Completion of BAX recruitment correlates with mitochondrial fission during apoptosis

BET inhibitors (BETi) influence oxidative phosphorylation metabolism by affecting mitochondrial dynamics leading to alterations in apoptotic pathways in triple-negative breast cancer (TNBC) cells

Repressing BET proteins' function using bromodomain inhibitors (BETi) has been shown to elicit antitumor effects by regulating the transcription of genes downstream of BRD4. We previously showed that BETi promoted cell death of triple-negative breast cancer (TNBC) cells. Here, we proved that BETi induce altered mitochondrial dynamics fitness in TNBC cells falling in cell death. We demonstrated that BETi treatment downregulated the expression of BCL-2, and proteins involved in mitochondrial fission and increased fused mitochondria. Impaired mitochondrial fission affected oxidative phosphorylation (OXPHOS) inducing the expression of OXPHOS-related genes, SDHa and ATP5a, and increased cell death. Consistently, the amount of mitochondrial DNA and mitochondrial membrane potential (∆Ψm) increased in BETi-treated cells compared to control cells. Lastly, BETi in combination with Metformin reduced cell growth. Our results indicate that mitochondrial dynamics and OXPHOS metabolism support breast cancer proliferation and represent novel BETi downstream targets in TNBC cells.

Ticking Brain: Circadian Rhythm as a New Target for Cerebroprotection

Circadian rhythm is a master process observed in nearly every type of cell throughout the body, and it macroscopically regulates daily physiology. Recent clinical trials have revealed the effects of circadian variation on the incidence, pathophysiological processes, and prognosis of acute ischemic stroke. Furthermore, core clock genes, the cell-autonomous pacemakers of the circadian rhythm, affect the neurovascular unit-composing cells in a nonparallel manner after the same pathophysiological processes of ischemia/reperfusion. In this review, we discuss the influence of circadian rhythms and clock genes on each type of neurovascular unit cell in the pathophysiological processes of acute ischemic stroke.

Bcl-2 Orthologues, Buffy and Debcl, Can Suppress Drp1-Dependent Age-Related Phenotypes in Drosophila

The relationship of Amyotrophic Lateral Sclerosis, Parkinson's disease, and other age-related neurodegenerative diseases with mitochondrial dysfunction has led to our study of the mitochondrial fission gene Drp1 in Drosophila melanogaster and aspects of aging. Previously, the Drp1 protein has been demonstrated to interact with the Drosophila Bcl-2 mitochondrial proteins, and Drp1 mutations can lead to mitochondrial dysfunction and neuronal loss. In this study, the Dopa decarboxylase-Gal4 (Ddc-Gal4) transgene was exploited to direct the expression of Drp1 and Drp1-RNAi transgenes in select neurons. Here, the knockdown of Drp1 seems to compromise locomotor function throughout life but does not alter longevity. The co-expression of Buffy suppresses the poor climbing induced by the knockdown of the Drp1 function. The consequences of Drp1 overexpression, which specifically reduced median lifespan and diminished climbing abilities over time, can be suppressed through the directed co-overexpression of pro-survival Bcl-2 gene Buffy or by the co-knockdown of the pro-cell death Bcl-2 homologue Debcl. Alteration of the expression of Drp1 acts to phenocopy neurodegenerative disease phenotypes in Drosophila, while overexpression of Buffy can counteract or rescue these phenotypes to improve overall health. The diminished healthy aging due to either the overexpression of Drp1 or the RNA interference of Drp1 has produced novel Drosophila models for investigating mechanisms underlying neurodegenerative disease.

IP3R2 regulates apoptosis by Ca2+ transfer through mitochondria-ER contacts in hypoxic photoreceptor injury

Mitochondria-associated ER membranes (MAMs) are contact sites that enable bidirectional communication between the ER (endoplasmic reticulum) and mitochondria, including the transfer of Ca2+ signals. MAMs are essential for mitochondrial function and cellular energy metabolism. However, unrestrained Ca2+ transfer to the mitochondria can lead to mitochondria-dependent apoptosis. IP3R2 (Inositol 1,4,5-trisphosphate receptor 2) is an important intracellular Ca2+ channel. This study investigated the contribution of IP3R2-MAMs to hypoxia-induced apoptosis in photoreceptor cells. A photoreceptor hypoxia model was established by subretinal injection of hyaluronic acid (1%) in C57BL/6 mice and 1% O2 treatment in 661W cells. Transmission electron microscopy (TEM), ER-mitochondria colocalization, and the MAM reporter were utilized to evaluate MAM alterations. Cell apoptosis and mitochondrial homeostasis were evaluated using immunofluorescence (IF), flow cytometry, western blotting (WB), and ATP assays. SiRNA transfection was employed to silence IP3R2 in 661W cells. Upon hypoxia induction, MAMs were significantly increased in photoreceptors both in vivo and in vitro. This was accompanied by the activation of mitochondrial apoptosis and disruption of mitochondrial homeostasis. Elevated MAM-enriched IP3R2 protein levels induced by hypoxic injury led to mitochondrial calcium overload and subsequent photoreceptor apoptosis. Notably, IP3R2 knockdown not only improved mitochondrial morphology but also restored mitochondrial function in photoreceptors by limiting MAM formation and thereby attenuating mitochondrial calcium overload under hypoxia. Our results suggest that IP3R2-MAM-mediated mitochondrial calcium overload plays a critical role in mitochondrial dyshomeostasis, ultimately contributing to photoreceptor cell death. Targeting MAM constitutive proteins might provide an option for a therapeutic approach to mitigate photoreceptor death in retinal detachment.

Epigallocatechin gallate attenuated high glucose-induced pancreatic beta cell dysfunction by modulating DRP1-mediated mitochondrial apoptosis pathways

Long-term exposure to hyperglycemic conditions leads to β-cell dysfunction, particularly mitochondrial dysfunction, and inflammatory and oxidative stress responses, which are considered the primary causes of β-cell death and the hallmarks of diabetes. Plant-active ingredients may play a key role in glycemic control. Epigallocatechin gallate (EGCG) is a characteristic catechin derived from tea that possesses anti-diabetic properties. Nonetheless, its underlying mechanisms remain elusive. Herein, the protective role of EGCG on high glucose (33 mM)-induced pancreatic beta cell dysfunction and its possible molecular mechanisms were investigated. Briefly, MIN6 cells were treated with glucose and EGCG (10 µM, 20 µM, and 40 µM) for 48 h. Our results revealed that EGCG dose-dependently restored mitochondrial membrane potential and concomitantly alleviated cell apoptosis. Mechanistically, the expression level of apoptotic protein BAX and Dynamic related protein 1 (DRP1) was significantly downregulated following EGCG treatment, whereas that of the anti-apoptotic protein BCL-2 was significantly upregulated. Taken together, EGCG alleviated high glucose-induced pancreatic beta cell dysfunction by targeting the DRP1-related mitochondrial apoptosis pathway and thus can serve as a nutritional intervention for the preservation of beta cell dysfunction in patients with type 2 diabetes mellitus.

Heparin-Modified Superparamagnetic Iron Oxide Nanoparticles Suppress Lithium Chloride/Pilocarpine-Induced Temporal Lobe Epilepsy in Rats through Attenuation of Inflammation and Oxidative Stress

The development of antiepileptic drugs is still a long process. In this study, heparin-modified superparamagnetic iron oxide nanoparticles (UFH-SPIONs) were prepared, and their antiepileptic effect and underlying mechanism were investigated. UFH-SPIONs are stable, homogeneous nanosystems with antioxidant enzyme activity that are able to cross the blood-brain barrier (BBB) and enriched in hippocampal epileptogenic foci. The pretreatment with UFH-SPIONs effectively prolonged the onset of seizures and reduced seizure severity after lithium/pilocarpine (LP)-induced seizures in rats. The pretreatment with UFH-SPIONs significantly decreased the expression of inflammatory factors in hippocampal tissues, including IL-6, IL-1β, and TNF-α. LP-induced oxidative stress in hippocampal tissues was in turn reduced upon pretreatment with UFH-SPIONs, as evidenced by an increase in the levels of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) and a decrease in the level of lipid peroxidation (MDA). Moreover, the LP-induced upregulation of apoptotic cells was decreased upon pretreatment with UFH-SPIONs. Together, these observations suggest that the pretreatment with UFH-SPIONs ameliorates LP-induced seizures and downregulates the inflammatory response and oxidative stress, which exerts neuronal protection during epilepsy.

Preparation of biogenic silver chloride nanoparticles from microalgae Spirulina Platensis extract: anticancer properties in MDA-MB231 breast cancer cells

BACKGROUND

Breast carcinoma is the second leading cause of cancer related-deaths among women. Given its high incidence and mortality rates, searching for innovative treatments represents a formidable challenge within the medical and pharmaceutical industries. This study delves into the preparation, characterization, and anticancer properties of silver chloride nanoparticles (AgCLNPs) as a novel therapeutic approach for breast cancer cells, employing a biological synthesis method.

METHODS

This investigation, utilized spirulina platensis extract to synthesize silver chloride nanoparticles (AgCLNPs-SP). The formation, size, and structure of the nanoparticles were characterized by Transmission Electron Microscopy (TEM), Scanning Electron Microscope (SEM), X-ray crystallography (XRD), and Energy-dispersive X-ray spectroscopy (EDS) analysis. Additionally, the apoptotic and anticancer properties of AgCLNPs-SP were thoroughly examined.

RESULTS

The results, revealed AgCLNPs-SP to exhibit a spherical, morphology with a size range of 40-70 nm, primarily silver and chlorine. The dose-dependent response of AgCLNP-SP against MDA-MB231 cells was ascertained using the MTT Assay, with an IC50 value of 34 µg/mL. Furthermore, the Annexin V-FITC/ PI apoptosis assay demonstrated a significant proportion of early apoptosis (43.67%) in MDA-MB231 cells. This apoptosis process was substantiated by up-regulation in mRNA expression levels of P53, CAD, and Bax genes, alongside a down-regulation of the of bcl2 gene expression. Additionally, an augmented production of reactive oxygen species (ROS), cell cycle analysis, Hoechst staining assay, and evaluated levels of Caspase - 3, -8 and - 9 were observed in AgCLNPs-SP-treated MDA_MB231 cancer cells.

CONCLUSIONS

In conclusion, the results suggest that AgCLNPs-SP may be a promising agent for treating breast cancer.

Modified Hu-lu-ba-wan protects diabetic glomerular podocytes via promoting PKM2-mediated mitochondrial dynamic homeostasis

BACKGROUND

Mitochondrial dysfunction is implicated in the progression of diabetic kidney disease (DKD). Damaged mitochondria produce excessive reactive oxygen species (ROS) that can cause apoptosis. Mitochondrial dynamics control the quality and function of mitochondria. Targeting mitochondrial dynamics may reduce ROS-induced apoptosis and improve renal injury in DKD. Modified Hu-lu-ba-wan (MHLBW) shows distinct clinical effects on DKD patients, which are related to its role in antioxidant stress modulation. However, the relevant mechanisms of MHLBW have not been clearly explored.

PURPOSE

This study was aimed to evaluate the therapeutic effects of MHLBW on spontaneous DKD mice and clarify the potential mechanisms.

METHODS

The main components of MHLBW were identified by HPLC. Using db/db mice as DKD models, we evaluated the therapeutic effects of MHLBW on mice after an 8-week administration. We investigated the molecular mechanism of MHLBW in regulating mitochondrial dynamic homeostasis, podocyte apoptosis, and glomerular damage. After that, computational docking analysis and in vitro experiments were conducted for further mechanism verification.

RESULTS

Intragastric administration of MHLBW for 8 weeks in db/db mice significantly improved glucose metabolism, basement membrane thickening, mesangial expansion, glomerular fibrosis, and podocyte injury. MHLBW can reverse podocyte apoptosis via promoting mitochondrial dynamic homeostasis, which was related to regulating the PKM2/ PGC-1α/Opa1 pathway. Berberine (BBR), one of the components of MHLBW, exhibited preeminent affinity with PKM2 as reflected by computational docking analysis. In cultured podocytes, BBR can also prevent apoptosis by promoting PKM2-mediated mitochondrial dynamic homeostasis.

CONCLUSION

Our study demonstrates that MHLBW can treat DKD by inhibiting glomerular damage and podocyte apoptosis through positive regulation of PKM2-mediated mitochondrial dynamic homeostasis. These results may provide a potential strategy against DKD.

SIRT1 inhibits mitochondrial hyperfusion associated mito-bulb formation to sensitize oral cancer cells for apoptosis in a mtROS-dependent signalling pathway

SIRT1 (NAD-dependent protein deacetylase sirtuin-1), a class III histone deacetylase acting as a tumor suppressor gene, is downregulated in oral cancer cells. Non-apoptotic doses of cisplatin (CDDP) downregulate SIRT1 expression advocating the mechanism of drug resistance. SIRT1 downregulation orchestrates inhibition of DNM1L-mediated mitochondrial fission, subsequently leading to the formation of hyperfused mitochondrial networks. The hyperfused mitochondrial networks preserve the release of cytochrome C (CYCS) by stabilizing the mitochondrial inner membrane cristae (formation of mitochondrial nucleoid clustering mimicking mito-bulb like structures) and reducing the generation of mitochondrial superoxide to inhibit apoptosis. Overexpression of SIRT1 reverses the mitochondrial hyperfusion by initiating DNM1L-regulated mitochondrial fission. In the overexpressed cells, inhibition of mitochondrial hyperfusion and nucleoid clustering (mito-bulbs) facilitates the cytoplasmic release of CYCS along with an enhanced generation of mitochondrial superoxide for the subsequent induction of apoptosis. Further, low-dose priming with gallic acid (GA), a bio-active SIRT1 activator, nullifies CDDP-mediated apoptosis inhibition by suppressing mitochondrial hyperfusion. In this setting, SIRT1 knockdown hinders apoptosis activation in GA-primed oral cancer cells. Similarly, SIRT1 overexpression in the CDDP resistance oral cancer-derived polyploid giant cancer cells (PGCCs) re-sensitizes the cells to apoptosis. Interestingly, synergistically treated with CDDP, GA induces apoptosis in the PGCCs by inhibiting mitochondrial hyperfusion.

Mitochondrial Bcl-xL promotes brain synaptogenesis by controlling non-lethal caspase activation

Non-lethal caspase activation (NLCA) has been linked to neurodevelopmental processes. However, how neurons control NLCA remains elusive. Here, we focused on Bcl-xL, a Bcl-2 homolog regulating caspase activation through the mitochondria. We generated a mouse model, referred to as ER-xL, in which Bcl-xL is absent in the mitochondria, yet present in the endoplasmic reticulum. Unlike bclx knockout mice that died at E13.5, ER-xL mice survived embryonic development but died post-partum because of altered feeding behavior. Enhanced caspase-3 activity was observed in the brain and the spinal cord white matter, but not the gray matter. No increase in cell death was observed in ER-xL cortical neurons, suggesting that the observed caspase-3 activation was apoptosis-independent. ER-xL neurons displayed increased caspase-3 activity in the neurites, resulting in impaired axon arborescence and synaptogenesis. Together, our findings suggest that mitochondrial Bcl-xL finely tunes caspase-3 through Drp-1-dependent mitochondrial fission, which is critical to neural network design.

BAX activation in mouse retinal ganglion cells occurs in two temporally and mechanistically distinct steps

Background Pro-apoptotic BAX is a central mediator of retinal ganglion cell (RGC) death after optic nerve damage. BAX activation occurs in two stages including translocation of latent BAX to the mitochondrial outer membrane (MOM) and then permeabilization of the MOM to facilitate the release of apoptotic signaling molecules. As a critical component of RGC death, BAX is an attractive target for neuroprotective therapies and an understanding of the kinetics of BAX activation and the mechanisms controlling the two stages of this process in RGCs is potentially valuable in informing the development of a neuroprotective strategy. Methods The kinetics of BAX translocation were assessed by both static and live-cell imaging of a GFP-BAX fusion protein introduced into RGCs using AAV2-mediated gene transfer in mice. Activation of BAX was achieved using an acute optic nerve crush (ONC) protocol. Live-cell imaging of GFP-BAX was achieved using explants of mouse retina harvested 7 days after ONC. Kinetics of translocation in RGCs were compared to GFP-BAX translocation in 661W tissue culture cells. Permeabilization of GFP-BAX was assessed by staining with the 6A7 monoclonal antibody, which recognizes a conformational change in this protein after MOM insertion. Assessment of individual kinases associated with both stages of activation was made using small molecule inhibitors injected into the vitreous either independently or in concert with ONC surgery. The contribution of the Dual Leucine Zipper-JUN-N-Terminal Kinase cascade was evaluated using mice with a double conditional knock-out of both Mkk4 and Mkk7 . Results ONC induces the translocation of GFP-BAX in RGCs at a slower rate and with less intracellular synchronicity than 661W cells, but exhibits less variability among mitochondrial foci within a single cell. GFP-BAX was also found to translocate in all compartments of an RGC including the dendritic arbor and axon. Approximately 6% of translocating RGCs exhibited retrotranslocation of BAX immediately following translocation. Unlike tissue culture cells, which exhibit simultaneous translocation and permeabilization, RGCs exhibited a significant delay between these two stages, similar to detached cells undergoing anoikis. Translocation, with minimal permeabilization could be induced in a subset of RGCs using an inhibitor of Focal Adhesion Kinase (PF573228). Permeabilization after ONC, in a majority of RGCs, could be inhibited with a broad spectrum kinase inhibitor (sunitinib) or a selective inhibitor for p38/MAPK14 (SB203580). Intervention of DLK-JNK axis signaling abrogated GFP-BAX translocation after ONC. Conclusions A comparison between BAX activation kinetics in tissue culture cells and in cells of a complex tissue environment shows distinct differences indicating that caution should be used when translating findings from one condition to the other. RGCs exhibit both a delay between translocation and permeabilization and the ability for translocated BAX to be retrotranslocated, suggesting several stages at which intervention of the activation process could be exploited in the design of a therapeutic strategy.

Mitochondrial Trafficking of MLKL, Bak/Bax, and Drp1 Is Mediated by RIP1 and ROS which Leads to Decreased Mitochondrial Membrane Integrity during the Hyperglycemic Shift to Necroptosis

Apoptosis and necroptosis overlap in their initial signaling but diverge to produce non-inflammatory and pro-inflammatory outcomes, respectively. High glucose pushes signaling in favor of necroptosis producing a hyperglycemic shift from apoptosis to necroptosis. This shift depends on receptor-interacting protein 1 (RIP1) and mitochondrial reactive oxygen species (ROS). Here, we show that RIP1, mixed lineage kinase domain-like (MLKL) protein, Bcl-2 agonist/killer (Bak), Bcl-2 associated x (Bax) protein, and dynamin-related protein 1 (Drp1) traffic to the mitochondria in high glucose. RIP1 and MLKL appear in the mitochondria in their activated, phosphorylated states while Drp1 appears in its activated, dephosphorylated state in high glucose. Mitochondrial trafficking is prevented in rip1 KO cells and upon treatment with N-acetylcysteine. Induction of ROS replicated the mitochondrial trafficking seen in high glucose. MLKL forms high MW oligomers in the outer and inner mitochondrial membranes while Bak and Bax form high MW oligomers in the outer mitochondrial membrane in high glucose, suggesting pore formation. MLKL, Bax, and Drp1 promoted cytochrome c release from the mitochondria as well as a decrease in mitochondrial membrane potential in high glucose. These results indicate that mitochondrial trafficking of RIP1, MLKL, Bak, Bax, and Drp1 are key events in the hyperglycemic shift from apoptosis to necroptosis. This is also the first report to show oligomerization of MLKL in the inner and outer mitochondrial membranes and dependence of mitochondrial permeability on MLKL.

Sodium New Houttuyfonate Induces Apoptosis of Breast Cancer Cells via ROS/PDK1/AKT/GSK3β Axis

BACKGROUND

Sodium new houttuyfonate (SNH) has been reported to have anti-inflammatory, anti-fungal, and anti-cancer effects. However, few studies have investigated the effect of SNH on breast cancer. The aim of this study was to investigate whether SNH has therapeutic potential for targeting breast cancer.

METHODS

Immunohistochemistry and Western blot analysis were used to examine the expression of proteins, flow cytometry was used to detect cell apoptosis and ROS levels, and transmission electron microscopy was used to observe mitochondria.

RESULTS

Differentially expressed genes (DEGs) between breast cancer-related gene expression profiles (GSE139038 and GSE109169) from GEO DataSets were mainly involved in the immune signaling pathway and the apoptotic signaling pathway. According to in vitro experiments, SNH significantly inhibited the proliferation, migration, and invasiveness of MCF-7 (human cells) and CMT-1211 (canine cells) and promoted apoptosis. To explore the reason for the above cellular changes, it was found that SNH induced the excessive production of ROS, resulting in mitochondrial impairment, and then promoted apoptosis by inhibiting the activation of the PDK1-AKT-GSK3β pathway. Tumor growth, as well as lung and liver metastases, were suppressed under SNH treatment in a mouse breast tumor model.

CONCLUSIONS

SNH significantly inhibited the proliferation and invasiveness of breast cancer cells and may have significant therapeutic potential in breast cancer.

Autophagy in Rat Müller Glial Cells Is Modulated by the Sirtuin 4/AMPK/mTOR Pathway and Induces Apoptosis under Oxidative Stress

Müller glial cells (MGCs) are a group of glial cells in the retina that provide essential support to retinal neurons; however, the understanding of MGC apoptosis and autophagy remains limited. This study was aimed at investigating the role of autophagy in MGCs under normal and oxidative conditions, and identifying the underlying mechanisms. In addition, the sirtuin 4 (SIRT4)-mediated signaling pathway was observed to regulate the autophagic process in MGCs. To assess the effect of autophagy on MGC mitochondrial function and survival, we treated rMC-1 cells—rat-derived Müller glial cells—with rapamycin and 3-methyladenine (3-MA), and found that MGC death was not induced by such treatment, while autophagic dysfunction could increase MGC apoptosis under oxidative stress, as reflected by the expression level of cleaved caspase 3 and PI staining. In addition, the downregulation of autophagy by 3-MA could influence the morphology of the mitochondrial network structure, the mitochondrial membrane potential, and generation of reactive oxygen species (ROS) under oxidative stress. Moreover, SIRT4 depletion enhanced autophagosome formation, as verified by an increase in the LC3 II/I ratio and a decrease in the expression of SQSTM1/p62, and vice versa. The inhibition of AMPK phosphorylation by compound C could reverse these changes in LC3 II/I and SQSTM1/p62 caused by SIRT4 knockdown. Our research concludes that MGCs can endure autophagic dysfunction in the absence of oxidative stress, while the downregulation of autophagy can cause MGCs to become more sensitized to oxidative stress. Simultaneous exposure to oxidative stress and autophagic dysfunction in MGCs can result in a pronounced impairment of cell survival. Mechanically, SIRT4 depletion can activate the autophagic process in MGCs by regulating the AMPK–mTOR signaling pathway.

Mitochondrial Dysfunction in Individuals with Diabetic Kidney Disease: A Systematic Review

Mitochondrial dysfunction is implicated in the pathogenesis of diabetic kidney disease (DKD). Compared to the vast body of evidence from preclinical in vitro and in vivo studies, evidence from human studies is limited. In a comprehensive search of the published literature, findings from studies that reported evidence of mitochondrial dysfunction in individuals with DKD were examined. Three electronic databases (PubMed, Embase, and Scopus) were searched in March 2022. A total of 1339 articles were identified, and 22 articles met the inclusion criteria. Compared to non-diabetic controls (NDC) and/or individuals with diabetes but without kidney disease (DC), individuals with DKD (age ~55 years; diabetes duration ~15 years) had evidence of mitochondrial dysfunction. Individuals with DKD had evidence of disrupted mitochondrial dynamics (11 of 11 articles), uncoupling (2 of 2 articles), oxidative damage (8 of 8 articles), decreased mitochondrial respiratory capacity (1 of 1 article), decreased mtDNA content (5 of 6 articles), and decreased antioxidant capacity (3 of 4 articles) compared to ND and/or DC. Neither diabetes nor glycemic control explained these findings, but rather presence and severity of DKD may better reflect degree of mitochondrial dysfunction in this population. Future clinical studies should include individuals closer to diagnosis of diabetes to ascertain whether mitochondrial dysfunction is implicated in the development of, or is a consequence of, DKD.

Ketone Body Improves Neurological Outcomes after Cardiac Arrest by Inhibiting Mitochondrial Fission in Rats

Ketone bodies including β-hydroxybutyrate (β-HB) have been proved the therapeutic potential in diverse neurological disorders. However, the role of β-HB in the regulation of neurological injury after cardiac arrest (CA) remains unclear. We investigated the effect of β-HB on brain mitochondrial dysfunction and neurological function after CA. A rat model of CA was established by asphyxia. The rats were randomly divided into three groups: sham group, control group, and β-HB group. Animals received 200 mg/kg β-HB or same volume vehicle at 10 minutes after return of spontaneous circulation by intraperitoneal injection. Neurological function was evaluated by neurologic deficit score and Y-maze. Neuronal cell loss and apoptosis were detected through hematoxylin-eosin staining, Nissl staining, and TdT-mediated dUTP nick-end labeling assay. Oxidative stress levels were determined by immunohistochemical staining of 4-hydoxynonenal and 8-hydroxy-2′-deoxyguanosine. Furthermore, mitochondrial ultrastructure of brain cells was observed by transmission electron microscopy. In addition, the protein expression levels of Bak, caspase 3, gasdermin D, caspase 1, brain-derived neurotrophic factor, dynamin-related protein 1 (Drp1), and phospho-Drp1 (ser616) were measured. We found that neurological function and survival rate were significantly higher in the β-HB group compared with the control group. β-HB also reduced neurons death and neurological oxidative stress after CA. Moreover, β-HB reduced neurological injury from apoptosis and pyroptosis after CA. In addition, β-HB maintained the structural integrity of brain mitochondria, prevented mitochondrial fission, and increased brain energy metabolism after CA. In conclusion, β-HB beneficially affected the neurological function of rats after global cerebral ischemia, associated with decreased mitochondrial fission, and improved mitochondrial function. Our results suggest that β-HB might benefit patients suffering from neurological dysfunction after CA.

The novel FGFR inhibitor F1-7 induces DNA damage and cell death in colon cells

BACKGROUND

Fibroblast growth factor receptor (FGFR) signaling influenced tumour occurrence and development. Overexpression of FGFR had been observed in many types of cancers, including colon cancer. FGFR inhibitor is considered to be effective in treating colon cancer patients.

METHODS

First, the kinase inhibition rate was determined. MTT, western blotting, colony formation, EdU and comet assays were performed to evaluate the anti-tumour effects of F1-7 in vitro. RNA-seq and bioinformatics analysis were used for further verification. Additionally, a xenograft model was generated to investigate the anti-tumour effect of F1-7.

RESULTS

F1-7 can inhibit the proliferation of colon cancer cells in vitro. It could significantly inhibit FGFR phosphorylation and its downstream signaling pathway. Whole-genome RNA-seq analysis found that the changed genes were not only functionally focused on MAPK signaling pathway but also related to cell apoptosis and ferroptosis. Experimental evidence demonstrated that F1-7 can directly increase the level of cellular DNA damage. The occurrence of DNA damage led to cell cycle arrest and inhibition of cell metastasis and cell apoptosis. Mouse model experiments also confirmed that F1-7 could inhibit tumour growth by inhibiting the FGFR pathway.

CONCLUSIONS

F1-7 exhibits anti-tumour activity by inhibiting the FGFR pathway. It could be a novel therapeutic agent for targeting colon cancer cells.

Mechanism of cell death pathways in status epilepticus and related therapeutic agents

The most severe form of epilepsy, status epilepticus (SE), causes brain damage and results in the development of recurring seizures. Currently, the management of SE remains a clinical challenge because patients do not respond adequately to conventional treatments. Evidence suggests that neural cell death worsens the occurrence and progression of SE. The main forms of cell death are apoptosis, necroptosis, pyroptosis, and ferroptosis. Herein, these mechanisms of neuronal death in relation to SE and the alleviation of SE by potential modulators that target neuronal death have been reviewed. An understanding of these pathways and their possible roles in SE may assist in the development of SE therapies and in the discovery of new agents.

Residue of thiram in food, suppresses immune system stress signals and disturbs sphingolipid metabolism in chickens

Thiram, a well-known sulfur containing organic compound is frequently and extensively used in agriculture because of high biological activity to control different pests. In certain cases, due to long persistence in the environment pesticides and other environmental contaminants induce undesirable toxic impacts to public health and environment. To ascertain the potential mechanisms of toxicity of thiram on different immune organs of broilers, a total of 100 one-day-old chicks were obtained and randomly divided into two groups including thiram group (50 mg/kg) and untreated control group. Thymus and spleen tissues were collected at the age of 14 days from the experimental birds. At necropsy level, thymus was congested, enlarged and hyperemic while spleen had no obvious lesions. The results on mechanisms (apoptosis and autophagy) of immunotoxicity showed significantly increased expression of bax, caspase3, cytc, ATG5, beclin1 and p62 in spleen of treated mice. Results indicated significantly decreased expression of m-TOR and bcl2 to activate apoptosis and autophagy. The expressions of bax, p53 and m-TOR were up-regulated in the thymus while the expressions of ATG5 and Beclin1 were down-regulated to mediate cell apoptosis and inhibit autophagy. The results on different metabolome investigation showed that the sphingolipid metabolism in the thymus of chicks exposed to thiram was disrupted resulting in up-regulation of metabolites related to cell membrane components such as SM, galactosylceramide and lactosylceramide. The results of our experimental research suggest that thiram can interfere with the sphingolipid metabolism in thymus and angiogenesis, inhibit the proliferation of vascular endothelial cells to induce potential toxic effects in chicken.

Mitochondrial Quality Control: A Pathophysiological Mechanism and Therapeutic Target for Stroke

Stroke is a devastating disease with high mortality and disability rates. Previous research has established that mitochondria, as major regulators, are both influenced by stroke, and further regulated the development of poststroke injury. Mitochondria are involved in several biological processes such as energy generation, calcium homeostasis, immune response, apoptosis regulation, and reactive oxygen species (ROS) generation. Meanwhile, mitochondria can evolve into various quality control systems, including mitochondrial dynamics (fission and fusion) and mitophagy, to maintain the homeostasis of the mitochondrial network. Various activities of mitochondrial fission and fusion are associated with mitochondrial integrity and neurological injury after stroke. Additionally, proper mitophagy seems to be neuroprotective for its effect on eliminating the damaged mitochondria, while excessive mitophagy disturbs energy generation and mitochondria-associated signal pathways. The balance between mitochondrial dynamics and mitophagy is more crucial than the absolute level of each process. A neurovascular unit (NVU) is a multidimensional system by which cells release multiple mediators and regulate diverse signaling pathways across the whole neurovascular network in a way with a high dynamic interaction. The turbulence of mitochondrial quality control (MQC) could lead to NVU dysfunctions, including neuron death, neuroglial activation, blood–brain barrier (BBB) disruption, and neuroinflammation. However, the exact changes and effects of MQC on the NVU after stroke have yet to be fully illustrated. In this review, we will discuss the updated mechanisms of MQC and the pathophysiology of mitochondrial dynamics and mitophagy after stroke. We highlight the regulation of MQC as a potential therapeutic target for both ischemic and hemorrhagic stroke.

Mitochondrial quality control in acute ischemic stroke

Mitochondria play a central role in the pathophysiological processes of acute ischemic stroke. Disruption of the cerebral blood flow during acute ischemic stroke interrupts oxygen and glucose delivery, leading to the dysfunction of mitochondrial oxidative phosphorylation and cellular bioenergetic stress. Cells can respond to such stress by activating mitochondrial quality control mechanisms, including the mitochondrial unfolded protein response, mitochondrial fission and fusion, mitophagy, mitochondrial biogenesis, and intercellular mitochondrial transfer. Collectively, these adaptive response strategies contribute to retaining the integrity and function of the mitochondrial network, thereby helping to recover the homeostasis of the neurovascular unit. In this review, we focus on mitochondrial quality control mechanisms occurring in acute ischemic stroke. A better understanding of how these regulatory pathways work in maintaining mitochondrial homeostasis will provide a rationale for developing innovative neuroprotectants when these mechanisms fail in acute ischemic stroke.

Control of host mitochondria by bacterial pathogens

Mitochondria control various processes that are integral to cellular and organismal homeostasis, including Ca²⁺ fluxes, bioenergetic metabolism, and cell death. Perhaps not surprisingly, multiple pathogenic bacteria have evolved strategies to subvert mitochondrial functions in support of their survival and dissemination. Here, we discuss nonimmunological pathogenic mechanisms that converge on the ability of bacteria to control the mitochondrial compartment of host cells.

Decrease in reproductive dysfunction using aflatoxin B1 exposure: a treatment with 3-indolepropionic acid in albino Wistar rat

We assessed the individual and combined consequence of 3-indolepropionic acid on aflatoxin B1-induced reproductive toxicity in rats. The experimental cohorts were dosed for four consecutive weeks with aflatoxin B1 (50 μg/kg), 3-indolepropionic acid (50 mg/kg), and both (aflatoxin B1: 50 μg/kg + 3-indolepropionic acid: 25 or 50 mg/kg), and the untreated control. Following sacrifice, biomarkers of testicular, epididymal and hypothalamic oxidative status, lipid peroxidation, reactive oxygen and nitrogen species, nitric oxide levels and myeloperoxidase activity were determined. Besides, tumour necrosis factor-alpha, Bcl-2 and Bax proteins were also assessed. Aflatoxin B1-induced testicular, epididymal and hypothalamic oxidative stress was significantly alleviated with 3-indolepropionic acid co-treatment. Also, increases in biomarkers of oxidative stress and reduced levels of antioxidants were abated significantly in rats co-treated with 3-indolepropionic acid. Aflatoxin B1-mediated increase in tumour necrosis factor-alpha, Bax, nitric oxide and myeloperoxidase activity in the examined organs was decreased significantly in aflatoxin B1 and 3-indolepropionic acid co-treated rats. Also, 3-indolepropionic acid dose dependently reduced Bcl-2 levels in the treated rats. The degree of aflatoxin B1-induced histopathological injuries was minimised in rats co-treated with 3-indolepropionic acid. Our results demonstrated that 3-indolepropionic acid protected experimental rats from aflatoxin B1-induced oxido-inflammatory stress and apoptotic response in the examined organs.

Bromodomain-containing protein 4 inhibitor JQ1 promotes melanoma cell apoptosis by regulating mitochondrial dynamics

Although the role of bromodomain-containing protein 4 (BRD4) in ovarian cancer, pancreatic cancer, lymphoma, and many other diseases is well known, its function in cutaneous melanoma is only partially understood. The results of the present study show that the BRD4 inhibitor JQ1 promotes the apoptosis of B16 melanoma cells by altering mitochondrial dynamics, thereby inducing mitochondrial dysfunction and increasing oxidative stress. We found that treatment of B16 cells with different concentrations of JQ1 (125 nmol/L or 250 nmol/L) significantly downregulated the expression of protein subunits involved in mitochondrial respiratory chain complexes I, III, IV, and V, increased reactive oxygen species, induced energy metabolism dysfunction, significantly enhanced apoptosis, and activated the mitochondrial apoptosis pathway. At the same time, JQ1 inhibited the activation of AMP-activated protein kinase, a metabolic energy sensor. In addition, we found that the mRNA and protein levels of mitochondrial dynamin-related protein 1 increased, whereas the levels of mitochondrial fusion protein 1 and optic atrophy protein 1 decreased. Mechanistically, we determined that JQ1 inhibited the expression of c-Myc and altered mitochondrial dynamics, eventually leading to changes in the mitochondrial function, metabolism, and apoptosis of B16 melanoma cells.

The Influence of Mitochondrial Dynamics and Function on Retinal Ganglion Cell Susceptibility in Optic Nerve Disease

The important roles of mitochondrial function and dysfunction in the process of neurodegeneration are widely acknowledged. Retinal ganglion cells (RGCs) appear to be a highly vulnerable neuronal cell type in the central nervous system with respect to mitochondrial dysfunction but the actual reasons for this are still incompletely understood. These cells have a unique circumstance where unmyelinated axons must bend nearly 90° to exit the eye and then cross a translaminar pressure gradient before becoming myelinated in the optic nerve. This region, the optic nerve head, contains some of the highest density of mitochondria present in these cells. Glaucoma represents a perfect storm of events occurring at this location, with a combination of changes in the translaminar pressure gradient and reassignment of the metabolic support functions of supporting glia, which appears to apply increased metabolic stress to the RGC axons leading to a failure of axonal transport mechanisms. However, RGCs themselves are also extremely sensitive to genetic mutations, particularly in genes affecting mitochondrial dynamics and mitochondrial clearance. These mutations, which systemically affect the mitochondria in every cell, often lead to an optic neuropathy as the sole pathologic defect in affected patients. This review summarizes knowledge of mitochondrial structure and function, the known energy demands of neurons in general, and places these in the context of normal and pathological characteristics of mitochondria attributed to RGCs.

Opa1 Deficiency Promotes Development of Retinal Vascular Lesions in Diabetic Retinopathy

This study investigates whether reduced optic atrophy 1 (Opa1) level promotes apoptosis and retinal vascular lesions associated with diabetic retinopathy (DR). Four groups of mice: wild type (WT) control mice, streptozotocin (STZ)-induced diabetic mice, Opa1^+/- mice, and diabetic Opa1^+/- mice were used in this study. 16 weeks after diabetes onset, retinas were assessed for Opa1 and Bax levels by Western blot analysis, and retinal networks were examined for acellular capillaries (AC) and pericyte loss (PL). Apoptotic cells were detected in retinal capillaries using TUNEL assay, and caspase-3 activity was assessed using fluorometric analysis. Opa1 expression was significantly downregulated in retinas of diabetic and Opa1^+/- mice compared with those of WT mice. Inducing diabetes further decreased Opa1 expression in retinas of Opa1^+/- mice. Increased cytochrome c release concomitant with increased level of pro-apoptotic Bax and elevated caspase-3 activity were observed in retinas of diabetic and Opa1^+/- mice; the number of TUNEL-positive cells and AC/PL was also significantly increased. An additional decrease in the Opa1 level in retinas of diabetic Opa1^+/- mice exacerbated the development of apoptotic cells and AC/PL compared with those of diabetic mice. Diabetes-induced Opa1 downregulation contributes, at least in part, to the development of retinal vascular lesions characteristic of DR.

The effects of a mitochondrial targeted peptide (elamipretide/SS31) on BAX recruitment and activation during apoptosis

OBJECTIVE

Elamipretide (SS31) is a mitochondria-targeted peptide that has reported functions of stabilizing mitochondrial cristae structure and improving mitochondrial bioenergetics. Several studies have documented cell protective features of this peptide, including impairment of intrinsic apoptosis by inhibiting the recruitment and activation of the pro-apoptotic BAX protein. We used live-cell imaging of ARPE-19 cells expressing fluorescently labeled BAX, cytochrome c, and a mitochondrial marker to investigate the effect of elamipretide on the kinetics of BAX recruitment, mitochondrial outer membrane permeabilization (as a function of cytochrome c release), and mitochondrial fragmentation, respectively.

RESULT

In nucleofected and plated ARPE-19 cells, elamipretide accelerated the formation of larger mitochondria. In the presence of the apoptotic stimulator, staurosporine, cells treated with elamipretide exhibited moderately slower rates of BAX recruitment. Peptide treatment, however, did not significantly delay the onset of BAX recruitment or the final total amount of BAX that was recruited. Additionally, elamipretide showed no impairment or delay of cytochrome c release or mitochondrial fragmentation, two events associated with normal BAX activation during cell death. These results indicate that the protective effect of elamipretide is not at the level of BAX activity to induce pro-apoptotic mitochondrial dysfunction after the initiation of staurosporine-induced apoptosis.

Pharmacological Targeting of Executioner Proteins: Controlling Life and Death

Small-molecule mediated modulation of protein interactions of Bcl-2 (B-cell lymphoma-2) family proteins was clinically validated in 2015 when Venetoclax, a selective inhibitor of the antiapoptotic protein BCL-2, achieved breakthrough status designation by the FDA for treatment of lymphoid malignancies. Since then, substantial progress has been made in identifying inhibitors of other interactions of antiapoptosis proteins. However, targeting their pro-apoptotic counterparts, the "executioners" BAX, BAK, and BOK that both initiate and commit the cell to dying, has lagged behind. However, recent publications demonstrate that these proteins can be positively or negatively regulated using small molecule tool compounds. The results obtained with these molecules suggest that pharmaceutical regulation of apoptosis will have broad implications that extend beyond activating cell death in cancer. We review recent advances in identifying compounds and their utility in the exogenous control of life and death by regulating executioner proteins, with emphasis on the prototype BAX.

Unraveling the Link Between Mitochondrial Dynamics and Neuroinflammation

Neuroinflammatory and neurodegenerative diseases are a major public health problem worldwide, especially with the increase of life-expectancy observed during the last decades. For many of these diseases, we still lack a full understanding of their etiology and pathophysiology. Nonetheless their association with mitochondrial dysfunction highlights this organelle as an important player during CNS homeostasis and disease. Markers of Parkinson (PD) and Alzheimer (AD) diseases are able to induce innate immune pathways induced by alterations in mitochondrial Ca2+ homeostasis leading to neuroinflammation. Additionally, exacerbated type I IFN responses triggered by mitochondrial DNA (mtDNA), failures in mitophagy, ER-mitochondria communication and mtROS production promote neurodegeneration. On the other hand, regulation of mitochondrial dynamics is essential for CNS health maintenance and leading to the induction of IL-10 and reduction of TNF-α secretion, increased cell viability and diminished cell injury in addition to reduced oxidative stress. Thus, although previously solely seen as power suppliers to organelles and molecular processes, it is now well established that mitochondria have many other important roles, including during immune responses. Here, we discuss the importance of these mitochondrial dynamics during neuroinflammation, and how they correlate either with the amelioration or worsening of CNS disease.

Regulation of mitochondrial dynamics in 2-methoxyestradiol-mediated osteosarcoma cell death

Osteosarcoma (OS) is one of the most malignant tumors of childhood and adolescence. Research on mitochondrial dynamics (fusion/fission) and biogenesis has received much attention in last few years, as they are crucial for death of cancer cells. Specifically, it was shown that increased expression of the cytoplasmic dynamin-related protein 1 (Drp1) triggers mitochondrial fission (division), which activates BAX and downstream intrinsic apoptosis, effectively inhibiting OS growth. In the presented study, human OS cells (metastatic 143B OS cell line) were incubated with 2-methoxyestradiol (2-ME) at both physiologically and pharmacologically relevant concentrations. Cell viability was determined by the MTT assay. Confocal microscopy and western blot methods were applied to examine changes in Drp1 and BAX protein levels. Mitochondrial Division Inhibitor 1, MDIVI-1, was used in the study to further examine the role of Drp1 in 2-ME-mediated mechanism of action. To determine quantitative and qualitative changes in mitochondria, electron microscopy was used. 2-ME at all used concentrations increased mitochondrial fission and induced autophagy in OS cells. At the concentration of 1 µM 2-ME increased the area density of mitochondria in OS cells. Subsequent, upregulated expression of Drp1 and BAX proteins by 2-ME strongly suggests the activation of the intrinsic apoptosis pathway. We further observed 2-ME-mediated regulation of glycolytic state of OS cells. Therefore, we suggest that changes of mitochondrial dynamics may represent a novel mechanism of anticancer action of 2-ME. This finding may open new approaches to improve the efficacy of chemotherapy in the treatment of OS, however, it has to be confirmed by in vivo studies.

Characteristics of intracellular propagation of mitochondrial BAX recruitment during apoptosis

Recent advancements in live cell imaging technologies have identified the phenomenon of intracellular propagation of late apoptotic events, such as cytochrome c release and caspase activation. The mechanism, prevalence, and speed of apoptosis propagation remain unclear. Additionally, no studies have demonstrated propagation of the pro-apoptotic protein, BAX. To evaluate the role of BAX in intracellular apoptotic propagation, we used high speed live-cell imaging to visualize fluorescently tagged-BAX recruitment to mitochondria in four immortalized cell lines. We show that propagation of mitochondrial BAX recruitment occurs in parallel to cytochrome c and SMAC/Diablo release and is affected by cellular morphology, such that cells with processes are more likely to exhibit propagation. The initiation of propagation events is most prevalent in the distal tips of processes, while the rate of propagation is influenced by the 2-dimensional width of the process. Propagation was rarely observed in the cell soma, which exhibited near synchronous recruitment of BAX. Propagation velocity is not affected by mitochondrial volume in segments of processes, but is negatively affected by mitochondrial density. There was no evidence of a propagating wave of increased levels of intracellular calcium ions. Alternatively, we did observe a uniform increase in superoxide build-up in cellular mitochondria, which was released as a propagating wave simultaneously with the propagating recruitment of BAX to the mitochondrial outer membrane.

The function of apolipoproteins L (APOLs): relevance for kidney disease, neurotransmission disorders, cancer and viral infection

The discovery that apolipoprotein L1 (APOL1) is the trypanolytic factor of human serum raised interest about the function of APOLs, especially following the unexpected finding that in addition to their protective action against sleeping sickness, APOL1 C-terminal variants also cause kidney disease. Based on the analysis of the structure and trypanolytic activity of APOL1, it was proposed that APOLs could function as ion channels of intracellular membranes and be involved in mechanisms triggering programmed cell death. In this review, the recent finding that APOL1 and APOL3 inversely control the synthesis of phosphatidylinositol-4-phosphate (PI(4)P) by the Golgi PI(4)-kinase IIIB (PI4KB) is commented. APOL3 promotes Ca2+ -dependent activation of PI4KB, but due to their increased interaction with APOL3, APOL1 C-terminal variants can inactivate APOL3, leading to reduction of Golgi PI(4)P synthesis. The impact of APOLs on several pathological processes that depend on Golgi PI(4)P levels is discussed. I propose that through their effect on PI4KB activity, APOLs control not only actomyosin activities related to vesicular trafficking, but also the generation and elongation of autophagosomes induced by inflammation.

Kill one or kill the many: interplay between mitophagy and apoptosis

Mitochondria are key players of cellular metabolism, Ca²⁺ homeostasis, and apoptosis. The functionality of mitochondria is tightly regulated, and dysfunctional mitochondria are removed via mitophagy, a specialized form of autophagy that is compromised in hereditary forms of Parkinson's disease. Through mitophagy, cells are able to cope with mitochondrial stress until the damage becomes too great, which leads to the activation of pro-apoptotic BCL-2 family proteins located on the outer mitochondrial membrane. Active pro-apoptotic BCL-2 proteins facilitate the release of cytochrome c from the mitochondrial intermembrane space (IMS) into the cytosol, committing the cell to apoptosis by activating a cascade of cysteinyl-aspartate specific proteases (caspases). We are only beginning to understand how the choice between mitophagy and the activation of caspases is determined on the mitochondrial surface. Intriguingly in neurons, caspase activation also plays a non-apoptotic role in synaptic plasticity. Here we review the current knowledge on the interplay between mitophagy and caspase activation with a special focus on the central nervous system.

Modeling the function of BAX and BAK in early human brain development using iPSC-derived systems

Intrinsic apoptosis relies on the ability of the BCL-2 family to induce the formation of pores on the outer mitochondrial membrane. Previous studies have shown that both BAX and BAK are essential during murine embryogenesis, and reports in human cancer cell lines identified non-canonical roles for BAX and BAK in mitochondrial fission during apoptosis. BAX and BAK function in human brain development remains elusive due to the lack of appropriate model systems. Here, we generated BAX/BAK double knockout human-induced pluripotent stem cells (hiPSCs), hiPSC-derived neural progenitor cells (hNPCs), neural rosettes, and cerebral organoids to uncover the effects of BAX and BAK deletion in an in vitro model of early human brain development. We found that BAX and BAK-deficient cells have abnormal mitochondrial morphology and give rise to aberrant cortical structures. We suggest crucial functions for BAX and BAK during human development, including maintenance of homeostatic mitochondrial morphology, which is crucial for proper development of progenitors and neurons of the cortex. Human pluripotent stem cell-derived systems can be useful platforms to reveal novel functions of the apoptotic machinery in neural development.

Targeting mitochondria to protect the heart: a matter of balance?

Mitochondria are dynamic, undergoing both fission and fusion. Evidence indicates that a balance between these two processes is necessary to maintain a healthy state. With ischemia/reperfusion (I/R) of the heart, fission is enhanced and is associated with mitochondrial swelling, depolarization, and production of reactive oxygen species (ROS), as well as apoptosis. Blocking fission is effective in reducing I/R-induced tissue damage and contractile dysfunction. In a groundbreaking study appearing in Clinical Science, Maneechote et al. assessed whether correcting the imbalance in mitochondrial dynamics with I/R by enhancing fusion would also be protective. Using a rat model, they investigated the efficacy of pharmacological intervention with mitochondrial fusion promoter-M1 (M1) given before ischemia, during ischemia, or at the onset of reperfusion. With pretreatment being the most effective, they found that M1 attenuated the incidence of arrhythmias, reduced infarct size, preserved cardiac function, and decreased mortality. M1 reduced I/R-induced increases in cytosolic cytochrome c, cleaved caspase 3, and apoptosis. All M1 groups exhibited modestly attenuated I/R-induced mitochondrial ROS levels and swelling, and preserved mitochondrial membrane potential. M1 also prevented a decrease in complex V levels with I/R. However, exactly how M1 stimulates mitochondrial fusion is unclear and other nonfusion-related actions of this phenylhydrazone compound should be considered, such as anti-oxidant actions, preconditioning signaling, or effects on putative mitochondrial connexin 43.