. HF can be classified into three groups based on the percentage of the ejection fraction (EF): heart failure with reduced EF (HFrEF), heart failure with mid-range-also called mildly reduced EF- (HFmrEF), and heart failure with preserved ejection fraction (HFpEF). HFmrEF can progress into either HFrEF or HFpEF, but its phenotype is dominated by coronary artery disease, as in HFrEF. HFrEF and HFpEF present with differences in both the development and progression of the disease secondary to changes at the cellular and molecular level. While recent medical advances have resulted in efficient and specific treatments for HFrEF, these treatments lack efficacy for HFpEF management. These differential response rates, coupled to increasing rates of HF, highlight the significant need to understand the unique pathogenesis of HFrEF and HFpEF. In this review, we summarize the differences in pathological development of HFrEF and HFpEF, focussing on disease-specific aspects of inflammation and endothelial function, cardiomyocyte hypertrophy and death, alterations in the giant spring titin, and fibrosis. We highlight the areas of difference between the two diseases with the aim of guiding research efforts for novel therapeutics in HFrEF and HFpEF.

Triple-marker cardiac MRI detects sequential tissue changes of healing myocardium after a hydrogel-based therapy

Regenerative therapies based on injectable biomaterials, hold an unparalleled potential for treating myocardial ischemia. Yet, noninvasive evaluation of their efficacy has been lagging behind. Here, we report the development and longitudinal application of multiparametric cardiac magnetic resonance imaging (MRI) to evaluate a hydrogel-based cardiac regenerative therapy. A pH-switchable hydrogel was loaded with slow releasing insulin growth factor 1 and vascular endothelial growth factor, followed by intramyocardial injection in a mouse model of ischemia reperfusion injury. Longitudinal cardiac MRI assessed three hallmarks of cardiac regeneration: angiogenesis, resolution of fibrosis and (re)muscularization after infarction. The multiparametric approach contained dynamic contrast enhanced MRI that measured improved vessel features by assessing fractional blood volume and permeability*surface area product, T₁-mapping that displayed reduced fibrosis, and tagging MRI that showed improved regional myocardial strain in hydrogel treated infarcts. Finally, standard volumetric MRI demonstrated improved left ventricular functioning in hydrogel treated mice followed over time. Histology confirmed MR-based vessel features and fibrotic measurements. Our novel triple-marker strategy enabled detection of ameliorated regeneration in hydrogel treated hearts highlighting the translational potential of these longitudinal MRI approaches.

Sustained release of bioactive IGF-1 from a silk fibroin microsphere-based injectable alginate hydrogel for the treatment of myocardial infarction

Low circulating levels of insulin-like growth factor 1 (IGF-1) have been correlated with an increased risk for cardiovascular diseases in humans. In this work, an injectable alginate hydrogel containing silk fibroin (SF) microspheres with the capability to sustain the release of IGF-1 was prepared to induce myocardial repair after myocardial infarction (MI). First, IGF-1 was physically adsorbed onto SF microspheres prepared by the coaxial needle system, and these IGF-1-containing microspheres were subsequently encapsulated into sodium alginate solutions at different concentrations (1.0-2.5%). Finally, this solution was crosslinked with 0.68% calcium gluconate solution to prepare the composite injectable hydrogel. The composite hydrogel prepared using a sodium alginate solution at a concentration of 1.5% could promote proliferation of H9C2 cardiomyocytes and reduce the cellular apoptosis rate under hypoxic conditions. The enzyme-linked immunosorbent assay results indicated that SF microspheres as microcarriers could effectively enhance the sustained release of IGF-1 from the hydrogels, causing the composite hydrogel to possess a better sustained release ability than the system without the SF microspheres. Moreover, echocardiography, hematoxylin-eosin staining, and Masson trichrome staining results indicated that an intramyocardial injection of the composite hydrogel into the peripheral region of a MI rat model could reduce the infarct size and improve the cardiac function after 28 days. The applications of such a composite hydrogel may comprise a powerful platform in cardiac tissue engineering.

Ghrelin-mediated pathway in Apolipoprotein-E deficient mice: a survival system

Renal diseases interfere with the regulation of several metabolic pathways including dyslipidemia. The latter includes increased triglycerides, very low-density lipoprotein levels and decreased high-density lipoproteins. These lipoproteins change during renal injury. Apolipoprotein-E deficient mice (ApoE^-/-) are considered a very well accepted model of hypercholesterolemia with marked renal pathological alterations. Ghrelin hormone is mainly secreted from the stomach when the stomach is empty, but it is also found in the kidney. In this organ it has autocrine and/or paracrine roles determining glomerular filtration rate, tubular phosphate and sodium reabsorption. Interestingly, it has been demonstrated that ghrelin levels increase after fasting. This mechanism induces an interaction with sirtuin 1 (SIRT1)/p53 pathway suggesting a link between ghrelin and SIRT1 in the regulation of salt and water metabolism. The mechanisms of ghrelin-induced SIRT1 expression are not yet fully understood. Recent studies indicate that SIRT1 exerts renoprotective properties against kidney diseases. This could be a very interesting point for underlining the important role of the ghrelin-SIRT1 system. Water movement across biological cell membranes is enhanced or facilitated by tetrameric membrane-bound channels, named aquaporin (AQP) family, and in particular, AQP1 and AQP2 proteins. In this study, we evaluated the possible pathway existing among the ghrelin/SIRT1/AQP1/AQP2 system in APOE^-/- mice in order to clarify or stress the role played by said system in renal diseases associated to aging with or without comorbities. The results could provide a basis for considering ghrelin as a new target for therapeutic strategies of renal injury.

Insulin-Like Growth Factor 1 in the Cardiovascular System

Non-communicable diseases, such as cardiovascular diseases, are the leading cause of mortality worldwide. For this reason, a tremendous effort is being made worldwide to effectively circumvent these afflictions, where insulin-like growth factor 1 (IGF1) is being proposed both as a marker and as a central cornerstone in these diseases, making it an interesting molecule to focus on. Firstly, at the initiation of metabolic deregulation by overfeeding, IGF1 is decreased/inhibited. Secondly, such deficiency seems to be intimately related to the onset of MetS and establishment of vascular derangements leading to atherosclerosis and finally playing a definitive part in cerebrovascular and myocardial accidents, where IGF1 deficiency seems to render these organs vulnerable to oxidative and apoptotic/necrotic damage. Several human cohort correlations together with basic/translational experimental data seem to confirm deep IGF1 implication, albeit with controversy, which might, in part, be given by experimental design leading to blurred result interpretation.

Global secretome analysis of resident cardiac progenitor cells from wild-type and transgenic heart failure mice: Why ambience matters

Resident cardiac progenitor cells (CPCs) have gained attention in cardiac regenerative medicine primarily due to their paracrine activity. In our current study we determined the role of pathological conditions such as heart failure on the autocrine-paracrine action of stem cell antigen-1 (Sca-1) expressing CPC. This comparative secretome profiling of Sca-1⁺ cells derived from transgenic heart failure (αMHC-cyclin-T1/Gαq overexpression [Cyc] cells) versus healthy (wild-type [Wt] cells) mice, achieved via mass-spectrometric quantification, enabled the identification of over 700 proteins. Our results demonstrate that the heart failure milieu caused a 2-fold enrichment of extracellular matrix proteins (ECM) like biglycan, versican, collagen XII, and angiogenic factors like heparan sulfate proteoglycan 2, plasminogen activator inhibitor 1 in the secretome. We further elucidated the direct influence of the secretome on the functional behavior of Sca-1 ⁺ cells via in vitro tube forming assay. Secreted factors present in the diseased milieu induced tube formation in Cyc cells (1.7-fold; p < 0.01) when compared with Wt cells after 24 hr of exposure. The presence of conditioned media moderately increased the proliferation of Cyc cells but had a more pronounced effect on Wt cells. Overall, these findings revealed global modifications in the secretory activity of adult Sca-1 ⁺ cells in the heart failure milieu. The secretion of ECM proteins and angiogenic factors, which are crucial for cardiac remodeling and recovery, was notably enriched in the supernatant of Cyc cells. Thus, during heart failure the microenvironment of Sca-1 ⁺ cells might favor angiogenesis and proliferation suggesting their potential to recover the damaged heart.

Hyperglycemia-induced mouse trophoblast spreading is mediated by reactive oxygen species

During embryo implantation, the outer layer of the blastocyst interacts with the endometrium giving rise to the development of the trophoblast cell lineage. The cells in this lineage participate in the penetration of endometrium due to their motility and invasive properties. The mechanisms that regulate the differentiation and invasive ability of these cells are essential for the establishment and maintenance of an efficient exchange between maternal and fetal tissues during pregnancy. In this context, hyperglycemia can induce oxidative stress causing alterations in the placenta. This study evaluated the role of reactive oxygen species (ROS) in the actions of high glucose concentration (HG) on trophoblast spreading and the expression of extracellular proteases in cultured mouse conceptuses. Blastocysts from gestational day 4 (GD4) were cultured until GD7 in HAM-F10 medium and further treated for 48 hr with HG (25 mM glucose) from GD7 to GD9. This treatment induced larger trophoblast outgrowths and increased ROS concentration, which was associated with increased expression levels of urokinase-type plasminogen activator (PLAU), plasminogen activator inhibitor 1 (PAI-1), and matrix metalloproteinase 9 (MMP-9). These effects were prevented by treatment with the non-specific antioxidant N-acetylcysteine (NAC) or apocynin, an inhibitor of NADPH oxidase. Our data suggest that the HG-induced trophoblast spreading and the expression of PLAU, PAI-1, and MMP-9 were mediated by the production of ROS via NADPH oxidase activity. Our results shed light on placental alterations in gestational diabetes mellitus.

Crosstalk between insulin-like growth factor-1 and angiotensin-II in dopaminergic neurons and glial cells: role in neuroinflammation and aging

The local renin-angiotensin system (RAS) and insulin-like growth factor 1 (IGF-1) have been involved in longevity, neurodegeneration and aging-related dopaminergic degeneration. However, it is not known whether IGF-1 and angiotensin-II (AII) activate each other. In the present study, AII, via type 1 (AT1) receptors, exacerbated neuroinflammation and dopaminergic cell death. AII, via AT1 receptors, also increased the levels of IGF-1 and IGF-1 receptors in microglial cells. IGF-1 inhibited RAS activity in dopaminergic neurons and glial cells, and also inhibited the AII-induced increase in markers of the M1 microglial phenotype. Consistent with this, IGF-1 decreased dopaminergic neuron death induced by the neurotoxin MPP⁺ both in the presence and in the absence of glia. Intraventricular administration of AII to young rats induced a significant increase in IGF-1 expression in the nigral region. However, aged rats showed decreased levels of IGF-1 relative to young controls, even though RAS activity is known to be enhanced in aged animals. The study findings show that IGF-1 and the local RAS interact to inhibit or activate neuroinflammation (i.e. transition from the M1 to the M2 phenotype), oxidative stress and dopaminergic degeneration. The findings also show that this mechanism is impaired in aged animals.

Insulin-Like Growth Factor-1 and Neuroinflammation

Insulin-like growth factor-1 (IGF-1) effects on aging and neurodegeneration is still controversial. However, it is widely admitted that IGF-1 is involved in the neuroinflammatory response. In peripheral tissues, several studies showed that IGF-1 inhibited the expression of inflammatory markers, although other studies concluded that IGF-1 has proinflammatory functions. Furthermore, proinflammatory cytokines such as TNF-α impaired IGF-1 signaling. In the brain, there are controversial results on effects of IGF-1 in neuroinflammation. In addition to direct protective effects on neurons, several studies revealed anti-inflammatory effects of IGF-1 acting on astrocytes and microglia, and that IGF-1 may also inhibit blood brain barrier permeability. Altogether suggests that the aging-related decrease in IGF-1 levels may contribute to the aging-related pro-inflammatory state. IGF-1 inhibits the astrocytic response to inflammatory stimuli, and modulates microglial phenotype (IGF-1 promotes the microglial M2 and inhibits of M1 phenotype). Furthermore, IGF-1 is mitogenic for microglia. IGF-1 and estrogen interact to modulate the neuroinflammatory response and microglial and astrocytic phenotypes. Brain renin-angiotensin and IGF-1 systems also interact to modulate neuroinflammation. Induction of microglial IGF-1 by angiotensin, and possibly by other pro-inflammatory inducers, plays a major role in the repression of the M1 microglial neurotoxic phenotype and the enhancement of the transition to an M2 microglial repair/regenerative phenotype. This mechanism is impaired in aged brains. Aging-related decrease in IGF-1 may contribute to the loss of capacity of microglia to undergo M2 activation. Fine tuning of IGF-1 levels may be critical for regulating the neuroinflammatory response, and IGF-1 may be involved in inflammation in a context-dependent mode.

Neferine modulates IGF-1R/Nrf2 signaling in doxorubicin treated H9c2 cardiomyoblasts

Doxorubicin (DOX) induced cardiotoxicity is a major problem during chemotherapy of cancers. DOX-mediated suppression of type 1 IGF receptor (IGF-1R) signaling leads to cardiac dysfunction. Neferine, a bisbezylisoquinoline alkaloid from the seed embryos of Nelumbo nucifera Gaertn possesses a distinct range of pharmacological properties. Herewith, the present study attempts to elucidate the protective role of neferine against DOX induced toxicity in H9c2 rat cardiomyoblast cell line model. DOX-treated H9c2 cells significantly increased mitochondrial superoxide generation, depleted cellular antioxidant status, suppressed the activation of IGF-1R signaling via PI3K/Akt/mTOR and induced autophagy by the activation of ULK1, Beclin1, Atg7, and LC3B. Neferine pre-treatment activated IGF-1R signaling, improved cellular antioxidant pool, increased the expression of down-stream targets of IGF-1R, such as PI3K/Akt/mTOR, inhibited mitochondrial superoxide generation and autophagy significantly with the induction of Nrf2 translocation and expressions of HO1 and SOD1. Our study suggests the use of neferine for amelioration of DOX-mediated cardiotoxicity.

The intracellular angiotensin system buffers deleterious effects of the extracellular paracrine system

The 'classical' renin-angiotensin system (RAS) is a circulating system that controls blood pressure. Local/paracrine RAS, identified in a variety of tissues, including the brain, is involved in different functions and diseases, and RAS blockers are commonly used in clinical practice. A third type of RAS (intracellular/intracrine RAS) has been observed in some types of cells, including neurons. However, its role is still unknown. The present results indicate that in brain cells the intracellular RAS counteracts the intracellular superoxide/H₂O₂ and oxidative stress induced by the extracellular/paracrine angiotensin II acting on plasma membrane receptors. Activation of nuclear receptors by intracellular or internalized angiotensin triggers a number of mechanisms that protect the cell, such as an increase in the levels of protective angiotensin type 2 receptors, intracellular angiotensin, PGC-1α and IGF-1/SIRT1. Interestingly, this protective mechanism is altered in isolated nuclei from brains of aged animals. The present results indicate that at least in the brain, AT1 receptor blockers acting only on the extracellular or paracrine RAS may offer better protection of cells.

Insulin-like growth factor-1 signaling in cardiac aging

Cardiovascular disease (CVD) is the leading cause of death in most developed countries. Aging is associated with enhanced risk of CVD. Insulin-like growth factor-1 (IGF-1) binds to its cognate receptor, IGF-1 receptor (IGF-1R), and exerts pleiotropic effects on cell growth, differentiation, development, and tissue repair. Importantly, IGF-1/IGF-1R signaling is implicated in cardiac aging and longevity. Cardiac aging is an intrinsic process that results in cardiac dysfunction, accompanied by molecular and cellular changes. In this review, we summarize the current state of knowledge regarding the link between the IGF-1/IGF-1R system and cardiac aging. The biological effects of IGF-1R and insulin receptor will be discussed and compared. Furthermore, we describe data regarding how deletion of IGF-1R in cardiomyocytes of aged knockout mice may delay the development of senescence-associated myocardial pathologies. This article is part of a Special issue entitled Cardiac adaptations to obesity, diabetes and insulin resistance, edited by Professors Jan F.C. Glatz, Jason R.B. Dyck and Christine Des Rosiers.

Partial IGF-1 deficiency is sufficient to reduce heart contractibility, angiotensin II sensibility, and alter gene expression of structural and functional cardiac proteins

Circulating levels of IGF-1 may decrease under several circumstances like ageing, metabolic syndrome, and advanced cirrhosis. This reduction is associated with insulin resistance, dyslipidemia, progression to type 2 diabetes, and increased risk for cardiovascular diseases. However, underlying mechanisms between IGF-1 deficiency and cardiovascular disease remain elusive.

The specific aim of the present work was to study whether the partial IGF-1 deficiency influences heart and/or coronary circulation, comparing vasoactive factors before and after of ischemia-reperfusion (I/R). In addition, histology of the heart was performed together with cardiac gene expression for proteins involved in structure and function (extracellular matrix, contractile proteins, active peptides); carried out using microarrays, followed by RT-qPCR confirmation of the three experimental groups. IGF-1 partial deficiency is associated to a reduction in contractility and angiotensin II sensitivity, interstitial fibrosis as well as altered expression pattern of genes involved in extracellular matrix proteins, calcium dynamics, and cardiac structure and function.

Although this work is descriptive, it provides a clear insight of the impact that partial IGF-1 deficiency on the heart and establishes this experimental model as suitable for studying cardiac disease mechanisms and exploring therapeutic options for patients under IGF-1 deficiency conditions.

Brain Renin-Angiotensin System and Microglial Polarization: Implications for Aging and Neurodegeneration

Microglia can transform into proinflammatory/classically activated (M1) or anti-inflammatory/alternatively activated (M2) phenotypes following environmental signals related to physiological conditions or brain lesions. An adequate transition from the M1 (proinflammatory) to M2 (immunoregulatory) phenotype is necessary to counteract brain damage. Several factors involved in microglial polarization have already been identified. However, the effects of the brain renin-angiotensin system (RAS) on microglial polarization are less known. It is well known that there is a “classical” circulating RAS; however, a second RAS (local or tissue RAS) has been observed in many tissues, including brain. The locally formed angiotensin is involved in local pathological changes of these tissues and modulates immune cells, which are equipped with all the components of the RAS. There are also recent data showing that brain RAS plays a major role in microglial polarization. Level of microglial NADPH-oxidase (Nox) activation is a major regulator of the shift between M1/proinflammatory and M2/immunoregulatory microglial phenotypes so that Nox activation promotes the proinflammatory and inhibits the immunoregulatory phenotype. Angiotensin II (Ang II), via its type 1 receptor (AT1), is a major activator of the NADPH-oxidase complex, leading to pro-oxidative and pro-inflammatory effects. However, these effects are counteracted by a RAS opposite arm constituted by Angiotensin II/AT2 receptor signaling and Angiotensin 1–7/Mas receptor (MasR) signaling. In addition, activation of prorenin-renin receptors may contribute to activation of the proinflammatory phenotype. Aged brains showed upregulation of AT1 and downregulation of AT2 receptor expression, which may contribute to a pro-oxidative pro-inflammatory state and the increase in neuron vulnerability. Several recent studies have shown interactions between the brain RAS and different factors involved in microglial polarization, such as estrogens, Rho kinase (ROCK), insulin-like growth factor-1 (IGF-1), tumor necrosis factor α (TNF)-α, iron, peroxisome proliferator-activated receptor gamma, and toll-like receptors (TLRs). Metabolic reprogramming has recently been involved in the regulation of the neuroinflammatory response. Interestingly, we have recently observed a mitochondrial RAS, which is altered in aged brains. In conclusion, dysregulation of brain RAS plays a major role in aging-related changes and neurodegeneration by exacerbation of oxidative stress (OS) and neuroinflammation, which may be attenuated by pharmacological manipulation of RAS components.

Recombinant human growth hormone and insulin-like growth factor-1 do not affect mitochondrial derived highly reactive oxygen species production in peripheral blood mononuclear cells under conditions of substrate saturation in-vitro

BACKGROUND

The purpose of this study was to investigate the mitochondrial effects exerted by physiological and supra-physiological concentrations of recombinant human growth hormone (rhGH) and recombinant insulin-like growth factor-1 (rIGF-1) under conditions of substrate saturation in peripheral blood mononuclear cells (PBMCs).

METHODS

PBMCs from healthy male subjects were treated with either rhGH, at concentrations of 0.5, 5 and 50 μg/L, or rIGF-1 at concentrations of 100, 300 and 500 μg/L for 4 h. Mitochondrial membrane potential (Δψm) and mitochondrial levels of highly reactive oxygen species (hROS) were subsequently analysed. This analysis was performed by flow cytometry in digitonin permeabilized cells, following treatment with saturating concentrations of various respiratory substrate combinations and the use of specific electron transport chain (ETC.) complex inhibitors, enabling control over both the sites of electron entry into the ETC. at complexes I and II and the entry of electrons from reduced carriers involved in β-oxidation at the level of ubiquinol.

RESULTS

Neither rhGH nor rIGF-1 exerted any significant effect on Δψm or the rate of hROS production in either lymphocyte or monocyte sub-populations under any of the respiratory conditions analysed.

CONCLUSION

That neither hormone was capable of attenuating levels of oxidative stress mediated via either complex I linked respiration or lipid-derived respiration could have serious health implications for the use of rhGH in healthy individuals, which is frequently associated with significant increases in the bioavailability of free fatty acids (FFA). Such elevated supplies of lipid-derived substrates to the mitochondria could lead to oxidative damage which would negatively impact mitochondrial function.

Mitochondrial function in hypoxic ischemic injury and influence of aging

Mitochondria are a major target in hypoxic/ischemic injury. Mitochondrial impairment increases with age leading to dysregulation of molecular pathways linked to mitochondria. The perturbation of mitochondrial homeostasis and cellular energetics worsens outcome following hypoxic-ischemic insults in elderly individuals. In response to acute injury conditions, cellular machinery relies on rapid adaptations by modulating posttranslational modifications. Therefore, post-translational regulation of molecular mediators such as hypoxia-inducible factor 1α (HIF-1α), peroxisome proliferator-activated receptor γ coactivator α (PGC-1α), c-MYC, SIRT1 and AMPK play a critical role in the control of the glycolytic-mitochondrial energy axis in response to hypoxic-ischemic conditions. The deficiency of oxygen and nutrients leads to decreased energetic reliance on mitochondria, promoting glycolysis. The combination of pseudohypoxia, declining autophagy, and dysregulation of stress responses with aging adds to impaired host response to hypoxic-ischemic injury. Furthermore, intermitochondrial signal propagation and tissue wide oscillations in mitochondrial metabolism in response to oxidative stress are emerging as vital to cellular energetics. Recently reported intercellular transport of mitochondria through tunneling nanotubes also play a role in the response to and treatments for ischemic injury. In this review we attempt to provide an overview of some of the molecular mechanisms and potential therapies involved in the alteration of cellular energetics with aging and injury with a neurobiological perspective.

Physiological and pathological cardiac hypertrophy

The heart must continuously pump blood to supply the body with oxygen and nutrients. To maintain the high energy consumption required by this role, the heart is equipped with multiple complex biological systems that allow adaptation to changes of systemic demand. The processes of growth (hypertrophy), angiogenesis, and metabolic plasticity are critically involved in maintenance of cardiac homeostasis. Cardiac hypertrophy is classified as physiological when it is associated with normal cardiac function or as pathological when associated with cardiac dysfunction. Physiological hypertrophy of the heart occurs in response to normal growth of children or during pregnancy, as well as in athletes. In contrast, pathological hypertrophy is induced by factors such as prolonged and abnormal hemodynamic stress, due to hypertension, myocardial infarction etc. Pathological hypertrophy is associated with fibrosis, capillary rarefaction, increased production of pro-inflammatory cytokines, and cellular dysfunction (impairment of signaling, suppression of autophagy, and abnormal cardiomyocyte/non-cardiomyocyte interactions), as well as undesirable epigenetic changes, with these complex responses leading to maladaptive cardiac remodeling and heart failure. This review describes the key molecules and cellular responses involved in physiological/pathological cardiac hypertrophy.

The Evolutionarily Conserved Tre2/Bub2/Cdc16 (TBC), Lysin Motif (LysM), Domain Catalytic (TLDc) Domain Is Neuroprotective against Oxidative Stress

Oxidative stress is a pathological feature of many neurological disorders; therefore, utilizing proteins that are protective against such cellular insults is a potentially valuable therapeutic approach. Oxidation resistance 1 (OXR1) has been shown previously to be critical for oxidative stress resistance in neuronal cells; deletion of this gene causes neurodegeneration in mice, yet conversely, overexpression of OXR1 is protective in cellular and mouse models of amyotrophic lateral sclerosis. However, the molecular mechanisms involved are unclear. OXR1 contains the Tre2/Bub2/Cdc16 (TBC), lysin motif (LysM), domain catalytic (TLDc) domain, a motif present in a family of proteins including TBC1 domain family member 24 (TBC1D24), a protein mutated in a range of disorders characterized by seizures, hearing loss, and neurodegeneration. The TLDc domain is highly conserved across species, although the structure-function relationship is unknown. To understand the role of this domain in the stress response, we carried out systematic analysis of all mammalian TLDc domain-containing proteins, investigating their expression and neuroprotective properties in parallel. In addition, we performed a detailed structural and functional study of this domain in which we identified key residues required for its activity. Finally, we present a new mouse insertional mutant of Oxr1, confirming that specific disruption of the TLDc domain in vivo is sufficient to cause neurodegeneration. Our data demonstrate that the integrity of the TLDc domain is essential for conferring neuroprotection, an important step in understanding the functional significance of all TLDc domain-containing proteins in the cellular stress response and disease.

Cardiac-Restricted IGF-1Ea Overexpression Reduces the Early Accumulation of Inflammatory Myeloid Cells and Mediates Expression of Extracellular Matrix Remodelling Genes after Myocardial Infarction

Strategies to limit damage and improve repair after myocardial infarct remain a major therapeutic goal in cardiology. Our previous studies have shown that constitutive expression of a locally acting insulin-like growth factor-1 Ea (IGF-1Ea) propeptide promotes functional restoration after cardiac injury associated with decreased scar formation. In the current study, we investigated the underlying molecular and cellular mechanisms behind the enhanced functional recovery. We observed improved cardiac function in mice overexpressing cardiac-specific IGF-1Ea as early as day 7 after myocardial infarction. Analysis of gene transcription revealed that supplemental IGF-1Ea regulated expression of key metalloproteinases (MMP-2 and MMP-9), their inhibitors (TIMP-1 and TIMP-2), and collagen types (Col 1α1 and Col 1α3) in the first week after injury. Infiltration of inflammatory cells, which direct the remodelling process, was also altered; in particular there was a notable reduction in inflammatory Ly6C+ monocytes at day 3 and an increase in anti-inflammatory CD206+ macrophages at day 7. Taken together, these results indicate that the IGF-1Ea transgene shifts the balance of innate immune cell populations early after infarction, favouring a reduction in inflammatory myeloid cells. This correlates with reduced extracellular matrix remodelling and changes in collagen composition that may confer enhanced scar elasticity and improved cardiac function.

Sirtuin regulation in aging and injury

Sirtuins or Sir2 family of proteins are a class of NAD(+) dependent protein deacetylases which are evolutionarily conserved from bacteria to humans. Some sirtuins also exhibit mono-ADP ribosyl transferase, demalonylation and desuccinylation activities. Originally identified in the yeast, these proteins regulate key cellular processes like cell cycle, apoptosis, metabolic regulation and inflammation. Humans encode seven sirtuin isoforms SIRT1-SIRT7 with varying intracellular distribution. Apart from their classic role as histone deacetylases regulating transcription, a number of cytoplasmic and mitochondrial targets of sirtuins have also been identified. Sirtuins have been implicated in longevity and accumulating evidence indicate their role in a spectrum of diseases like cancer, diabetes, obesity and neurodegenerative diseases. A number of studies have reported profound changes in SIRT1 expression and activity linked to mitochondrial functional alterations following hypoxic-ischemic conditions and following reoxygenation injury. The SIRT1 mediated deacetylation of targets such as PGC-1α, FOXO3, p53 and NF-κb has profound effect on mitochondrial function, apoptosis and inflammation. These biological processes and functions are critical in life-span determination and outcome following injury. Aging is reported to be characterized by declining SIRT1 activity, and its increased expression or activation demonstrated prolonged life-span in lower forms of animals. A pseudohypoxic state due to declining NAD(+) has also been implicated in aging. In this review we provide an overview of studies on the role of sirtuins in aging and injury.

Kaempferol protects cardiomyocytes against anoxia/reoxygenation injury via mitochondrial pathway mediated by SIRT1

Mitochondria-mediated apoptosis is a critical mechanism of anoxia/ reoxygenation (A/R)-induced injury in cardiomyocytes. Kaempferol (Kae) is a natural polyphenol and a type of flavonoid, which has been demonstrated to protect myocardium against ischemia/reperfusion (I/R) injury. However, the mechanism is still not fully elucidated. We hypothesize that Kae may improve the mitochondrial function during I/R injury via a potential signal pathway. In this study, an in vitro I/R model was replicated on neonatal rat primary cardiomyocytes by A/R treatment. Cell viability was monitored by the 3-(4,5-dimethylthiazol- 2-yl)-5-(3- carboxymethoxyphenyl)-2-(4-sulfophenyl)-2 H-tetrazolium (MTS) assay. The levels of intracellular reactive oxygen species, mitochondrial membrane potential (Δψm) and apoptosis were determined by flow cytometry. Protein expression was detected by Western Blotting. mPTP opening and the activity of caspase-3 were measured by colorimetric method. The results showed that Kae effectively enhanced the cell viability and decreased the LDH release in cardiomyocytes subjected to A/R injury. Kae reduced the A/R-induced reactive oxygen species generation, the loss of Δψm, and the release of cytochrome c from mitochondria into cytosol. Kae inhibited the A/R-stimulated mPTP opening and activation of caspase-3, and ultimate decrease in cardiomyocytes apoptosis. Furthermore, we found Kae up-regulated Human Silent Information Regulator Type 1 (SIRT1) expression, indicating SIRT1 signal pathway likely involved the cardioprotection of Kae. Sirtinol, a SIRT1 inhibitor, abolished the protective effect of Kae in cardiomyocytes subjected to A/R. Additionally, Kae significantly increased the expression of Bcl-2. Thus, we firstly demonstrate that Kae protects cardiomyocytes against A/R injury through mitochondrial pathway mediated by SIRT1.

Histone variants and lipid metabolism

Within nucleosomes, canonical histones package the genome, but they can be opportunely replaced with histone variants. The incorporation of histone variants into the nucleosome is a chief cellular strategy to regulate transcription and cellular metabolism. In pathological terms, cellular steatosis is an abnormal accumulation of lipids, which reflects impairment in the turnover of triacylglycerols, affecting any organ but mainly the liver. The present review aims to summarize the experimental evidence for histone variant functions in lipid metabolism.

[D-Lys3]-GHRP-6 exhibits pro-autophagic effects on skeletal muscle

[D-Lys3]-GHRP-6 is regarded as a highly selective growth-hormone secretagogue receptor (GHSR) antagonist and has been widely used to investigate the dependency of GHSR-1a signalling mediated by acylated ghrelin. However, [D-Lys3]-GHRP-6 has been reported to influence other cellular processes which are unrelated to GHSR-1a. This study aimed to examine the effects of [D-Lys3]-GHRP-6 on autophagic and apoptotic cellular signalling in skeletal muscle. [D-Lys3]-GHRP-6 enhanced the autophagic signalling demonstrated by the increases in protein abundances of beclin-1 and LC3 II-to-LC3 1 ratio in both normal muscle and doxorubicin-injured muscle. [D-Lys3]-GHRP-6 reduced the activation of muscle apoptosis induced by doxorubicin. No histological abnormalities were observed in the [D-Lys3]-GHRP-6-treated muscle. Intriguingly, the doxorubicin-induced increase in centronucleated muscle fibres was not observed in muscle treated with [D-Lys3]-GHRP-6, suggesting the myoprotective effects of [D-Lys3]-GHRP-6 against doxorubicin injury. The [D-Lys3]-GHRP-6-induced activation of autophagy was found to be abolished by the co-treatment of CXCR4 antagonist, suggesting that the pro-autophagic effects of [D-Lys3]-GHRP-6 might be mediated through CXCR4. In conclusion, [D-Lys3]-GHRP-6 exhibits pro-autophagic effects on skeletal muscle under both normal and doxorubicin-injured conditions.

Mouse models of PAK function

p21-activated kinases are a family of highly conserved protein serine/threonine kinases that are increasingly recognized as playing essential roles in a variety of key signaling processes. Genetic analyses in mice, using constitutive or regulated gene disruption, have provided important new insights into PAK function. In this paper, we review the genetic analysis of all six PAK genes in mice. These data address the singular and redundant functions of the various PAK genes and suggest therapeutic possibilities for small molecule PAK inhibitors or activators.

The TRPA1 channel is a cardiac target of mIGF-1/SIRT1 signaling

Cardiac overexpression of locally acting muscle-restricted (m)IGF-1 and the consequent downstream activation of NAD(+)-dependent protein deacetylase sirtuin 1 (SIRT1) trigger potent cardiac antioxidative and antihypertrophic effects. Transient receptor potential (TRP) cation channel A1 (TRPA1) belongs to the TRP ion channel family of molecular detectors of thermal and chemical stimuli that activate sensory neurons to produce pain. Recently, it has been shown that TRPA1 activity influences blood pressure, but the significance of TRPA1 in the cardiovascular system remains elusive. In the present work, using genomic screening in mouse hearts, we found that TRPA1 is a target of mIGF-1/SIRT1 signaling. TRPA1 expression is increased in the heart of cardiac-restricted mIGF-1 transgenic (Tg) mice, both in cardiomyocytes and noncardiomyocytes. In wild-type mice, SIRT1 occupied the TRPA1 promoter, inhibiting its expression, whereas in the presence of the cardiac mIGF-1 transgene, SIRT1 was displaced from the TRPA1 promoter, leading to an increase in its expression. Cardiac-specific ablation of SIRT1 (cardiac-specific knockout) in mIGF-1 Tg mice paradoxically did not increase TRPA1 expression. We have recently reported a systemic "hormetic" effect in mIGF-1 Tg mice, mild hypertension, which was depleted upon cardiac-specific knockout of SIRT1. Administration of the selective TRPA1 antagonist HC-030031 to mIGF-1 Tg mice restored blood pressure to basal levels. We identified TRPA1 as a functional target of the cardiac mIGF-1/SIRT1 signaling pathway, which may have pharmacological implications for the management of cardiovascular stress.

SIRT1 in cardiovascular aging

Cardiovascular disease (CVD) is the leading cause of death worldwide, with aging as the key independent risk factor. Effective interventions are necessary to delay aging. Sirtuin1 (SIRT1), a NAD(+)-dependent histone deacetylase, is closely related to lifespan extension. SIRT1 exerts beneficial effects on aging and age-related diseases, such as atherosclerosis. In this review, we summarize the current knowledge on the functions of SIRT1 in cardiovascular aging, focusing on the underlying molecular mechanisms, including inhibition of oxidative stress and inflammation, and induction of autophagy. We also demonstrate that moderate up-regulation or activation of SIRT1 in cardiovascular aging and age-related CVD may confer important application values.