DJ-1 protects against cell death following acute cardiac ischemia-reperfusion injury

DJ-1/Park7 Sensitive Na+ /H+ Exchanger 1 (NHE1) in CD4+ T Cells

DJ-1/Park7 is a redox-sensitive chaperone protein counteracting oxidation and presumably contributing to the control of oxidative stress responses and thus inflammation. DJ-1 gene deletion exacerbates the progression of Parkinson's disease presumably by augmenting oxidative stress. Formation of reactive oxygen species (ROS) is paralleled by activation of the Na⁺ /H⁺ exchanger 1 (NHE1). ROS formation in CD4⁺ T cells plays a decisive role in regulating inflammatory responses. In the present study, we explored whether DJ-1 is expressed in CD4⁺ T cells, and affects ROS production as well as NHE1 in those cells. To this end, DJ-1 and NHE1 transcript, and protein levels were quantified by qRT-PCR and Western blotting, respectively, intracellular pH (pH_i ) utilizing bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF) fluorescence, NHE activity from realkalinization after an ammonium pulse, and ROS production utilizing 2',7' -dichlorofluorescin diacetate (DCFDA) fluorescence. As a result DJ-1 was expressed in CD4⁺ T cells. ROS formation, NHE1 transcript levels, NHE1 protein, and NHE activity were higher in CD4⁺ T cells from DJ-1 deficient mice than in CD4⁺ T cells from wild type mice. Antioxidant N-acetyl-cysteine (NAC) and protein tyrosine kinase (PTK) inhibitor staurosporine decreased the NHE activity in DJ-1 deficient CD4⁺ T cells, and blunted the difference between DJ-1^-/- and DJ-1^+/+ CD4⁺ T cells, an observation pointing to a role of ROS in the up-regulation of NHE1 in DJ-1^-/- CD4⁺ T cells. In conclusion, DJ-1 is a powerful regulator of ROS production as well as NHE1 expression and activity in CD4⁺ T cells. J. Cell. Physiol. 232: 3050-3059, 2017. © 2016 Wiley Periodicals, Inc.

DJ-1 overexpression restores ischaemic post-conditioning-mediated cardioprotection in diabetic rats: role of autophagy

IPO (ischaemic post-conditioning) is a promising method of alleviating myocardial IR (ischaemia-reperfusion) injury; however, IPO-mediated cardioprotection is lost in diabetic hearts via mechanisms that remain largely unclear. We hypothesized that decreased cardiac expression of DJ-1, a positive modulator of autophagy, compromises the effectiveness of IPO-induced cardioprotection in diabetic rats. Diabetic rats subjected to myocardial IR (30 min of coronary artery occlusion followed by 120 min of reperfusion) exhibited more severe myocardial injury, less cardiac autophagy, lower DJ-1 expression and AMPK (adenosine monophosphate-activated protein kinase)/mTOR (mammalian target of rapamycin) pathway activity than non-diabetic rats. IPO significantly attenuated myocardial injury and up-regulated cardiac DJ-1 expression, AMPK/mTOR activity and autophagy in non-diabetic rats but not in diabetic rats. AAV9 (adeno-associated virus 9)-mediated cardiac DJ-1 overexpression as well as pretreatment with the autophagy inducer rapamycin restored IPO-induced cardioprotection in diabetic rats, an effect accompanied by AMPK/mTOR activation and autophagy up-regulation. Combining HPO (hypoxic post-conditioning) with DJ-1 overexpression markedly attenuated HR (hypoxia-reoxygenation) injury in H9c2 cells with high glucose (HG, 30 mM) exposure, accompanied by AMPK/mTOR signalling activation and autophagy up-regulation. The DJ-1 overexpression-mediated preservation of HPO-induced cardioprotection was completely inhibited by the AMPK inhibitor compound C (CC) and the autophagy inhibitor 3-MA (3-methyladenine). Thus, decreased cardiac DJ-1 expression, which results in impaired AMPK/mTOR signalling and decreased autophagy, could be a major mechanism underlying the loss of IPO-induced cardioprotection in diabetes.

Mitochondrial-Shaping Proteins in Cardiac Health and Disease - the Long and the Short of It!

Mitochondrial health is critically dependent on the ability of mitochondria to undergo changes in mitochondrial morphology, a process which is regulated by mitochondrial shaping proteins. Mitochondria undergo fission to generate fragmented discrete organelles, a process which is mediated by the mitochondrial fission proteins (Drp1, hFIS1, Mff and MiD49/51), and is required for cell division, and to remove damaged mitochondria by mitophagy. Mitochondria undergo fusion to form elongated interconnected networks, a process which is orchestrated by the mitochondrial fusion proteins (Mfn1, Mfn2 and OPA1), and which enables the replenishment of damaged mitochondrial DNA. In the adult heart, mitochondria are relatively static, are constrained in their movement, and are characteristically arranged into 3 distinct subpopulations based on their locality and function (subsarcolemmal, myofibrillar, and perinuclear). Although the mitochondria are arranged differently, emerging data supports a role for the mitochondrial shaping proteins in cardiac health and disease. Interestingly, in the adult heart, it appears that the pleiotropic effects of the mitochondrial fusion proteins, Mfn2 (endoplasmic reticulum-tethering, mitophagy) and OPA1 (cristae remodeling, regulation of apoptosis, and energy production) may play more important roles than their pro-fusion effects. In this review article, we provide an overview of the mitochondrial fusion and fission proteins in the adult heart, and highlight their roles as novel therapeutic targets for treating cardiac disease.

Regulation of Signal Transduction by DJ-1

The ability of DJ-1 to modulate signal transduction has significant effects on how the cell regulates normal processes such as growth, senescence, apoptosis, and autophagy to adapt to changing environmental stimuli and stresses. Perturbations of DJ-1 levels or function can disrupt the equilibrium of homeostatic signaling networks and set off cascades that play a role in the pathogenesis of conditions such as cancer and Parkinson's disease.DJ-1 plays a major role in various pathways. It mediates cell survival and proliferation by activating the extracellular signal-regulated kinase (ERK1/2) pathway and the phosphatidylinositol-3-kinase (PI3K)/Akt pathway. It attenuates cell death signaling by inhibiting apoptosis signal-regulating kinase 1 (ASK1) activation as well as by inhibiting mitogen-activated protein kinase kinase kinase 1 (MEKK1/MAP3K1) activation of downstream apoptotic cascades. It also modulates autophagy through the ERK, Akt, or the JNK/Beclin1 pathways. In addition, DJ-1 regulates the transcription of genes essential for male reproductive function, such as spermatogenesis, by relaying nuclear receptor androgen receptor (AR) signaling. In this chapter, we summarize the ways that DJ-1 regulates these pathways, focusing on how its role in signal transduction contributes to cellular homeostasis and the pathologic states that result from dysregulation.

Roles of MicroRNA-195 in cardiomyocyte apoptosis induced by myocardial ischemia-reperfusion injury

This study aims to investigate microRNA-195 (miR-195) expression in myocardial ischaemia-reperfusion (I/R) injury and the roles of miR-195 in cardiomyocyte apoptosis though targeting Bcl-2. A mouse model of I/R injury was established. MiR- 195 expression levels were detected by real-time quantitative PCR (qPCR), and the cardiomyocyte apoptosis was detected by TUNEL assay. After cardiomyocytes isolated from neonatal rats and transfected with miR-195 mimic or inhibitor, the hypoxia/reoxygenation (H/R) injury model was established. Cardiomyocyte apoptosis and mitochondrial membrane potential were evaluated using flow cytometry. Bcl-2 and Bax mRNA expressions were detected by RT-PCR. Bcl-2, Bax and cytochrome c (Cyt-c) protein levels were determined by Western blot. Caspase-3 and caspase-9 activities were assessed by luciferase assay. Compared with the sham group, miR-195 expression levels and rate of cardiomyocyte apoptosis increased significantly in I/R group (both P < 0.05). Compared to H/R + negative control (NC) group, rate of cardiomyocyte apoptosis increased in H/R + miR-195 mimic group while decreased in H/R + miR-195 inhibitor group (both P <0.05). MiR-195 knockdown alleviated the loss of mitochondrial membrane potential (P <0.05). MiR-195 overexpression decreased Bcl-2 mRNA and protein expression, increased BaxmRNA and protein expression, Cyt-c protein expression and caspase-3 and caspase-9 activities (all P <0.05).While, downregulated MiR-195 increased Bcl-2 mRNA and protein expression, decreased Bax mRNA and protein expression, Cyt-c protein expression and caspase-3 and caspase-9 activities (all P < 0.05). Our study identified that miR-195 expression was upregulated in myocardial I/R injury, and miR-195 overexpression may promote cardiomyocyte apoptosis by targeting Bcl-2 and inducing mitochondrial apoptotic pathway.

Emerging (and converging) pathways in Parkinson's disease: keeping mitochondrial wellness

The selective cell loss in the ventral component of the substantia nigra pars compacta and the presence of alpha-synuclein (α-syn)-rich intraneuronal inclusions called Lewy bodies are the pathological hallmarks of Parkinson's disease (PD), the most common motor system disorder whose aetiology remains largely elusive. Although most cases of PD are idiopathic, there are rare familial forms of the disease that can be traced to single gene mutations that follow Mendelian inheritance pattern. The study of several nuclear encoded proteins whose mutations are linked to the development of autosomal recessive and dominant forms of familial PD enhanced our understanding of biochemical and cellular mechanisms contributing to the disease and suggested that many signs of neurodegeneration result from compromised mitochondrial function. Here we present an overview of the current understanding of PD-related mitochondrial dysfunction including defects in bioenergetics and Ca²⁺ homeostasis, mitochondrial DNA mutations, altered mitochondrial dynamics and autophagy. We emphasize, in particular, the convergence of many "apparently" different pathways towards a common route involving mitochondria. Understanding whether mitochondrial dysfunction in PD represents the cause or the consequence of the disease is challenging and will help to define the pathogenic processes at the basis of the PD onset and progression.

Cyclosporine A Treatment Abrogates Ischemia-Induced Neuronal Cell Death by Preserving Mitochondrial Integrity through Upregulation of the Parkinson's Disease-Associated Protein DJ-1

Aims

Hypoxic‐ischemia alters mitochondrial membrane potential (Δψm), respiratory‐related enzymes, and mitochondrial DNA (mtDNA). Drugs acting on mitochondria, such as cyclosporine A (CsA), may reveal novel mitochondria‐based cell death signaling targets for stroke. Our previous studies showed that Parkinson's disease‐associated protein DJ‐1 participates in the acute endogenous neuroprotection after stroke via mitochondrial pathway. DJ‐1 was detected immediately after stroke and efficiently translocated into the mitochondria offering a new venue for developing treatment strategies against stroke. Here, we examined a molecular interaction between CsA and mitochondrial integrity in the in vitro acute stroke model of oxygen glucose deprivation/reperfusion (OGD/R) injury with emphasis on DJ‐1.

Methods

Primary rat neuronal cells (PRNCs) were exposed to OGD/R injury and processed for immunocytochemistry, ELISA, and mitochondria‐based molecular assays to reveal the role of DJ‐1 in CsA modulation of mitochondrial integrity.

Results

Administration of CsA before stroke onset (24 h pre‐OGD/R) afforded significantly much more robust neuroprotective effects than when CsA was initiated after stroke (2 h post‐OGD/R), revealing that CsA exerted neuroprotection in the early phase of ischemic stroke. CsA prevented the mitochondria‐dependent cell death signaling pathway involved in cytochrome c (Cyt c)‐induced intrinsic apoptotic process. CsA preserved cellular ATP content, but not hexokinase activity under hypoxic conditions. CsA prevented both mtDNA decrement and Δψm degradation after reperfusion, and enhanced secretion of DJ‐1 in the mitochondria, coupled with reduced oxidative stress.

Conclusion

These observations provided evidence that CsA maintained mitochondrial integrity likely via DJ‐1 upregulation, supporting the concept that mitochondria‐based treatments targeting the early phase of disease progression may prove beneficial in stroke.

Hearts deficient in both Mfn1 and Mfn2 are protected against acute myocardial infarction

Mitochondria alter their shape by undergoing cycles of fusion and fission. Changes in mitochondrial morphology impact on the cellular response to stress, and their interactions with other organelles such as the sarcoplasmic reticulum (SR). Inhibiting mitochondrial fission can protect the heart against acute ischemia/reperfusion (I/R) injury. However, the role of the mitochondrial fusion proteins, Mfn1 and Mfn2, in the response of the adult heart to acute I/R injury is not clear, and is investigated in this study. To determine the effect of combined Mfn1/Mfn2 ablation on the susceptibility to acute myocardial I/R injury, cardiac-specific ablation of both Mfn1 and Mfn2 (DKO) was initiated in mice aged 4-6 weeks, leading to knockout of both these proteins in 8-10-week-old animals. This resulted in fragmented mitochondria (electron microscopy), decreased mitochondrial respiratory function (respirometry), and impaired myocardial contractile function (echocardiography). In DKO mice subjected to in vivo regional myocardial ischemia (30 min) followed by 24 h reperfusion, myocardial infarct size (IS, expressed as a % of the area-at-risk) was reduced by 46% compared with wild-type (WT) hearts. In addition, mitochondria from DKO animals had decreased MPTP opening susceptibility (assessed by Ca(2+)-induced mitochondrial swelling), compared with WT hearts. Mfn2 is a key mediator of mitochondrial/SR tethering, and accordingly, the loss of Mfn2 in DKO hearts reduced the number of interactions measured between these organelles (quantified by proximal ligation assay), attenuated mitochondrial calcium overload (Rhod2 confocal microscopy), and decreased reactive oxygen species production (DCF confocal microscopy) in response to acute I/R injury. No differences in isolated mitochondrial ROS emissions (Amplex Red) were detected in response to Ca(2+) and Antimycin A, further implicating disruption of mitochondria/SR tethering as the protective mechanism. In summary, despite apparent mitochondrial dysfunction, hearts deficient in both Mfn1 and Mfn2 are protected against acute myocardial infarction due to impaired mitochondria/SR tethering.

DJ-1 protects the heart against ischemia-reperfusion injury by regulating mitochondrial fission

Recent data indicates that DJ-1 plays a role in the cellular response to stress. Here, we aimed to examine the underlying molecular mechanisms mediating the actions of DJ-1 in the heart following myocardial ischemia-reperfusion (I/R) injury. In response to I/R injury, DJ-1 KO mice displayed increased areas of infarction and worsened left ventricular function when compared to WT mice, confirming a protective role for DJ-1 in the heart. In an effort to evaluate the potential mechanism(s) responsible for the increased injury in DJ-1 KO mice, we focused on SUMOylation, a post-translational modification process that regulates various aspects of protein function. DJ-1 KO hearts after I/R injury were found to display enhanced accumulation of SUMO-1 modified proteins and reduced SUMO-2/3 modified proteins. Further analysis, revealed that the protein expression of the de-SUMOylation enzyme SENP1 was reduced, whereas the expression of SENP5 was enhanced in DJ-1 KO hearts after I/R injury. Finally, DJ-1 KO hearts were found to display enhanced SUMO-1 modification of dynamin-related protein 1, excessive mitochondrial fission, and dysfunctional mitochondria. Our data demonstrates that the activation of DJ-1 in response to myocardial I/R injury protects the heart by regulating the SUMOylation status of Drp1 and attenuating excessive mitochondrial fission.

The protective effect of lycopene on hypoxia/reoxygenation-induced endoplasmic reticulum stress in H9C2 cardiomyocytes

Nowadays, drugs protecting ischemia/reperfusion (I/R) myocardium become more suitable for clinic. It has been confirmed lycopene has various protections, but lacking the observation of its effect on endoplasmic reticulum stress (ERS)-mediated apoptosis caused by hypoxia/reoxygenation (H/R). This study aims to clarify the protective effect of lycopene on ERS induced by H/R in H9C2 cardiomyocytes. Detect the survival rate, lactic dehydrogenase (LDH) activity, apoptosis ratio, glucose-regulated proteins 78 (GRP78), C/EBP homologous protein (CHOP), c-Jun-N-terminal protein Kinase (JNK) and Caspase-12 mRNA and protein expression and phosphorylation of JNK (p-JNK) protein expression. LDH activity, apoptosis ratio and GRP78 protein expression increase in the H/R group, reduced by lycopene. The survival rate reduces in the H/R and thapsigargin (TG) groups; lycopene and 4-phenyl butyric acid (4-PBA) can improve it caused by H/R, lycopene also can improve it caused by TG. The apoptosis ratio, the expression of GRP78, CHOP and Caspase-12 mRNA and protein and p-JNK protein increase in the H/R and TG groups, weaken in the lycopene+H/R, 4-PBA+H/R and lycopene+TG groups. There is no obvious change in the expression of JNK mRNA or protein. Hence, our results provide the evidence that 10 μM lycopene plays an obviously protective effect on H/R H9C2 cardiomyocytes, realized through reducing ERS and apoptosis. The possible mechanism may be related to CHOP, p-JNK and Caspase-12 pathways.

Differential effect of DJ-1/PARK7 on development of natural and induced regulatory T cells

Regulatory T cells (Tregs) are essential for maintaining an effective immune tolerance and a homeostatic balance of various other immune cells. To manipulate the immune response during infections and autoimmune disorders, it is essential to know which genes or key molecules are involved in the development of Tregs. Transcription factor Foxp3 is required for the development of Tregs and governs most of the suppressive functions of these cells. Inhibited PI3K/AKT/mTOR signalling is critical for Foxp3 stability. Previous studies have suggested that DJ-1 or PARK7 protein is a positive regulator of the PI3K/AKT/mTOR pathway by negatively regulating the activity of PTEN. Thus, we hypothesised that a lack of DJ-1 could promote the development of Tregs. As a result, loss of DJ-1 decreased the total CD4(+) T cell numbers but increased the fraction of thymic and peripheral nTregs. In contrast, Foxp3 generation was not augmented following differentiation of DJ-1-deficient naïve CD4(+) T cells. DJ-1-deficient-iTregs were imperfect in replication, proliferation and more prone to cell death. Furthermore, DJ-1 deficient iTregs were less sensitive to pSmad2 and pStat5 signalling but had activated AKT/mTOR signalling. These observations reveal an unexpected differential role of DJ-1 in the development of nTregs and iTregs.

Parkinson's disease proteins: Novel mitochondrial targets for cardioprotection

Ischemic heart disease (IHD) is the leading cause of death and disability worldwide. Therefore, novel therapeutic targets for protecting the heart against acute ischemia/reperfusion injury (IRI) are required to attenuate cardiomyocyte death, preserve myocardial function, and prevent the onset of heart failure. In this regard, a specific group of mitochondrial proteins, which have been linked to familial forms of Parkinson's disease (PD), may provide novel therapeutic targets for cardioprotection. In dopaminergic neurons of the substantia nigra, these PD proteins, which include Parkin, PINK1, DJ-1, LRRK2, and α-synuclein, play essential roles in preventing cell death-through maintaining normal mitochondrial function, protecting against oxidative stress, mediating mitophagy, and preventing apoptosis. These rare familial forms of PD may therefore provide important insights into the pathophysiology underlying mitochondrial dysfunction and the development of PD. Interestingly, these PD proteins are also present in the heart, but their role in myocardial health and disease is not clear. In this article, we review the role of these PD proteins in the heart and explore their potential as novel mitochondrial targets for cardioprotection.

Overexpression of microRNA-133a inhibits ischemia-reperfusion-induced cardiomyocyte apoptosis by targeting DAPK2

To examine microRNA-133a (miR-133a) endogenous expression in cardiomyocytes after ischemia-reperfusion (I/R) injury and study the effects of miR-133a overexpression on I/R injury-induced cardiomyocyte apoptosis. Dual-Luciferase Reporter Assay detected dynamic expression of miR-133a. In an in vitro hypoxia-reoxygenation (HR) injury model and an in vivo rat model of I/R injury, rat cardiomyocytes were transfected with miR-133a mimic to test the effects of miR-133a overexpression on apoptosis. MiR-133a and Death Associated Protein Kinase 2 (DAPK2) mRNA expression was measured using real-time-PCR, and DAPK2 protein expression was detected by western blotting. Annexin V-fluorescein isothiocyanate/propidium iodide (PI) double-staining measured the apoptosis rate in H9C2 cells and transferase dUTP nick end labeling assay quantified the cardiomyocyte apoptosis rate in tissues obtained from in vivo the rat model. DAPK2 is a target of miR-133a. Both in vitro and in vivo results confirmed that after expression of miR-133a mimics, miR-133a levels increased, which was accompanied by decrease in DAPK2 mRNA and protein expression. In H9C2 cells, HR injury caused a sharp decrease in miR-133a expression and a significant upregualtion of DAPK2 mRNA and protein levels. However, exogenous miR-133a expression led to a significant reduction in DAPK2 mRNA and protein levels despite HR injury. Similar results were obtained from in vivo I/R injury model. After HR injury or I/R injury the apoptosis rate of myocardial cells was highly elevated and decreased significantly only after transfection of miR-133a into cardiomyocytes. MiR-133a overexpression may inhibit I/R injury-mediated cardiomyocyte apoptosis by targeting DAPK2, leading to reduced DAPK2 protein, thus miR-133a may potentially have a high therapeutic value in I/R injury.

Remote conditioning the heart overview: translatability and mechanism

Conditioning the heart to resist predictable and unpredictable ischaemia-reperfusion (IR) injury is one of the fastest growing areas of bench to bedside research within cardiology. Basic science has provided important insights into signalling pathways and protective mechanisms in the heart, and a growing number of clinical studies have, with important exceptions, shown the potential applicability and beneficial effect of various mechanical conditioning strategies achieved by intermittent short-lasting-induced ischaemia of the heart itself or a remote tissue. Remote ischaemic conditioning (RIC) in particular has been utilized in a number of clinical settings with promising results. However, while many novel 'downstream' mechanisms of RIC have been discovered, translation to pharmacological conditioning has not yet been convincingly demonstrated in clinical studies. One explanation for this apparent failure may be that most pharmacological approaches mimic a single instrument in a complex orchestra activated by mechanical conditioning. Recent studies, however, provide important insights into upstream events occurring in RIC, which may allow for development of drugs activating more complex systems of biological organ protection. With this review, we will systematically examine the first generation of pharmacological cardioprotection studies and then provide a summary of the recent discoveries in basic science that could illuminate the path towards more advanced approaches in the next generation of pharmacological agents that may work by reproducing the diverse effects of RIC, thereby providing protection against IR injury.

A new split-GFP-based probe reveals DJ-1 translocation into the mitochondrial matrix to sustain ATP synthesis upon nutrient deprivation

The Parkinson's disease-related protein DJ-1 has a role in the protection against oxidative stress and maintenance of mitochondria structure. Whether this action depends on its localization and activity within the mitochondria is not clear. Here we develop an approach to resolve intra-mitochondrial distribution of DJ-1 and monitor its translocation under specific conditions. By a new split-green fluorescent protein (GFP)-based tool, we can observe that a small DJ-1 fraction is located within the mitochondrial matrix and that it consistently increases upon nutrient depletion. We also find that the targeting of DJ-1 to the mitochondrial matrix enhances mitochondrial and cytosolic adenosine triphosphate levels. Intriguingly, DJ-1 pathogenic mutants fail to improve bioenergetics and translocate within the mitochondrial matrix, suggesting that the DJ-1 protective role requires both these actions. By this new split-GFP-based tool, we can resolve mitochondrial compartmentalization of proteins which are not constitutively resident in mitochondria but translocate to them in response to specific stimuli.