Neuroprotection by leptin in a rat model of permanent cerebral ischemia: effects on STAT3 phosphorylation in discrete cells of the brain

Molecular mechanisms of the effects of photodynamic therapy on the brain: A review of the literature

Malignant gliomas are the most common primary brain tumors in adults. These tumors have a diverse molecular origin and a very poor prognosis. There is a lack of effective treatment at WHO grade IV glioma, and all glioblastomas progress or recur. Current treatments including surgical intervention, radiation therapy, and chemotherapy are insufficient and can cause damage to healthy brain tissue and neurological deficits. The preservation of healthy brain tissue during therapeutic intervention is made extremely difficult by the ability of malignant gliomas to diffusely infiltrate the surrounding brain parenchyma. Photodynamic therapy (PDT) is a treatment modality for glioma that can possibly overcome the inherent shortcommings of traditional therapies. Photodynamic therapy involves the use of a photosensitizer (PS) which, upon absorption of light by photosensitized tissue, triggers photochemical reactions generating reactive oxygen species (ROS) leading to the killing of tumor cells. Research focusing on the effective use of PDT in the treatment of glioma is already underway with promising results. Clinical studies on PDT for the treatment of gliomas have shown it to be a safe therapeutic modality with acceptable levels of side effects. However, some adverse sequelae have been observed during PDT of these tumours, such as increased photosensitivity, increased intracranial pressure or transient aphasia and worsening of pre-existing neurological deficits. Although the clinical sequelae of PDT are well described, the molecular mechanisms of PDT's effects on the healthy brain have not yet been thoroughly characterized. In our work, we attempt to summarize the molecular mechanisms of the effects of photosensitization on neural tissue, brain vasculature and the blood-brain barrier (BBB). We also point to findings presenting molecular approaches to protect the healthy brain from the adverse effects of photodynamic damage.

Nesfatin-1 Neurons in the Ventral Premammillary Nucleus Integrate Metabolic and Reproductive Signals in Male Rats

The ability to reproduce depends on metabolic status. In rodents, the ventral premammillary nucleus (PMv) integrates metabolic and reproductive signals. While leptin (adiposity-related) signaling in the PMv is critical for female fertility, male reproductive functions are strongly influenced by glucose homeostasis. The anorexigenic peptide nesfatin-1 is a leptin-independent central regulator of blood glucose. Therefore, its integrative role in male rats can be assumed. To investigate this, we mapped the distribution of nesfatin-1 mRNA- and protein-producing cells in the PMv during postnatal development via in situ hybridization and immunohistochemistry, respectively. Fos-nesfatin-1, double immunostaining was used to determine the combined effect of heterosexual pheromone challenge and insulin-induced hypoglycemia on neuronal activation in adults. We found that ~75% of the pheromone-activated neurons were nesfatin-1 cells. Hypoglycemia reduced pheromone-induced cell activation, particularly in nesfatin-1 neurons. Immuno-electron microscopy revealed innervation of PMv nesfatin-1 neurons by urocortin3-immunoreactive terminals, reportedly originating from the medial amygdala. Nesfatin-1 immunopositive neurons expressed GPR10 mRNA, a receptor associated with metabolic signaling, but did not respond with accumulation of phosphorylated STAT3 immunopositivity, a marker of leptin receptor signaling, in response to intracerebroventricular leptin treatment. Our results suggest that PMv nesfatin-1 neurons are primarily responsible for integrating reproductive and metabolic signaling in male rats.

Rhynchophylline promotes microglia phenotypic transformation and repair of cerebral ischaemic injury through the JAK2/STAT3 pathway

BACKGROUND

Rhynchophylline (RIN) is an alkaloid known for its ability to effectively block signal transduction related to various neurodegenerative diseases. However, the specific mechanism by which RIN regulates microglial activation and cerebral ischemia remains unexplored. This study aims to investigate the function and molecular pathways through which RIN activates the JAK2/STAT3 signaling cascade, promoting the transformation of microglial phenotypes that contribute to recovery from cerebral ischemic injury.

METHODS

By establishing a microglia oxygen glucose deprivation/reoxygenation (OGD/R) model and a middle cerebral artery occlusion animal model, we assessed changes in the expression of phenotype-specific marker factors for M1 and M2 microglia, as well as key proteins in the JAK2/STAT3 pathway, utilizing ELISA and Western blot techniques. Histological examination, including HE staining, TUNEL assay, and immunofluorescence, was employed to evaluate pathological changes in brain tissue, along with cell apoptosis and proliferation.

RESULTS

The results indicated that microglial activity was significantly reduced and shifted towards the M1 phenotype following OGD/R. However, RIN treatment reversed these changes. When JAK2/STAT3 inhibitors were combined with RIN, it inhibited RIN's protective effect. Animal studies have shown that RIN reduces histopathological changes associated with cerebral ischemia. Additionally, RIN inhibited microglial proliferation in ischemic cortical tissue and increased the expression of M2-type marker proteins, as well as the levels of phosphorylated JAK2 and STAT3 in the ischemic tissue.

CONCLUSION

In conclusion, this study indicates that RIN may protect against cerebral ischemic injury by activating the JAK2/STAT3 pathway, which promotes the transition of microglia to the M2 phenotypic.

Novel Leptin-Based Therapeutic Strategies to Limit Synaptic Dysfunction in Alzheimer's Disease

Accumulation of hyper-phosphorylated tau and amyloid beta (Aβ) are key pathological hallmarks of Alzheimer's disease (AD). Increasing evidence indicates that in the early pre-clinical stages of AD, phosphorylation and build-up of tau drives impairments in hippocampal excitatory synaptic function, which ultimately leads to cognitive deficits. Consequently, limiting tau-related synaptic abnormalities may have beneficial effects in AD. There is now significant evidence that the hippocampus is an important brain target for the endocrine hormone leptin and that leptin has pro-cognitive properties, as activation of synaptic leptin receptors markedly influences higher cognitive processes including learning and memory. Clinical studies have identified a link between the circulating leptin levels and the risk of AD, such that AD risk is elevated when leptin levels fall outwith the physiological range. This has fuelled interest in targeting the leptin system therapeutically. Accumulating evidence supports this possibility, as numerous studies have shown that leptin has protective effects in a variety of models of AD. Recent findings have demonstrated that leptin has beneficial effects in the preclinical stages of AD, as leptin prevents the early synaptic impairments driven by tau protein and amyloid β. Here we review recent findings that implicate the leptin system as a potential novel therapeutic target in AD.

Reduction of acute radiation-induced brain injury in rats by anlotinib

OBJECTIVES

Radiation therapy in the treatment of brain tumors also leads to the occurrence of radiation brain injury (RBI). Anlotinib is a small-molecule inhibitor of multi-receptor tyrosine kinase with high selectivity for vascular endothelial growth factor receptor-2. In this study, we constructed a rat model of RBI and investigated the effect of anlotinib on RBI and its mechanism of action through drug intervention during the acute phase of RBI.

METHODS

Six-week-old male (Sprague-Dawley) rats were used to construct an animal model of RBI to evaluate the protective effect of anlotinib on acute RBI by histopathological staining, brain edema determination, blood-brain barrier integrity evaluation and quick real time-polymerase chain reaction , ELISA detection of inflammation-related indexes, and western-blot detection of related gene protein expression.

RESULTS

Anlotinib reduced the degree of edema in the hippocampal region of rats, improved the pathological morphology of neural cells and vascular endothelial cells, and decreased blood-brain barrier permeability. Anlotinib reduced glial fibrillary acidic protein protein expression in the hippocampal region of rat brain tissue and inhibited astrocyte activation. It inhibited the release of inflammatory factors (interleukin [IL]-6, IL-8 and vascular endothelial growth factor) and down-regulated the expression of janus kinase-2/signal transducer and activator of transcription-3 (JAK2/STAT3) signaling pathway-related proteins.

CONCLUSION

This study found that anlotinib has a protective effect against RBI in rats and anlotinib may be a new candidate for the treatment of RBI.

Leptin Promotes the Proliferation and Neuronal Differentiation of Neural Stem Cells through the Cooperative Action of MAPK/ERK1/2, JAK2/STAT3 and PI3K/AKT Signaling Pathways

The potential of neural stem cells (NSCs) for neurological disorders the treatment has relied in large part upon identifying the NSCs fate decision. The hormone leptin has been reported to be a crucial regulator of brain development, able to influence the glial and neural development, yet, the underlying mechanism of leptin acting on NSCs' biological characteristics is still poorly understood. This study aims to investigate the role of leptin in the biological properties of NSCs. In this study, we investigate the possibility that leptin may regulate the NSCs' fate decision, which may promote the proliferation and neuronal differentiation of NSCs and thus act positively in neurological disorders. NSCs from the embryonic cerebral cortex were used in this study. We used CCK-8 assay, ki67 immunostaining, and FACS analysis to confirm that 25-100 ng/mL leptin promotes the proliferation of NSCs in a concentration-dependent pattern. This change was accompanied by the upregulation of p-AKT and p-ERK1/2, which are the classical downstream signaling pathways of leptin receptors b (LepRb). Inhibition of PI3K/AKT or MAPK/ERK signaling pathways both abolished the effect of leptin-induced proliferation. Moreover, leptin also enhanced the directed neuronal differentiation of NSCs. A blockade of the PI3K/AKT pathway reversed leptin-stimulated neurogenesis, while a blockade of JAK2/STAT3 had no effect on it. Taken together, our results support a role for leptin in regulating the fate of NSCs differentiation and promoting NSCs proliferation, which could be a promising approach for brain repair via regulating the biological characteristics of NSCs.

Relationship Between Adipokines, Cognition, and Brain Structures in Old Age Depending on Obesity

BACKGROUND

Adipokines such as leptin and adiponectin are associated with cognitive function. Although adiposity crucially affects adipokine levels, it remains unclear whether the relationship between adipokines and cognition is influenced by obesity.

METHODS

We enrolled 171 participants and divided them into participants with obesity and without obesity to explore the effect of obesity on the relationship between adipokines and cognition. In addition to plasma levels of leptin and adiponectin, multidomain cognitive functions and brain structures were assessed using neuropsychological testing and magnetic resonance imaging. Association between levels of these adipokines and Alzheimer's disease (AD) was then assessed by logistic regression.

RESULTS

We found that cognitive function was negatively associated with leptin levels and leptin-to-adiponectin ratio (LAR). Such correlations between leptin and cognitive domains were prominent in participants with obesity but were not observed in those without obesity. Leptin levels were associated with lower hippocampal volumes in participants with obesity. A significant interaction of leptin and obesity was found mostly in the medial temporal lobe. Both leptin and LAR were positively associated with insulin resistance and inflammation markers in all participants. Of note, LAR was associated with a higher risk of AD after adjusting for demographic variables, Apolipoprotein E genotype, and body mass index.

CONCLUSIONS

Obesity might be a factor that determines how adipokines affect brain structure and cognition. Leptin resistance might influence the relationship between adipokines and cognition. In addition, LAR rather than each adipokine levels alone may be a better indicator of AD risk in older adults with metabolic stress.

Neuroprotective effect of leptin on a primate model of cerebral ischemia

The purpose of this study was to evaluate the neuroprotective effect of leptin on a non-human primate model of cerebral ischemia. A total of 39 Guangxi macaques were used to establish the primate cerebral-ischemia model. HE staining was used to evaluated the pathological changes. Moreover, magnetic resonance imaging was used for the detection of embolic area. The measurements of behavior observation and cerebral infarction area were also performed. They all received autologous thrombus operation. Furthermore, western blot and RT-PCR were also used to detect the protein and mRNA expression levels of apoptosis-related factors. Our results showed that leptin could reduce the volume of cerebral infarction by about 35%. Behavioral defects can be significantly improved. In addition, mid-term and long-term behavioral deficiencies had been significantly improved by leptin. Moreover, leptin significantly decreased the expression levels of caspase-3 and Bax, and increased the expression levels of Bcl-2. In conclusion, leptin has neuroprotective effects on cerebral ischemia by effectively reducing the volume of cerebral infarction.

Bibliometric analysis of tumor necrosis factor in post-stroke neuroinflammation from 2003 to 2021

Objective

Tumor necrosis factor (TNF), a crucial cytokine, has important research value in post-stroke neuroinflammation (PSN). We analyzed the studies that have been conducted in this area and used bibliometric methods to predict research hotspots and identify trends regarding TNF in PSN.

Methods

Publications were accessed at the Science Citation Index Expanded 1975-2021 (SCI expanded), Web of Science Core Collection (WoSCC), on May 1, 2022. Additionally, software such as CiteSpace and VOSviewer were utilized for bibliometric analyses.

Results

In total, 1391 original articles and reviews on TNF in PSN published from 2003 to 2021 were identified. An upward trend was observed in the number of publications on TNF in PSN. These publications were primarily from 57 countries and 1446 institutions, led by China and the United States with China leading the number of publications (NP) and the US with the number of citations (NC). The League of European Research Universities (LERU) and Journal of Neuroinflammation, respectively were the most prolific branches and journals. Zhang, John H. published the most papers and Finsen, Bente had the most cited papers. One paper by Kettenmann, H. published in 2011 reached the highest level of Global Citation Score (GCS). The keyword co-occurrence and reference co-citation analyses suggest that poststroke therapy and potential mechanistic pathways are important topics related to PSN in recent years. Reference burst detection suggests new burst hotspots after 2015, focusing on pathway modulation and discovery of therapeutic targets, suggesting a substantial development in the study of TNF in PSN research.

Conclusion

The present bibliometric analysis shows a continuous trend of increasing literature related to TNF in PSN, and shows that TNF plays an important role in PSN involves multiple immune mechanisms and may contribute as a potential target for neuroprotective therapeutics after stroke. Prior to 2011, most of the research was focused on discovering the specific role of TNF in PSN, and in recent years studies have mainly targeted the exploration of the signaling pathways. Future research prospects may lie in finding key therapeutic targets in pathway of TNF in PSN.

Role of Endothelial STAT3 in Cerebrovascular Function and Protection from Ischemic Brain Injury

STAT3 plays a protective role against ischemic brain injury; however, it is not clear which brain cell type mediates this effect, and by which mechanism. We tested the hypothesis that endothelial STAT3 contributes to protection from cerebral ischemia, by preserving cerebrovascular endothelial function and blood-brain barrier (BBB) integrity. The objective of this study was to determine the role of STAT3 in cerebrovascular endothelial cell (EC) survival and function, and its role in tissue outcome after cerebral ischemia. We found that in primary mouse brain microvascular ECs, STAT3 was constitutively active, and its phosphorylation was reduced by oxygen-glucose deprivation (OGD), recovering after re-oxygenation. STAT3 inhibition, using two mechanistically different pharmacological inhibitors, increased EC injury after OGD. The sub-lethal inhibition of STAT3 caused endothelial dysfunction, demonstrated by reduced nitric oxide release in response to acetylcholine and reduced barrier function of the endothelial monolayer. Finally, mice with reduced endothelial STAT3 (Tie2-Cre; STAT3flox/wt) sustained larger brain infarcts after middle cerebral artery occlusion (MCAO) compared to wild-type (WT) littermates. We conclude that STAT3 is vital to maintaining cerebrovascular integrity, playing a role in EC survival and function, and protection against cerebral ischemia. Endothelial STAT3 may serve as a potential target in preventing endothelial dysfunction after stroke.

Neuroinflammation in Cerebral Ischemia and Ischemia/Reperfusion Injuries: From Pathophysiology to Therapeutic Strategies

Its increasing incidence has led stroke to be the second leading cause of death worldwide. Despite significant advances in recanalization strategies, patients are still at risk for ischemia/reperfusion injuries in this pathophysiology, in which neuroinflammation is significantly involved. Research has shown that in the acute phase, neuroinflammatory cascades lead to apoptosis, disruption of the blood-brain barrier, cerebral edema, and hemorrhagic transformation, while in later stages, these pathways support tissue repair and functional recovery. The present review discusses the various cell types and the mechanisms through which neuroinflammation contributes to parenchymal injury and tissue repair, as well as therapeutic attempts made in vitro, in animal experiments, and in clinical trials which target neuroinflammation, highlighting future therapeutic perspectives.

Neferine Protects Against Brain Damage in Permanent Cerebral Ischemic Rat Associated with Autophagy Suppression and AMPK/mTOR Regulation

Neferine is the major alkaloid compound isolated from the seed embryos of lotus. Neferine has many pharmacological effects, such as anti-inflammatory, antioxidative stress, and antiapoptotic effects, and it maintains autophagic balance. The purpose of this study was to explore the mechanism by which neferine attenuates autophagy after permanent cerebral ischemia in rats. We performed permanent cerebral ischemia in rats by middle cerebral artery occlusion (pMCAO) for 12 h with or without administration of neferine or nimodipine, a calcium (Ca²⁺) channel blocker. Neuroprotective effects were determined by evaluating the infarct volume and neurological deficits. Autophagy and its signaling pathway were determined by evaluating the expression of phosphorylated AMP-activated protein kinase alpha (AMPKα), phosphorylated mammalian target of rapamycin (mTOR), beclin-1, microtubule-associated protein 1A/1B-light chain 3 class II (LC3-II), and p62 by western blotting. Autophagosomes were evaluated by transmission electron microscopy. Neferine treatment significantly reduced infarct volumes and improved neurological deficits. Neferine significantly attenuated the upregulation of autophagy-associated proteins such as LC3-II, beclin-1, and p62 as well as autophagosome formation, all of which were induced by pMCAO. Neferine exerted remarkable protection against cerebral ischemia, possibly via the regulation of autophagy mediated by the Ca²⁺-dependent AMPK/mTOR pathway.

The bidirectional role of the JAK2/STAT3 signaling pathway and related mechanisms in cerebral ischemia-reperfusion injury

The Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) signaling pathway, a well-conserved and basic intracellular signaling cascade, is mostly inactivated under basal conditions, although it can be phosphorylated under extracellular stimulation; in addition, it can influence the transcription and expression of multiple genes involved in biological processes such as cellular growth, metabolism, differentiation, degradation and angiogenesis. The inflammatory response, apoptosis, oxidative stress and angiogenesis are the main factors involved in the pathogenesis of ischemic stroke. Numerous studies have confirmed that the JAK2/STAT3 axis can be activated rapidly by ischemic stress, which is closely related to the regulation of these important pathological processes. However, different opinions on the specific role of this signaling pathway remain. In this paper, we review and summarize previous studies on the JAK2/STAT3 pathway in ischemic stroke.

The Neuronal Actions of Leptin and the Implications for Treating Alzheimer's Disease

It is widely accepted that the endocrine hormone leptin controls food intake and energy homeostasis via activation of leptin receptors expressed on hypothalamic arcuate neurons. The hippocampal formation also displays raised levels of leptin receptor expression and accumulating evidence indicates that leptin has a significant impact on hippocampal synaptic function. Thus, cellular and behavioural studies support a cognitive enhancing role for leptin as excitatory synaptic transmission, synaptic plasticity and glutamate receptor trafficking at hippocampal Schaffer collateral (SC)-CA1 synapses are regulated by leptin, and treatment with leptin enhances performance in hippocampus-dependent memory tasks. Recent studies indicate that hippocampal temporoammonic (TA)-CA1 synapses are also a key target for leptin. The ability of leptin to regulate TA-CA1 synapses has important functional consequences as TA-CA1 synapses are implicated in spatial and episodic memory processes. Moreover, degeneration is initiated in the TA pathway at very early stages of Alzheimer's disease, and recent clinical evidence has revealed links between plasma leptin levels and the incidence of Alzheimer's disease (AD). Additionally, accumulating evidence indicates that leptin has neuroprotective actions in various AD models, whereas dysfunctions in the leptin system accelerate AD pathogenesis. Here, we review the data implicating the leptin system as a potential novel target for AD, and the evidence that boosting the hippocampal actions of leptin may be beneficial.

Uric Acid Neuroprotection Associated to IL-6/STAT3 Signaling Pathway Activation in Rat Ischemic Stroke

Despite the promising neuroprotective effects of uric acid (UA) in acute ischemic stroke, the seemingly pleiotropic underlying mechanisms are not completely understood. Recent evidence points to transcription factors as UA targets. To gain insight into the UA mechanism of action, we investigated its effects on pertinent biomarkers for the most relevant features of ischemic stroke pathophysiology: (1) oxidative stress (antioxidant enzyme mRNAs and MDA), (2) neuroinflammation (cytokine and Socs3 mRNAs, STAT3, NF-κB p65, and reactive microglia), (3) brain swelling (Vegfa, Mmp9, and Timp1 mRNAs), and (4) apoptotic cell death (Bcl-2, Bax, caspase-3, and TUNEL-positive cells). Adult male Wistar rats underwent intraluminal filament transient middle cerebral artery occlusion (tMCAO) and received UA (16 mg/kg) or vehicle (Locke's buffer) i.v. at 20 min reperfusion. The outcome measures were neurofunctional deficit, infarct, and edema. UA treatment reduced cortical infarct and brain edema, as well as neurofunctional impairment. In brain cortex, increased UA: (1) reduced tMCAO-induced increases in Vegfa and Mmp9/Timp1 ratio expressions; (2) induced Sod2 and Cat expressions and reduced MDA levels; (3) induced Il6 expression, upregulated STAT3 and NF-κB p65 phosphorylation, induced Socs3 expression, and inhibited microglia activation; and (4) ameliorated the Bax/Bcl-2 ratio and induced a reduction in caspase-3 cleavage as well as in TUNEL-positive cell counts. In conclusion, the mechanism for morphological and functional neuroprotection by UA in ischemic stroke is multifaceted, since it is associated to activation of the IL-6/STAT3 pathway, attenuation of edematogenic VEGF-A/MMP-9 signaling, and modulation of relevant mediators of oxidative stress, neuroinflammation, and apoptotic cell death.

Chronic exposure to methylmercury enhances the anorexigenic effects of leptin in C57BL/6J male mice

Several studies have demonstrated that heavy metals disrupt energy homeostasis. Leptin inhibits food intake and decreases body weight through activation of its receptor in the hypothalamus. The impact of heavy metals on leptin signaling in the hypothalamus is unclear. Here, we show that the environmental pollutant, methylmercury (MeHg), favors an anorexigenic profile in wild-type males. C57BL/6J mice were exposed to MeHg via drinking water (5 ppm) up to 30 days. Our data shows that MeHg exposure was associated with changes in leptin induced activation of Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway in the hypothalamus. In males, the activation of JAK2/STAT3 signaling pathway was sustained by an increase in SOCS3 protein levels. In females, MeHg-activated STAT3 was inhibited by a concomitant increase in PTP1B. Taken together, our data suggest that MeHg enhanced leptin effects in males, favoring an anorexigenic profile in males, which notably, have been shown to be more sensitive to the neurological effects of this organometal than females. A better understanding of MeHg-induced molecular mechanism alterations in the hypothalamus advances the understanding of its neurotoxicity and provides molecular sites for novel therapies.

Leptin protects brain from ischemia/reperfusion-induced infarction by stabilizing the blood-brain barrier to block brain infiltration by the blood-borne neutrophils

The cellular and molecular mechanisms underlying leptin-mediated brain protection against cerebral ischemia were investigated at the blood-brain barrier (BBB) and neutrophil level. Through the ischemia/reperfusion (I/R) animal model, we found that leptin expression level was significantly decreased in ischemic hemisphere. Brain injection with leptin (15 μg/kg, intracisternally) could block the I/R-increased BBB permeability, activation of matrix metallopeptidase 9 (MMP-9) and brain infiltration of blood-borne neutrophils to reduce the infarct volume of ischemic brain. The brain expression level of tight junction protein ZO-1 as well as number and motility of neutrophils in blood was all increased by the same injection, indicating BBB stability (rather than reduction in neutrophils) played a major role in the leptin-inhibited brain infiltration of neutrophils. Leptin-mediated protection of BBB was further confirmed in vitro, through a BBB cellular model under the in vitro ischemic condition (G/R: glucose-oxygen-serum deprivation followed by GOS restoration). The results showed that leptin again could block the G/R-increased neutrophil adherence to EC layer as well as BBB permeability, likely by stimulating the endothelial expression of ZO-1 and VE-Cadherin. The study has demonstrated that leptin could protect ischemic brain via multiple ways (other than neuronal protection), by inhibiting the BBB permeability, brain infiltration of the blood-borne neutrophils and neutrophil adherence to vascular ECs. The role of leptin in vascular biology of stroke could further support its therapeutic potential in other neurodegenerative diseases, associated with BBB disorder.

Neuroprotective effects of leptin on cerebral ischemia through JAK2/STAT3/PGC-1-mediated mitochondrial function modulation

Neuroprotective effects of leptin have been shown in mouse model of cerebral ischemia/reperfusion injury and primary cortical neuronal culture with oxygen-glucose deprivation (OGD), while the underlying mechanisms are less understood. In the present study, we investigated whether leptin modulated mitochondrial function through JAK2/STAT3 in vivo mouse model of transient middle cerebral artery occlusion (MCAO) and in OGD-challenged primary neuronal cultures. JAK2/STAT3; mitochondrial biogenesis markers (PGC-1α); and apoptosis-associated proteins (caspase-3, BCL-2, BCL-XL, and cytochrome c) were detected by western blotting and reverse transcription-polymerase chain reaction at 1 h before and after ischemia/reperfusion. P-STAT3 and PGC-1α in neurons and astrocytes were detected. Moreover, mitochondrial morphology of the ischemic ipsilateral penumbra is examined using transmission electron microscopy. Primary cerebral cortical neurons were evaluated for viability, mitochondrial membrane potential (MMP), and apoptosis to assess whether dose-dependent neuroprotective effects of leptin during OGD were mitigated by the JAK2/STAT3 inhibitor AG490. Leptin activated JAK2/STAT3 signaling in neurons and astrocytes distributed in the ischemic ipsilateral penumbra, with peak p-STAT3 levels observed at 1 h after reperfusion. Leptin increased PGC-1α, BCL-2, and BCL-XL protein levels, cell viability, and MMP and decreased apoptosis both in vitro and in vivo; these effects were reversed by AG490 treatment. Our findings suggest that leptin-mediated neuroprotective effects in tMCAO may peak at 1 h to induce the transcription of its target gene PGC-1α, stabilization of MMP, inhibition of mitochondrial permeability transition pore opening, release of cytochrome c, and apoptosis.

Azithromycin Affords Neuroprotection in Rat Undergone Transient Focal Cerebral Ischemia

Repurposing existing drugs represents a promising approach for successful development of acute stroke therapies. In this context, the macrolide antibiotic azithromycin has been shown to exert neuroprotection in mice due to its immunomodulatory properties. Here, we have demonstrated that acute administration of a single dose of azithromycin upon reperfusion produces a dose-dependent (ED₅₀ = 1.40 mg/kg; 95% CI = 0.48-4.03) reduction of ischemic brain damage measured 22 h after transient (2 h) middle cerebral artery occlusion (MCAo) in adult male rats. Neuroprotection by azithromycin (150 mg/kg, i.p., upon reperfusion) was associated with a significant elevation of signal transducer and activator of transcription 3 (STAT3) phosphorylation in astrocytes and neurons of the peri-ischemic motor cortex as detected after 2 and 22 h of reperfusion. By contrast, in the core region of the striatum, drug administration resulted in a dramatic elevation of STAT3 phosphorylation only after 22 h of reperfusion, being the signal mainly ascribed to infiltrating leukocytes displaying an M2 phenotype. These early molecular events were associated with a long-lasting neuroprotection, since a single dose of azithromycin reduced brain infarct damage and neurological deficit measured up to 7 days of reperfusion. These data, together with the evidence that azithromycin was effective in a clinically relevant time-window (i.e., when administered after 4.5 h of MCAo), provide robust preclinical evidence to support the importance of developing azithromycin as an effective acute therapy for ischemic stroke.

Neuroprotective Effect of SCM-198 through Stabilizing Endothelial Cell Function

Leonurine, also named SCM-198, which was extracted from Herba leonuri, displayed a protective effect on various cardiovascular and brain diseases, like ischemic stroke. Ischemic stroke which is the leading cause of morbidity and mortality, ultimately caused irreversible neuron damage. This study is aimed at exploring the possible therapeutic potential of SCM-198 in the protection against postischemic neuronal injury and possible underlying mechanisms. A transient middle cerebral artery occlusion (tMCAO) rat model was utilized to measure the protective effect of SCM-198 on neurons. TEM was used to determine neuron ultrastructural changes. The brain slices were stained with Nissl staining solution for Nissl bodies. Fluoro-Jade B (FJB) was used for staining the degenerating neurons. In the oxygen-glucose deprivation and re-oxygenation (OGD/R) model of bEnd.3 cells treated with SCM-198 (0.1, 1, 10 μM). Then, the bEnd.3 cells were cocultured with SH-SY5Y cells. Cell viability, MDA level, CAT activity, and apoptosis were examined to evaluate the cytotoxicity of these treatments. Western blot and immunofluorescent assays were used to examine the expression of protein related to the p-STAT3/NOX4/Bcl-2 signaling pathway. Coimmunoprecipitation was performed to determine the interaction between p-STAT3 and NOX4. In the transient middle cerebral artery occlusion (tMCAO) rat model, we found that treatment with SCM-198 could ameliorate neuron morphology and reduce the degenerating cell and neuron loss. In the in vitro model of bEnd.3 cell oxygen-glucose deprivation and reoxygenation (OGD/R), treatment with SCM-198 restored the activity of catalase (CAT), improved the expression of Cu-Zn superoxide dismutase (SOD1), and decreased the malondialdehyde (MDA) production. SCM-198 treatment prevented OGD/R-induced cell apoptosis as indicated by increased cell viability and decreased the number of TUNEL-positive cells, accompanied with upregulation of Bcl-2 and Bcl-xl protein and downregulation Bax protein. The results were consistent with SH-SY5Y cells which coculture with bEnd.3 cells. The forthcoming study revealed that SCM-198 activated the p-STAT3/NOX4/Bcl-2 signaling pathway. All the data indicated that SCM-198 protected against oxidative stress and neuronal damage in in vivo and in vitro injury models via the p-STAT3/NOX4/Bcl-2 signaling pathway. Our results suggested that SCM-198 could be the potential drug for neuroprotective effect through stabilizing endothelial cell function.

Neuroprotective effect of chlorogenic acid in global cerebral ischemia-reperfusion rat model

The ischemic cascade is initiated in the hypoperfused region of the brain that leads to neuronal cell death. Identification of multi-target inhibitor against prominent molecular mediators of ischemic cascade might be a suitable strategy to combat cerebral ischemic stroke. The present study is designed to evaluate the neuroprotective efficacy of chlorogenic acid (CGA) in the global cerebral ischemic rat model. The effective dose of CGA was evaluated on the basis of reduction in cerebral infarction area percentage, Evans blue extravasation, and restoration of brain water content. The expression of tumor necrosis factor-α (TNF-α), inducible nitric oxide synthase (iNOS), and caspase-3 was evaluated by immunohistochemistry and morphological and cellular alterations in the cortex were observed by brain histology. The level of glutamate, calcium, and nitrate in different regions of the brain, as well as cerebrospinal fluid (CSF), was evaluated. The level of calcium and nitrate was compared with ifenprodil-an antagonist of N-methyl-D-aspartate receptor (NMDAR) and 7-nitroindazole-an inhibitor of neuronal nitric oxide synthase (nNOS) respectively. Further, molecular docking was performed to compare the inhibition potential of CGA against NMDAR and nNOS with their inhibitors. Dose optimization results revealed that intranasal administration of CGA (10 mg/kg b.w.) significantly reduced the cerebral infarction area, Evans blue extravasation and restored the brain water content compared with ischemia group. It also significantly reduced the calcium, nitrate, and glutamate levels compared with ischemia group in the cortex, hippocampus cerebellum, and CSF. Immunohistochemical analysis revealed that CGA significantly reduced the expression of TNF-α, iNOS, and caspase-3 as compared with the ischemia group. In molecular docking study, CGA displayed similar binding interaction as that of Ifenprodil and 7-nitroindazole with NMDAR and nNOS respectively. The current findings suggest that the treatment with CGA confers neuroprotection in global ischemic insult by inhibiting and downregulating the different molecular markers of cerebral ischemia.

Protective effects of leptin against cerebral ischemia/reperfusion injury

In recent years, the use of thrombolytic therapy for treating ischemia/reperfusion injury has resulted in damage to the self-regulatory mechanisms of the brain. This is due to the increased production of free radicals, excitatory amino acids and pro-inflammatory cytokines causing secondary damage to the brain. Simple thrombolytic therapy has not been the best approach for treating ischemia/reperfusion injury. Excessive perfusion leads to failure of the body's self-regulatory functions, which in turn increases the area of cerebral edema and aggravates cerebral ischemia. Previous studies have evaluated the satiety hormone leptin as a link between energy expenditure and obesity. Of note, leptin, which is involved in brain development, synaptic transmission and angiogenesis following ischemia/reperfusion injury, has been considered an important factor for treating ischemia/reperfusion injury. The present review outlines the discovery of leptin and discusses its association with cerebral ischemia/reperfusion.

Leptin attenuates cerebral ischemic injury in rats by modulating the mitochondrial electron transport chain via the mitochondrial STAT3 pathway

BACKGROUND

According to recent studies, leptin may exert a neuroprotective function by affecting the phosphorylation of signal transducer and activator of transcription 3 (STAT3). During stress, STAT3 regulates mitochondrial oxidative stress and reduces apoptosis.

OBJECTIVE

In the present study, we hypothesized that leptin increases STAT3 phosphorylation in the mitochondria and protects against mitochondrial oxidative stress in rats subjected to permanent middle cerebral artery occlusion (MCAO).

RESULTS

Leptin reduced reactive oxygen species (ROS) production, and we confirmed that the mechanism underlying this change involved the enzymatic activities of mitochondrial respiratory chain complexes I and II. In addition, leptin increased the level of STAT3 Ser727 phosphorylation in the mitochondria.

CONCLUSIONS

Based on these results, leptin may regulate mitochondrial respiratory chain enzymatic activities via mitochondria-targeted STAT3 to reduce ROS production and protect brain tissues from mitochondrial oxidative stress during cerebral ischemia.

Inhibition of Connexin43 hemichannels with Gap19 protects cerebral ischemia/reperfusion injury via the JAK2/STAT3 pathway in mice

Functional disruption of the neurovascular unit may lead to aggravation of ischemic cerebral injury. Connexin43 (Cx43)-dependent gap junctional channels (GJCs) are critical in maintaining brain homeostasis. However, excessive opening of hemichannels (HCs) after cerebral ischemia may cause apoptosis and finally lead to amplification of ischemic injury. Previous studies indicated that Cx43 mimetic peptides Gap26 and Gap27 may protect cerebral ischemic injury, but the latest studies showed they also inhibit the opening of GJCs, which are beneficial for neuroprotection. Recent studies showed that Gap19 is a new specific inhibitor of Cx43 HCs. We investigated the role of Gap19 on cerebral ischemia/reperfusion (I/R) injury in a mouse model of middle cerebral artery occlusion (MCAO). Ventricle-injected Gap19 significantly alleviated infarct volume, neuronal cell damage and neurological deficits after ischemia, the neuroprotective effect of Gap19 was significant stronger than Gap26. Post-treatment with TAT-Gap19 still provided neuroprotection when it was administered intraperitoneally at 4 h after reperfusion. In addition, we found that Gap19 decreased the levels of cleaved caspase-3 and Bax and increased the level of Bcl-2, suggesting the anti-apoptotic activity of specifically blocking the Cx43 HCs. Furthermore, our data indicate that Gap19 treatment increased the levels of phosphorylated JAK2 and STAT3 both in vivo and in vitro. Gap19 inhibited hemichannel activity assessed by dye uptake in astrocytes. And we detected that pSTAT3 co-localized with Cx43 together in astrocytes after oxygen glucose deprivation (OGD) injury. Finally, AG490, a blocker of the JAK2/STAT3 pathway, could reverse the neuroprotective effects of Gap19 both in vivo and in vitro. Our experiment investigated the anti-apoptotic activity of Gap19, the specific inhibitor of Cx43 HCs, and the potential mechanisms. Our results demonstrated that Gap19 plays an anti-apoptotic role via activating the JAK2/STAT3 pathway after cerebral I/R injury, indicating that specific blocking of Cx43 HCs is a potential target for ischemic stroke.

Association of higher waist circumference with milder stroke severity in acute ischaemic stroke

OBJECTIVES

Although higher body mass index (BMI) was reported to be associated with increased stroke incidence, having a higher BMI is known to be associated with better clinical outcomes after stroke. However, BMI has shown conflicting associations with baseline stroke severity. The aim of our study was to assess the relationship between waist circumference (WC) at admission and baseline stroke severity among patients with ischaemic stroke.

METHODS

The WC of acute stroke patients was divided into sex-specific quartiles. Baseline stroke severity was categorised as mild [National Institutes of Health Stroke Scale (NIHSS) score 0-4], moderate (NIHSS score 5-10), and severe (NIHSS score ≥11). Multinomial logistic regression was used and reference categories were men or women in the lowest sex-specific WC quartiles who had experienced a mild stroke.

RESULTS

A total of 637 female and 766 male patients were included. The adjusted OR of severe stroke were 1.3 (95% CI, 0.7-2.4) for male patients in the third WC quartile, 0.7 (95% CI, 0.3-1.5) for male patients in the second WC quartile, and 0.4 (95% CI, 0.2-0.8) for male patients in the top WC quartile. The adjusted OR of severe stroke for female patients in the third WC quartile, the second WC quartile, and the top WC quartile were 0.8 (95% CI, 0.4-1.5), 0.4 (95% CI, 0.2-0.9), and 0.7 (95% CI, 0.3-1.3), respectively.

DISCUSSION

Higher WC at admission is associated with milder baseline stroke severity among patients with acute ischaemic stroke.

ABBREVIATIONS

BMI: body mass index; CE: cardioembolism; CI: confidence interval; LAA: large-artery atherosclerosis; NIHSS: National Institutes of Health Stroke Scale; OR: odds ratio; SAO: small-artery occlusion; WC: waist circumference.

The novel exercise-induced hormone irisin protects against neuronal injury via activation of the Akt and ERK1/2 signaling pathways and contributes to the neuroprotection of physical exercise in cerebral ischemia

BACKGROUND

Irisin is a novel exercise-induced myokine involved in the regulation of adipose browning and thermogenesis. In this study, we investigated the potential role of irisin in cerebral ischemia and determined whether irisin is involved in the neuroprotective effect of physical exercise in mice.

MATERIALS AND METHODS

The middle cerebral artery occlusion (MCAO) model was used to produce cerebral ischemia in mice. First, the plasma irisin levels and changes in expression of the irisin precursor protein FNDC5 in skeletal muscle were determined post ischemic stroke. Second, the association between plasma irisin levels and the neurological deficit score, brain infarct volume, or plasma concentrations of tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β in mice with MCAO were evaluated. Third, the therapeutic effect of irisin on ischemic brain injury was evaluated in vivo and in vitro. Recombinant irisin was injected directly into the tail vein 30min after the MCAO operation, and then the effects of irisin treatment on brain infarct volume, neurological deficit, neuroinflammation, microglia activation, monocyte infiltration, oxidative stress and intracellular signaling pathway activation (Akt and ERK1/2) were measured. Irisin was also administered in cultured PC12 neuronal cells with oxygen and glucose deprivation (OGD). Finally, to assess the potential involvement of irisin in the neuroprotection of physical exercise, mice were exercised for 2weeks and an irisin neutralizing antibody was injected into these mice to block irisin 1h before the MCAO operation.

RESULTS

The plasma irisin concentration and intramuscular FNDC5 protein expression decreased after ischemic stroke. Plasma irisin levels were negatively associated with brain infarct volume, the neurological deficit score, plasma TNF-α and plasma IL-6 concentrations. In OGD neuronal cells, irisin protected against cell injury. In mice with MCAO, irisin treatment reduced the brain infarct volume, neurological deficits, brain edema and the decline in body weight. Irisin treatment inhibited activation of Iba-1⁺ microglia, infiltration of MPO-1⁺ monocytes and expression of both TNF-α and IL-6 mRNA. Irisin significantly suppressed the levels of nitrotyrosine, superoxide anion and 4-hydroxynonenal (4-HNE) in peri-infarct brain tissues. Irisin treatment increased Akt and ERK1/2 phosphorylation, while blockade of Akt and ERK1/2 by specific inhibitors reduced the neuroprotective effects of irisin. Finally, the exercised mice injected with irisin neutralizing antibody displayed more severe neuronal injury than the exercised mice injected with control IgG.

CONCLUSION

Irisin reduces ischemia-induced neuronal injury via activation of the Akt and ERK1/2 signaling pathways and contributes to the neuroprotective effect of physical exercise against cerebral ischemia, suggesting that irisin may be a factor linking metabolism and cardio-cerebrovascular diseases.

Tackling myocardial ischemic injury: the signal transducer and activator of transcription 3 (STAT3) at a good site

Myocardial ischemia is one of the main causes of cardiac remodeling and heart failure. As a highly evolutionarily conserved pathway, the signal transducer and activator of transcription 3 (STAT3) signaling controls intercellular communication, signaling transduction and gene transcription. Interestingly, STAT3 signaling has been demonstrated to take part in myocardial ischemia. Furthermore, activation of STAT3 signaling contributes to the protective efficacy of various interventions, including pharmacological and non-pharmacological treatment of myocardial ischemic injury. Areas covered: We first introduce the protective mechanisms of STAT3. We then discuss STAT3 signaling in various cells and the roles of STAT3 in myocardial processes during myocardial ischemia. Finally, the roles of STAT3 in myocardial ischemia and the upstream regulators of STAT3 activation are summarized. Expert opinion: In various animal experiments, STAT3 has been demonstrated to take part in myocardial responses to myocardial ischemic injury and to be activated during various modes of protection against myocardial ischemia and ischemia/reperfusion (I/R) injury. However, further clinical evidence on the role of STAT3 in such protection is needed. Treatments targeting STAT3 as a means of reducing myocardial ischemic injury need to be tested in a clinical setting. Furthermore, biotechnology can be used to develop effective drugs for this purpose.

Diffusion-weighted magnetic resonance imaging reflects activation of signal transducer and activator of transcription 3 during focal cerebral ischemia/reperfusion

Signal transducer and activator of transcription (STAT) is a unique protein family that binds to DNA, coupled with tyrosine phosphorylation signaling pathways, acting as a transcriptional regulator to mediate a variety of biological effects. Cerebral ischemia and reperfusion can activate STATs signaling pathway, but no studies have confirmed whether STAT activation can be verified by diffusion-weighted magnetic resonance imaging (DWI) in rats after cerebral ischemia/reperfusion. Here, we established a rat model of focal cerebral ischemia injury using the modified Longa method. DWI revealed hyperintensity in parts of the left hemisphere before reperfusion and a low apparent diffusion coefficient. STAT3 protein expression showed no significant change after reperfusion, but phosphorylated STAT3 expression began to increase after 30 minutes of reperfusion and peaked at 24 hours. Pearson correlation analysis showed that STAT3 activation was correlated positively with the relative apparent diffusion coefficient and negatively with the DWI abnormal signal area. These results indicate that DWI is a reliable representation of the infarct area and reflects STAT phosphorylation in rat brain following focal cerebral ischemia/reperfusion.

Combination treatment with leptin and pioglitazone in a mouse model of Alzheimer's disease

INTRODUCTION

Combination therapy approaches may be necessary to address the many facets of pathologic change in the brain in Alzheimer's disease (AD). The drugs leptin and pioglitazone have previously been shown individually to have neuroprotective and anti-inflammatory actions, respectively, in animal models.

METHODS

We studied the impact of combined leptin and pioglitazone treatment in 6-month-old APP/PS1 (APPswe/PSEN1dE9) transgenic AD mouse model.

RESULTS

We report that an acute 2-week treatment with combined leptin and pioglitazone resulted in a reduction of spatial memory deficits (Y maze) and brain β-amyloid levels (soluble β-amyloid and amyloid plaque burden) relative to vehicle-treated animals. Combination treatment was also associated with amelioration in plaque-associated neuritic pathology and synapse loss, and also a significantly reduced neocortical glial response.

DISCUSSION

Combination therapy with leptin and pioglitazone ameliorates pathologic changes in APP/PS1 mice and may represent a potential treatment approach for AD.

The role of leptin in central nervous system diseases

Leptin is a peptide hormone produced by adipose tissue and acts in brain centers to control critical physiological functions. Leptin receptors are especially abundant in the hypothalamus and trigger specific neuronal subpopulations, and activate several intracellular signaling events, including the JAK/STAT, MAPK, PI3K, and mTOR pathway. Although most studies focus on its role in energy intake and expenditure, leptin also plays a critical role in many central nervous system diseases.

Serum leptin levels may be correlated with cerebral infarction

BACKGROUND

To investigate the relation between serum leptin levels and cerebral infarction (CI) by meta-analysis.

MATERIALS AND METHODS

Scientific literature databases were searched for studies published in Chinese and English. After retrieving relevant articles through database searches and screening using predefined selection criteria, high-quality studies related to our research topic were selected for inclusion in this meta-analysis. All statistical analyses were conducted using Comprehensive Meta-Analysis 2.0 (CMA 2.0, Biostat Inc., Englewood, New Jersey, USA).

RESULTS

The study results revealed that serum leptin levels were significantly higher in CI patients as compared to normal controls. The outcomes of subgroup analysis by ethnicity suggested that the serum leptin levels in CI patients were significantly higher than normal controls in both Asian and Caucasian populations. Further, subgroup analysis based on the detection method indicated that the serum leptin levels in CI patients were significantly higher compared with normal controls when measured by radioimmunoassay (RIA) but enzyme-linked immunosorbent assay (ELISA)-based measurements did not show such statistically significant differences.

CONCLUSION

Our meta-analysis results suggest that serum leptin levels in CI patients may be closely correlated with CI risks.

Erythropoietin reduces apoptosis of brain tissue cells in rats after cerebral ischemia/reperfusion injury: a characteristic analysis using magnetic resonance imaging

Some in vitro experiments have shown that erythropoietin (EPO) increases resistance to apoptosis and facilitates neuronal survival following cerebral ischemia. However, results from in vivo studies are rarely reported. Perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI) have been applied successfully to distinguish acute cerebral ischemic necrosis and penumbra in living animals; therefore, we hypothesized that PWI and DWI could be used to provide imaging evidence in vivo for the conclusion that EPO could reduce apoptosis in brain areas injured by cerebral ischemia/reperfusion. To validate this hypothesis, we established a rat model of focal cerebral ischemia/reperfusion injury, and treated with intra-cerebroventricular injection of EPO (5,000 U/kg) 20 minutes before injury. Brain tissue in the ischemic injury zone was sampled using MRI-guided localization. The relative area of abnormal tissue, changes in PWI and DWI in the ischemic injury zone, and the number of apoptotic cells based on TdT-mediated dUTP-biotin nick end-labeling (TUNEL) were assessed. Our findings demonstrate that EPO reduces the relative area of abnormally high signal in PWI and DWI, increases cerebral blood volume, and decreases the number of apoptotic cells positive for TUNEL in the area injured by cerebral ischemia/reperfusion. The experiment provides imaging evidence in vivo for EPO treating cerebral ischemia/reperfusion injury.

Role of metabolism in neurodegenerative disorders

Along with the increase in life expectancy over the last century, the prevalence of age-related disorders, such as neurodegenerative diseases continues to rise. This is the case of Alzheimer's, Parkinson's, Huntington's diseases and Multiple sclerosis, which are chronic disorders characterized by neuronal loss in motor, sensory or cognitive systems. Accumulating evidence has suggested the presence of a strong correlation between metabolic changes and neurodegeneration. Indeed epidemiologic studies have shown strong associations between obesity, metabolic dysfunction, and neurodegeneration, while animal models have provided insights into the complex relationships between these conditions. In this context, hormones such as leptin, ghrelin, insulin and IGF-1 seem to play a key role in the regulation of neuronal damage, toxic insults and several other neurodegenerative processes. This review aims to presenting the most recent evidence supporting the crosstalk linking energy metabolism and neurodegeneration, and will focus on metabolic manipulation as a possible therapeutic tool in the prevention and treatment of neurodegenerative diseases.

Neuroprotective Properties of a Macrolide Antibiotic in a Mouse Model of Middle Cerebral Artery Occlusion: Characterization of the Immunomodulatory Effects and Validation of the Efficacy of Intravenous Administration

Repurposing the macrolide antibiotic azithromycin has recently been suggested as a promising neuroprotective strategy for the acute treatment of ischemic stroke. Here, we aim at further characterizing the immunomodulatory properties of intraperitoneal (i.p.) administration of this drug and, more importantly, at assessing whether neuroprotection can also be achieved by the more clinically relevant intravenous (i.v.) route of administration in a mouse model of focal cerebral ischemia induced by transient (30-min) middle cerebral artery occlusion (MCAo). A single i.p. injection of azithromycin (150 mg/kg) upon reperfusion prevented ischemia-induced spleen contraction and increased the number of MAC-1-immunopositive microglia/macrophages in the ischemic hemisphere 48 h after the insult. This was paralleled by an elevation of alternatively activated phenotypes (i.e., Ym1-immunopositive M2-polarized cells) and by a reduced expression of the pro-inflammatory marker myeloperoxidase. More importantly, i.v. administration of azithromycin upon reperfusion reduced MCAo-induced infarct volume and cerebral edema to an extent comparable to that obtained via the i.p. route. Although the i.p. route is often used for research purposes, it is impractical in the clinical setting; however, i.v. administration can easily be used in ischemic stroke patients who usually have i.v. access already established on hospital admission. The neuroprotective efficacy of the clinically relevant i.v. administration of azithromycin, together with its beneficial immunomodulatory properties reported in mice subjected to transient MCAo, suggests that this macrolide antibiotic can be effectively repurposed for the acute treatment of ischemic stroke. To this end, further work is needed to validate the efficacy of azithromycin in the clinical setting.

Leptin changes differentiation fate and induces senescence in chondrogenic progenitor cells

Body weight is a component of the mechanical theory of OA (osteoarthritis) pathogenesis. Obesity was also found to be a risk factor for digital OA involving non-weight-bearing joints, which suggested that metabolism influences the occurrence and progression of OA. The metabolic origin of OA has been partially attributed to the involvement of adipokines, such as leptin, the levels of which are significantly and positively correlated with cartilage degeneration in OA patients. However, the mechanisms by which leptin-induced cartilage degeneration occurs are poorly understood. The discovery of chondrogenic progenitor cells (CPCs) opened up new opportunities for investigation. Investigating the effects of leptin on differentiation and proliferation in CPCs would increase our understanding of the roles played by leptin in the aetiology and development of OA. Here, CPCs were harvested using single-cell sorting from rat cartilage tissues to obtain mesenchymal stem-like cells, which possess clonogenicity, proliferation and stemness. High doses of leptin decreased the ability of the CPCs to migrate, inhibited their chondrogenic potential and increased their osteogenic potential, suggesting that leptin changes differentiation fates in CPCs. High doses of leptin induced cell cycle arrest and senescence in CPCs by activating the p53/p21 pathway and inhibiting the Sirt1 pathway. Inhibiting the Sirt1 pathway accelerated cartilage senescence in knockout (KO) mice. Activating the leptin pathway induced higher Ob-Rb expression and was significantly correlated with cartilage degeneration (lower levels of Coll-2) and tissue senescence (higher levels of p53/p21 and lower levels of Sirt1) in OA patients, suggesting that leptin-induced CPCs senescence contributes to the development of OA. Taken together, our results reveal new links between obesity and cartilage damage that are induced by leptin-mediated effects on cell behaviour and senescence.

Rational modulation of the innate immune system for neuroprotection in ischemic stroke

The innate immune system plays a dualistic role in the evolution of ischemic brain damage and has also been implicated in ischemic tolerance produced by different conditioning stimuli. Early after ischemia, perivascular astrocytes release cytokines and activate metalloproteases (MMPs) that contribute to blood–brain barrier (BBB) disruption and vasogenic oedema; whereas at later stages, they provide extracellular glutamate uptake, BBB regeneration and neurotrophic factors release. Similarly, early activation of microglia contributes to ischemic brain injury via the production of inflammatory cytokines, including tumor necrosis factor (TNF) and interleukin (IL)-1, reactive oxygen and nitrogen species and proteases. Nevertheless, microglia also contributes to the resolution of inflammation, by releasing IL-10 and tumor growth factor (TGF)-β, and to the late reparative processes by phagocytic activity and growth factors production. Indeed, after ischemia, microglia/macrophages differentiate toward several phenotypes: the M1 pro-inflammatory phenotype is classically activated via toll-like receptors or interferon-γ, whereas M2 phenotypes are alternatively activated by regulatory mediators, such as ILs 4, 10, 13, or TGF-β. Thus, immune cells exert a dualistic role on the evolution of ischemic brain damage, since the classic phenotypes promote injury, whereas alternatively activated M2 macrophages or N2 neutrophils prompt tissue remodeling and repair. Moreover, a subdued activation of the immune system has been involved in ischemic tolerance, since different preconditioning stimuli act via modulation of inflammatory mediators, including toll-like receptors and cytokine signaling pathways. This further underscores that the immuno-modulatory approach for the treatment of ischemic stroke should be aimed at blocking the detrimental effects, while promoting the beneficial responses of the immune reaction.

Effects of high-fat diet on neuronal damage, gliosis, inflammatory process and oxidative stress in the hippocampus induced by transient cerebral ischemia

In this study, we investigated the effects of a normal diet (ND) and high-fat diet (HFD) on delayed neuronal death in the gerbil hippocampal CA1 region after transient cerebral ischemia. In the HFD-fed gerbils, ischemia-induced hyperactivity was significantly increased and neuronal damage was represented more severely compared to the ND-fed gerbils. Ischemia-induced glial activation was accelerated in the HFD-fed gerbils. Cytokines including interleukin-2 and -4 were more sensitive in the hippocampal CA1 region of the HFD-fed gerbils after ischemia-reperfusion. Additionally, we found that decreased 4-HNE and SODs immunoreactivity and protein levels in the hippocampal CA1 region of the HFD-fed gerbils after ischemia-reperfusion. These results indicate that HFD may lead to the exacerbated effects on ischemia-induced neuronal death in the hippocampal CA1 region after ischemia-reperfusion. These effects of HFD may be associated with more accelerated activations of glial cells and imbalance of pro- and anti-inflammatory cytokines and/or antioxidants after transient cerebral ischemia.

Clinicotherapeutic Potential of Leptin in Alzheimer’s Disease and Parkinson’s Disease

Chronic neurodegenerative diseases are a group of devastating neurological disorders that result in significant morbidity and mortality in the elderly population worldwide. Recent researches have shown some interesting associations of the classical antiobesity hormone leptin with two most important neurodegenerative diseases—Alzheimer’s disease (AD) and Parkinson’s disease (PD). Although several clinical studies have found the procognitive and memory-enhancing role of this peptide hormone in leptin-deficient patients, surprisingly it has not been used in any clinical trials involving patients with developing or full-blown neurodegenerative conditions. This review article is an attempt to bring together the existing information about the clinical associations of leptin with AD and PD. It starts with the basic understanding of leptin action in the brain and its derangements in these diseases and eventually discusses the potential of this hormone as a neuroprotective agent in clinical scenario.

Early reperfusion injury is associated to MMP2 and IL-1β elevation in cortical neurons of rats subjected to middle cerebral artery occlusion

The pathophysiological processes implicated in ischemic brain damage are strongly affected by an inflammatory reaction characterized by activation of immune cells and release of soluble mediators, including cytokines and chemokines. The pro-inflammatory cytokine interleukin (IL)-1β has been implicated in ischemic brain injury, however, to date, the mechanisms involved in the maturation of this cytokine in the ischemic brain have not been completely elucidated. We have previously suggested that matrix metalloproteinases (MMPs) may be implicated in cytokine production under pathological conditions. Here, we demonstrate that significant elevation of IL-1β occurs in the cortex as early as 1h after the beginning of reperfusion in rats subjected to 2-h middle cerebral artery occlusion (MCAo). At this early stage, we observe increased expression of IL-1β in pericallosal astroglial cells and in cortical neurons and this latter signal colocalizes with elevated gelatinolytic activity. By gel zymography, we demonstrate that the increased gelatinolytic signal at 1-h reperfusion is mainly ascribed to MMP2. Thus, MMP2 seems to contribute to early brain elevation of IL-β after transient ischemia and this mechanism may promote damage since pharmacological inhibition of gelatinases by the selective MMP2/MMP9 inhibitor V provides neuroprotection in rats subjected to transient MCAo.

Fetal brain genomic reprogramming following asphyctic preconditioning

Background

Fetal asphyctic (FA) preconditioning is effective in attenuating brain damage incurred by a subsequent perinatal asphyctic insult. Unraveling mechanisms of this endogenous neuroprotection, activated by FA preconditioning, is an important step towards new clinical strategies for asphyctic neonates. Genomic reprogramming is thought to be, at least in part, responsible for the protective effect of preconditioning. Therefore we investigated whole genome differential gene expression in the preconditioned rat brain. FA preconditioning was induced on embryonic day 17 by reversibly clamping uterine circulation. Male control and FA offspring were sacrificed 96 h after FA preconditioning. Whole genome transcription was investigated with Affymetrix Gene1.0ST chip.

Results

Data were analyzed with the Bioconductor Limma package, which showed 53 down-regulated and 35 up-regulated transcripts in the FA-group. We validated these findings with RT-qPCR for adh1, edn1, leptin, rdh2, and smad6. Moreover, we investigated differences in gene expression across different brain regions. In addition, we performed Gene Set Enrichment Analysis (GSEA) which revealed 19 significantly down-regulated gene sets, mainly involved in neurotransmission and ion transport. 10 Gene sets were significantly up-regulated, these are mainly involved in nucleosomal structure and transcription, including genes such as mecp2.

Conclusions

Here we identify for the first time differential gene expression after asphyctic preconditioning in fetal brain tissue, with the majority of differentially expressed transcripts being down-regulated. The observed down-regulation of cellular processes such as neurotransmission and ion transport could represent a restriction in energy turnover which could prevent energy failure and subsequent neuronal damage in an asphyctic event. Up-regulated transcripts seem to exert their function mainly within the cell nucleus, and subsequent Gene Set Enrichment Analysis suggests that epigenetic mechanisms play an important role in preconditioning induced neuroprotection.