Akt and Erk1/2 activate the ornithine decarboxylase/polyamine system in cardioprotective ischemic preconditioning in rats: the role of mitochondrial permeability transition pores

LncRNA-MEG3 Mediated Diabetic Cerebral Ischemia-Reperfusion Injury-Induced Apoptosis via Modulating Interaction Between Annexin A2 and Akt in Mitochondria

BACKGROUND

In clinical domains, encompassing neurosurgery and macrovascular cardiac procedures, certain interventions result in cerebral ischemia- reperfusion injury (CIRI). Diabetes mellitus (DM) increases the risk of CIRI and worsens the severity of neurological impairment. It was documented that lncRNA-MEG3 contributed to the pathogenesis of CIRI. However, the pivotal significance of lncRNA-MEG3 in diabetic CIRI has never been studied.

AIMS

This study's aims were two-fold, to (1) figure out the influence of lncRNA-MEG3 on neurological dysfunction subsequent to diabetic cerebral ischemic injury, (2) elucidate its potential role in mitochondria-related apoptosis via modulating the Anxa2 signaling pathway.

MATERIALS AND METHODS

We mainly collected plasma from clinical patients to measure the expression of lncRNA-MEG3, and explored the molecular mechanism of lncRNA-MEG3 in CIRI combined with DM by immunofluorescence, western blot, co-ip and other molecular biology experiments in rat MACO+DM model and cellular OGD/R+HG model.

RESULTS

LncRNA-MEG3 expression in DM+AIS cases was remarkably higher than that in cases with AIS and healthy controls. Moreover, lncRNA-MEG3 expression was strongly linked to the National Institutes of Health Stroke Scale (NIHSS) score. Additionally, the findings unveiled that lncRNA-MEG3 depletion alleviated neurological impairments following CIRI in diabetic rats, and cellular death resulted from Oxygen-glucose deprivation (OGD) plus hyperglycemic reperfusion in rat brain microvascular endothelial cells (RBMVECs) that was concomitant with the increased phosphorylation of Annexin A2 (Anxa2) at Tyr23. Meanwhile, over expression of Anxa2, identified as a lncRNA-MEG3-associated mitochondrial protein, remarkably suppressed mitochondria-derived apoptosis. Importantly, lncRNA-MEG3 knockdown enhanced the mitochondrial translocation of Anxa2 via promoting its phosphorylation at Tyr23 in OGD+HG-treated RBMVECs. Furthermore, Anxa2 enhanced Akt phosphorylation at Ser473 and bound to Akt in mitochondria, which was involved in lncRNA-MEG3 depletion-induced neuroprotection. However, lncRNA-MEG3 mobilized to mitochondria in a Plectin-dependent manner and subsequently impeded the interaction between p-Anxa2 and p-Akt.

DISCUSSION AND CONCLUSION

The outcomes provided clinical evidence that lncRNA-MEG3 appeared as an unfavorable prognostic factor for diabetic CIRI and revealed that lncRNA-MEG3 knockdown could be protective against diabetic CIRI-induced mitochondria-related apoptosis through modulating Anxa2 binding to Akt in mitochondria.

Functional analysis of Ornithine decarboxylase in manipulating the wing dimorphism in Nilaparvata lugens (Stål) (Hemiptera: Delphacidae)

The brown planthopper (BPH, Nilaparvata lugens), a major insect pest of rice, can make a shift in wing dimorphism to adapt to complex external environments. Our previous study showed that NlODC (Ornithine decarboxylase in N. lugens) was involved in wing dimorphism of the brown planthopper. Here, further experiments were conducted to reveal possible molecular mechanism of NlODC in manipulating the wing dimorphism. We found that the long-winged rate (LWR) of BPH was significantly reduced after RNAi of NlODC or injection of DFMO (D, L-α-Difluoromethylornithine), and LWR of males and females significantly decreased by 21.7% and 34.6%, respectively. Meanwhile, we also examined the contents of three polyamines under DFMO treatment and found that the contents of putrescine and spermidine were significantly lower compared to the control. After 3rd instar nymphs were injected with putrescine and spermidine, LWR was increased significantly in both cases, and putrescine was a little bit more effective, with 5.6% increase in males and 11.4% in females. Three days after injection of dsNlODC, injection of putrescine and spermidine rescued LWR to the normal levels. In the regulation of wing differentiation in BPH, NlODC mutually antagonistic to NlAkt may act through other signaling pathways rather than the classical insulin signaling pathway. This study illuminated a physiological function of an ODC gene involved in wing differentiation in insects, which could be a potential target for pest control.

Cocoa Flavonoids Reduce Inflammation and Oxidative Stress in a Myocardial Ischemia-Reperfusion Experimental Model

: Consumption of flavonoid-rich nutraceuticals has been associated with a reduction in coronary events. The present study analyzed the effects of cocoa flavonols on myocardial injury following acute coronary ischemia-reperfusion (I/R). A commercially available cocoa extract was identified by chromatographic mass spectrometry. Nineteen different phenolic compounds were identified and 250 mg of flavan-3-ols (procyanidin) were isolated in 1 g of extract. Oral administration of cocoa extract in incremental doses from 5 mg/kg up to 25 mg/kg daily for 15 days in Sprague Dawley rats (n = 30) produced a corresponding increase of blood serum polyphenols and become constant after 15 mg/kg. Consequently, the selected dose (15 mg/kg) of cocoa extract was administered orally daily for 15 days in a treated group (n = 10) and an untreated group served as control (n = 10). Both groups underwent surgical occlusion of the left anterior descending coronary artery and reperfusion. Cocoa extract treatment significantly reversed membrane peroxidation, nitro-oxidative stress, and decreased inflammatory markers (IL-6 and NF-kB) caused by myocardial I/R injury and enhanced activation of both p-Akt and p-Erk1/2. Daily administration of cocoa extract in rats is protective against myocardial I/R injury and attenuate nitro-oxidative stress, inflammation, and mitigates myocardial apoptosis.

The Molecular and Physiological Effects of Protein-Derived Polyamines in the Intestine

Consumption of a high-protein diet increases protein entry into the colon. Colonic microbiota can ferment proteins, which results in the production of protein fermentation end-products, like polyamines. This review describes the effects of polyamines on biochemical, cellular and physiological processes, with a focus on the colon. Polyamines (mainly spermine, spermidine, putrescine and cadaverine) are involved in the regulation of protein translation and gene transcription. In this, the spermidine-derived hypusination modification of EIF5A plays an important role. In addition, polyamines regulate metabolic functions. Through hypusination of EIF5A, polyamines also regulate translation of mitochondrial proteins, thereby increasing their expression. They can also induce mitophagy through various pathways, which helps to remove damaged organelles and improves cell survival. In addition, polyamines increase mitochondrial substrate oxidation by increasing mitochondrial Ca2+-levels. Putrescine can even serve as an energy source for enterocytes in the small intestine. By regulating the formation of the mitochondrial permeability transition pore, polyamines help maintain mitochondrial membrane integrity. However, their catabolism may also reduce metabolic functions by depleting intracellular acetyl-CoA levels, or through production of toxic by-products. Lastly, polyamines support gut physiology, by supporting barrier function, inducing gut maturation and increasing longevity. Polyamines thus play many roles, and their impact is strongly tissue- and dose-dependent. However, whether diet-derived increases in colonic luminal polyamine levels also impact intestinal physiology has not been resolved yet.

Myofibrillogenesis Regulator 1 Rescues Renal Ischemia/Reperfusion Injury by Recruitment of PI3K-Dependent P-AKT to Mitochondria

To investigate whether myofibrillogenesis regulator 1 (MR-1) attenuates renal ischemia/reperfusion (I/R) injury via inhibiting phosphorylated Akt (p-Akt) mitochondrial translocation-mediated opening of the mitochondrial permeability transition pore (mPTP), we injected adenovirus containing MR-1 gene or its siRNAs to the left kidney subcapsular areas of Sprague-Dawley rats, which subsequently underwent experimental renal I/R injury. Renal functions and the severity of the tubular injury were evaluated by the serum creatinine and blood urea nitrogen levels and the pathological scores. We also examined the mitochondrial morphology and functions. Total/p-Akt were assessed by western blot using the mitochondrial and the cytosolic fractions of cortex of renal tissue, respectively. We found that mitochondrial and cytosolic MR-1 levels and mitochondrial p-Akt decreased, and cytosolic p-Akt increased after reperfusion. Subcapsular injection of adenovirus led to higher MR-1 expression in the mitochondria/cytosol, inhibited mPTP opening, and alleviated renal I/R injury; adenovirus injection also upregulated mitochondrial total and p-Akt levels more prominently compared with the normal saline (NS) group. Subcapsular injection of MR-1 siRNAs significantly lowered MR-1 expression and induced renal injury, with increased mPTP opening and mitochondrial damage, similar to I/R injury. MR-1 interacted with Akt in renal cortex homogenate. Wortmannin, a phosphatidylinositol 3 kinase (PI3K) inhibitor, abolished both mitochondrial p-Akt recruitment and the protective effect of MR-1 overexpression on I/R injury. To conclude, MR-1 protects kidney against I/R injury through inhibiting mPTP opening and maintaining mitochondrial integrity, through the recruitment of PI3K-dependent p-Akt to the mitochondria. MR-1 could be a new therapeutic strategy for renal I/R injury.

Exogenous spermine inhibits hypoxia/ischemia-induced myocardial apoptosis via regulation of mitochondrial permeability transition pore and associated pathways

Myocardial infarction (MI) is associated with a high mortality rate, which is attributed to the effects of myocyte loss that occurs as a result of ischemia-induced cell death. Very few therapies can effectively prevent or delay the effects of ischemia. Polyamines (PAs) are polycations required for cell growth and division, and their use may prevent cell loss. The aim of this study was to investigate the relationship between hypoxia/ischemia (H/I)-induced cell apoptosis and PA metabolism and to investigate the ability of spermine to limit H/I injury in cardiomyocytes by blocking the mitochondrial apoptotic pathway. Neonatal rat cardiomyocytes were placed under hypoxic conditions for 24 h after being subjected to 5 μM of spermine as a pretreatment therapy. H/I induced PA catabolism, which was indicated by a 1.3-fold up-regulation of spermidine/spermine N(1)-acetyltransferase expression. Exogenous spermine significantly reduced H/I-induced cell death rate (60 ± 2 to 36 ± 2%) and apoptosis rate (42 ± 2 to 21 ± 2%); it also attenuated lactate dehyodrogenase and creatine kinase leakage (440 ± 13 and 336 ± 16 U/L to 275 ± 15 and 235 ± 13 U/L). Furthermore, it decreases calcium overload (3.8 ± 0.2 to 2.2 ± 0.1 a.u.). Moreover, spermine pretreatment remarkably decreased cytochrome c release from the mitochondria to the cytosol, lowering the expression of cleaved caspase-3 and -9. With spermine pretreatment, there was an increase in Bcl-2 levels and phosphorylation of ERK1/2, phosphoinositide 3-kinase, Akt, and GSK-3β, preserving mitochondrial membrane potential and inducing an mitochondrial permeability transition pore opening. In conclusion, H/I decreased endogenous spermine concentrations in cardiomyocytes, which ultimately induced apoptosis. The addition of exogenous spermine effectively prevented myocyte cell death.

Targets of polyamine dysregulation in major depression and suicide: Activity-dependent feedback, excitability, and neurotransmission

Major depressive disorder (MDD) is a leading cause of disability worldwide characterized by altered neuronal activity in brain regions involved in the control of stress and emotion. Although multiple lines of evidence suggest that altered stress-coping mechanisms underlie the etiology of MDD, the homeostatic control of neuronal excitability in MDD at the molecular level is not well established. In this review, we examine past and current evidence implicating dysregulation of the polyamine system as a central factor in the homeostatic response to stress and the etiology of MDD. We discuss the cellular effects of abnormal metabolism of polyamines in the context of their role in sensing and modulation of neuronal, electrical, and synaptic activity. Finally, we discuss evidence supporting an allostatic model of depression based on a chronic elevation in polyamine levels resulting in self-sustained stress response mechanisms maintained by maladaptive homeostatic mechanisms.

Hes1 is upregulated by ischemic postconditioning and contributes to cardioprotection

The expression of Hes1 is increased following myocardial infarct and other ischemic cardiomyopathies, but the role of Hes1 in cardioprotection provided by ischemic postconditioning (IPost) remains unclear. In this study, we used gain and loss of function approaches to investigate the role of Hes1 in cardioprotection during IPost. Primary cardiac myocytes exposed to ischemia reperfusion injury (IRI) and IPost were used as the experimental model. The results showed that Hes1 expression was increased during myocardial IPost, and Hes1 promoted the viability while inhibited the apoptosis of cardiomyocytes. Moreover, Hes1 inhibited the opening of mitochondrial permeability transition pore (mPTP) and the generation of reactive oxygen species in primary cardiac myocytes exposed to IRI. Mechanistically, we found that Hes1-mediated cardioprotection was related to the downregulation of phosphatase and tensin homolog and the activation of phosphatidylinositol 3-kinase/Akt and signal transducer and activator of transcription 3 signalling. These data demonstrate that Hes1 is upregulated and mediates cardioprotection provided by IPost and suggest that Hes1 is a potential new target for the treatment of ischemic cardiomyopathy.

The detection of thrombin using a mixture of a fluorescent conjugated polyelectrolyte and fibrinogen and implementation of a logic gate

A highly sensitive and selective detection of thrombin is accomplished using an emission color-tunable conjugated polyelectrolyte. An implementation of a combined logic gate was realized upon emission modulation of the system including the polymer, fibrinogen, thrombin, and heparin.