TIGAR contributes to ischemic tolerance induced by cerebral preconditioning through scavenging of reactive oxygen species and inhibition of apoptosis

N-Acety-L-Cysteine Alleviates Isoflurane-Triggered Neuronal Cell Parthanatos by Suppressing Reactive Oxygen Species Accumulation Through the Induction of c-Jun N-Terminal Kinase Signaling Pathway Inhibition

In recent years, the potential neurotoxicity of inhaled anesthetics on the developing brain has increasingly garnered attention, yet its mechanism remains unclear. Parthanatos is a newly discovered form of programmed cell death dependent on PARP-1, and it is believed to be closely associated with cellular oxidative stress response. However, it is still to be proven whether isoflurane, a commonly used clinical anesthetic, can induce parthanatos in developing brain neurons and whether it activates the oxidative stress signaling pathway in neuronal cells. In this study, we treated SH-SY5Y cells and rat hippocampus neuron cells (RN-h) with isoflurane, measured cell viability using the MTT assay, examined the activation of the parthanatos-related PARP-1/AIF/PAR signaling pathway using western blot analysis, detected the accumulation of ROS using DCFH-DA, detected mitochondrial membrane potential (Δψm) by a JC-1 assay, and assessed the activation of the oxidative stress-related JNK signaling pathway using western blot. In vivo, we examined the damaging effects of inhaled isoflurane on neonatal rat hippocampal neurons using HE staining. The results showed that 2% and 4% concentrations of isoflurane significantly inhibited cell survival and upregulated the expression levels of PARP-1, AIF, and PAR in both types of neuronal cells. Moreover, isoflurane significantly enhanced ROS levels and decreased Δψm, and activated the JNK signaling pathway in both cell types. Importantly, we found that pretreatment with N-Acetylcysteine (NAC) could inhibit isoflurane-induced parthanatos and the accumulation of ROS in cells, as well as the activation of the JNK pathway. The experimental results in neonatal rats also demonstrated that isoflurane led to significant neuronal death in the hippocampal CA1 region. However, pretreatment with NAC significantly increased the survival rate of pyramidal neurons in this region. In summary, through our experiments, we confirmed that isoflurane can induce parthanatos in neuronal cells, and NAC can decrease ROS accumulation in neuronal cells and thus mitigate the damage isoflurane causes to neuronal cells.

TIGAR Suppresses ER Stress-Induced Neuronal Injury through Targeting ATF4 Signaling in Cerebral Ischemia/Reperfusion

Endoplasmic reticulum (ER) stress is crucial in cerebral ischemia/reperfusion injury by triggering cellular apoptosis and exacerbating neuronal damage. This study elucidates the dynamics of TP53-induced glycolysis and apoptosis regulator (TIGAR) translocation and its role in regulating neural fate during cerebral ischemia-induced ER stress, specifically in male mice. We found enhanced nuclear localization of TIGAR in neurons after transient middle cerebral artery occlusion/reperfusion (tMCAO/R) in male mice, as well as oxygen glucose deprivation/reperfusion (OGD/R) and treatment with ER stress inducer (tunicamycin and thapsigargin) in neuronal cells. Conditional neuronal knockdown of Tigar aggravated the injury following ischemia-reperfusion, whereas overexpression of Tigar attenuated cerebral ischemic injury and ameliorated intraneuronal ER stress. Additionally, TIGAR overexpression reduced the elevation of ATF4 target genes and attenuated ER stress-induced cell death. Notably, TIGAR colocalized and interacted with ATF4 in the nucleus, inhibiting its downstream proapoptotic gene transcription, consequently protecting against ischemic injury. In vitro and in vivo experiments revealed that ATF4 overexpression reversed the protective effects of TIGAR against cerebral ischemic injury. Intriguingly, our study identified the Q141/K145 residues of TIGAR, crucial for its nuclear translocation and interaction with ATF4, highlighting a novel aspect of TIGAR's function distinct from its known phosphatase activity or mitochondrial localization domains. These findings reveal a novel neuroprotective mechanism of TIGAR in regulating ER stress through ATF4-mediated signaling pathways. These insights may guide targeted therapeutic strategies to protect neuronal function and alleviate the deleterious effects of cerebral ischemic injury.

Targeting intracellular autophagic process for the treatment of post-stroke ischemia/reperfusion injury

Cerebral ischemia/reperfusion (I/R) injury is an important pathophysiological condition of ischemic stroke that involves a variety of physiological and pathological cell death pathways, including autophagy, apoptosis, necroptosis, and phagoptosis, among which autophagy is the most studied. We have reviewed studies published in the past 5 years regarding the association between autophagy and cerebral I/R injury. To the best of our knowledge, this is the first review article summarizing potential candidates targeting autophagic pathways in the treatment of I/R injury post ischemic stroke. The findings of this review may help to better understand the pathogenesis and mechanisms of I/R events and bridge the gap between basic and translational research that may lead to the development of novel therapeutic approaches for I/R injury.

Investigation of preconditioning and the protective effects of nicotinamide against cerebral ischemia-reperfusion injury in rats

This study investigated the antioxidant and neuroprotective effects of nicotinamide combined with ischemic preconditioning against cerebral ischemia reperfusion (CIR) injury. Thirty-five Wistar albino male rats were randomly divided into five groups: sham, preconditioned ischemia/reperfusion (IP+IR), ischemia/reperfusion (IR), preconditioned ischemia/reperfusion + nicotinamide (IP+IR+N), and ischemia/reperfusion + nicotinamide (IR+N). CIR was achieved with bilateral common carotid artery occlusion. IP+IR and IP+IR+N groups 30 min before ischemia; Three cycles of 10 sec ischemia/30 sec reperfusion followed by 20 min IR were applied. The IP+IR+N and IR+N groups received 500 mg/kg nicotinamide intraperitoneally. After 24 h of reperfusion, a neurological evaluation was performed and vertıcal pole test. Biochemically, malondialdehyde (MDA), glutathione (GSH) levels and catalase (CAT) activity were measured in blood and brain tissue samples. Rates of red neurons, sateliosis and spongiosis were determined histopathologically in the prefrontal cortex areas. After CIR, MDA levels increased significantly in serum and brain tissue in the IR group compared to the sham group, while GSH and CAT activity decreased in the brain tissue (p < 0.05). MDA levels in the tissues were found significantly decreased in the IR+N group compared to the IR group (p < 0.05). Administration of nicotinamide together with IP significantly decreased MDA levels in brain tissue and increased GSH and CAT activity (p < 0.05). Compared to the IR group, the morphological and neurological damage in the prefrontal cortex areas decreased in the IP+IR, IP+IR+N, and IR+N groups (p < 0.05). In addition, red neuron, sateliosis and spongiosis rates increased significantly in the IR group compared to the Sham, IP+IR+N, IR+N groups (p < 0.001 for all). In neurological evaluation, while the neurological score increased and the time on the vertical pole decreased significantly in the IR group, preconditioning, and nicotinamide groups reversed (p < 0.05). The study's results show that nicotinamide administration with ischemic preconditioning alleviates cerebral ischemia/reperfusion injury.

TMEM79 Ameliorates Cerebral Ischemia/Reperfusion Injury Through Regulating Inflammation and Oxidative Stress via the Nrf2/NLRP3 Pathway

BACKGROUND

Cerebral ischemia/reperfusion injury (CIRI) is still a complicated disease with high fatality rates worldwide. Transmembrane Protein 79 (TMEM79) regulates inflammation and oxidative stress in some other diseases.

METHODS

CIRI mouse model was established using C57BL/6J mice through middle cerebral artery occlusion-reperfusion (MCAO/R), and BV2 cells were subjected to oxygen and glucose deprivation/reoxygenation (OGD/R) to simulate CIRI. Brain tissue or BV2 cells were transfected or injected with lentivirus-carried TMEM79 overexpression vector. The impact of TMEM79 on CIRI-triggered oxidative stress was ascertained by dihydroethidium (DHE) staining and examination of oxidative stress indicators. Regulation of TMEM79 in neuronal apoptosis and inflammation was determined using TUNEL staining and ELISA.

RESULTS

TMEM79 overexpression mitigated neurological deficit induced by MCAO/R and decreased the extent of cerebral infarct. TMEM79 prevented neuronal death in brain tissue of MCAO/R mouse model and suppressed inflammatory response by reducing inflammatory cytokines levels. Moreover, TMEM79 significantly attenuated inflammation and oxidative stress caused by OGD/R in BV2 cells. TMEM79 facilitated the activation of Nrf2 and inhibited NLRP3 and caspase-1 expressions. Rescue experiments indicated that the Nrf2/NLRP3 signaling pathway mediated the mitigative effect of TMEM79 on CIRI in vivo and in vitro.

CONCLUSION

Overall, TMEM79 was confirmed to attenuate CIRI via regulating the Nrf2/NLRP3 signaling pathway.

The role of TIGAR in nervous system diseases

TP53-induced glycolysis and apoptosis regulator (TIGAR) mainly regulates pentose phosphate pathway by inhibiting glycolysis, so as to synthesize ribose required by DNA, promote DNA damage repair and cell proliferation, maintain cell homeostasis and avoid body injury. Its physiological functions include anti-oxidative stress, reducing inflammation, maintaining mitochondrial function, inhibiting apoptosis, reducing autophagy etc. This paper reviews the research of TIGAR in neurological diseases, including stroke, Parkinson’s disease (PD), Alzheimer’s disease (AD), seizures and brain tumors, aiming to provide reference for the development of new therapeutic targets.

Fascaplysin Induces Apoptosis and Ferroptosis, and Enhances Anti-PD-1 Immunotherapy in Non-Small Cell Lung Cancer (NSCLC) by Promoting PD-L1 Expression

Fascaplysin is a natural product isolated from sponges with a wide range of anticancer activities. However, the mechanism of fascaplysin against NSCLC has not been clearly studied. In this study, fascaplysin was found to inhibit migration by regulating the wnt/β-catenin signaling pathway and reversing the epithelial-mesenchymal transition phenotype. Further research showed that the anti-NSCLC effect of fascaplysin was mainly through the induction of ferroptosis and apoptosis. Fascaplysin-induced ferroptosis in lung cancer cells, evidenced by increased levels of ROS and Fe2+ and downregulation of ferroptosis-associated protein and endoplasmic reticulum stress, was involved in fascaplysin-induced ferroptosis. In addition, ROS was found to mediate fascaplysin-induced apoptosis. Fascaplysin significantly upregulated the expression of PD-L1 in lung cancer cells, and enhanced anti-PD-1 antitumor efficacy in a syngeneic mouse model. Therefore, these results suggest that fascaplysin exerts anticancer effects by inducing apoptosis and ferroptosis in vitro, and improving the sensitivity of anti-PD-1 immunotherapy in vivo. Fascaplysin is a promising compound for the treatment of NSCLC.

Specificity Protein 1: A Protein With a Two-Sided Role in Ischemic Stroke

Stroke is one of the leading causes of death and disability worldwide. However, there is a lack of effective medications to speed up the recovery process. Ischemic stroke, as the result of cerebral infarction or cerebral artery narrowing, is accompanied by hemiplegia or impaired consciousness. There are many transcription factors involved in the development of this condition, whose alterations can influence or signal the prognostic outcomes of ischemic stroke. Among them, the augmented expression of specificity protein 1 (SP1) can participate in the progression of the disease by binding DNA to regulate the transcriptions of many genes. Different studies have provided different answers as to whether SP1 plays a positive or a negative role in ischemic stroke. On the one hand, SP1 can play a cytoprotective role as both an antioxidant and anti-apoptotic agent for neurons and glial cells. On the other hand, it can also damage neuronal cells by promoting inflammation and exacerbating brain edema. In this review, we highlight the roles of SP1 in ischemic stroke and shed light on the underlying mechanism.

Proteomic identification of ruminal epithelial protein expression profiles in response to starter feed supplementation in pre-weaned lambs

The present study aimed to comparatively characterize the ruminal epithelial protein expression profiles in lambs fed ewe milk or milk plus starter diet using proteome analysis. Twenty new-born lambs were randomly divided into a group receiving ewe milk (M, n = 10) and a group receiving milk plus starter diet (M + S, n = 10). From 10 d old, M group lambs remained with the ewe and suckled ewe milk without receiving the starter diet. The lambs in the M + S group were separated from the ewe and received starter feed. All lambs were slaughtered at 56 d old. Eight rumen epithelia samples (4 per group) were collected to characterize their protein expression profiles using proteomic technology. Proteome analysis showed that 31 upregulated proteins and 40 downregulated proteins were identified in the rumen epithelium of lambs in response to starter diet supplementation. The results showed that starter feeding regulates a variety of biological processes in the epithelium, especially blood vessel development and extracellular matrix protein expression. Meanwhile, the expression of proteins associated with synthesis and degradation of ketone bodies, butanoate metabolism, and citrate cycle signaling transduction pathway were upregulated in the group with starter diet supplementation, including 3-hydroxy-3-methylglutaryl coenzyme A synthase (HMGCS2, fold change [FC] = 1.93), 3-hydroxybutyrate dehydrogenase 1 (BDH1, FC = 1.91), and isocitrate dehydrogenase 1 (IDH1, FC = 8.12). The metabolic processes associated with ammonia detoxification and antioxidant stress were also affected by starter diet supplementation, with proteins, microsomal glutathione S-transferase 3 (MGST3, FC = 2.37) and IDH1, linked to the biosynthesis of glutamate and glutathione metabolism pathway being upregulated in the group with starter diet supplementation. In addition, starter feeding decreased the expression of Ras-related protein rap-1A (RAP1A, FC = 0.48) enriched in Rap1 signaling pathway, Ras signaling pathway, cyclic adenosine monophosphate (cAMP) signaling pathway, and mitogen-activated protein kinase (MAPK) signaling pathway. In summary, starter feed supplementation changed the expression of proteins related to energy production, ammonia detoxification, antioxidant stress, and signaling pathways related to proliferation and apoptosis, which facilitates the rumen epithelia development in lambs. The results provide new insights into the molecular adaptation of rumen epithelia in response to starter diet supplementation at the protein level in lambs.

GATA3 (GATA-Binding Protein 3)/KMT2A (Lysine-Methyltransferase-2A) Complex by Increasing H3K4-3me (Trimethylated Lysine-4 of Histone-3) Upregulates NCX3 (Na+-Ca2+ Exchanger 3) Transcription and Contributes to Ischemic Preconditioning Neuroprotection

Background and Purpose

NCX3 (Na+-Ca2+ exchanger 3) plays a relevant role in stroke; indeed its pharmacological blockade or its genetic ablation exacerbates brain ischemic damage, whereas its upregulation takes part in the neuroprotection elicited by ischemic preconditioning. To identify an effective strategy to induce an overexpression of NCX3, we examined transcription factors and epigenetic mechanisms potentially involved in NCX3 gene regulation.

Methods

Brain ischemia and ischemic preconditioning were induced in vitro by exposure of cortical neurons to oxygen and glucose deprivation plus reoxygenation (OGD/Reoxy) and in vivo by transient middle cerebral artery occlusion. Western blot and quantitative real-time polymerase chain reaction were used to evaluate transcripts and proteins of GATA3 (GATA-binding protein 3), KMT2A (lysine-methyltransferase-2A), and NCX3. GATA3 and KMT2A binding on NCX3 gene was evaluated by chromatin immunoprecipitation and Rechromatin immunoprecipitation experiments.

Results

Among the putative transcription factors sharing a consensus sequence on the ncx3 brain promoter region, GATA3 was the only able to up-regulate ncx3. Interestingly, GATA3 physically interacted with KMT2A, and their overexpression or knocking-down increased or downregulated NCX3 mRNA and protein, respectively. Notably, site-direct mutagenesis of GATA site on ncx3 brain promoter region counteracted GATA3 and KMT2A binding on NCX3 gene. More importantly, we found that in the perischemic cortical regions of preconditioned rats GATA3 recruited KMT2A and the complex H3K4-3me (trimethylated lysine-4 of histone-3) on ncx3 brain promoter region, thus reducing transient middle cerebral artery occlusion–induced damage. Consistently, in vivo silencing of either GATA3 or KMT2A prevented NCX3 upregulation and consequently the neuroprotective effect of preconditioning stimulus. The involvement of GATA3/KMT2A complex in neuroprotection elicited by ischemic preconditioning was further confirmed by in vitro experiments in which the knocking-down of GATA3 and KMT2A reverted the neuroprotection induced by NCX3 overexpression in cortical neurons exposed to anoxic preconditioning followed by oxygen and glucose deprivation plus reoxygenation.

Conclusions

Collectively, our results revealed that GATA3/KMT2A complex epigenetically activates NCX3 gene transcription during ischemic preconditioning.

Structure, regulation, and biological functions of TIGAR and its role in diseases

TIGAR (TP53-induced glycolysis and apoptosis regulator) is the downstream target gene of p53, contains a functional sequence similar to 6-phosphofructose kinase/fructose-2, 6-bisphosphatase (PFKFB) bisphosphatase domain. TIGAR is mainly located in the cytoplasm; in response to stress, TIGAR is translocated to nucleus and organelles, including mitochondria and endoplasmic reticulum to regulate cell function. P53 family members (p53, p63, and p73), some transcription factors (SP1 and CREB), and noncoding miRNAs (miR-144, miR-885-5p, and miR-101) regulate the transcription of TIGAR. TIGAR mainly functions as fructose-2,6-bisphosphatase to hydrolyze fructose-1,6-diphosphate and fructose-2,6-diphosphate to inhibit glycolysis. TIGAR in turn facilitates pentose phosphate pathway flux to produce nicotinamide adenine dinucleotide phosphate (NADPH) and ribose, thereby promoting DNA repair, and reducing intracellular reactive oxygen species. TIGAR thus maintains energy metabolism balance, regulates autophagy and stem cell differentiation, and promotes cell survival. Meanwhile, TIGAR also has a nonenzymatic function and can interact with retinoblastoma protein, protein kinase B, nuclear factor-kappa B, hexokinase 2, and ATP5A1 to mediate cell cycle arrest, inflammatory response, and mitochondrial protection. TIGAR might be a potential target for the prevention and treatment of cardiovascular and neurological diseases, as well as cancers.

Targeting neuroinflammation to treat cerebral ischemia - The role of TIGAR/NADPH axis

Cerebral ischemia is a disease of ischemic necrosis of brain tissue caused by intracranial artery stenosis or occlusion and cerebral artery embolization. Neuroinflammation plays an important role in the pathophysiology of cerebral ischemia. Microglia, astrocytes, leukocytes and other cells that release a variety of inflammatory factors involved in neuroinflammation may play a damaging or protective role during the process of cerebral ischemia. TP53-induced glycolysis and apoptotic regulators (TIGAR) may facilitate the production of nicotinamide adenine dinucleotide phosphoric acid (NADPH) via the pentose phosphate pathway (PPP) to inhibit oxidative stress and neuroinflammation. TIGAR can also directly inhibit NF-κB to inhibit neuroinflammation. TIGAR thus protect against cerebral ischemic injury. Exogenous NADPH can inhibit neuroinflammation by inhibiting oxidative stress and regulating a variety of signals. However, since NADPH oxidase (NOX) may use NADPH as a substrate to generate reactive oxygen species (ROS) to mediate neuroinflammation, the combination of NADPH and NOX inhibitors may produce more powerful anti-neuroinflammatory effects. Here, we review the cells and regulatory signals involved in neuroinflammation during cerebral ischemia, and discuss the possible mechanisms of targeting neuroinflammation in the treatment of cerebral ischemia with TIGAR/NADPH axis, so as to provide new ideas for the prevention and treatment of cerebral ischemia.

A sphingosine kinase 2-mimicking TAT-peptide protects neurons against ischemia-reperfusion injury by activating BNIP3-mediated mitophagy

We have previously shown that sphingosine kinase 2 (SPK2) interacts with Bcl-2 via its BH3 domain, activating autophagy by inducing the dissociation of Beclin-1/Bcl-2 complexes, and that a TAT-SPK2 peptide containing the BH3 domain of SPK2 protects neurons against ischemic injury. The goals of the present study were to establish the functional significance of these findings, by testing whether TAT-SPK2 was effective in a mouse model of ischemic stroke, and to explore potential underlying mechanisms. Mice were administered with TAT-SPK2 by intraperitoneal injection before or after transient middle cerebral artery occlusion (tMCAO). Infarct volume, neurological deficit and brain water content were assessed 24 h after reperfusion. Mitophagy inhibitor Mdivi-1 and BNIP3 siRNAs were used to examine the involvement of BNIP3-dependent mitophagy in the neuroprotection of TAT-SPK2. Mitophagy was quantified by immunoblotting, immunofluorescence and electron microscopy. The interaction between TAT-SPK2 and Bcl-2, Bcl-2 and BNIP3 was detected by co-immunoprecipitation. In the tMCAO model, pre-treatment with TAT-SPK2 significantly reduced infarct volume, improved neurological function and decreased brain edema. Neuroprotection by TAT-SPK2 was still seen when the peptide was administered 3 h after reperfusion. TAT-SPK2 also significantly improved functional recovery and reduced long-term brain atrophy of the ischemic hemisphere 30 days after administration. Our studies further showed that TAT-SPK2 directly binds to Bcl-2 and disrupts Bcl-2/Beclin-1 or Bcl-2/BNIP3 complexes to induce mitophagy. These results suggest that TAT-SPK2 protects neurons against ischemia reperfusion injury by activating BNIP3-mediated mitophagy. Agents exploiting this molecular mechanism are potential candidates for the treatment of ischemic stroke.

Syntaxin 17 inhibits ischemic neuronal injury by resuming autophagy flux and ameliorating endoplasmic reticulum stress

Previous studies have shown that syntaxin 17 (STX17) is involved in mediating the fusion of autophagosomes and lysosomes. This study aimed to investigate the role and mechanism of STX17 in neuronal injury following cerebral ischemia/reperfusion. The ischemia/reperfusion (I/R) models were established by transient middle cerebral artery occlusion (tMCAO) in mice and oxygen glucose deprivation/reperfusion (O/R) in primary cultured cortical neurons and HT22 cells. Cerebral ischemia/reperfusion significantly up-regulated the expression of STX17 in neurons. Lentivirus mediated knockdown of STX17 in neurons reduced neuronal viability and increased LDH leakage. Injection of AAV9-shSTX17 into the brain of mice then subjected to tMCAO also significantly augmented the infarct area and exacerbated neurobehavioral deficits and mortality. Depletion of STX17 caused accumulation of autophagic marker/substrate LC3 II and p62, blockade of the autophagic flux, and the accumulation of dysfunctional lysosomes. Knockdown of STX17 also aggravated endoplasmic reticulum (ER) stress-dependent neuronal apoptosis induced by ischemia/reperfusion. Importantly, induction of autophagy-lysosomal pathway and alleviation of ER stress partially rescued STX17 knockdown-induced neuronal damage. These results suggest that STX17 may ameliorate ischemia/reperfusion-induced neuronal damage by enhancing autophagy flux and reducing ER stress-dependent neuronal apoptosis.

Metabolism and immunity in breast cancer

Breast cancer is one of the most common malignancies that seriously threaten women's health. In the process of the malignant transformation of breast cancer, metabolic reprogramming and immune evasion represent the two main fascinating characteristics of cancer and facilitate cancer cell proliferation. Breast cancer cells generate energy through increased glucose metabolism. Lipid metabolism contributes to biological signal pathways and forms cell membranes except energy generation. Amino acids act as basic protein units and metabolic regulators in supporting cell growth. For tumor-associated immunity, poor immunogenicity and heightened immunosuppression cause breast cancer cells to evade the host's immune system. For the past few years, the complex mechanisms of metabolic reprogramming and immune evasion are deeply investigated, and the genes involved in these processes are used as clinical therapeutic targets for breast cancer. Here, we review the recent findings related to abnormal metabolism and immune characteristics, regulatory mechanisms, their links, and relevant therapeutic strategies.

Exogenous NADPH ameliorates myocardial ischemia-reperfusion injury in rats through activating AMPK/mTOR pathway

Our previous study shows that nicotinamide adenine dinucleotide phosphate (NADPH) plays an important role in protecting against cerebral ischemia injury. In this study we investigated whether NADPH exerted cardioprotection against myocardial ischemia/reperfusion (I/R) injury. To induce myocardial I/R injury, rats were subjected to ligation of the left anterior descending branch of coronary artery for 30 min followed by reperfusion for 2 h. At the onset of reperfusion, NADPH (4, 8, 16 mg· kg⁻¹· d⁻¹, iv) was administered to the rats. We found that NADPH concentrations in plasma and heart were significantly increased at 4 h after intravenous administration. Exogenous NADPH (8−16 mg/kg) significantly decreased myocardial infarct size and reduced serum levels of lactate dehydrogenase (LDH) and cardiac troponin I (cTn-I). Exogenous NADPH significantly decreased the apoptotic rate of cardiomyocytes, and reduced the cleavage of PARP and caspase-3. In addition, exogenous NADPH reduced mitochondrial vacuolation and increased mitochondrial membrane protein COXIV and TOM20, decreased BNIP3L and increased Bcl-2 to protect mitochondrial function. We conducted in vitro experiments in neonatal rat cardiomyocytes (NRCM) subjected to oxygen–glucose deprivation/restoration (OGD/R). Pretreatment with NADPH (60, 500 nM) significantly rescued the cell viability and inhibited OGD/R-induced apoptosis. Pretreatment with NADPH significantly increased the phosphorylation of AMPK and downregulated the phosphorylation of mTOR in OGD/R-treated NRCM. Compound C, an AMPK inhibitor, abolished NADPH-induced AMPK phosphorylation and cardioprotection in OGD/R-treated NRCM. In conclusion, exogenous NADPH exerts cardioprotection against myocardial I/R injury through the activation of AMPK/mTOR pathway and inhibiting mitochondrial damage and cardiomyocyte apoptosis. NADPH may be a potential candidate for the prevention and treatment of myocardial ischemic diseases.

NADPH protects against kainic acid-induced excitotoxicity via autophagy-lysosome pathway in rat striatum and primary cortical neurons

PURPOSE

To investigate the effects and mechanisms of NADPH on Kainic acid (KA)-induced excitotoxicity.

METHODS

KA, a non-N-methyl-d-aspartate glutamate receptor agonist, was exposed to adult SD rats via intrastriatal injection and rat primary cortical neurons to establish excitotoxic models in vivo and in vitro, respectively. To determine the effects of NADPH on KA-induced excitotoxicity, neuronal survival, neurologically behavioral score and oxidative stress were evaluated. To explore the mechanisms of neuroprotective effects of NADPH, the autophagy-lysosome pathway related proteins were detected.

RESULTS

In vivo, NADPH (1 mg/kg or 2 mg/kg) diminished KA (2.5 nmol)-induced enlargement of lesion size in striatum, improved KA-induced dyskinesia and reversed KA-induced activation of glial cells. Nevertheless, the neuroprotective effect of NADPH was not significant under the condition of autophagy activation. NADPH (2 mg/kg) inhibited KA (2.5 nmol)-induced down-regulation of TP-53 induced glycolysis and apoptosis regulator (TIGAR) and p62, and up-regulation of the protein levels of LC3-II/LC3-I, Beclin-1 and Atg5. In vitro, the excitotoxic neuronal injury was induced after KA (50 μM, 100 μM or 200 μM) treatment as demonstrated by decreased cell viability. Moreover, KA (100 μM) increased the intracellular levels of calcium and reactive oxygen species (ROS) and declined the levels of the reduced form of glutathione (GSH). Pretreatment of NADPH (10 μM) effectively reversed these changes. Meanwhile NADPH (10 μM) inhibited KA (100 μM)-induced down-regulation of TIGAR and p62, and up-regulation of the ratio of LC3-II/LC3-I, Beclin-1, Atg5, active-cathepsin B and active-cathepsin D.

CONCLUSIONS

Our data provide a possible mechanism that NADPH ameliorates KA-induced excitotoxicity by blocking the autophagy-lysosome pathway and up-regulating TIGAR along with its antioxidant properties.

Malic enzyme 1 is important for uterine decidualization in response to progesterone/cAMP/PKA/HB-EGF pathway

Malic enzyme 1 (Me1), a member of the malic enzymes involving in glycolytic pathway and citric acid cycle, is essential for the energy metabolism and maintenance of intracellular redox balance state, but its physiological role and regulatory mechanism in the uterine decidualization are still unknown. Current study showed that Me1 was strongly expressed in decidual cells, and could promote the proliferation and differentiation of stromal cells followed by an accelerated cell cycle transition, indicating an importance of Me1 in the uterine decidualization. Silencing of Me1 attenuated NADPH generation and reduced GR activity, while addition of NADPH improved the defect of GR activity elicited by Me1 depletion. Further analysis found that Me1 modulated intracellular GSH content via GR. Meanwhile, Me1 played a role in maintaining mitochondrial function as indicated by these observations that blockadge of Me1 led to the accumulation of mitochondrial O 2 - level and decreased ATP production and mtDNA copy numbers accompanied with defective mitochondrial membrane potential. In uterine stromal cells, progesterone induced Me1 expression through PR-cAMP-PKA pathway. Knockdown of HB-EGF might impede the regulation of progesterone and cAMP on Me1. Collectively, Me1 is essential for uterine decidualization in response to progesterone/cAMP/PKA/HB-EGF pathway and plays an important role in preventing mitochondrial dysfunction.

Phosphatidylethanolamine-binding protein 1 protects CA1 neurons against ischemic damage via ERK-CREB signaling in Mongolian gerbils

In the present study, we made a PEP-1-phosphatidylethanolamine-binding protein 1 (PEP-1-PEBP1) fusion protein to facilitate the transduction of PEBP1 into cells and observed significant ameliorative effects of PEP-1-PEBP1 against H₂O₂-induced neuronal damage and the formation of reactive oxygen species in the HT22 hippocampal cells. In addition, administration of PEP-1-PEBP1 fusion protein ameliorated H₂O₂-induced phosphorylation of extracellular signal-regulated kinases (ERK1/2) and facilitated the phosphorylation of cyclic-AMP response element binding protein (CREB) in HT22 cells after exposure to H₂O₂. We also investigated the temporal and spatial changes of phosphorylated phosphatidylethanolamine-binding protein 1 (pPEBP1) in the hippocampus, after 5 min of transient forebrain ischemia in gerbils. In the sham-operated animals, pPEBP1 immunoreactivity was not detectable in the hippocampal CA1 region. pPEBP1 immunoreactivity was significantly increased in the hippocampal CA1 region, 1-2 days after ischemia, compared to that in the sham-operated group and pPEBP1 immunoreactivity was returned to levels in sham-operated group at 3-4 days after ischemia. pPEBP1 immunoreactivity significantly increased at day 7 after ischemia and decreased to sham-operated group levels by day 10 after ischemia/reperfusion. In addition, administration of PEP-1-PEBP1 fusion protein significantly reduced the ischemia-induced hyperactivity of locomotion, 1 day after ischemia and PEP-1-PEBP1 reduced neuronal damage and reactive gliosis (astrocytosis and microgliosis) in the gerbil hippocampal CA1 region, 4 days after ischemia. Administration of PEP-1-PEBP1 fusion protein ameliorated the ischemia-induced phosphorylation of ERK at 3 h and 6 h after ischemia/reperfusion and accelerated the phosphorylation of CREB in ischemic hippocampus at 6 h after ischemia. These results suggest that the increase in PEBP1 phosphorylation causes neuronal damage in the hippocampus and treatment with PEP-1-PEBP1 fusion protein provides neuroprotection from increasing phosphorylation of ERK-CREB pathways in the hippocampal CA1 region, during ischemic damage.

TIGAR Attenuates High Glucose-Induced Neuronal Apoptosis via an Autophagy Pathway

Hyperglycemia-induced neuronal apoptosis is one of the important reasons for diabetic neuropathy. Long-time exposure to high glucose accelerates many aberrant glucose metabolic pathways and eventually leads to neuronal injury. However, the underlying mechanisms of metabolic alterations remain unknown. TP53-inducible glycolysis and apoptosis regulator (TIGAR) is an endogenous inhibitor of glycolysis and increases the flux of pentose phosphate pathway (PPP) by regulating glucose 6-phosphate dehydrogenase (G6PD). TIGAR is highly expressed in neurons, but its role in hyperglycemia-induced neuronal injury is still unclear. In this study, we observed that TIGAR and G6PD are decreased in the hippocampus of streptozotocin (STZ)-induced diabetic mice. Correspondingly, in cultured primary neurons and Neuro-2a cell line, stimulation with high glucose induced significant neuronal apoptosis and down-regulation of TIGAR expression. Overexpression of TIGAR reduced the number of TUNEL-positive neurons and prevented the activation of Caspase-3 in cultured neurons. Furthermore, enhancing the expression of TIGAR rescued high glucose-induced autophagy impairment and the decrease of G6PD. Nitric oxide synthase 1 (NOS1), a negative regulator of autophagy, is also inhibited by overexpression of TIGAR. Inhibition of autophagy abolished the protective effect of TIGAR in neuronal apoptosis in Neuro-2a. Importantly, overexpression of TIGAR in the hippocampus ameliorated STZ-induced cognitive impairment in mice. Therefore, our data demonstrated that TIGAR may have an anti-apoptosis effect via up-regulation of autophagy in diabetic neuropathy.

TIGAR impedes compression-induced intervertebral disc degeneration by suppressing nucleus pulposus cell apoptosis and autophagy

To investigate whether TP53-induced glycolysis and apoptosis regulator (TIGAR) participates in compression-induced intervertebral disc (IVD) degeneration, and to determine the regulatory effect of TIGAR on nucleus pulposus (NP) cell autophagy and apoptosis following compression-induced injuries. IVD tissues were collected from human patients undergoing surgery (n = 20) and skeletally mature Sprague-Dawley rats (n = 15). Initially, the effect of compression on the expression of TIGAR was evaluated with in vivo and in vitro models. In addition, TIGAR was silenced to investigate the regulatory effect of TIGAR on compression-induced intracellular reactive oxygen species (ROS) levels, autophagy, and apoptosis in rat NP cells. Furthermore, the P53 inhibitor pifithrin-α (PFTα) and SP1 inhibitor mithramycin A were employed to detect expression level changes of TIGAR and autophagy-associated target molecules. TIGAR expression of NP cells increased gradually in human degenerative IVDs and in rat NP cells under compression both in vivo and in vitro. TIGAR knockdown enhanced compression-induced intracellular ROS generation and the NADPH/NADP⁺ and GSH/GSSG ratios. Moreover, TIGAR knockdown amplified the compression-induced caspase-3 activation and the apoptosis rate of rat NP cells. Likewise, knockdown of TIGAR significantly accelerated LC3B expression and autophagosome formation in rat NP cells during compression-induced injuries. The results also established that mithramycin A could inhibit TIGAR expression and autophagy levels in NP cells under compression conditions, while PFTα had no similar effect. Our data demonstrated that TIGAR acted as an important endogenous negative regulator of ROS levels, which might inhibit compression-induced apoptosis and autophagy through SP1-dependent mechanisms.

GCN2 suppression attenuates cerebral ischemia in mice by reducing apoptosis and endoplasmic reticulum (ER) stress through the blockage of FoxO3a-regulated ROS production

Ischemic stroke is one of the leading causes of morbidity and mortality among human worldwide. Unfortunately, cerebral I/R still lacks effective therapeutic targets and strategies. In the study, we found that general control nonderepressible 2 (GCN2) expression was increased following ischemia in the ischemic penumbra in vivo and in vitro. GCN2 suppression using its significant inhibitor, GCN2iB, exhibited a protective role in cerebral I/R injury in mice, as evidenced by the improved neurological deficits and function. GCN2 inhibition with either GCN2iB or genetic knockdown led to significant reduction of pro-apoptotic protein expression, endoplasmic reticulum stress (ERS)-related protein and oxidative stress both in I/R-induced cerebral injury and oxygen-glucose deprivation and reoxygenation (OGD/R) stimulation in N2a cells. OGD/R-triggered apoptosis and ERS were significantly depended on oxidative stress in vitro. In addition, Forkhead box O 3a (FoxO3a), involved in the reactive oxygen species (ROS) production, was increased during OGD/R stimulation-regulated apoptosis and ERS, which could be abrogated by GCN2 suppression. Consistently, FoxO3a-regulated generation of ROS was markedly ameliorated upon GCN2 suppression with GCN2iB. Thereby, our findings indicated that GCN2 suppression alleviated apoptosis and ERS in cerebral ischemia through reducing FoxO3a-dependent ROS production, illustrating that GCN2 could be a promising target for the therapeutic interventions in cerebral ischemic stroke.

TIGAR suppresses seizures induced by kainic acid through inhibiting oxidative stress and neuronal apoptosis

TP53-induced glycolysis and apoptosis regulator (TIGAR) activates the pentose phosphate pathway (PPP), which feeds reduced nicotinamide adenine dinucleotide phosphate (NADPH) to the antioxidant glutathione pathway. Oxidative stress-induced neuronal apoptosis is the pathological basis of several neurological disorders, including epilepsy. To determine the potential anti-epileptic action TIGAR in a rodent kainic acid (KA)-induced seizure model. Seizures were induced by the intra-cerebroventricular injection of KA, followed by injection of empty or TIGAR-expressing lentiviral vectors. Immunofluorescence was used to detect the localization of TIGAR in the cortices and hippocampi, and the expression levels of relevant proteins were determined by Western blotting. Oxidative stress-related markers were detected using commercially available kits. Neuronal apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining. TIGAR were mainly expressed in the neurons and rarely located in the astrocytes, and increased in the cortices and hippocampi of KA-treated rats in a time-dependent manner. Lentivirus-mediated TIGAR overexpression significantly decreased the oxidative stress and neuronal apoptosis induced by KA, resulting in prolonged seizure latency and lower Racine scores. Our findings indicate that TIGAR has anti-epileptic, anti-oxidant and anti-apoptotic effects, and is therefore a promising therapeutictarget for epilepsy.

Heme Oxygenase-1 Inhibition Sensitizes Human Prostate Cancer Cells towards Glucose Deprivation and Metformin-Mediated Cell Death

High levels of heme oxygenase (HO)-1 have been frequently reported in different human cancers, playing a major role in drug resistance and regulation of cancer cell redox homeostasis. Metformin (MET), a drug widely used for type 2 diabetes, has recently gained interest for treating several cancers. Recent studies indicated that the anti-proliferative effects of metformin in cancer cells are highly dependent on glucose concentration. The present work was directed to determine whether use of a specific inhibitor of HO-1 activity, alone or in combination with metformin, affected metastatic prostate cancer cell viability under different concentrations of glucose. MTT assay and the xCELLigence system were used to evaluate cell viability and cell proliferation in DU145 human prostate cancer cells. Cell apoptosis and reactive oxygen species were analyzed by flow cytometry. The activity of HO-1 was inhibited using a selective imidazole-based inhibitor; genes associated with antioxidant systems and cell death were evaluated by qRT-PCR. Our study demonstrates that metformin suppressed prostate cancer growth in vitro and increased oxidative stress. Disrupting the antioxidant HO-1 activity, especially under low glucose concentration, could be an attractive approach to potentiate metformin antineoplastic effects and could provide a biochemical basis for developing HO-1-targeting drugs against solid tumors.

Wnt Signaling Activates TP53-Induced Glycolysis and Apoptosis Regulator and Protects Against Cisplatin-Induced Spiral Ganglion Neuron Damage in the Mouse Cochlea

AIMS

Cisplatin can damage spiral ganglion neurons (SGNs) and cause sensorineural hearing loss. Wnt activation protects against neomycin-induced hair cell damage in the mouse cochlea, but the role of Wnt signaling in protecting SGNs from cisplatin treatment has not yet been elucidated. This study was designed to investigate the neuroprotective effects of Wnt signaling against cisplatin-induced SGN damage.

RESULTS

First, we found that Wnt signaling was activated in SGNs after cisplatin treatment. Next, we discovered that overexpression (OE) of Wnt signaling in SGNs reduced cisplatin-induced SGN loss by inhibiting caspase-associated apoptosis, thus preventing the loss of SGN function after cisplatin treatment. In contrast, inhibition of Wnt signaling increased apoptosis, made SGNs more vulnerable to cisplatin treatment, and exacerbated hearing loss. TP53-induced glycolysis and apoptosis regulator (TIGAR), which scavenges intracellular reactive oxygen species (ROS), was upregulated in SGNs in response to cisplatin administration. Wnt/β-catenin activation increased TIGAR expression and reduced ROS level, while inhibition of Wnt/β-catenin in SGNs reduced TIGAR expression and increased the ROS level. Moreover, OE of TIGAR reduced ROS and decreased caspase 3 expression, as well as increased the survival of SGNs in Wnt-inhibited SGNs. Finally, antioxidant treatment rescued the more severe SGN loss induced by β-catenin deficiency after cisplatin treatment. Innovation and Conclusion: This study is the first to indicate that Wnt signaling activates TIGAR and protects SGNs against cisplatin-induced damage through the inhibition of oxidative stress and apoptosis in SGNs, and this might offer novel therapeutic targets for the prevention of SGN injury. Antioxid. Redox Signal. 00, 000-000.

Potent effects of dioscin against hepatocellular carcinoma through regulating TP53-induced glycolysis and apoptosis regulator (TIGAR)-mediated apoptosis, autophagy, and DNA damage

BACKGROUND AND PURPOSE

Dioscin shows potent effects against cancers. We aimed to elucidate its pharmacological effects and mechanisms of action on hepatocellular carcinoma (HCC) in vivo and in vitro.

EXPERIMENTAL APPROACH

Effects of dioscin were investigated in SMMC7721 and HepG2 cells, diethylnitrosamine-induced primary liver cancer in rats, and cell xenografts in nude mice. Isobaric tags for relative and absolution quantitation (iTRAQ)-based proteomics was used to find dioscin's targets and investigate its mechanism.

KEY RESULTS

In SMMC7721 and HepG2 cells dioscin markedly inhibited cell proliferation and migration, induced apoptosis, autophagy, and DNA damage. It inhibited DEN-induced primary liver cancer in rats, markedly changed body weights and restored levels of α fetoprotein, alanine transaminase, aspartate transaminase, γ-glutamyltransferase, alkaline phosphatase, and Ki67. It also inhibited growth of xenografts in mice. In SMMC7721 cells, 191 differentially expressed proteins were found after dioscin, based on iTRAQ-based assay. TP53-inducible glycolysis and apoptosis regulator (TIGAR) was identified as being significantly down-regulated by dioscin. Dioscin induced cell apoptosis, autophagy, and DNA damage via increasing expression levels of p53, cleaved PARP, Bax, cleaved caspase-3/9, Beclin-1, and LC3 and suppressing those of Bcl-2, p-Akt, p-mammalian target of rapamycin (mTOR), CDK5, p-ataxia telangiectasia-mutated gene (ATM). The transfection of TIGAR siRNA into SMMC7721 cells and xenografts in nude mice further confirmed that the potent activity of dioscin against HCC is evoked by adjusting TIGAR-mediated inhibition of p53, Akt/mTOR, and CDK5/ATM pathways.

CONCLUSIONS AND IMPLICATIONS

The data suggest that dioscin has potential as a therapeutic, and TIGAR as a drug target for treating HCC.

TIGAR regulates mitochondrial functions through SIRT1-PGC1α pathway and translocation of TIGAR into mitochondria in skeletal muscle

TP53-induced glycolysis and apoptosis regulator (TIGAR), a glycolytic inhibitor, plays vital roles in regulating cellular metabolism and oxidative stress. However, the role of highly expressed TIGAR in skeletal muscle remains unexplored. In the present study, TIGAR levels varied in different skeletal muscles and fibers. An exhaustive swimming test with a load corresponding to 5% of body weight was utilized in mice to assess the effects of TIGAR on exercise-induced fatigue and muscle damage. The running time and metabolic indicators were significantly greater in wild-type (WT) mice compared with TIGAR knockout (KO) mice. Poor exercise capacity was accompanied by decreased type IIA fibers in TIGAR KO mice. Decreased mitochondrial number and mitochondrial oxidative phosphorylation were observed more in TIGAR KO mice than in WT mice, which were involved in sirtuin 1 (SIRT1)-mediated deacetylation of peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α), and resveratrol treatment in TIGAR KO mice can increase mitochondrial content and exercise time. Much more TIGAR was also detected in mitochondria during exhaustive exercise. In addition, TIGAR, rather than mitochondria-targeted TIGAR achieved by in vitro plasmid transfection, promoted SIRT1-PGC1α pathway. Glutathione S-transferase-TIGAR pull-down assay followed by liquid chromatography mass spectrometry found that TIGAR interacted with ATP synthase F1 subunit α (ATP5A1), and its binding to ATP5A1 increased during exhaustive exercise. Overexpression of mitochondrial-TIGAR enhanced ATP generation, maintained mitochondrial membrane potential and reduced mitochondrial oxidative stress under hypoxia condition. Taken together, our results uncovered a novel role for TIGAR in mitochondrial regulation in fast-twitch oxidative skeletal muscle through SIRT1-PGC1α and translocation into mitochondria, which contribute to the increase in exercise endurance of mice.-Geng, J., Wei, M., Yuan, X., Liu, Z., Wang, X., Zhang, D., Luo, L., Wu, J., Guo, W., Qin, Z.-H. TIGAR regulates mitochondrial functions through SIRT1-PGC1α pathway and translocation of TIGAR into mitochondria in skeletal muscle.

NADPH ameliorates MPTP-induced dopaminergic neurodegeneration through inhibiting p38MAPK activation

Parkinson's disease (PD) is the second most common neurodegenerative disorder characterized by the selective loss of dopaminergic neurons in substantia nigra pars compacta (SNpc). Although the pathogenic mechanism underlying PD remains largely unknown, decreased nigral glutathione (GSH) in postmortem brains of PD patients supports the presence of oxidative stress in PD. We found that Nicotinamide adenine dinucleotide phosphate (NADPH), which is important for maintaining the level of GSH, protected dopaminergic (DA) neurons from neurotoxicity of MPTP/MPP⁺. In the present study, NADPH prevented DA neurons from MPTP toxicity with increased GSH and decreased reactive oxygen species (ROS) levels in the ventral midbrain of mice, and improved motor activity. Our present results demonstrated that NADPH inhibited the phosphorylation of p38MAPK, decreased the level of TP53 protein, and inhibited TP53 nuclear translocation in DA neurons of SNpc and in MES23.5 cells. Furthermore, NADPH decreased the protein level of TP53 target gene, Bax, cleavage of PARP, and nuclei condensation. Taken together, NADPH abrogated MPTP-induced p38MAPK phosphorylation, TP53 nuclear translocation, and Bax induction, and finally, MPTP/MPP⁺-induced apoptosis of DA neurons. This study suggests that NADPH may be a novel therapeutic candidate for PD.

Reduced Nicotinamide Adenine Dinucleotide Phosphate Inhibits MPTP-Induced Neuroinflammation and Neurotoxicity

It is generally believed that oxidative stress and neuroinflammation are implicated in the pathogenesis of Parkinson's disease (PD). Reduced nicotinamide adenine dinucleotide phosphate (NADPH) has been demonstrated to have potent neuroprotective effects against oxidative stress. In the present research, we investigated if NADPH could offer neuroprotection by inhibiting glia-mediated neuroinflammation induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a mechanism contributing to PD pathogenesis. The current data demonstrated that MPTP/MPP+ increased levels of reactive oxygen species (ROS), activated glial cells, and inflammasome proteins in the substantia nigra (SNpc), in addition to inducing the nuclear translocation of nuclear factor-κB (NF-κB) and phosphorylation of p38 MAPK. These responses were inhibited by supplementation of exogenous NADPH. Moreover, NADPH effectively decreased MPP+-induced excessive production of ROS, p38 phosphorylation and inflammatory protein of Cyclooxygenase2 (COX2) in cultured microglial BV-2 cells in vitro studies. Similarly, the p38 MAPK inhibitor SB203580 suppressed the upregulation of MPP+-induced p38 phosphorylation and COX2 protein levels. Co-culture of neuronal cells with MPP+-primed BV-2 cells increased the levels of tumor necrosis factor-alpha (TNF-α) and induced cell death of neuronal cells. These effects were diminished by TNF-α neutralizing antibody and NADPH. NADPH reduced motor dysfunction and the loss of dopaminergic (DA) cells induced by MPTP. Therefore, the present study demonstrates that NADPH protects DA neurons by inhibiting oxidative stress and glia-mediated neuroinflammation both in vitro and in vivo, thus suggesting a potential of clinical application for PD and other neurodegenerative diseases.

The diverse role of TIGAR in cellular homeostasis and cancer

TP53-induced glycolysis and apoptosis regulator (TIGAR) is a p53 target protein that plays critical roles in glycolysis and redox balance. Accumulating evidence shows that TIGAR is highly expressed in cancer. TIGAR redirects glycolysis and promotes carcinoma growth by providing metabolic intermediates and reductive power derived from pentose phosphate pathway (PPP). The expression of TIGAR in cancer is positively associated with chemotherapy resistance, suggesting that TIGAR could be a novel therapeutic target. In this review, we briefly presented the function of TIGAR in metabolic homeostasis in normal and cancer cells. Finally, we discussed the future directions of TIGAR research in cancer.

Metabolic features and regulation of the healing cycle-A new model for chronic disease pathogenesis and treatment

Without healing, multicellular life on Earth would not exist. Without healing, one injury predisposes to another, leading to disability, chronic disease, accelerated aging, and death. Over 60% of adults and 30% of children and teens in the United States now live with a chronic illness. Advances in mass spectrometry and metabolomics have given scientists a new lens for studying health and disease. This study defines the healing cycle in metabolic terms and reframes the pathophysiology of chronic illness as the result of metabolic signaling abnormalities that block healing and cause the normal stages of the cell danger response (CDR) to persist abnormally. Once an injury occurs, active progress through the stages of healing is driven by sequential changes in cellular bioenergetics and the disposition of oxygen and carbon skeletons used for fuel, signaling, defense, repair, and recovery. >100 chronic illnesses can be organized into three persistent stages of the CDR. One hundred and two targetable chemosensory G-protein coupled and ionotropic receptors are presented that regulate the CDR and healing. Metabokines are signaling molecules derived from metabolism that regulate these receptors. Reframing the pathogenesis of chronic illness in this way, as a systems problem that maintains disease, rather than focusing on remote trigger(s) that caused the initial injury, permits new research to focus on novel signaling therapies to unblock the healing cycle, and restore health when other approaches have failed.

Protective Effect of Nicotinamide Adenine Dinucleotide Phosphate on Renal Ischemia-Reperfusion Injury

BACKGROUND/AIMS

Renal ischemia-reperfusion injury (IRI) is a common consequence of acute kidney injury. Nicotinamide adenine dinucleotide phosphate (NADPH), which is derived from the pentose phosphate pathway, is essential for the proper functioning of essential redox and antioxidant defense systems. Previous studies have indicated that NADPH is responsible for protecting the brain from ischemic injury. The goal of this study was to analyze the protective function of NADPH in renal IRI.

METHODS

The IRI animal model was generated through a midline laparotomy surgery that clamped both sides of the renal pedicles for 40 min to induce renal ischemia. The in vitro model was generated by removing oxygen and glucose from human kidney epithelial cells (HK-2 cells), followed by reoxygenation to imitate IRI. Renal function and histopathological changes were observed and evaluated. Additionally, malondialdehyde and glutathione levels were determined in renal tissue homogenate as indicators of oxidative stress. ROS production in cells was determined by DHE staining. Protein biomarker expression was evaluated by western blot, apoptosis was analyzed by TUNEL staining, and p65 nuclear translocation was visualized by immunofluorescence.

RESULTS

Our data indicated that NADPH safeguarded the kidneys from histological and functional damage, and significantly reduce cell injury along with preventing potential increases in blood urea nitrogen and creatinine levels. Furthermore, we observed that NADPH increased glutathione levels, while reducing levels of malondialdehyde and reactive oxygen species. Additionally, our results suggested that NADPH treatment may alleviate IRI-induced apoptosis and inflammation.

CONCLUSION

NADPH treatment may protect against renal IRI and should be further developed as a new treatment for acute kidney injury.

Sphingosine kinase 2 activates autophagy and protects neurons against ischemic injury through interaction with Bcl-2 via its putative BH3 domain

Our previous findings suggest that sphingosine kinase 2 (SPK2) mediates ischemic tolerance and autophagy in cerebral preconditioning. The aim of this study was to determine by which mechanism SPK2 activates autophagy in neural cells. In both primary murine cortical neurons and HT22 hippocampal neuronal cells, overexpression of SPK2 increased LC3II and enhanced the autophagy flux. SPK2 overexpression protected cortical neurons against oxygen glucose deprivation (OGD) injury, as evidenced by improvement of neuronal morphology, increased cell viability and reduced lactate dehydrogenase release. The inhibition of autophagy effectively suppressed the neuroprotective effect of SPK2. SPK2 overexpression reduced the co-immunoprecipitation of Beclin-1 and Bcl-2, while Beclin-1 knockdown inhibited SPK2-induced autophagy. Both co-immunoprecipitation and GST pull-down analysis suggest that SPK2 directly interacts with Bcl-2. SPK2 might interact to Bcl-2 in the cytoplasm. Notably, an SPK2 mutant with L219A substitution in its putative BH3 domain was not able to activate autophagy. A Tat peptide fused to an 18-amino acid peptide encompassing the native, but not the L219A mutated BH3 domain of SPK2 activated autophagy in neural cells. The Tat-SPK2 peptide also protected neurons against OGD injury through autophagy activation. These results suggest that SPK2 interacts with Bcl-2 via its BH3 domain, thereby dissociating it from Beclin-1 and activating autophagy. The observation that Tat-SPK2 peptide designed from the BH3 domain of SPK2 activates autophagy and protects neural cells against OGD injury suggest that this structure may provide the basis for a novel class of therapeutic agents against ischemic stroke.

TIGAR knockdown radiosensitizes TrxR1-overexpressing glioma in vitro and in vivo via inhibiting Trx1 nuclear transport

The up-regulation of thioredoxin reductase-1 (TrxR1) is detected in more than half of gliomas, which is significantly associated with increased malignancy grade and recurrence rate. The biological functions of NADPH-dependent TrxR1 are mainly associated with reduced thioredoxin-1 (Trx1) which plays critical roles in cellular redox signaling and tumour radio-resistance. Our previous work has proved that TP53 induced glycolysis and apoptosis regulator (TIGAR) knockdown could notably radiosensitize glioma cells. However, whether TrxR1-overexpressing glioma cells could be re-radiosensitized by TIGAR silence is still far from clear. In the present study, TrxR1 was stably over-expressed in U-87MG and T98G glioma cells. Both in vitro and in vivo data demonstrated that the radiosensitivity of glioma cells was considerably diminished by TrxR1 overexpression. TIGAR abrogation was able to radiosensitize TrxR1-overexpressing gliomas by inhibiting IR-induced Trx1 nuclear transport. Post-radiotherapy, TIGAR low-expression predicted significant longer survival time for animals suffering from TrxR1-overexpessing xenografts, which suggested that TIGAR abrogation might be a promising strategy for radiosensitizing TrxR1-overexpressing glial tumours.