Glycogen synthase kinase 3 inhibition protects the heart from acute ischemia-reperfusion injury via inhibition of inflammation and apoptosis

Glycogen Synthase Kinase 3β inhibits BMSCs Chondrogenesis in Inflammation via the Cross-Reaction between NF-κB and β-Catenin in the Nucleus

Inflammation can influence the pluripotency and self-renewal of mesenchymal stem cells (MSCs), thereby altering their cartilage regeneration ability. Sprague-Dawley (SD) rat bone marrow mesenchymal stem cells (BMSCs) were isolated and found to be defective in differentiation potential in the interleukin-1β- (IL-1β-) induced inflammatory microenvironment. Glycogen synthase kinase-3β (GSK-3β) is an evolutionarily conserved serine/threonine kinase that plays a role in numerous cellular processes. The role of GSK-3β in inflammation may be related to the nuclear factor-κB (NF-κB) signaling pathway and the Wnt/β-catenin signaling pathway, whose mechanism remains unclear. In this study, we found that GSK-3β can inhibit chondrogenesis of IL-1β-impaired BMSCs by disrupting metabolic balance and promoting cell apoptosis. By using the inhibitors LiCl and SN50, we demonstrated that GSK-3β regulates the chondrogenesis via the NF-κB and Wnt/β-catenin signaling pathways and possibly mediates the cross-reaction between NF-κB and β-catenin in the nucleus. Given the molecular mechanisms of GSK-3β in chondrogenic differentiation in inflammation, GSK-3β is a crucial target for the treatment of inflammation-induced cartilage disease.

Tideglusib Ameliorates Ischemia/Reperfusion Damage by Inhibiting GSK-3β and Apoptosis in Rat Model of Ischemic Stroke

OBJECTIVES

Glycogen synthase kinase-3β (GSK-3β), a serine/threonine protein kinase, gets activated and worsen stroke outcome after ischemia/reperfusion (I/R) injury by inducing inflammation and apoptosis. In this study, tideglusib, a selective irreversible and non-ATP competitive inhibitor of GSK-3β, was explored in cerebral I/R damage using middle cerebral artery occlusion (MCAo) model in rats.

MATERIALS AND METHODS

MCAo was done for 90 min in male Wistar rats (250-280 g) using doccol suture. In pre-treatment group, tideglusib (50 mg/kg) was administered once daily for 2 days and on the day of surgery, 30 min before MCAo. Next day, rats were examined for neurobehavioral parameters and MRI was performed to assess brain damage. In post-treatment group, tideglusib was started at 30 min after MCAo and continued for the next 2 days. After 72 h of MCAo, behavioral parameters and brain damage by MRI were assessed. Further, oxidative stress markers (MDA and GSH), inflammatory cytokines (TNF-α, IL-1β and IL-10) and expression levels of pGSK-3β S9, Bcl-2 and Bax were estimated in pre-treatment group.

RESULTS

Tideglusib pre-treatment but not post-treatment significantly improved neurobehavioral parameters (p < 0.05) and reduced brain damage (p < 0.01) when compared with MCAo group. I/R induced changes in MDA (p < 0.01), TNF-α and IL-1β (p < 0.05) were significantly attenuated by pre-treatment. Further, tideglusib pre-treatment ameliorated MCAo induced altered expressions of pGSK-3β S9, Bcl-2 and Bax.

CONCLUSION

The results of our exploratory study indicated prophylactic potential of tideglusib in I/R injury by modulating pGSK-3β S9, apoptosis and neuro-inflammation.

Azathioprine pretreatment ameliorates myocardial ischaemia reperfusion injury in diabetic rats by reducing oxidative stress, apoptosis, and inflammation

This study was presented to observe the therapeutic effects of azathioprine (AZA) pretreatment on myocardial ischaemia reperfusion (I/R) damage in diabetic rats. All rats were randomly separated into control + sham operation; control +I/R; diabetes mellitus (DM) +I/R and DM +I/R + AZA groups. Diabetic rat models were established by intraperitoneally injecting 60 mg/kg streptozotocin (STZ). Diabetic rats were given 3 mg/kg AZA daily by gavage for 5 days. Then, myocardial I/R rat models were constructed. Myocardial infarction size and myocardial damage were respectively detected by TTC and H&E staining. Cardiac injury markers (CK-MB and MPO) and oxidative stress factors (SOD and MDA) were measured via ELISA. The protein expression of apoptotic markers (Caspase8, Caspase3, BAX and Bcl2), inflammatory factors (TLR4 and TNF-α) and AKT1/GSK3β in myocardial tissues was measured by western blot, immunohistochemistry or immunofluorescence. Data showed that AZA pretreatment could lessen myocardial infarction size and myocardial damage, and could down-regulate serum CK-MB, MPO, SOD and MDA levels in diabetic rats under I/R. Furthermore, AZA pretreatment decreased Caspase8, Caspase3, BAX, TLR4 and TNF-α expression, and increased Bcl2 expression in myocardial tissues of diabetic rats following I/R. Also, AZA pretreatment lowered AKT1, p-AKT1, GSK3β and p-GSK3β expression in diabetic heart after I/R. This study found that AZA may reduce myocardial injury in diabetic rats following I/R via reducing oxidative stress, cardiomyocyte apoptosis, and inflammatory response, which could be related to AKT1/GSK3β pathway inactivation.

Ischemia Reperfusion Injury: Opportunities for Nanoparticles

Ischemia reperfusion (IR)-induced oxidative stress, accompanied by inflammatory responses, contributes to morbidity and mortality in numerous diseases such as acute coronary syndrome, stroke, organ transplantation, and limb injury. Ischemia results in profound hypoxia and tissue dysfunction, whereas subsequent reperfusion further aggravates ischemic tissue damage through inducing cell death and activating inflammatory responses. In this review, we highlight recent studies of therapeutic strategies against IR injury. Furthermore, nanotechnology offers significant improvements in this area. Hence, we also review recent advances in nanomedicines for IR therapy, suggesting them as potent and promising strategies to improve drug delivery to IR-injured tissues and achieve protective effects.

Immunometabolic cross-talk in the inflamed heart

Inflammatory processes underlie many diseases associated with injury of the heart muscle, including conditions without an obvious inflammatory pathogenic component such as hypertensive and diabetic cardiomyopathy. Persistence of cardiac inflammation can cause irreversible structural and functional deficits. Some are induced by direct damage of the heart muscle by cellular and soluble mediators but also by metabolic adaptations sustained by the inflammatory microenvironment. It is well established that both cardiomyocytes and immune cells undergo metabolic reprogramming in the site of inflammation, which allow them to deal with decreased availability of nutrients and oxygen. However, like in cancer, competition for nutrients and increased production of signalling metabolites such as lactate initiate a metabolic cross-talk between immune cells and cardiomyocytes which, we propose, might tip the balance between resolution of the inflammation versus adverse cardiac remodeling. Here we review our current understanding of the metabolic reprogramming of both heart tissue and immune cells during inflammation, and we discuss potential key mechanisms by which these metabolic responses intersect and influence each other and ultimately define the prognosis of the inflammatory process in the heart.

Conditioning-induced cardioprotection: Aging as a confounding factor

The aging process induces a plethora of changes in the body including alterations in hormonal regulation and metabolism in various organs including the heart. Aging is associated with marked increase in the vulnerability of the heart to ischemia-reperfusion injury. Furthermore, it significantly hampers the development of adaptive response to various forms of conditioning stimuli (pre/post/remote conditioning). Aging significantly impairs the activation of signaling pathways that mediate preconditioning-induced cardioprotection. It possibly impairs the uptake and release of adenosine, decreases the number of adenosine transporter sites and down-regulates the transcription of adenosine receptors in the myocardium to attenuate adenosine-mediated cardioprotection. Furthermore, aging decreases the expression of peroxisome proliferator-activated receptor gamma co-activator 1-alpha (PGC-1α) and subsequent transcription of catalase enzyme which subsequently increases the oxidative stress and decreases the responsiveness to preconditioning stimuli in the senescent diabetic hearts. In addition, in the aged rat hearts, the conditioning stimulus fails to phosphorylate Akt kinase that is required for mediating cardioprotective signaling in the heart. Moreover, aging increases the concentration of Na⁺ and K⁺, connexin expression and caveolin abundance in the myocardium and increases the susceptibility to ischemia-reperfusion injury. In addition, aging also reduces the responsiveness to conditioning stimuli possibly due to reduced kinase signaling and reduced STAT-3 phosphorylation. However, aging is associated with an increase in MKP-1 phosphorylation, which dephosphorylates (deactivates) mitogen activated protein kinase that is involved in cardioprotective signaling. The present review describes aging as one of the major confounding factors in attenuating remote ischemic preconditioning-induced cardioprotection along with the possible mechanisms.

ZP2495 Protects against Myocardial Ischemia/Reperfusion Injury in Diabetic Mice through Improvement of Cardiac Metabolism and Mitochondrial Function: The Possible Involvement of AMPK-FoxO3a Signal Pathway

Coronary heart disease patients with type 2 diabetes were subject to higher vulnerability for cardiac ischemia-reperfusion (I/R) injury. This study was designed to evaluate the impact of ZP2495 (a glucagon-GLP-1 dual-agonist) on cardiac function and energy metabolism after myocardial I/R injury in db/db mice with a focus on mitochondrial function. C57BLKS/J-lepr⁺/lepr⁺ (BKS) and db/db mice received 4-week treatment of glucagon, ZP131 (GLP-1 receptor agonist), or ZP2495, followed by cardiac I/R injury. The results showed that cardiac function, cardiac glucose metabolism, cardiomyocyte apoptosis, cardiac mitochondrial morphology, and energetic transition were improved or ameliorated by ZP2495 to a greater extent than that of glucagon and ZP131. In vitro study showed that ZP2495, rather than glucagon, alleviated mitochondrial depolarization, cytochrome C release, and mitochondria ROS generation in neonatal rat ventricular myocytes subjected to high-glucose and simulated I/R injury conditions, the effects of which were weaker in the ZP131 group. Furthermore, the expressions of Akt, FoxO3a, and AMPK phosphorylation were elevated by ZP2495 to a greater extent than that of ZP131. In conclusion, ZP2495 may contribute to the improvement of cardiac function and energy metabolism in db/db mice after myocardial I/R injury by improving mitochondrial function possibly through Akt/FoxO3a and AMPK/FoxO3a signal pathways.

Murine splenic B cells express corticotropin-releasing hormone receptor 2 that affect their viability during a stress response

Chronic stress is now recognized as a risk factor for disease development and/or exacerbation. It has been shown to affect negatively the immune system and notably the humoral immune response. Corticotropin-releasing hormone (CRH) is known to play a crucial role in stress response. CRH receptors are expressed on different immune cells such as granulocytes, monocytes and T cells. However, up to now, no CRH receptor has been described on B cells which are key players of the humoral immune response. In order to highlight new pathways by which stress may impact immunity, we investigated the role of CRH in B cells. Here we show that splenic B cells express the CRH receptor 2 (CRHR2), but not CRHR1. This receptor is functional since CRH treatment of B cells activates different signaling pathways (e.g. p38) and decreases B cell viability. Finally, we show that immunization of mice with two types of antigens induces a more intense CRHR staining in secondary lymphoid organs where B cells are known to respond to the antigen. Altogether our results demonstrate, for the first time, that CRH is able to modulate directly B cell activity through the presence of CRHR2.

Biochemical targets of drugs mitigating oxidative stress via redox-independent mechanisms

Acute or chronic oxidative stress plays an important role in many pathologies. Two opposite approaches are typically used to prevent the damage induced by reactive oxygen and nitrogen species (RONS), namely treatment either with antioxidants or with weak oxidants that up-regulate endogenous antioxidant mechanisms. This review discusses options for the third pharmacological approach, namely amelioration of oxidative stress by 'redox-inert' compounds, which do not inactivate RONS but either inhibit the basic mechanisms leading to their formation (i.e. inflammation) or help cells to cope with their toxic action. The present study describes biochemical targets of many drugs mitigating acute oxidative stress in animal models of ischemia-reperfusion injury or N-acetyl-p-aminophenol overdose. In addition to the pro-inflammatory molecules, the targets of mitigating drugs include protein kinases and transcription factors involved in regulation of energy metabolism and cell life/death balance, proteins regulating mitochondrial permeability transition, proteins involved in the endoplasmic reticulum stress and unfolded protein response, nuclear receptors such as peroxisome proliferator-activated receptors, and isoprenoid synthesis. The data may help in identification of oxidative stress mitigators that will be effective in human disease on top of the current standard of care.

Investigating the involvement of glycogen synthase kinase-3β and gap junction signaling in TRPV1 and remote hind preconditioning-induced cardioprotection

Remote ischemic preconditioning (RIPC) is the phenomenon that harnesses the body's endogenous protective mechanisms against prolonged ischemia-reperfusion-induced injury. The present study aimed to explore the involvement of glycogen synthase kinase-3β and gap junction signaling in TRPV₁ and remote hind preconditioning-induced cardioprotection. In the present study, four consecutive cycles (5min of ischemia-reperfusion) of remote hind limb preconditioning stimulus were delivered using a blood pressure cuff fastened at the inguinal level of the rat. The isolated rat hearts were mounted on the Langendorff's apparatus and were exposed to 30min of global ischemia-120min of reperfusion. Sustained ischemia-reperfusion led to cardiac injury that was assessed in terms of infarct size, LDH release, CK release, LVDP, +dp/dt_max, -dp/dt_min, heart rate and coronary flow rate. The pharmacological agents employed in the present study included capsaicin (10mg/kg) as TRPV₁ channel activator, AR-A014418 (1 and 3mg/kg) as glycogen synthase kinase-3β inhibitor and carbenoxolone disodium (50 and 100mg/kg) as gap junction blocker. Remote hind limb, capsaicin and AR-A014418 preconditioning led to significant reduction in the infarct size, LDH release, CK release and improved LVDP, +dp/dt_max, -dp/dt_min, heart rate and coronary flow rate. However, remote hind limb, capsaicin and AR-A014418 preconditioning-induced cardioprotective effects were remarkably reduced in the presence of carbenoxolone (100mg/kg). This indicates that remote preconditioning stimulus probably activates TRPV₁ channels that may inhibit glycogen synthase kinase-3β activity which subsequently enhances gap junction coupling to produce cardioprotective effects.

Pharmacological postconditioning with atorvastatin calcium attenuates myocardial ischemia/reperfusion injury in diabetic rats by phosphorylating GSK3β

Diabetes is an independent risk factor for myocardial ischemia, and many epidemiological data and laboratory studies have revealed that diabetes significantly exacerbated myocardial ischemia/reperfusion injury and ameliorated protective effects. The present study aimed to determine whether pharmacological postconditioning with atorvastatin calcium lessened diabetic myocardial ischemia/reperfusion injury, and investigated the role of glycogen synthase kinase (GSK3β) in this. A total of 72 streptozotocin-induced diabetic rats were randomly divided into six groups, and 24 age-matched male non-diabetic Sprague-Dawley rats were randomly divided into two groups. Rats all received 40 min myocardial ischemia followed by 180 min reperfusion, except sham-operated groups. Compared with the non-diabetic ischemia/reperfusion model group, the diabetic ischemia/reperfusion group had a comparable myocardial infarct size, but a higher level of serum cardiac troponin I (cTnI) and morphological alterations to their myocardial cells. Compared with the diabetic ischemia/reperfusion group, the group that received pharmacological postconditioning with atorvastatin calcium had smaller myocardial infarct sizes, lower levels of cTnI, reduced morphological alterations to myocardial cells, higher levels of p-GSK3β, heat shock factor (HSF)-1 and heat shock protein (HSP)70. The cardioprotective effect conferred by atorvastatin calcium did not attenuate myocardial ischemia/reperfusion injury following application of TDZD-8, which phosphorylates and inactivates GSK3β. Pharmacological postconditioning with atorvastatin calcium may attenuate diabetic heart ischemia/reperfusion injury in the current context. The phosphorylation of GSK3β serves a critical role during the cardioprotection in diabetic rats, and p-GSK3β may accelerate HSP70 production partially by activating HSF-1 during myocardial ischemic/reperfusion injury.

Wnt/Glycogen Synthase Kinase 3β/β-catenin Signaling Activation Mediated Sevoflurane Preconditioning-induced Cardioprotection

Background:

Sevoflurane preconditioning (SP) has been shown to invoke potent myocardial protection in animal studies and clinical trials. However, the mechanisms underlying SP are complex and not yet well understood. We investigated the hypothesis that the cardioprotection afforded by SP is mediated via the Wnt/glycogen synthase kinase 3β (GSK3β)/β-catenin signaling pathway.

Methods:

Two models were established: A Langendorff perfused rat heart model and the H9C2 cell hypoxia/reoxygenation model. Both rats and H9C2 cells were randomly divided into 6 groups as follows: S group, ischemia-reperfusion (I/R) group, DMSO group, IWP group, SP group, and SP + IWP group. Hemodynamic parameters, lactate dehydrogenase (LDH) activity in coronary effluent and cell culture supernatant, and the infarct size were measured to evaluate myocardial ischemia-reperfusion injuries. To determine the activity of Wnt/GSK3β/β-catenin signaling pathway, the expressions of Wnt3a, phospho-GSK3β, and β-catenin were measured by Western blotting.

Results:

SP improved cardiac function recovery, reduced infarct size (18 ± 2% in the SP group compared with 35 ± 4% in the I/R group; P < 0.05), decreased LDH activity in coronary effluent, and culture supernatant. IWP-2, an inhibitor of Wnt, abolished the cardioprotection by SP. In addition, Western blotting analysis demonstrated that the expressions of Wnt3a, phospho-GSK3β, and β-catenin significantly (P < 0.05) increased in the I/R group, compared with the S group; and compared to I/R group, SP significantly (P < 0.05) increased Wnt3a, phospho-GSK3β, and β-catenin expressions. Pretreatment with IWP-2 significantly (P < 0.05) abolished SP-induced Wnt/GSK3β/β-catenin signaling activation.

Conclusions:

The results showed for the first time that cardioprotection afforded by SP may be mediated partly via the Wnt/GSK3β/β-catenin signaling pathway.

Protective Effects of Kaempferol against Myocardial Ischemia/Reperfusion Injury in Isolated Rat Heart via Antioxidant Activity and Inhibition of Glycogen Synthase Kinase-3β

Objective. This study aimed to evaluate the protective effect of kaempferol against myocardial ischemia/reperfusion (I/R) injury in rats. Method. Left ventricular developed pressure (LVDP) and its maximum up/down rate (±dp/dt_max) were recorded as myocardial function. Infarct size was detected with 2,3,5-triphenyltetrazolium chloride staining. Cardiomyocyte apoptosis was determined using terminal deoxynucleotidyl nick-end labeling (TUNEL). The levels of creatine kinase (CK), lactate dehydrogenase (LDH), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione/glutathione disulfide (GSH/GSSG) ratio, and tumor necrosis factor-alpha (TNF-α) were determined using enzyme linked immunosorbent assay (ELISA). Moreover, total glycogen synthase kinase-3β (GSK-3β), phospho-GSK-3β (P-GSK-3β), precaspase-3, cleaved caspase-3, and cytoplasm cytochrome C were assayed using Western blot analysis. Results. Pretreatment with kaempferol significantly improved the recovery of LVDP and ±dp/dt_max, as well as increased the levels of SOD and P-GSK-3β and GSH/GSSG ratio. However, the pretreatment reduced myocardial infarct size and TUNEL-positive cell rate, as well as decreased the levels of cleaved caspase-3, cytoplasm cytochrome C, CK, LDH, MDA, and TNF-α. Conclusion. These results suggested that kaempferol provides cardioprotection via antioxidant activity and inhibition of GSK-3β activity in rats with I/R.

Inhibition of glycogen synthase kinase-3β enhances cognitive recovery after stroke: the role of TAK1

Memory deficits are common among stroke survivors. Identifying neuroprotective agents that can prevent memory impairment or improve memory recovery is a vital area of research. Glycogen synthase kinase-3β (GSK-3β) is involved in several essential intracellular signaling pathways. Unlike many other kinases, GSK-3β is active only when dephosphorylated and activation promotes inflammation and apoptosis. In contrast, increased phosphorylation leads to reduced GSK-3β (pGSK-3β) activity. GSK-3β inhibition has beneficial effects on memory in other disease models. GSK-3β regulates both the 5'AMP-activated kinase (AMPK) and transforming growth factor-β-activated kinase (TAK1) pathways. In this work, we examined the effect of GSK-3β inhibition, both independently, in conjunction with a TAK inhibitor, and in AMPK-α2 deficient mice, after stroke to investigate mechanistic interactions between these pathways. GSK-3β inhibition was neuroprotective and ameliorated stroke-induced cognitive impairments. This was independent of AMPK signaling as the protective effects of GSK-3β inhibition were seen in AMPK deficient mice. However, GSK-3β inhibition provided no additive protection in mice treated with a TAK inhibitor suggesting that TAK1 is an upstream regulator of GSK-3β. Targeting GSK-3β could be a novel therapeutic strategy for post-stroke cognitive deficits.

Lin28a protects against cardiac ischaemia/reperfusion injury in diabetic mice through the insulin-PI3K-mTOR pathway

The insulin-PI3K-mTOR pathway exhibits a variety of cardiovascular activities including protection against I/R injury. Lin28a enhanced glucose uptake and insulin-sensitivity via insulin-PI3K-mTOR signalling pathway. However, the role of lin28a on experimental cardiac I/R injury in diabetic mice are not well understood. Diabetic mice underwent 30 min. of ischaemia followed by 3 hrs of reperfusion. Animals were randomized to be treated with lentivirus carrying lin28a siRNA (siLin28a) or lin28a cDNA (Lin28a) 72 hrs before coronary artery ligation. Myocardial infarct size (IS), cardiac function, cardiomyocyte apoptosis and mitochondria morphology in diabetic mice who underwent cardiac I/R injury were compared between groups. The target proteins of lin28a were examined by western blot analysis. Lin28a overexpression significantly reduced myocardial IS, improved LV ejection fraction (LVEF), decreased myocardial apoptotic index and alleviated mitochondria cristae destruction in diabetic mice underwent cardiac I/R injury. Lin28a knockdown exacerbated cardiac I/R injury as demonstrated by increased IS, decreased LVEF, increased apoptotic index and aggravated mitochondria cristae destruction. Interestingly, pre-treatment with rapamycin abolished the beneficial effects of lin28a overexpression. Lin28a overexpression increased, while Lin28a knockdown decreased the expression of IGF1R, p-Akt, p-mTOR and p-p70s6k after cardiac I/R injury in diabetic mice. Rapamycin pre-treatment abolished the effects of increased p-mTOR and p-p70s6k expression exerted by lin28a overexpression. This study indicates that lin28a overexpression reduces IS, improves cardiac function, decreases cardiomyocyte apoptosis index and alleviates cardiomyocyte mitochondria impairment after cardiac I/R injury in diabetic mice. The mechanism responsible for the effects of lin28a is associated with the insulin-PI3K-mTOR dependent pathway.

Lin28a protects against hypoxia/reoxygenation induced cardiomyocytes apoptosis by alleviating mitochondrial dysfunction under high glucose/high fat conditions

Aim

The aim of the present study was to investigate the role of Lin28a in protecting against hypoxia/reoxygenation (H/R)-induced cardiomyocytes apoptosis under high glucose/high fat (HG/HF) conditions.

Methods

Primary cardiomyocytes which were isolated from neonatal mouse were randomized to be treated with lentivirus carrying Lin28a siRNA, Lin28acDNA 72 h before H/R (9 h/2 h). Cardiomyocytes biomarkers release (LDH and CK), cardiomyocytes apoptosis, mitochondria biogenesis and morphology, intracellular reactive oxygen species (ROS) production, ATP content and inflammatory cytokines levels after H/R injury in high glucose/high fat conditions were compared between groups. The target proteins of Lin28a were examined by western blot analysis.

Results

Our results revealed that Lin28a cDNA transfection (overexpression) significantly inhibited cardiomyocyte apoptotic index, improved mitochondria biogenesis, increased ATP production and reduced ROS production as compared with the H/R group in HG/HF conditions. Lin28a siRNA transfection (knockdown) rendered the cardiomyocytes more susceptible to H/R injury as evidenced by increased apoptotic index, impaired mitochondrial biogenesis, decreased ATP production and increased ROS level. Interestingly, these effects of Lin28a were blocked by pretreatment with the PI3K inhibitor wortmannin. Lin28a overexpression increased, while Lin28a knockdown inhibited IGF1R, Nrf-1, Tfam, p-IRS-1, p-Akt, p-mTOR, p-p70s6k, p-AMPK expression levels after H/R injury in HG/HF conditions. Moreover, pretreatment with wortmannin abolished the effects of Lin28a on the expression levels of p-AKT, p-mTOR, p-p70s6k, p-AMPK.

Conclusions

The present results suggest that Lin28a inhibits cardiomyocytes apoptosis by enhancing mitochondrial biogenesis and function under high glucose/high fat conditions. The mechanism responsible for the effects of Lin28a is associated with the PI3K/Akt dependent pathway.

Involvement of the Wnt signaling pathway and cell apoptosis in the rat hippocampus following cerebral ischemia/reperfusion injury

We investigated the role of the Wnt signaling pathway in cerebral ischemia/reperfusion injury by examining β-catenin and glycogen synthase kinase-3β protein expression in the rat hippocampal CA1 region following acute cerebral ischemia/reperfusion. Our results demonstrate that cell apoptosis increases in the CA1 region following ischemia/reperfusion. In addition, β-catenin and glycogen synthase kinase-3β protein expression gradually increases, peaking at 48 hours following reperfusion. Dickkopf-1 administration, after cerebral ischemia/reperfusion injury, results in decreased cell apoptosis, and β-catenin and glycogen synthase kinase-3β expression, in the CA1 region. This suggests that β-catenin and glycogen synthase kinase-3β, both components of the Wnt signaling pathway, participate in cell apoptosis following cerebral ischemia/reperfusion injury.

Genome-wide RNAi screen reveals a new role of a WNT/CTNNB1 signaling pathway as negative regulator of virus-induced innate immune responses

To identify new regulators of antiviral innate immunity, we completed the first genome-wide gene silencing screen assessing the transcriptional response at the interferon-β (IFNB1) promoter following Sendai virus (SeV) infection. We now report a novel link between WNT signaling pathway and the modulation of retinoic acid-inducible gene I (RIG-I)-like receptor (RLR)-dependent innate immune responses. Here we show that secretion of WNT2B and WNT9B and stabilization of β-catenin (CTNNB1) upon virus infection negatively regulate expression of representative inducible genes IFNB1, IFIT1 and TNF in a CTNNB1-dependent effector mechanism. The antiviral response is drastically reduced by glycogen synthase kinase 3 (GSK3) inhibitors but restored in CTNNB1 knockdown cells. The findings confirm a novel regulation of antiviral innate immunity by a canonical-like WNT/CTNNB1 signaling pathway. The study identifies novel avenues for broad-spectrum antiviral targets and preventing immune-mediated diseases upon viral infection.

3,5-Dimethoxy-4-(3-(2-carbonyl-ethyldisulfanyl)-propionyl)-benzoic acid 4-guanidino-butyl ester: a novel twin drug that prevents primary cardiac myocytes from hypoxia-induced apoptosis

Leonurine possesses cardioprotective effects in myocardial ischemia due to its anti-apoptotic properties. However, the process to isolate and purify leonurine is difficult, because of its low content in the Herb Leonuri and its impurity. Moreover, the high dosage used indicates low potency of leonurine. To overcome these defects, we had synthesized a novel twin drug of leonurine, 3,5-dimethoxy-4-(3-(2-carbonyl-ethyldisulfanyl)-propionyl)-benzoic acid 4-guanidino-butyl ester (compound 2). In this paper, we focused on investigating the cardioprotective effect and underlying mechanisms of compound 2. Our data showed that cell viability was significantly increased in a dose-dependent manner and the levels of lactate dehydrogenase (LDH) and creatine kinase (CK) were also significantly attenuated in the compound 2-treated group. In addition, we observed the cardioprotective effects by Hoechst 33258 nucleus staining, JC-1 staining, Annexin V-FITC/PI staining and transmission electron microscopy. Compound 2 inhibited apoptosis by reducing the ratio of Bcl-2/Bax, decreasing cleaved-caspase-3 expression and enhancing the phosphorylation of Akt. Furthermore, the phosphorylation effect of compound 2 was reversed by LY294002 the phosphatidylinositol-3-kinase (PI3K) inhibitor from happening. We concluded that compound 2 played a cardioprotective role in hypoxia-induced primary cardiac myocytes apoptosis partly via modulating the PI3K/Akt pathway at a 10-fold lower concentration than leonurine.

Pressure overload regulates expression of cytokines, γH2AX, and growth arrest- and DNA-damage inducible protein 153 via glycogen synthase kinase-3β in ischemic-reperfused hearts

The growth arrest- and DNA-damage inducible protein 153 (GADD153) regulates both apoptosis and inflammatory response. Importantly, glycogen synthase kinase-3β (GSK-3β) may provide a mechanistic link for cellular expression of GADD153, inflammatory response, and cell death. We previously showed that pressure overload exacerbates myocardial ischemia reperfusion injury associated with significant reduction in phosphorylated (inactive) GSK-3β. This raises the possibility that pressure overload, through a GSK-3β-dependent mechanism, increases GADD153 expression, thereby upregulating inflammatory cytokine production and contributing to worsening of myocardial ischemia reperfusion injury. Accordingly, Langendorff-perfused rat hearts were subjected to global ischemia reperfusion protocol in the absence or presence of the GSK-3β inhibitor, lithium chloride (1 mmol/L), with perfusion pressure set at 80 or 160 cmH(2)O; normoxic hearts served as controls. Compared with normoxia, an ischemia reperfusion insult increased expressions of proinflammatory cytokines, γH2AX, and GADD153 in association with increased cell death. In the ischemic-reperfused hearts, pressure overload did the following: (1) reduced interleukin-10 but increased interleukin-17 (cardiomyocytes), without affecting interleukin-23; (2) increased expressions of γH2AX and GADD153; (3) decreased 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide (JC-1) aggregates but increased JC-1 monomers (suggestive of reduced mitochondrial membrane potential, ψ(m)); and (4) increased annexin V immunostaining as well as apoptotic and necrotic cell death. Treatment with lithium chloride caused a robust increase in interleukin-10, preserved ψ(m), and markedly decreased all other parameters with the effect being most prominent for hearts perfused at the high pressure. In conclusion, pressure overload, via a GSK-3β-dependent mechanism, exacerbates cell death in the isolated ischemic-reperfused heart involving regulation of inflammatory response, DNA injury, and GADD153 expression.

Mitochondrial network in the heart

Mitochondria are subcellular organelles that provide energy for the cell. They form a dynamic tubular network and play an important role in maintaining the cell function and integrity. Heart is a powerful organ that supplies the motivation for circulation, thereby requiring large amounts of energy. Thus, the healthiness of cardiomyocytes and mitochondria is necessary for the normal cardiac function. Mitochondria not only lie in the center of the cell apoptotic pathway, but also are the major source of reactive oxygen species (ROS) generation. Mitochondrial morphological change includes fission and fusion that are regulated by a large number of proteins. In this review we discuss the regulators of mitochondrial fission/fusion and their association with cell apoptosis, autophagy and ROS production in the heart.

Glycogen synthase kinase-3 beta inhibitor suppresses Porphyromonas gingivalis lipopolysaccharide-induced CD40 expression by inhibiting nuclear factor-kappa B activation in mouse osteoblasts

Bone-forming osteoblasts have been recently reported capable of expressing the critical co-stimulatory molecule CD40 upon exposure to bacterial infection, which supports the unappreciated role of osteoblasts in modulating bone inflammation. Recent studies highlight the anti-inflammatory potential of glycogen synthase kinase-3β (GSK-3β) inhibitors; however, their effect on osteoblasts remains largely unclear. In the present study, we showed that treatment with SB216763, a highly specific GSK-3β inhibitor, resulted in a dose-dependent decrease in the mRNA and protein expression of CD40, as well as production of pro-inflammatory cytokines IL-6, TNF-α and IL-1β, in the Porphyromonas gingivalis-lipopolysaccharide (LPS)-stimulated murine osteoblastic-like MC3T3-E1 cells. Furthermore, inhibition of GSK-3β remarkably represses the LPS-induced activation of the nuclear factor kappa B (NF-κB) signaling pathway by suppressing IκBα phosphorylation, NF-κBp65 nuclear translocation, and NF-κBp65 DNA binding activity. Closer investigation by immunoprecipitation assay revealed that β-catenin can physically interact with NF-κBp65. The negative regulation effect of GSK-3β inhibitor on CD40 expression is mediated through β-catenin, for siRNA of β-catenin attenuated the GSK-3β inhibitor-induced repression of NF-κB activation and, consequently, the expression of CD40 and production of pro-inflammatory cytokines in LPS-stimulated MC3T3-E1 cells. Thus our results elucidate the molecular mechanisms whereby GSK-3β inhibitor prevents the LPS-induced CD40 expression on osteoblasts and provide supportive evidence of the potential role of GSK-3β inhibitors in suppressing the immune function of osteoblasts in inflammatory bone diseases.

New drug targets in depression: inflammatory, cell-mediated immune, oxidative and nitrosative stress, mitochondrial, antioxidant, and neuroprogressive pathways. And new drug candidates--Nrf2 activators and GSK-3 inhibitors

This paper reviews new drug targets in the treatment of depression and new drug candidates to treat depression. Depression is characterized by aberrations in six intertwined pathways: (1) inflammatory pathways as indicated by increased levels of proinflammatory cytokines, e.g. interleukin-1 (IL-1), IL-6, and tumour necrosis factor α. (2) Activation of cell-mediated immune pathways as indicated by an increased production of interferon γ and neopterin. (3) Increased reactive oxygen and nitrogen species and damage by oxidative and nitrosative stress (O&NS), including lipid peroxidation, damage to DNA, proteins and mitochondria. (4) Lowered levels of key antioxidants, such as coenzyme Q10, zinc, vitamin E, glutathione, and glutathione peroxidase. (5) Damage to mitochondria and mitochondrial DNA and reduced activity of respiratory chain enzymes and adenosine triphosphate production. (6) Neuroprogression, which is the progressive process of neurodegeneration, apoptosis, and reduced neurogenesis and neuronal plasticity, phenomena that are probably caused by inflammation and O&NS. Antidepressants tend to normalize the above six pathways. Targeting these pathways has the potential to yield antidepressant effects, e.g. using cytokine antagonists, minocycline, Cox-2 inhibitors, statins, acetylsalicylic acid, ketamine, ω3 poly-unsaturated fatty acids, antioxidants, and neurotrophic factors. These six pathways offer new, pathophysiologically guided drug targets suggesting that novel therapies could be developed that target these six pathways simultaneously. Both nuclear factor (erythroid-derived 2)-like 2 (Nrf2) activators and glycogen synthase kinase-3 (GSK-3) inhibitors target the six above-mentioned pathways. GSK-3 inhibitors have antidepressant effects in animal models of depression. Nrf2 activators and GSK-3 inhibitors have the potential to be advanced to phase-2 clinical trials to examine whether they augment the efficacy of antidepressants or are useful as monotherapy.

Regulation by glycogen synthase kinase-3 of inflammation and T cells in CNS diseases

Elevated markers of neuroinflammation have been found to be associated with many psychiatric and neurodegenerative diseases, such as mood disorders, Alzheimer's disease, and multiple sclerosis (MS). Since neuroinflammation is thought to contribute to the pathophysiology of these diseases and to impair responses to therapeutic interventions and recovery, it is important to identify mechanisms that regulate neuroinflammation and potential targets for controlling neuroinflammation. Recent findings have demonstrated that glycogen synthase kinase-3 (GSK3) is an important regulator of both the innate and adaptive immune systems' contributions to inflammation. Studies of the innate immune system have shown that inhibitors of GSK3 profoundly alter the repertoire of cytokines that are produced both by peripheral and central cells, reducing pro-inflammatory cytokines, and increasing anti-inflammatory cytokines. Furthermore, inhibitors of GSK3 promote tolerance to inflammatory stimuli, reducing inflammatory cytokine production upon repeated exposure. Studies of the adaptive immune system have shown that GSK3 regulates the production of cytokines by T cells and the differentiation of T cells to subtypes, particularly Th17 cells. Regulation of transcription factors by GSK3 appears to play a prominent role in its regulation of immune responses, including of NF-κB, cyclic AMP response element binding protein, and signal transducer and activator of transcription-3. Invivo studies have shown that GSK3 inhibitors ameliorate clinical symptoms of both peripheral and central inflammatory diseases, particularly experimental autoimmune encephalomyelitis, the animal model of MS. Therefore, the development and application of GSK3 inhibitors may provide a new therapeutic strategy to reduce neuroinflammation associated with many central nervous system diseases.

Glycogen synthase kinase-3 facilitates con a-induced IFN-γ-- mediated immune hepatic injury

Immune hepatic injury induced by Con A results primarily from IFN-γ-mediated inflammation, followed by hepatic cell death. Glycogen synthase kinase (GSK)-3, which acts proapoptotically and is proinflammatory, is also important for facilitating IFN-γ signaling. We hypothesized a pathogenic role for GSK-3 in Con A hepatic injury. Con A stimulation caused GSK-3 activation in the livers of C57BL/6 mice. Inhibiting GSK-3 reduced Con A hepatic injury, including hepatic necrosis and apoptosis, inflammation, infiltration of T cells and granulocytes, and deregulated expression of adhesion molecule CD54. Con A induced hepatic injury in an IFN-γ receptor 1-dependent manner. Con A/IFN-γ induced activation and expression of STAT1 in a GSK-3-dependent manner. GSK-3 facilitated IFN-γ-induced inducible NO synthase, but had limited effects on CD95 upregulation and CD95-mediated hepatocyte apoptosis in vitro. Notably, inhibiting GSK-3 decreased Con A-induced IFN-γ production in both wild-type and IFN-γ receptor 1-deficient C57BL/6 mice. In Con A-activated NKT cells, GSK-3 was also activated and was required for nuclear translocation of T-box transcription factor Tbx21, a transcription factor of IFN-γ, but it was not required for CD95 ligand expression or activation-induced cell death. These results demonstrate the dual and indispensable role of GSK-3 in Con A hepatic injury by facilitating IFN-γ-induced hepatopathy.

Cardioprotective effects of tanshinone IIA pretreatment via kinin B2 receptor-Akt-GSK-3β dependent pathway in experimental diabetic cardiomyopathy

Aims

Diabetic cardiomyopathy, characterized by myocardial structural and functional changes, is a specific cardiomyopathy develops in patients with diabetes mellitus. The present study was to investigate the role of kinin B2 receptor-Akt-glycogen synthase kinase (GSK)-3β signalling pathway in mediating the protective effects of tanshinone IIA (TSN) on diabetic cardiomyopathy.

Methods and results

Streptozocin (STZ) induced diabetic rats (n = 60) were randomized to receive TSN, TSN plus HOE140 (a kinin B2 receptor antagonist), or saline. Healthy Sprague-Dawley (SD) rats (n = 20) were used as control. Left ventricular function, myocardial apoptosis, myocardial ultrastructure, Akt, GSK-3β and NF-κB phosphorylation, the expression of TNF-α, IL-6 and myeloperoxidase (MPO) were examined. Cardiac function was well preserved as evidenced by increased left ventricular ejection fraction (LVEF) and ± dp/dt (maximum speed of contraction/relaxation), along with decreased myocardial apoptotic death after TSN administration. TSN pretreatment alleviated mitochondria ultrastructure changes. TSN also enhanced Akt and GSK-3β phosphorylation and inhibited NF-κB phosphorylation, resulting in decreased TNF-α, IL-6 and MPO activities. Moreover, pretreatment with HOE140 abolished the beneficial effects of TSN: a decrease in LVEF and ± dp/dt, an inhibition of cardiomyocyte apoptosis, a destruction of cardiomyocyte mitochondria cristae, a reduction of Akt and GSK-3β phosphorylation, an enhancement of NF-κB phosphorylation and an increase of TNF-α, IL-6 and MPO production.

Conclusion

These data indicated that TSN is cardioprotective in the context of diabetic cardiomyopathy through kinin B2 receptor-Akt-GSK-3β dependent pathway.

Nitric oxide and calcium signaling regulate myocardial tumor necrosis factor-α expression and cardiac function in sepsis

Myocardial tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine, is a critical inducer of myocardial dysfunction in sepsis. The purpose of this review is to summarize the mechanisms through which TNF-alpha production is regulated in cardiomyocytes in response to lipopolysaccharide (LPS), a key pathogen-associated molecular pattern (PAMP) in sepsis. These mechanisms include Nox2-containing NAD(P)H oxidase, phospholipase C (PLC)gamma1, and Ca2+ signaling pathways. Activation of these pathways increases TNF-alpha expression via activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK). Conversely, activation of c-Jun NH2-terminal kinase 1 (JNK1) negatively regulates TNF-alpha production through inhibition of ERK1/2 and p38 MAPK activity. Interestingly, endothelial nitric oxide synthase (eNOS) promotes TNF-alpha expression by enhancing p38 MAPK activation, whereas neuronal NOS (nNOS) inhibits TNF-alpha production by reducing Ca2+-dependent ERK1/2 activity. Therefore, the JNK1 and nNOS inhibitory pathways represent a "brake" that limits myocardial TNF-alpha expression in sepsis. Further understanding of these signal transduction mechanisms may lead to novel pharmacological therapies in sepsis.

Glycogen synthase kinase 3: a point of convergence for the host inflammatory response

The phosphatidylinositol 3-kinase (PI3K) pathway has been shown to play a central role in regulating the host inflammatory response. Recent studies characterizing the downstream effector molecules within the PI3K pathway have identified that the serine/threonine kinase, glycogen synthase kinase 3 (GSK3), plays a pivotal role in regulating the production of pro- and anti-inflammatory cytokines. In innate immune cells, GSK3 inactivation augments anti-inflammatory cytokine production while concurrently suppressing the production of pro-inflammatory cytokines. The role of GSK3 in T cell biology has also been studied in detail and is involved in regulating multiple downstream signaling processes mediated by the T cell receptor (TCR), the co-stimulatory molecule CD28, and the IL-17 receptor. In vivo studies assessing the therapeutic properties of GSK3 inhibitors have shown that the inactivation of GSK3 can protect the host from immune-mediated pathology and death. This review will highlight the immunological importance GSK3 plays within different signal transduction pathways of the immune system, the cellular mechanisms regulating the activity of GSK3, the role of GSK3 in innate and adaptive immune responses, and the in vivo use of GSK3 inhibitors to treat inflammatory mediated diseases in animals.

Activation of peroxisome proliferator-activated receptor-beta/delta attenuates myocardial ischemia/reperfusion injury in the rat

Peroxisome proliferator-activated receptor-beta/delta (PPAR-beta/delta) is a transcription factor that belongs to the PPAR nuclear hormone receptor family. There is little information about the effects of the immediate administration of specific ligands of PPAR-beta/delta (e.g., GW0742) in animal models of myocardial I/R injury. Using a rat model of regional myocardial I/R in vivo, we have investigated the effects of immediate administration of GW0742 on myocardial infarct size. Male Wistar rats were subjected to 25 min of regional ischemia followed by 2 h of reperfusion and treated with GW0742 (3, 30, or 300microg/kg i.v. given at 30 min before ischemia and again at the start of reperfusion). Higher doses (30 or 300 microg/kg i.v.) of GW0742 caused a reduction in infarct size, whereas the lowest dose used was not effective. The degree of cardioprotection was similar when GW0742 (30 microg/kg i.v.) was given on reperfusion alone. The reduction in infarct size afforded by GW0742 was not reduced by the competitive irreversible PPAR-alpha antagonist GW6471 (1 mg/kg i.v., 15 min before ischemia). GW0742 (30 microg/kg i.v.) reduced the I/R-induced (a) decrease in the phosphorylation of Akt and glycogen synthase kinase-3beta, (b) nuclear translocation of the p65 subunit of nuclear factor-kappaB (activation of nuclear factor-kappaB), and (c) increase in the expression of iNOS and cyclooxygenase-2. Thus, immediate administration of the PPAR-beta/delta ligand GW0742 during reperfusion reduces myocardial infarct size in the rat by a mechanism that may involve inhibition of the activity of glycogen synthase kinase-3beta secondary to activation of the Akt pathway.

Inhibition of glioblastoma growth by the thiadiazolidinone compound TDZD-8

BACKGROUND

Thiadiazolidinones (TDZD) are small heterocyclic compounds first described as non-ATP competitive inhibitors of glycogen synthase kinase 3β (GSK-3β). In this study, we analyzed the effects of 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8), on murine GL261 cells growth in vitro and on the growth of established intracerebral murine gliomas in vivo.

METHODOLOGY/PRINCIPAL FINDINGS

Our data show that TDZD-8 decreased proliferation and induced apoptosis of GL261 glioblastoma cells in vitro, delayed tumor growth in vivo, and augmented animal survival. These effects were associated with an early activation of extracellular signal-regulated kinase (ERK) pathway and increased expression of EGR-1 and p21 genes. Also, we observed a sustained activation of the ERK pathway, a concomitant phosphorylation and activation of ribosomal S6 kinase (p90RSK) and an inactivation of GSK-3β by phosphorylation at Ser 9. Finally, treatment of glioblastoma stem cells with TDZD-8 resulted in an inhibition of proliferation and self-renewal of these cells.

CONCLUSIONS/SIGNIFICANCE

Our results suggest that TDZD-8 uses a novel mechanism to target glioblastoma cells, and that malignant progenitor population could be a target of this compound.

Microglial activation and chronic neurodegeneration

Microglia, the resident innate immune cells in the brain, have long been implicated in the pathology of neurodegenerative diseases. Accumulating evidence points to activated microglia as a chronic source of multiple neurotoxic factors, including tumor necrosis factor-α, nitric oxide, interleukin-1β, and reactive oxygen species (ROS), driving progressive neuron damage. Microglia can become chronically activated by either a single stimulus (e.g., lipopolysaccharide or neuron damage) or multiple stimuli exposures to result in cumulative neuronal loss with time. Although the mechanisms driving these phenomena are just beginning to be understood, reactive microgliosis (the microglial response to neuron damage) and ROS have been implicated as key mechanisms of chronic and neurotoxic microglial activation, particularly in the case of Parkinson's disease. We review the mechanisms of neurotoxicity associated with chronic microglial activation and discuss the role of neuronal death and microglial ROS driving the chronic and toxic microglial phenotype.

Tanshinone IIA pretreatment protects myocardium against ischaemia/reperfusion injury through the phosphatidylinositol 3-kinase/Akt-dependent pathway in diabetic rats

AIM

Diabetes Mellitus (DM) is widely acknowledged to increase the risk of cardiovascular death, which warrants the use of aggressive primary prevention strategies. The aim of the present study was to investigate the pretreatment effects of tanshinone IIA (TSN), a traditional Chinese medicine, on myocardial infarct size, apoptosis, inflammation and cardiac functional recovery in diabetic rats subjected to myocardial ischaemia/reperfusion (I/R).

METHODS

Streptozocin (STZ) induced diabetic rats (n = 80) were randomized to receive TSN, TSN plus wortmannin [a phosphatidylinositol 3-kinase (PI3K) inhibitor] or saline. They were exposed to a 30-min ischaemia by ligation of the left coronary artery except for the sham group. Haemodynamics, infarct size and myocardial apoptosis were examined 3 h after reperfusion. The effects of TSN on Akt and NF-kappaB phosphorylation and the expression of tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in cardiac tissues were examined.

RESULTS

Our results revealed that TSN administration significantly reduced myocardial infarct size (0.252 +/- 0.038 vs. 0.327 +/- 0.027, p < 0.05), improved left ventricular ejection fraction (LVEF) (0.774 +/- 0.058 vs. 0.716 +/- 0.054, p < 0.05), decreased myocardial apoptotic death (0.114 +/- 0.026 vs. 0.191 +/- 0.023, p < 0.05) compared with I/R group. Western blot analysis showed that TSN treatment enhanced Akt phosphorylation and inhibited NF-kappaB phosphorylation in cardiac tissues. Moreover, pretreatment with wortmannin abolished the beneficial effects of TSN: a reduction of infarct size, a decrease in LVEF, inhibition of myocardial apoptosis and Akt phosphorylation, enhancement of NF-kappaB phosphorylation and an increase of cytokine production including TNF-alpha and IL-6 after I/R injury in diabetic rats.

CONCLUSIONS

This study indicates that TSN pretreatment reduces infarct size and improves cardiac dysfunction after I/R injury in diabetic rats. This was accompanied with decreased cardiac apoptosis and inflammation. The possible mechanism responsible for the effects of TSN is associated with the PI3K/Akt-dependent pathway.

Alcohol dehydrogenase accentuates ethanol-induced myocardial dysfunction and mitochondrial damage in mice: role of mitochondrial death pathway

Objectives

Binge drinking and alcohol toxicity are often associated with myocardial dysfunction possibly due to accumulation of the ethanol metabolite acetaldehyde although the underlying mechanism is unknown. This study was designed to examine the impact of accelerated ethanol metabolism on myocardial contractility, mitochondrial function and apoptosis using a murine model of cardiac-specific overexpression of alcohol dehydrogenase (ADH).

Methods

ADH and wild-type FVB mice were acutely challenged with ethanol (3 g/kg/d, i.p.) for 3 days. Myocardial contractility, mitochondrial damage and apoptosis (death receptor and mitochondrial pathways) were examined.

Results

Ethanol led to reduced cardiac contractility, enlarged cardiomyocyte, mitochondrial damage and apoptosis, the effects of which were exaggerated by ADH transgene. In particular, ADH exacerbated mitochondrial dysfunction manifested as decreased mitochondrial membrane potential and accumulation of mitochondrial O₂^•−. Myocardium from ethanol-treated mice displayed enhanced Bax, Caspase-3 and decreased Bcl-2 expression, the effect of which with the exception of Caspase-3 was augmented by ADH. ADH accentuated ethanol-induced increase in the mitochondrial death domain components pro-caspase-9 and cytochrome C in the cytoplasm. Neither ethanol nor ADH affected the expression of ANP, total pro-caspase-9, cytosolic and total pro-caspase-8, TNF-α, Fas receptor, Fas L and cytosolic AIF.

Conclusions

Taken together, these data suggest that enhanced acetaldehyde production through ADH overexpression following acute ethanol exposure exacerbated ethanol-induced myocardial contractile dysfunction, cardiomyocyte enlargement, mitochondrial damage and apoptosis, indicating a pivotal role of ADH in ethanol-induced cardiac dysfunction possibly through mitochondrial death pathway of apoptosis.

Innate and adaptive immune responses regulated by glycogen synthase kinase-3 (GSK3)

In just a few years, the view of glycogen synthase kinase-3 (GSK3) has been transformed from an obscure enzyme seldom encountered in the immune literature to one implicated in an improbably large number of roles. GSK3 is a crucial regulator of the balance between pro- and anti-inflammatory cytokine production in both the periphery and the central nervous system, so that GSK3 inhibitors such as lithium can diminish inflammation. GSK3 influences T-cell proliferation, differentiation and survival. Many effects stem from GSK3 regulation of critical transcription factors, such as NF-kappaB, NFAT and STATs. These discoveries led to the rapid application of GSK3 inhibitors to animal models of sepsis, arthritis, colitis, multiple sclerosis and others, demonstrating their potential for therapeutic intervention.

GSK-3beta, a therapeutic target for cardiomyocyte protection

Glycogen synthase kinase-3beta (GSK-3beta) is a multifunctional Ser/Thr kinase that plays important roles in necrosis and apoptosis of cardiomyocytes. A major mechanism of cell necrosis is the opening of the mitochondrial permeability transition pore (mPTP), which consists of multiple protein subunits, including adenine nucleotide translocase (ANT). The threshold for mPTP opening is elevated by phosphorylation of GSK-3beta at Ser9, which reduces activity of this kinase. How inactivation of GSK-3beta suppresses mPTP opening has not been fully understood, but evidence to date suggests that preservation of hexokinase-II in the mPTP complex, inhibition of cyclophilin-D-ANT binding, inhibition of p53 and inhibition of ANT into the mitochondria are contributory. GSK-3beta phosphorylation is a step to which multiple protective signaling pathways converge, and thus GSK-3beta phosphorylation is crucial in cardioprotection of a variety of interventions against ischemia/reperfusion injury. Apoptosis of cardiomyocytes by pressure overload or ischemia/reperfusion is also suppressed by inactivation of GSK-3beta, in which reduced phosphorylation of p53, heat shock factor-1 and myeloid cell leukemia sequence-1 and inhibition of Bax translocation might be involved. Considering predominant roles of GSK-3beta in cardiomyocyte death, manipulation of this protein kinase is a promising strategy for myocardial protection in coronary artery disease and heart failure.

Role of apoptosis in cardiovascular disease

Apoptosis plays a key role in the pathogenesis in a variety of cardiovascular diseases due to loss of terminally differentiated cardiac myocytes. Cardiac myocytes undergoing apoptosis have been identified in tissue samples from patients suffering from myocardial infarction, diabetic cardiomyopathy, and end-stage congestive heart failure. Apoptosis is a highly regulated program of cell death and can be mediated by death receptors in the plasma membrane, as well as the mitochondria and the endoplasmic reticulum. The cell death program is activated in cardiac myocytes by various stressors including cytokines, increased oxidative stress and DNA damage. Many studies have demonstrated that inhibition of apoptosis is cardioprotective and can prevent the development of heart failure. This review provides a current overview of the evidence of apoptosis in cardiovascular diseases and discusses the molecular pathways involved in cardiac myocyte apoptosis.