Lactate potentiates angiogenesis and neurogenesis in experimental intracerebral hemorrhage

Astrocytes, reactive astrogliosis, and glial scar formation in traumatic brain injury

Traumatic brain injury is a global health crisis, causing significant death and disability worldwide. Neuroinflammation that follows traumatic brain injury has serious consequences for neuronal survival and cognitive impairments, with astrocytes involved in this response. Following traumatic brain injury, astrocytes rapidly become reactive, and astrogliosis propagates from the injury core to distant brain regions. Homeostatic astroglial proteins are downregulated near the traumatic brain injury core, while pro-inflammatory astroglial genes are overexpressed. This altered gene expression is considered a pathological remodeling of astrocytes that produces serious consequences for neuronal survival and cognitive recovery. In addition, glial scar formed by reactive astrocytes is initially necessary to limit immune cell infiltration, but in the long term impedes axonal reconnection and functional recovery. Current therapeutic strategies for traumatic brain injury are focused on preventing acute complications. Statins, cannabinoids, progesterone, beta-blockers, and cerebrolysin demonstrate neuroprotective benefits but most of them have not been studied in the context of astrocytes. In this review, we discuss the cell signaling pathways activated in reactive astrocytes following traumatic brain injury and we discuss some of the potential new strategies aimed to modulate astroglial responses in traumatic brain injury, especially using cell-targeted strategies with miRNAs or lncRNA, viral vectors, and repurposed drugs.

MicroRNA-451 Regulates Angiogenesis in Intracerebral Hemorrhage by Targeting Macrophage Migration Inhibitory Factor

Intracerebral hemorrhage (ICH) is a subtype of stroke with the highest fatality and disability rate. Up to now, commonly used first-line therapies have limited value in improving prognosis. Angiogenesis is essential to neurological recovery after ICH. Recent studies have shown that microRNA-451(miR-451) plays an important role in angiogenesis by regulating the function of vascular endothelial cells. We found miR-451 was significantly decreased in the peripheral blood of ICH patients in the acute stage. Based on the clinical findings, we conducted this study to investigate the potential regulatory effect of miR-451 on angiogenesis after ICH. The expression of miR-451 in ICH mouse model and in a hemin toxicity model of human brain microvascular endothelial cells (hBMECs) was decreased the same as in ICH patients. MiR-451 negatively regulated the proliferation, migration, and tube formation of hBMECs in vitro. MiR-451 negatively regulated the microvessel density in the perihematoma tissue and affected neural functional recovery of ICH mouse model. Knockdown of miR-451 could recovered tight junction and protect the integrity of blood-brain barrier after ICH. Based on bioinformatic programs, macrophage migration inhibitory factor (MIF) was predicted to be the target gene and identified to be regulated by miR-451 inhibiting the protein translation. And p-AKT and p-ERK were verified to be downstream of MIF in angiogenesis. These results all suggest that miR-451 will be a potential target for regulating angiogenesis in ICH.

Glycolytic PFKFB3 and Glycogenic UGP2 Axis Regulates Perfusion Recovery in Experimental Hind Limb Ischemia

BACKGROUND

Despite being in an oxygen-rich environment, endothelial cells (ECs) use anaerobic glycolysis (Warburg effect) as the primary metabolic pathway for cellular energy needs. PFKFB (6-phosphofructo-2-kinase/fructose-2,6-biphosphatase)-3 regulates a critical enzymatic checkpoint in glycolysis and has been shown to induce angiogenesis. This study builds on our efforts to determine the metabolic regulation of ischemic angiogenesis and perfusion recovery in the ischemic muscle.

METHODS

Hypoxia serum starvation (HSS) was used as an in vitro peripheral artery disease (PAD) model, and hind limb ischemia by femoral artery ligation and resection was used as a preclinical PAD model.

RESULTS

Despite increasing PFKFB3-dependent glycolysis, HSS significantly decreased the angiogenic capacity of ischemic ECs. Interestingly, inhibiting PFKFB3 significantly induced the angiogenic capacity of HSS-ECs. Since ischemia induced a significant in PFKFB3 levels in hind limb ischemia muscle versus nonischemic, we wanted to determine whether glucose bioavailability (rather than PFKFB3 expression) in the ischemic muscle is a limiting factor behind impaired angiogenesis. However, treating the ischemic muscle with intramuscular delivery of D-glucose or L-glucose (osmolar control) showed no significant differences in the perfusion recovery, indicating that glucose bioavailability is not a limiting factor to induce ischemic angiogenesis in experimental PAD. Unexpectedly, we found that shRNA-mediated PFKFB3 inhibition in the ischemic muscle resulted in an increased perfusion recovery and higher vascular density compared with control shRNA (consistent with the increased angiogenic capacity of PFKFB3 silenced HSS-ECs). Based on these data, we hypothesized that inhibiting HSS-induced PFKFB3 expression/levels in ischemic ECs activates alternative metabolic pathways that revascularize the ischemic muscle in experimental PAD. A comprehensive glucose metabolic gene qPCR arrays in PFKFB3 silenced HSS-ECs, and PFKFB3-knock-down ischemic muscle versus respective controls identified UGP2 (uridine diphosphate-glucose pyrophosphorylase 2), a regulator of protein glycosylation and glycogen synthesis, is induced upon PFKFB3 inhibition in vitro and in vivo. Antibody-mediated inhibition of UGP2 in the ischemic muscle significantly impaired perfusion recovery versus IgG control. Mechanistically, supplementing uridine diphosphate-glucose, a metabolite of UGP2 activity, significantly induced HSS-EC angiogenic capacity in vitro and enhanced perfusion recovery in vivo by increasing protein glycosylation (but not glycogen synthesis).

CONCLUSIONS

Our data present that inhibition of maladaptive PFKFB3-driven glycolysis in HSS-ECs is necessary to promote the UGP2-uridine diphosphate-glucose axis that enhances ischemic angiogenesis and perfusion recovery in experimental PAD.

The effect of physical exercise intervention on the ability of daily living in patients with Alzheimer's dementia: a meta-analysis

Objective

To systematically evaluate the effect of physical exercise intervention on the activities of daily living (ADL) on patients with Alzheimer's dementia (AD) and explore the optimal exercise scheme.

Methods

PubMed, EMBASE, the Cochrane Library, Web of Science, and Science Direct databases were searched from 1987 to December 2023 to collect randomized controlled trials (RCTs). Two investigators independently screened the literature and extracted data according to the inclusion and exclusion criteria. The quality of the included studies was evaluated using Cochrane Review Manager 5.3. And STATA 16.0 was used for performing the meta-analysis.

Results

Fifteen randomized controlled trials were included. The results of the meta-analysis showed that physical exercise had a positive effect on the improvement of ADL in patients with AD [standardized mean difference (SMD) = 0.312, 95% confidence interval (CI 0.039-0.585), P = 0.02], and the difference was statistically significant. The results of subgroup analysis showed that anaerobic exercises such as strength and balance training with a medium cycle of 12-16 weeks and lasting 30-45 min each time were more ideal for the improvement of basic daily living ability of AD patients.

Conclusion

Physical exercise can effectively improve activities of daily living in patients with Alzheimer's dementia and it may be a potential non-drug treatment for AD patients.

MCT4-driven CAF-mediated metabolic reprogramming in breast cancer microenvironment is a vulnerability targetable by miR-425-5p

Multiple oncogenic alterations contribute to breast cancer development. Metabolic reprogramming, deeply contributing to tumor microenvironment (TME) education, is now widely recognized as a hallmark of cancer. The reverse Warburg effect induces cancer-associated fibroblasts (CAFs) to produce and secrete L-lactate, enhancing malignant characteristics such as neoangiogenesis, metastatic dissemination, and treatment resistance. Monocarboxylate transporter (MCT) 4 is involved in lactate efflux from CAFs into stromal and epithelial cells. Here, we first assess the expression of miR-425-5p and its target MCT4 in breast cancer CAFs and normal fibroblasts. We analyzed the metabolic changes induced by miR-425-5p in CAFs and its role in the education of breast cancer epithelial cells. We show that miR-425-5p-induced MCT4 knockdown decreased lactate extrusion from CAFs and its availability in the TME. miR-425-5p overexpression induced profound metabolic transformation in CAFs, ultimately influencing breast cancer metabolism. Furthermore, miR-425-5p impaired the capacity of CAFs to sustain vessel formation and breast cancer cell migration, viability, and proliferation. These findings emphasize the key role of miR-425-5p in breast cancer metabolism and aggressiveness, and its possible importance for breast cancer therapy and monitoring.

Long non-coding RNA MIR17HG impedes FOSL2-mediated transcription activation of HIC1 to maintain a pro-inflammatory phenotype of microglia during intracerebral haemorrhage

Activation and polarization of microglia play decisive roles in the progression of intracerebral haemorrhage (ICH), and lactate exposure correlates with microglia polarization. This study explores molecules influencing lactate production and microglia phenotype alteration following ICH. A murine model of ICH was induced by intracerebral injection of collagenase. The mice experienced autonomous neurological function recovery, haematoma resolution and rapid lactate production, along with a gradual increase in angiogenesis activity, neuronal recovery and an M1-to-M2 phenotype change of microglia. Galloflavin, a lactate dehydrogenase antagonist, suppressed this phenotype change and the functional recovery in mice. FOS like 2 (FOSL2) was significantly upregulated in the brain tissues from day 7 post-ICH. Overexpression of FOSL2 induced an M1-to-M2 phenotype shift in microglia and accelerated lactate production in vivo and in haemoglobin-treated microglia in vitro. Long non-coding RNA MIR17HG impeded FOSL2-mediated transcription activation of hypermethylated in cancer 1 (HIC1). MIR17HG overexpression induced pro-inflammatory activation of microglia in mice, which was blocked by further HIC1 overexpression. Overall, this study demonstrates that MIR17HG maintains a pro-inflammatory phenotype of microglia during ICH progression by negating FOSL2-mediated transcription activation of HIC1. Specific inhibition of MIR17HG or upregulation of FOSL2 or HIC1 may favour inflammation inhibition and haematoma resolution in ICH.

History and Function of the Lactate Receptor GPR81/HCAR1 in the Brain: A Putative Therapeutic Target for the Treatment of Cerebral Ischemia

GPR81 is a G-protein coupled receptor (GPCR) discovered in 2001, but deorphanized only 7 years later, when its affinity for lactate as an endogenous ligand was demonstrated. More recently, GPR81 expression and distribution in the brain were also confirmed and the function of lactate as a volume transmitter has been suggested since then. These findings shed light on a new function of lactate acting as a signaling molecule in the central nervous system, in addition to its well-known role as a metabolic fuel for neurons. GPR81 seems to act as a metabolic sensor, coupling energy metabolism, synaptic activity, and blood flow. Activation of this receptor leads to Gi-mediated downregulation of adenylyl cyclase and subsequent reduction in cAMP levels, regulating several downstream pathways. Recent studies have also suggested the potential role of lactate as a neuroprotective agent, mainly under brain ischemic conditions. This effect is usually attributed to the metabolic role of lactate, but the underlying mechanisms need further investigation and could be related to lactate signaling via GPR81. The activation of GPR81 showed promising results for neuroprotection: it modulates many processes involved in the pathophysiology of ischemia. In this review, we summarize the history of GPR81, starting with its deorphanization; then, we discuss GPR81 expression and distribution, signaling transduction cascades, and neuroprotective roles. Lastly, we propose GPR81 as a potential target for the treatment of cerebral ischemia.

Association of lactate-to-albumin ratio with in-hospital and intensive care unit mortality in patients with intracerebral hemorrhage

Background

Intracerebral hemorrhage (ICH) is a severe stroke subtype with a high mortality rate; the lactate-to-albumin ratio (LAR) is a new biomarker for predicting clinical outcomes in patients with ICH. However, the relationship between LAR and mortality in patients with ICH treated in the intensive care unit (ICU) remains controversial. Therefore, in this study, we aimed to investigate the association between LAR and in-hospital and ICU mortality in patients with ICH.

Methods

Patients with ICH were selected from the Medical Information Mart for Intensive Care III (MIMIC-III) database; their clinical information, including baseline characteristics, vital signs, comorbidities, laboratory test results, and scoring systems, was extracted. Univariate and multivariate Cox proportional hazards analyses were used to investigate the association of LAR with in-hospital and ICU mortality. The maximum selection statistical method and subgroup analysis were used to investigate these relationships further. Kaplan-Meier (KM) analysis was used to draw survival curves.

Results

This study enrolled 237 patients with ICH whose lactate and albumin levels, with median values of 1.975 and 3.6 mg/dl, respectively, were measured within the first 24 h after ICU admission. LAR had an association with increased risk of in-hospital mortality [unadjusted hazards ratio (HR), 1.79; 95% confidence interval (CI), 1.32-2.42; p < 0.001] and ICU mortality (unadjusted HR, 1.88; 95% CI, 1.38-2.55; p < 0.001). A cut-off value of 0.963 mg/dl was used to classify patients into high LAR (≥0.963) and low LAR (<0.963) groups, and survival curves suggested that those two groups had significant survival differences (p = 0.0058 and 0.0048, respectively). Furthermore, the high LAR group with ICH had a significantly increased risk of in-hospital and ICU mortality compared to the low LAR group.

Conclusion

Our study suggests that a high LAR is associated with an increased risk of in-hospital and ICU mortality in patients with ICH. Thus, the LAR is a useful prognostic predictor of clinical outcomes in patients with ICH.

Current understanding of the contribution of lactate to the cardiovascular system and its therapeutic relevance

Research during the past decades has yielded numerous insights into the presence and function of lactate in the body. Lactate is primarily produced via glycolysis and plays special roles in the regulation of tissues and organs, particularly in the cardiovascular system. In addition to being a net consumer of lactate, the heart is also the organ in the body with the greatest lactate consumption. Furthermore, lactate maintains cardiovascular homeostasis through energy supply and signal regulation under physiological conditions. Lactate also affects the occurrence, development, and prognosis of various cardiovascular diseases. We will highlight how lactate regulates the cardiovascular system under physiological and pathological conditions based on evidence from recent studies. We aim to provide a better understanding of the relationship between lactate and cardiovascular health and provide new ideas for preventing and treating cardiovascular diseases. Additionally, we will summarize current developments in treatments targeting lactate metabolism, transport, and signaling, including their role in cardiovascular diseases.

METTL3 silenced inhibited the ferroptosis development via regulating the TFRC levels in the Intracerebral hemorrhage progression

Intracerebral hemorrhage (ICH) refers to the hemorrhage caused by the increase and rupture of vascular brittleness in non traumatic brain parenchyma, which has been demonstrated to be closely related to ferroptosis. This study aimed to examine the effects of methyltransferase like 3 (METTL3) on the ferroptosis in the ICH progression. The PC12 cells was stimulated by hemin to establish a ICH model. The cell viability was tested by CCK8 assay. The Fe²⁺, reactive oxygen species (ROS), and malondialdehyde (MDA) levels were determined by the corresponding commercial kits. The cell death was analyzed by propidium Iodide (PI) staining. The lactylation levels were detected by western blot. M6A dot blot assay was performed to detected the total m6A levels and MeRIP assay was conducted to determine the m6A levels of transferrin receptor (TFRC). We found that the METTL3 and m6A levels were increased in the hemin treated PC12 cells. METTL3 knockdown increased the cell viability and decreased Fe²⁺, ROS and MDA levels in the hemin treated PC12 cells. The role of METTL3 knockdown in the hemin treated PC12 cells was reversed after TFRC overexpression. Mechanistically, the METTL3 lactylation was increased in the hemin treated PC12 cells, which further enhanced the protein stability and expression of METTL3. The up-regulated METTL3 increased the m6A levels and mRNA expressions of TFRC, which further induced the ferroptosis of the PC12 cells. In conclusion, the up-regulation of METTL3 lactylation enhanced the METTL3 protein stability and expression levels in hemin treated PC12 cells. METTL3 silenced suppressed the ferroptosis development through regulating the m6A levels of TFRC mRNA.

Effects of High-Intensity Interval Training Protocols on Blood Lactate Levels and Cognition in Healthy Adults: Systematic Review and Meta-Regression

BACKGROUND

Some health benefits from high-intensity interval training (HIIT) are facilitated by peripheral blood lactate levels. However, the lactate response from HIIT is variable and dependent on protocol parameters.

OBJECTIVES

We aimed to determine the HIIT protocol parameters that elicited peak lactate levels, and how these levels are associated with post-HIIT cognitive performance.

STUDY DESIGN

We conducted a systematic review with meta-regression.

METHODS

MEDLINE, Embase, CENTRAL, SPORTDiscus, and CINAHL + were searched from database inception to 8 April, 2022. Peer-reviewed primary research in healthy adults that determined lactate (mmol/L) and cognitive performance after one HIIT session was included. Mixed-effects meta-regressions determined the protocol parameters that elicited peak lactate levels, and linear regressions modelled the relationship between lactate levels and cognitive performance.

RESULTS

Study entries (n = 226) involving 2560 participants (mean age 24.1 ± 4.7 years) were included in the meta-regression. A low total work-interval volume (~ 5 min), recovery intervals that are about five times longer than work intervals, and a medium session volume (~ 15 min), elicited peak lactate levels, even when controlling for intensity, fitness (peak oxygen consumption) and blood measurement methods. Lactate levels immediately post-HIIT explained 14-17% of variance in Stroop interference condition at 30 min post-HIIT.

CONCLUSIONS

A HIIT protocol that uses the above parameters (e.g., 8 × 30-s maximal intensity with 90-s recovery) can elicit peak lactate, a molecule that is known to benefit the central nervous system and be involved in exercise training adaptations. This review reports the state of the science in regard to the lactate response following HIIT, which is relevant to those in the sports medicine field designing HIIT training programs.

TRIAL REGISTRY

Clinical Trial Registration: PROSPERO (CRD42020204400).

Hypoxia induced lactate acidosis modulates tumor microenvironment and lipid reprogramming to sustain the cancer cell survival

It is well known that solid hypoxic tumour cells oxidise glucose through glycolysis, and the end product of this pathway is fermented into lactate which accumulates in the tumour microenvironment (TME). Initially, it was proclaimed that cancer cells cannot use lactate; therefore, they dump it into the TME and subsequently augment the acidity of the tumour milieu. Furthermore, the TME acts as a lactate sink with stope variable amount of lactate in different pathophysiological condition. Regardless of the amount of lactate pumped out within TME, it disappears immediately which still remains an unresolved puzzle. Recent findings have paved pathway in exploring the main role of lactate acidosis in TME. Cancer cells utilise lactate in the de novo fatty acid synthesis pathway to initiate angiogenesis and invasiveness, and lactate also plays a crucial role in the suppression of immunity. Furthermore, lactate re-programme the lipid biosynthetic pathway to develop a metabolic symbiosis in normoxic, moderately hypoxic and severely hypoxic cancer cells. For instance: severely hypoxic cancer cells enable to synthesizing poly unsaturated fatty acids (PUFA) in oxygen scarcity secretes excess of lactate in TME. Lactate from TME is taken up by the normoxic cancer cells whereas it is converted back to PUFAs after a sequence of reactions and then liberated in the TME to be utilized in the severely hypoxic cancer cells. Although much is known about the role of lactate in these biological processes, the exact molecular pathways that are involved remain unclear. This review attempts to understand the molecular pathways exploited by lactate to initiate angiogenesis, invasiveness, suppression of immunity and cause re-programming of lipid synthesis. This review will help the researchers to develop proper understanding of lactate associated bimodal regulations of TME.

Acute hypoxia promotes the liver angiogenesis of largemouth bass (Micropterus salmoides) by HIF - Dependent pathway

A 24-h hypoxia exposure experiment was conducted to determine how hypoxia exposure induce liver angiogenesis in largemouth bass. Nitrogen (N₂) was pumped into water to exclude dissolved oxygen into 1.2 ± 0.2 mg/L, and liver tissues were sampled during hypoxia exposure of 0 h, 4 h, 8 h, 12 h, 24 h and re-oxygenation for 12 h. Firstly, the results showed that hypoxia exposure promoted the angiogenesis occurrence by immunohistochemical analysis of vascular endothelial growth factor receptor 2 (VEGFR2). Secondly, the concentration of vasodilation factor increased and it's activity was elevated during 8 h exposure, such as nitric oxide (NO) and nitric oxide synthase (NOS) (p < 0.05). Thirdly, hypoxia exposure promoted angiogenesis through up-regulation the expression of matrix metalloproteinase 2 (MMP-2), jagged, protein kinase B (AKT), phosphoinositide-3-kinase (PI3K), mitogen-activated protein kinase (MAPK) at 4 h; contrarily, the expression of inhibiting angiogenesis genes presented up-regulated at 8 h (p < 0.05), such as matrix metalloproteinase inhibitor-2 (TIMP-2), matrix metalloproteinase inhibitor-3 (TIMP-3). Finally, the genes and proteins that regulate angiogenesis presented obvious chronological order. Parts of them promoted the budding and extension of blood vessels were up-regulated during 4 h-8 h (p < 0.05), such as vascular endothelial growth factor a (VEGFA), VEGFR2, monocarboxylic acid transporter 1 (MCT1), CD147, prolyl hydroxylase (PHD), nuclear factor kappa-B (NF-κB); other part of them promoted blood vessel maturation were highly expressed during 12 h-24 h (p < 0.05), such as angiogenin-1 (Ang-1) and angiogenin-2 (Ang-2). In short, acute hypoxia can promote the liver angiogenesis of largemouth bass by HIF - dependent pathway.

Buyang Huanwu Decoction: A Traditional Chinese Medicine, Promotes Lactate-Induced Angiogenesis in Experimental Intracerebral Hemorrhage

Identifying the underlying mechanisms and exploring effective therapies for intracerebral hemorrhage (ICH) are urgently needed. Here, we aim to elucidate the potential roles and underlying mechanisms of Buyang Huanwu decoction (BYHWD) in ICH. In the first set of experiments, rats were randomly divided into five groups: Sham, ICH, ICH + sodium oxamate (OXA), ICH + BYHWD, and ICH + BYHWD + OXA. The lactate level around the hematoma was evaluated. PCNA+/vWF+ nuclei were observed. Additionally, an online bioinformatics analysis tool was used to predict the BYHWD druggable targets related to angiogenesis. Then, we validated these predictions. In the second set, exogenous sodium L-lactate (Lac) was infused into the intact brains of rats. Rats were randomly divided into three groups: Sham, Lac, and Lac + YC-1. The numbers of PCNA+/vWF+ nuclei and the expression of HIF-1α and VEGF were evaluated. In the first set of experiments, compared with the ICH group, the BYHWD group exhibited significantly increased numbers of PCNA+/vWF+ nuclei, and neurological dysfunction was markedly improved. Bioinformatics analysis revealed that the improvements caused by BYHWD indicated a role for the HIF-1α pathway. The HIF-1α and VEGF protein levels were upregulated after BYHWD administration. Moreover, we verified that lactate was involved in the predicted mechanisms. In the second set, lactate facilitated angiogenesis and HIF-1α and VEGF expression. Co-infusion with a HIF-1α inhibitor, YC-1, significantly inhibited these effects. Our data suggest that the pharmacological effects of BYHWD involve lactate-induced angiogenesis, these data may provide new evidence for its use in ICH.

Dexmedetomidine post-conditioning protects blood-brain barrier integrity by modulating microglia/macrophage polarization via inhibiting NF-κB signaling pathway in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is one of the most devastating forms of stroke. Dexmedetomidine (DEX) has shown certain neuroprotective roles in ICH. Nevertheless, the details concerning the underlying molecular mechanism of DEX’s protective effects still need further elucidation. Herein, a model of ICH was established. The rats were randomly divided into the sham group, the ICH group, and the ICH + DEX group. Neurological outcomes, neuronal injury, and apoptosis were evaluated. Brain water content, Evans blue extravasation, and the expression of tight junction-associated proteins were also detected to assess the blood-brain barrier (BBB) integrity. Subsequently, the microglia/macrophage polarization state and inflammatory cytokine levels were observed. To further explore the underlying mechanism, NF-κB signaling pathway-associated proteins were detected. The results showed that DEX exerted neuroprotective effects against ICH-induced neurological deficits. DEX significantly increased the numbers of the surviving neurons and ameliorated neuronal cell loss and apoptosis in ICH. The rats that received the DEX displayed a lower level of brain water content and EB extravasation, moreover, ZO-1, occludin, and claudin-5 were markedly increased by DEX. Additionally, DEX facilitated M2 microglia/macrophage polarization, the M1-associated markers were reduced by DEX, while the M2-associated identification significantly increased. We found that DEX dramatically diminished pro-inflammatory cytokines expression, simultaneously promoting anti-inflammatory cytokines expression. DEX inhibited nuclear translocation of NF-κB in ICH rats. Our data suggest that DEX post-conditioning protects BBB integrity by modulating microglia/macrophage polarization via inhibiting the NF-κB signaling pathway in ICH.

Insights into the regulation of podocyte and glomerular function by lactate and its metabolic sensor G-protein-coupled receptor 81

Podocytes and their foot processes are an important cellular layer of the renal filtration barrier that is involved in regulating glomerular permeability. Disturbances of podocyte function play a central role in the development of proteinuria in diabetic nephropathy. The retraction and effacement of podocyte foot processes that form slit diaphragms are a common feature of proteinuria. Correlations between the retraction of foot processes and the development of proteinuria are not well understood. Unraveling peculiarities of podocyte energy metabolism notably under diabetic conditions will provide insights into the pathogenesis of diabetic nephropathy. Intracellular metabolism in the cortical area of podocytes is regulated by glycolysis, whereas energy balance in the central area is controlled by oxidative phosphorylation and glycolysis. High glucose concentrations were recently reported to force podocytes to switch from mitochondrial oxidative phosphorylation to glycolysis, resulting in lactic acidosis. In this review, we hypothesize that the lactate receptor G-protein-coupled receptor 81 (also known as hydroxycarboxylic acid receptor 81) may contribute to the control of podocyte function in both health and disease.

Leptin Promotes Angiogenesis via Pericyte STAT3 Pathway upon Intracerebral Hemorrhage

Angiogenesis is a vital endogenous brain self-repair processes for neurological recovery after intracerebral hemorrhage (ICH). Increasing evidence suggests that leptin potentiates angiogenesis and plays a beneficial role in stroke. However, the proangiogenic effect of leptin on ICH has not been adequately explored. Moreover, leptin triggers post-ICH angiogenesis through pericyte, an important component of forming new blood vessels, which remains unclear. Here, we reported that exogenous leptin infusion dose-dependent promoted vascular endothelial cells survival and proliferation at chronic stage of ICH mice. Additionally, leptin robustly ameliorated pericytes loss, enhanced pericytes proliferation and migration in ICH mice in vivo, and in ICH human brain microvascular pericytes (HBVPC) in vitro. Notably, we showed that pericytes-derived pro-angiogenic factors were responsible for enhancing the survival, proliferation and tube formation followed leptin treatment in human brain microvascular endothelial cells (HCMEC/D3)/HBVPC co-culture models. Importantly, considerable improvements in neurobehavioral function and hostile microenvironment were observed in leptin treatment ICH mice, indicating that better vascular functionality post ICH improves outcome. Mechanistically, this study unveiled that leptin boost post-ICH angiogenesis potentially through modulation of leptin receptor (leptinR)/Signal Transducer and Activator of Transcription 3 (STAT3) signaling pathway in pericyte. Thus, leptin may be a lucrative option for the treatment of ICH.

Glycometabolism Reprogramming of Glial Cells in Central Nervous System: Novel Target for Neuropathic Pain

Neuropathic pain is characterized by hyperalgesia and allodynia. Inflammatory response is conducive to tissue recovery upon nerve injury, but persistent and exaggerated inflammation is detrimental and participates in neuropathic pain. Synaptic transmission in the nociceptive pathway, and particularly the balance between facilitation and inhibition, could be affected by inflammation, which in turn is regulated by glial cells. Importantly, glycometabolism exerts a vital role in the inflammatory process. Glycometabolism reprogramming of inflammatory cells in neuropathic pain is characterized by impaired oxidative phosphorylation in mitochondria and enhanced glycolysis. These changes induce phenotypic transition of inflammatory cells to promote neural inflammation and oxidative stress in peripheral and central nervous system. Accumulation of lactate in synaptic microenvironment also contributes to synaptic remodeling and central sensitization. Previous studies mainly focused on the glycometabolism reprogramming in peripheral inflammatory cells such as macrophage or lymphocyte, little attention was paid to the regulation effects of glycometabolism reprogramming on the inflammatory responses in glial cells. This review summarizes the evidences for glycometabolism reprogramming in peripheral inflammatory cells, and presents a small quantity of present studies on glycometabolism in glial cells, expecting to promote the exploration in glycometabolism in glial cells of neuropathic pain.

Traditional Chinese medicine use in the pathophysiological processes of intracerebral hemorrhage and comparison with conventional therapy

Intracerebral hemorrhage (ICH) refers to hemorrhage caused by non-traumatic vascular rupture in the brain parenchyma, which is characterized by acute onset, severe illness, and high mortality and disability. The influx of blood into the brain tissue after cerebrovascular rupture causes severe brain damage, including primary injury caused by persistent hemorrhage and secondary brain injury (SBI) induced by hematoma. The mechanism of brain injury is complicated and is a significant cause of disability after ICH. Therefore, it is essential to understand the mechanism of brain injury after ICH to develop drugs to prevent and treat ICH. Studies have confirmed that many traditional Chinese medicines (TCM) can reduce brain injury by improving neurotoxicity, inflammation, oxidative stress (OS), blood-brain barrier (BBB), apoptosis, and neurological dysfunction after ICH. Starting from the pathophysiological process of brain injury after ICH, this paper summarizes the mechanisms by which TCM improves cerebral injury after ICH and its comparison with conventional western medicine, so as to provide clues and a reference for the clinical application of TCM in the prevention and treatment of hemorrhagic stroke and further research and development of new drugs.

Astrocytes as Key Regulators of Brain Energy Metabolism: New Therapeutic Perspectives

Astrocytes play key roles in the regulation of brain energy metabolism, which has a major impact on brain functions, including memory, neuroprotection, resistance to oxidative stress and homeostatic tone. Energy demands of the brain are very large, as they continuously account for 20–25% of the whole body’s energy consumption. Energy supply of the brain is tightly linked to neuronal activity, providing the origin of the signals detected by the widely used functional brain imaging techniques such as functional magnetic resonance imaging and positron emission tomography. In particular, neuroenergetic coupling is regulated by astrocytes through glutamate uptake that triggers astrocytic aerobic glycolysis and leads to glucose uptake and lactate release, a mechanism known as the Astrocyte Neuron Lactate Shuttle. Other neurotransmitters such as noradrenaline and Vasoactive Intestinal Peptide mobilize glycogen, the reserve for glucose exclusively localized in astrocytes, also resulting in lactate release. Lactate is then transferred to neurons where it is used, after conversion to pyruvate, as a rapid energy substrate, and also as a signal that modulates neuronal excitability, homeostasis, and the expression of survival and plasticity genes. Importantly, glycolysis in astrocytes and more generally cerebral glucose metabolism progressively deteriorate in aging and age-associated neurodegenerative diseases such as Alzheimer’s disease. This decreased glycolysis actually represents a common feature of several neurological pathologies. Here, we review the critical role of astrocytes in the regulation of brain energy metabolism, and how dysregulation of astrocyte-mediated metabolic pathways is involved in brain hypometabolism. Further, we summarize recent efforts at preclinical and clinical stages to target brain hypometabolism for the development of new therapeutic interventions in age-related neurodegenerative diseases.

All roads lead to Rome - a review of the potential mechanisms by which exerkines exhibit neuroprotective effects in Alzheimer's disease

Age-related neurodegenerative disorders such as Alzheimer’s disease (AD) have become a critical public health issue due to the significantly extended human lifespan, leading to considerable economic and social burdens. Traditional therapies for AD such as medicine and surgery remain ineffective, impractical, and expensive. Many studies have shown that a variety of bioactive substances released by physical exercise (called “exerkines”) help to maintain and improve the normal functions of the brain in terms of cognition, emotion, and psychomotor coordination. Increasing evidence suggests that exerkines may exert beneficial effects in AD as well. This review summarizes the neuroprotective effects of exerkines in AD, focusing on the underlying molecular mechanism and the dynamic expression of exerkines after physical exercise. The findings described in this review will help direct research into novel targets for the treatment of AD and develop customized exercise therapy for individuals of different ages, genders, and health conditions.

Effects of lactate and carbon monoxide interactions on neuroprotection and neuropreservation

Lactate, historically considered a waste product of anerobic metabolism, is a metabolite in whole-body metabolism needed for normal central nervous system (CNS) functions and a potent signaling molecule and hormone in the CNS. Neuronal activity signals normally induce its formation primarily in astrocytes and production is dependent on anerobic and aerobic metabolisms. Functions are dependent on normal dynamic, expansive, and evolving CNS functions. Levels can change under normal physiologic conditions and with CNS pathology. A readily combusted fuel that is sshuttled throughout the body, lactate is used as an energy source and is needed for CNS hemostasis, plasticity, memory, and excitability. Diffusion beyond the neuron active zone impacts activity of neurons and astrocytes in other areas of the brain. Barriergenesis, function of the blood-brain barrier, and buffering between oxidative metabolism and glycolysis and brain metabolism are affected by lactate. Important to neuroprotection, presence or absence is associated with L-lactate and heme oxygenase/carbon monoxide (a gasotransmitter) neuroprotective systems. Effects of carbon monoxide on L-lactate affect neuroprotection - interactions of the gasotransmitter with L-lactate are important to CNS stability, which will be reviewed in this article.

Central Nervous System Tissue Regeneration after Intracerebral Hemorrhage: The Next Frontier

Despite marked advances in surgical techniques and understanding of secondary brain injury mechanisms, the prognosis of intracerebral hemorrhage (ICH) remains devastating. Harnessing and promoting the regenerative potential of the central nervous system may improve the outcomes of patients with hemorrhagic stroke, but approaches are still in their infancy. In this review, we discuss the regenerative phenomena occurring in animal models and human ICH, provide results related to cellular and molecular mechanisms of the repair process including by microglia, and review potential methods to promote tissue regeneration in ICH. We aim to stimulate research involving tissue restoration after ICH.

Energy metabolism in childhood neurodevelopmental disorders

Whereas energy function in the aging brain and their related neurodegenerative diseases has been explored in some detail, there is limited knowledge about molecular mechanisms and brain networks of energy metabolism during infancy and childhood. In this review we describe current insights on physiological brain energetics at prenatal and neonatal stages, and in childhood. We then describe the main groups of inborn errors of energy metabolism affecting the brain. Of note, scarce basic neuroscience research in this field limits the opportunity for these disorders to provide paradigms of energy utilization during neurodevelopment. Finally, we report energy metabolism disturbances in well-known non-metabolic neurodevelopmental disorders. As energy metabolism is a fundamental biological function, brain energy utilization is likely altered in most neuropediatric diseases. Precise knowledge on mechanisms of brain energy disturbance will open the possibility of metabolic modulation therapies regardless of disease etiology.

Lactate as Potential Mediators for Exercise-Induced Positive Effects on Neuroplasticity and Cerebrovascular Plasticity

The accumulated evidence from animal and human studies supports that exercise is beneficial to physical health. Exercise can upregulate various neurotrophic factors, activate neuroplasticity, and play a positive role in improving and enhancing cerebrovascular function. Due to its economy, convenience, and ability to prevent or ameliorate various aging-related diseases, exercise, a healthy lifestyle, is increasingly popularized by people. However, the mechanism by which exercise performs this function and how it is transmitted from muscles to the brain remains incompletely understood. Here, we review the beneficial effects of exercise with different intensities on the brain with a focus on the positive effects of lactate on neuroplasticity and cerebrovascular plasticity. Based on these recent studies, we propose that lactate, a waste previously misunderstood as a by-product of glycolysis in the past, may be a key signal molecule that regulates the beneficial adaptation of the brain caused by exercise. Importantly, we speculate that a central protective mechanism may underlie the cognitive benefits induced by exercise.

Exercise Factors Released by the Liver, Muscle, and Bones Have Promising Therapeutic Potential for Stroke

Stroke is one of the leading causes of death and disability in the world. Stroke not only affects the patients, but also their families who serve as the primary caregivers. Discovering novel therapeutic targets for stroke is crucial both from a quality of life perspective as well as from a health economic perspective. Exercise is known to promote neuroprotection in the context of stroke. Indeed, exercise induces the release of blood-borne factors that promote positive effects on the brain. Identifying the factors that mediate the positive effects of exercise after ischemic stroke is crucial for the quest for novel therapies. This approach will yield endogenous molecules that normally cross the blood brain barrier (BBB) and that can mimic the effects of exercise. In this minireview, we will discuss the roles of exercise factors released by the liver such as beta-hydroxybutyrate (DBHB), by the muscle such as lactate and irisin and by the bones such as osteocalcin. We will also address their therapeutic potential in the context of ischemic stroke.

Hydroxycarboxylic Acid Receptor 1 and Neuroprotection in a Mouse Model of Cerebral Ischemia-Reperfusion

Lactate is an intriguing molecule with emerging physiological roles in the brain. It has beneficial effects in animal models of acute brain injuries and traumatic brain injury or subarachnoid hemorrhage patients. However, the mechanism by which lactate provides protection is unclear. While there is evidence of a metabolic effect of lactate providing energy to deprived neurons, it can also activate the hydroxycarboxylic acid receptor 1 (HCAR1), a Gi-coupled protein receptor that modulates neuronal firing rates. After cerebral hypoxia-ischemia, endogenously produced brain lactate is largely increased, and the exogenous administration of more lactate can decrease lesion size and ameliorate the neurological outcome. To test whether HCAR1 plays a role in lactate-induced neuroprotection, we injected the agonists 3-chloro-5-hydroxybenzoic acid and 3,5-dihydroxybenzoic acid into mice subjected to 30-min middle cerebral artery occlusion. The in vivo administration of HCAR1 agonists at reperfusion did not appear to exert any relevant protective effect as seen with lactate administration. Our results suggest that the protective effects of lactate after hypoxia-ischemia come rather from the metabolic effects of lactate than its signaling through HCAR1.

Thrombin-induced miRNA-24-1-5p upregulation promotes angiogenesis by targeting prolyl hydroxylase domain 1 in intracerebral hemorrhagic rats

OBJECTIVE

Thrombin is a unique factor that triggers post-intracerebral hemorrhage (ICH) angiogenesis by increasing hypoxia-inducible factor-1α (HIF-1α) at the protein level. However, HIF-1α mRNA remains unchanged. MicroRNAs (miRNAs) mediate posttranscriptional regulation by suppressing protein translation from mRNAs. This study aimed to determine if miRNAs might be involved in thrombin-induced angiogenesis after ICH by targeting HIF-1α or its upstream prolyl hydroxylase domains (PHDs).

METHODS

The study was divided into two parts. In part 1, rats received an injection of thrombin into the right globus pallidus. An miRNA array combined with miRNA target prediction, luciferase activity assay, and miRNA mimic/inhibitor transfection were used to identify candidate miRNAs and target genes. Part 2 included experiments 1 and 2. In experiment 1, rats were randomly divided into the sham group, ICH group, and ICH+hirudin-treated (thrombin inhibitor) group. In experiment 2, the rats were randomly divided into the sham group, ICH group, ICH+antagomir group, ICH+antagomir-control group, and ICH+vehicle group. Western blotting and quantitative real-time polymerase chain reaction were used to determine the expression of protein and miRNA, respectively. The coexpression of miR-24-1-5p (abbreviated to miR-24) and von Willebrand factor was detected by in situ hybridization and immunohistochemical analysis. The angiogenesis was evaluated by double-labeling immunofluorescence. Neurological function was evaluated by body weight, modified Neurological Severity Scores, and corner turn and foot-fault tests.

RESULTS

In part 1, it was shown that miR-24, which is predicted to target PHD1, was upregulated (fold-change of 1.83) after thrombin infusion, and that the miR-24 mimic transfection decreased luciferase activity and downregulated PHD1 expression (p < 0.05). miR-24 inhibitor transfection increased PHD1 expression (p < 0.05). In part 2, it was shown that miR-24 was expressed in endothelial cells. The HIF-1α protein level and proliferating cell nuclear antigen-positive (PCNA+) nuclei in vessels were increased, while the PHD1 protein level was decreased after ICH, and these effects were reversed by hirudin (p < 0.05). The antagomiR-24-treated rats exhibited a markedly lower body weight and significantly poorer recovery from neurological deficit compared with those in ICH groups (p < 0.05). AntagomiR-24 intervention also led to lower miR-24 expression, a higher PHD1 protein level, and fewer PCNA+ nuclei in vessels compared with those in ICH groups (p < 0.05).

CONCLUSIONS

The present study suggests that thrombin reduces HIF-1α degradation and initiates angiogenesis by increasing miR-24, which targets PHD1 after ICH.

Adult Hippocampal Neurogenesis: One Lactate to Rule Them All

Adult hippocampal neurogenesis is a dynamic process involved in cognitive functions, like learning and memory. Numerous intrinsic and extrinsic factors regulate and affect hippocampal neurogenesis. An exceptionally beneficial external factor is physical exercise due to the impact of the lactate accumulated during physical effort on neural plasticity. Lactate has recently emerged as one of the most interesting and potent factors in health and disease due to its involvement in the metabolism and signaling of most, if not all, of the cells in the CNS. Herein, we illustrate the effects induced by lactate on the different cell types within the neurogenic niche, in light of their described roles in regulating adult hippocampal neurogenesis.

Insulin stimulation reduces aortic wave reflection in adults with metabolic syndrome

Adults with metabolic syndrome (MetS) have increased fasting arterial stiffness and altered central hemodynamics that contribute, partly, to increased cardiovascular disease (CVD) risk. Although insulin affects aortic wave reflections in healthy adults, the effects in individuals with MetS are unclear. We hypothesized that insulin stimulation would reduce measures of pressure waveforms and hemodynamics in people with MetS. Thirty-five adults with obesity (27 women; 54.2 ± 6.0 yr; 37.1 ± 4.8 kg/m²) were selected for MetS (ATP III criteria) following an overnight fast. Pulse wave analysis was assessed using applanation tonometry before and after a 2-h euglycemic-hyperinsulinemic clamp (90 mg/dL, 40 mU/m²/min). Deconvolution analysis was used to decompose the aortic waveform [augmentation index corrected to heart rate of 75 beats/min (AIx@75); augmentation pressure (AP)] into backward and forward pressure components. Aerobic fitness (V̇o_2max), body composition (DXA), and blood biochemistries were also assessed. Insulin significantly reduced augmentation index (AIx@75, 28.0 ± 9.6 vs. 23.0 ± 9.9%, P < 0.01), augmentation pressure (14.8 ± 6.4 vs. 12.0 ± 5.7 mmHg, P < 0.01), pulse pressure amplification (1.26 ± 0.01 vs. 0.03 ± 0.01, P = 0.01), and inflammation [high-sensitivity C-reactive protein (hsCRP): P = 0.02; matrix metallopeptidase 7 (MMP-7): P = 0.03] compared to fasting. In subgroup analyses to understand HTN influence, there were no insulin stimulation differences on any outcome. V̇o_2max, visceral fat, and blood potassium correlated with fasting AIx@75 (r = -0.39, P = 0.02; r = 0.41, P = 0.03; r = -0.53, P = 0.002). Potassium levels were also associated with insulin-mediated reductions in AP (r = 0.52, P = 0.002). Our results suggest insulin stimulation improves indices of aortic reflection in adults with MetS.NEW & NOTEWORTHY This study is one of the first to investigate the effects of insulin on central and peripheral hemodynamics in adults with metabolic syndrome. We provide evidence that insulin infusion reduces aortic wave reflection, potentially through a reduction in inflammation and/or via a potassium-mediated vascular response.

Temporal metabolomic alteration in rat brains of experimental intracerebral hemorrhage

BACKGROUND

Intracerebral hemorrhage (ICH) is the top lethal and disabling form of stroke. The pathophysiology of ICH is not fully understood yet. Metabolites are indicators and regulators of cellular processes. However, the overall brain metabolic pattern and the temporal alterations after ICH remain unknown.

METHODS

A total of 40 male rats were randomly assigned to sham group and ICH group. ICH was induced by collagenase Ⅶ. Body weight was assessed. Neurological deficits were evaluated by modified neurological severity score. Then, the perihematomal brain tissues were collected for metabolites detection using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS). The metabolic profiles were displayed by principal component analysis (PCA), partial least-squares-discriminant analysis (PLS-DA) and cluster analysis. The significant differential metabolites were screened by fold change > 2.0, the false discovery rate (FDR) < 0.05 and Variable Importance of Projection (VIP) > 1. Next, the relevant metabolic pathways were discerned by MetaboAnalyst website. A metabolite-protein interaction network was subsequentially constructed to further annotate the function of differential metabolites.

RESULTS

Rats suffered from compromised body weight increasement and impaired neurological function. The metabolomics profiles of brain tissues in the post-ICH rats were markedly different from those in the sham group on days 3 and 14. Thirty-four metabolites (bilirubin, uric acid, 6-Methylnicotinamide et al.) were abnormally upregulated in the acute stage, while 27 metabolites were disturbed in the recovery stage, including bilirubin, uric acid, and histamine et al. Seven and three metabolic pathways altered in the acute and recovery stage, respectively. Metabolite-protein interaction analysis revealed that the disturbed metabolites may participate in ICH pathophysiology by altering amino acid metabolism, peroxisome proliferators-activated receptor signaling pathway, fatty acid metabolism and urea cycle in the acute stage, while influencing amino acid metabolism, urea cycle and peroxisome in the recovery stage.

CONCLUSIONS

Our study mapped the pathological metabolomics profiles of the post-ICH rat brains in the acute and recovery phases. This work will assist in discovering novel therapeutic targets and treatments for ICH.

A pro-inflammatory mediator USP11 enhances the stability of p53 and inhibits KLF2 in intracerebral hemorrhage

Microglial cell activation and neuroinflammation after intracerebral hemorrhage (ICH) lead to secondary brain damage. Ubiquitin-specific protease 11 (USP11) has been correlated with ICH-induced neuron apoptosis. This study aims to explore the molecular mechanism of USP11 regulating neuroinflammation in ICH. First, an ICH rat model was developed by intracranial administration of collagenase. Silencing USP11 was found to alleviate nerve injury in rats with ICH-like symptoms. Then, through loss- and gain-of-function assays, USP11 knockdown was revealed to alleviate ICH-induced symptoms, corresponding to reduced modified neurological severity scores (mNSS) value, brain water content, blood-brain barrier permeability, neuron apoptosis, microglial cell activation, neutrophil infiltration, and inflammatory factor secretion. It was subsequently shown in microglial cells that USP11 stabilized p53 by deubiquitination and p53 targeted the Kruppel-like factor 2 (KLF2) promoter to repress KLF2 transcription, thereby activating the nuclear factor κB (NF-κB) pathway. Further, rescue experiments were conducted in vivo to validate the function of the USP11/p53/KLF2/NF-κB axis in ICH-induced inflammation, which confirmed that USP11 silencing blocked the release of pro-inflammatory cytokines following ICH by downregulating p53, thus protecting against neurological impairment. Hence silencing USP11 may be a novel anti-inflammatory method for ICH treatment.

Recovery From Repeat Mild Traumatic Brain Injury in Adolescent Rats Is Dependent on Pre-injury Activity State

Adolescents and young adults have the highest incidence of mild traumatic brain injury (mTBI); sport-related activities are a major contributor. Roughly a third of these patients diagnosed with mTBI are estimated to have received a subsequent repeat mTBI (rTBI). Previously, animal studies have only modeled mTBI in sedentary animals. This study utilizes physical activity as a dependent variable prior to rTBI in adolescent rats by allowing voluntary exercise in males, establishing the rat athlete (rathlete). Rats were given access to locked or functional running wheels for 10 d prior to sham or rTBI injury. Following rTBI, rathletes were allowed voluntary access to running wheels beginning on different days post-injury: no run (rTBI+no run), immediate run (rTBI+Immed), or 3 day delay (rTBI+3dd). Rats were tested for motor and cognitive-behavioral (anxiety, social, memory) and mechanosensory (allodynia) dysfunction using a novel rat standardized concussion assessment tool on post-injury days 1,3,5,7, and 10. Protein expression of brain derived neurotrophic factor (BDNF) and proliferator-activated gamma coactivator 1-alpha (PGC1α) was measured in the parietal cortex, hippocampus, and gastrocnemius muscle. Sedentary shams displayed lower anxiety-like behaviors compared to rathlete shams on all testing days. BDNF and PGC1α levels increased in the parietal cortex and hippocampus with voluntary exercise. In rTBI rathletes, the rTBI+Immed group showed impaired social behavior, memory impairment in novel object recognition, and increased immobility compared to rathlete shams. All rats showed greater neuropathic mechanosensory sensitivity than previously published uninjured adults, with rTBI+3dd showing greatest sensitivity. These results demonstrate that voluntary exercise changes baseline functioning of the brain, and that among rTBI rathletes, delayed return to activity improved cognitive recovery.

Hypoxia-inducible Factor 2α Exerts Neuroprotective Effects by Promoting Angiogenesis via the VEGF/Notch Pathway after Intracerebral Hemorrhage Injury in Rats

Angiogenesis after intracerebral hemorrhage (ICH) injury can effectively alleviate brain damage and improve neurological function. Hypoxia-inducible factor 2α (HIF-2α) is an important angiogenic regulator and exhibits protective effects in several neurological diseases; however, its role in ICH has not yet been reported. Hence, in the present study, we explored whether HIF-2α reduces ICH injury by promoting angiogenesis. In addition, we explored the role of the vascular endothelial growth factor (VEGF)/Notch pathway in HIF-2α-mediated angiogenesis. We injected 50 μL of autologous blood taken from the femoral artery into the right striatum of healthy male adult Sprague-Dawley rats to create an autologous-blood-induced rat model of ICH. Lentiviral vectors were injected to both overexpress and knock down HIF-2α expression. VEGF receptor 2 (VEGFR2) and Notch-specific inhibitors were injected intraperitoneally to block VEGFR2- and Notch-mediated signaling after lentiviral injections. Our data showed that HIF-2α overexpression reduced neurological-damage scores and brain-water content, suggesting it had a protective effect on ICH injury. In addition, overexpression of HIF-2α promoted angiogenesis, increased focal cerebral blood flow (CBF), and reduced neuronal damage, whereas HIF-2α knockdown resulted in the opposite effects. Furthermore, we found that HIF-2α-mediated angiogenesis was blocked by a Notch-specific inhibitor. Likewise, the HIF-2α-mediated increase in phospho-VEGFR-2, cleaved-Notch1 and Notch1 expression was reversed via a VEGFR2-specific inhibitor. Taken together, our results indicate that HIF-2α promotes angiogenesis via the VEGF/Notch pathway to attenuate ICH injury. Moreover, our findings may contribute to the development of a novel strategy for alleviating ICH injury via HIF-2α-mediated upregulation of angiogenesis.

[Effect of mild hypothermia on behaviors of rats with intracerebral hemorrhage and the possible mechanism]

OBJECTIVE

To explore the effect of mild hypothermia on inflammatory response and angiogenesis in brain tissues of rats with intracerebral hemorrhage (ICH) and its possible mechanism for improving behavioral deficits of the rats After ICH.

METHODS

A total of 120 healthy male SD rats were randomly divided into sham operation group, ICH group and mild hypothermia group. Rat models of ICH were established in the latter two groups by stereotactic injection of autogenous blood in the brain, and the rats in the sham operation group received injection of normal saline in the same manner. At 15 min after modeling, the rats in hypothermia group were subjected to mild hypothermia (30-32 ℃) for 8 h followed by rewarming (37-38 ℃); the body temperature was maintained at 37-38 ℃ in the other two groups. At 2, 4, 7, 14 and 21 days after the treatment, Longa scoring, balance beam scoring and Berderson scoring were used to evaluate the behavioral deficits of the rats. Immunohistochemical staining was used to detect the protein expressions of tumor necrosis factor-α (TNF-α) and nuclear factor-κB (NF-κB) in the brain tissue of the rats, and the mRNA expressions of α subunit of hypoxia-inducible factor 1 (HIF1-α) and vascular endothelial growth factor (VEGF) were detected using RT- PCR.

RESULTS

At 2, 4, 7, 14 and 21 days after the treatment, the behavioral scores of the rats were significantly higher in ICH group and mild induced hypothermia group than in the sham operation group (P < 0.05 or 0.01). The protein expressions of TNF-α and NF-κB and mRNA expressions of HIF1-α and VEGF were significantly higher in ICH group and mild hypothermia group than in the sham operation group (P < 0.01). The behavioral scores were significantly lower in mild hypothermia group than in ICH group (P < 0.05), and the protein expressions of TNF-α and NF-κB were lower and the mRNA expressions of HIF1- α and VEGF were higher in mild hypothermia group than in ICH group (P < 0.05 or 0.01).

CONCLUSIONS

Mild hypothermia can improve behavioral deficits in rats with ICH possibly by antagonizing brain inflammation and promoting angiogenesis.

The effects of microglia‐ and astrocyte‐derived factors on neurogenesis in health and disease

Hippocampal neurogenesis continues throughout life and has been suggested to play an essential role in maintaining spatial cognitive function under physiological conditions. An increasing amount of evidence has indicated that adult neurogenesis is tightly controlled by environmental conditions in the neurogenic niche, which consists of multiple types of cells including microglia and astrocytes. Microglia maintain the environment of neurogenic niche through their phagocytic capacity and interaction with neurons via fractalkine‐CX3CR1 signaling. In addition, microglia release growth factors such as brain‐derived neurotrophic factor (BDNF) and cytokines such as tumor necrosis factor (TNF)‐α to support the development of adult born neurons. Astrocytes also manipulate neurogenesis by releasing various soluble factors including adenosine triphosphate and lactate. Whereas, under pathological conditions such as Alzheimer's disease, depression, and epilepsy, microglia and astrocytes play a leading role in inflammation and are involved in attenuating the normal process of neurogenesis. The modulation of glial functions on neurogenesis in these brain diseases are attracting attention as a new therapeutic target. This review describes how these glial cells play a role in adult hippocampal neurogenesis in both health and disease, especially focusing glia‐derived factors.

Signalling, Metabolic Pathways and Iron Homeostasis in Endothelial Cells in Health, Atherosclerosis and Alzheimer's Disease

Endothelial cells drive the formation of new blood vessels in physiological and pathological contexts such as embryonic development, wound healing, cancer and ocular diseases. Once formed, all vessels of the vasculature system present an endothelial monolayer (the endothelium), lining the luminal wall of the vessels, that regulates gas and nutrient exchange between the circulating blood and tissues, contributing to maintaining tissue and vascular homeostasis. To perform their functions, endothelial cells integrate signalling pathways promoted by growth factors, cytokines, extracellular matrix components and signals from mechanosensory complexes sensing the blood flow. New evidence shows that endothelial cells rely on specific metabolic pathways for distinct cellular functions and that the integration of signalling and metabolic pathways regulates endothelial-dependent processes such as angiogenesis and vascular homeostasis. In this review, we provide an overview of endothelial functions and the recent advances in understanding the role of endothelial signalling and metabolism in physiological processes such as angiogenesis and vascular homeostasis and vascular diseases. Also, we focus on the signalling pathways promoted by the transmembrane protein Neuropilin-1 (NRP1) in endothelial cells, its recently discovered role in regulating mitochondrial function and iron homeostasis and the role of mitochondrial dysfunction and iron in atherosclerosis and neurodegenerative diseases.

Exercise benefits on Alzheimer's disease: State-of-the-science

Although there is no unanimity, growing evidence supports the value of regular physical exercise to prevent Alzheimer's disease as well as cognitive decline in affected patients. Together with an introductory summary on epidemiological evidence, the aim of this review is to summarize the current knowledge on the potential biological mechanisms underlying exercise benefits in this condition. Regular physical exercise has proven to be beneficial for traditional cardiovascular risk factors (e.g., reduced vascular flow, diabetes) involved in the pathogenesis of Alzheimer's disease. Exercise also promotes neurogenesis via increases in exercise-induced metabolic factors (e.g., ketone bodies, lactate) and muscle-derived myokines (cathepsin-B, irisin), which in turn stimulate the production of neurotrophins such as brain-derived neurotrophic factor. Finally, regular exercise exerts anti-inflammatory effects and improves the brain redox status, thereby ameliorating the pathophysiological hallmarks of Alzheimer's disease (e.g., amyloid-β deposition). In summary, physical exercise might provide numerous benefits through different pathways that might, in turn, help prevent risk and progression of Alzheimer's disease. More evidence is needed, however, based on human studies.

Nicotine promotes angiogenesis in mouse brain after intracerebral hemorrhage

Here we examined the effect of nicotine on angiogenesis in the brain after intracerebral hemorrhage (ICH), as angiogenesis is considered to provide beneficial effects on brain tissues during recovery from injury after stroke. Nicotine was administered to C57BL/6 mice suffering from collagenase-induced ICH in the striatum, either by inclusion in drinking water or by daily intraperitoneal injection. Nicotine administration by both routes enhanced angiogenesis within the hematoma-affected regions, as revealed by increased CD31-immunopositive area at 7 and 14 d after ICH. Double immunofluorescence histochemistry against CD31 and proliferating cell nuclear antigen revealed that nicotine increased the number of newly generated vascular endothelial cells within the hematoma. In spite of enhanced angiogenesis, nicotine did not worsen vascular permeability after ICH, as assessed by Evans Blue extravasation. These effects of nicotine were accompanied by an increased number of surviving neurons in the hematoma at 7 d after ICH. Unexpectedly, nicotine did not increase expression of vascular endothelial growth factor mRNA in the brain and did not enhance recruitment of endothelial progenitor cells from the bone marrow. These results suggest that nicotine enhances angiogenesis in the brain after ICH, via mechanisms distinct from those involved in its action on angiogenesis in peripheral tissues.

Functions of lactate in the brain of rat with intracerebral hemorrhage evaluated with MRI/MRS and in vitro approaches

Introduction

Lactate accumulation in the brain is caused by the anaerobic metabolism induced by ischemic damages, which always accompanies intracerebral hemorrhages (ICH). Our former findings showed that microglia's movement was always directly toward hemorrhagic center with the highest lactate concentration, and penumbra area has the largest density of compactly arrayed microglia. However, the relationship between microglia and lactate concentration has not been well documented.

Methods

Cerebral hemorrhage model was successfully achieved by injecting collagenase VII (causing stabile localized bleeding) in CPu (striatum) of SD rats. Emodin was used as a potential therapeutic for ICH. The function of the lactate was examined with in vitro culture studies. Then, the effect of lactate on the proliferation, cell survival, migration, and phagocytosis property of microglia was investigated by in vitro culture studies.

Results

Lactate accumulation was observed with in vivo MRS method, and its concentration was monitored during the recovery of ICH and treatment of emodin. Lactate concentration significantly increased in the core and penumbra regions of hemorrhagic foci, and it decreased after the treatment of emodin. The in vitro culture study was verified that lactate was beneficial for the proliferation, cell survival, migration, and phagocytosis property of the microglia.

Conclusion

Results from in vitro verification study, investigations from the recovery of ICH, and treatment of emodin verify that lactate plays an important role during the recovery of ICH. This could provide a novel therapeutic approach for ICH.

Association between the hydrogenase level and the occurrence of remote diffusion-weighted imaging lesions after spontaneous intracerebral hemorrhage

To explore the influence of serum lactate dehydrogenase (LDH) level on remote diffusion-weighted imaging lesions (rDWILs) after spontaneous intracerebral hemorrhage (ICH). A consecutive cohort of 160 patients with spontaneous ICH who had brain MRI within 4 weeks of ICH onset were collected and analyzed retrospectively. rDWILs showed high signal on diffusion-weighted image (DWI) while low signal on apparent diffusion coefficient (ADC), and at least 20 mm away from the hemorrhage focus. The blood samples were obtained within 24 h after ICH onset from all patients. Lactate dehydrogenase (LDH) levels in blood were collected from serum biochemical tests. We use multivariate logistic regression analyses to investigate the association between serum LDH level and rDWILs after ICH. The average serum LDH level was 186.5 ± 35.6 U/L. And this level was higher in patients who presented rDWILs than in those without rDWILs. With the best cut-off value of 191 by using receiver operating characteristic (ROC) analysis, elevated LDH was associated with the presence of rDWILs independently (OR = 1.024, 95%CI = 1.011-1.037, P < 0.001) in the bivariate logistic regression analysis with adjustment for age, sex, previous ischemic stroke/TIA, smoker, SBP on admission, hematoma volume, and intraventricular hemorrhage (IVH). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) of LDH ≥ 191 U/L for rDWILs were 70.4%, 72.2%, 33.9%, 94.2%, respectively. Our study suggests serum LDH level has a significant correlation with rDWILs after spontaneous ICH. Patients with higher serum LDH level in 24 h after ICH onset may be a useful predictor for rDWILs occurrence.

Extended preclinical investigation of lactate for neuroprotection after ischemic stroke

Lactate has been shown to have beneficial effect both in experimental ischemia–reperfusion models and in human acute brain injury patients. To further investigate lactate’s neuroprotective action in experimental in vivo ischemic stroke models prior to its use in clinics, we tested (1) the outcome of lactate administration on permanent ischemia and (2) its compatibility with the only currently approved drug for the treatment of acute ischemic stroke, recombinant tissue plasminogen activator (rtPA), after ischemia–reperfusion. We intravenously injected mice with 1 µmol/g sodium l-lactate 1 h or 3 h after permanent middle cerebral artery occlusion (MCAO) and looked at its effect 24 h later. We show a beneficial effect of lactate when administered 1 h after ischemia onset, reducing the lesion size and improving neurological outcome. The weaker effect observed at 3 h could be due to differences in the metabolic profiles related to damage progression. Next, we administered 0.9 mg/kg of intravenous (iv) rtPA, followed by intracerebroventricular injection of 2 µL of 100 mmol/L sodium l-lactate to treat mice subjected to 35-min transient MCAO and compared the outcome (lesion size and behavior) of the combined treatment with that of single treatments. The administration of lactate after rtPA has positive influence on the functional outcome and attenuates the deleterious effects of rtPA, although not as strongly as lactate administered alone. The present work gives a lead for patient selection in future clinical studies of treatment with inexpensive and commonly available lactate in acute ischemic stroke, namely patients not treated with rtPA but mechanical thrombectomy alone or patients without recanalization therapy.

Energy Dynamics in the Brain: Contributions of Astrocytes to Metabolism and pH Homeostasis

Regulation of metabolism is complex and involves enzymes and membrane transporters, which form networks to support energy dynamics. Lactate, as a metabolic intermediate from glucose or glycogen breakdown, appears to play a major role as additional energetic substrate, which is shuttled between glycolytic and oxidative cells, both under hypoxic and normoxic conditions. Transport of lactate across the cell membrane is mediated by monocarboxylate transporters (MCTs) in cotransport with H⁺, which is a substrate, a signal and a modulator of metabolic processes. MCTs form a “transport metabolon” with carbonic anhydrases (CAs), which not only provide a rapid equilibrium between CO₂, HCO₃^– and H⁺, but, in addition, enhances lactate transport, as found in Xenopus oocytes, employed as heterologous expression system, as well as in astrocytes and cancer cells. Functional interactions between different CA isoforms and MCTs have been found to be isoform-specific, independent of the enzyme’s catalytic activity, and they require physical interaction between the proteins. CAs mediate between different states of metabolic acidosis, induced by glycolysis and oxidative phosphorylation, and play a relay function in coupling pH regulation and metabolism. In the brain, metabolic processes in astrocytes appear to be linked to bicarbonate transport and to neuronal activity. Here, we focus on physiological processes of energy dynamics in astrocytes as well as on the transfer of energetic substrates to neurons.

White matter repair and treatment strategy after intracerebral hemorrhage

The predilection site of intracerebral hemorrhage (ICH) is in the basal ganglia, which is rich in white matter (WM) fiber bundles, such as cerebrospinal tract in the internal capsule. ICH induced damage to this area can easily lead to severe neurological dysfunction and affects the prognosis and quality of life of patients. At present, the pathophysiological mechanisms of white matter injury (WMI) after ICH have attracted researchers' attention, but studies on the repair and recovery mechanisms and therapy strategies remain rare. In this review, we mainly summarized the WM recovery and treatment strategies after ICH by updating the WMI-related content by reviewing the latest researches and proposing the bottleneck of the current research.

Lithium chloride promoted hematoma resolution after intracerebral hemorrhage through GSK-3β-mediated pathways-dependent microglia phagocytosis and M2-phenotype differentiation, angiogenesis and neurogenesis in a rat model

Some neuroprotective agents have been used clinically to address the resulting various adverse effects after intracerebral hemorrhage (ICH). Particularly, effectively removing the hematoma is of practical significance to exert neuroprotective effects following ICH. However, such agents are still in need of development. Lithium chloride (LiCl) has shown neuroprotective effects through glycogen synthase kinase-3β (GSK-3β) inhibition in a variety of central nervous system diseases. However, the impact of LiCl on hematoma clearance and the potential molecular mechanisms have not been reported. We hypothesize that LiCl may exert neuroprotective roles after ICH, partly through promoting hematoma resolution. In this study, male Sprague-Dawley rats were subjected to ICH followed by intraperitoneal injection of LiCl (60 mg/kg). The hematoma volumes of ipsilateral hemisphere were determined using Drabkin's method. The sensorimotor deficits were evaluated by neurobehavioral tests. The expressions of target molecules involved in the process of hematoma clearance were assayed using immunofluorescence and Western blot. Our results showed that animals treated with LiCl presented significantly reduced hematoma volume after ICH, which was coupled with enhanced microglia phagocytosis and its differentiation into M2-phenotype within the first 7 days and up-regulated angiogenesis and neurogenesis in the next 7 days. Meanwhile, GSK-3β was inhibited by LiCl and β-catenin became stabilized, which was followed by up-regulation of nuclear factor erythroid 2-related factor 2 and CD36 from days 3 to 7, and increase of vascular endothelial growth factor and brain-derived neurotrophic factor from days 7 to 14. These data suggest that LiCl promotes hematoma resolution via enhancing microglia phagocytosis and M2-phenotype differentiation in the early stage (< 7 days) and angiogenesis and neurogenesis in the chronic phase (days 7-14), thus eventually improving the functional outcomes of ICH rats.

L-Lactate Promotes Adult Hippocampal Neurogenesis

Neurogenesis, the formation of new neurons in the adult brain, is important for memory formation and extinction. One of the most studied external interventions that affect the rate of adult neurogenesis is physical exercise. Physical exercise promotes adult neurogenesis via several factors including brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF). Here, we identified L-lactate, a physical exercise-induced metabolite, as a factor that promotes adult hippocampal neurogenesis. While prolonged exposure to L-lactate promoted neurogenesis, no beneficial effect was exerted on cognitive learning and memory. Systemic pharmacological blocking of monocarboxylate transporter 2 (MCT2), which transports L-lactate to the brain, prevented lactate-induced neurogenesis, while 3,5-dihydroxybenzoic acid (3,5-DHBA), an agonist for the lactate-receptor hydroxycarboxylic acid receptor 1 (HCAR1), did not affect adult neurogenesis. These data suggest that L-lactate partially mediates the effect of physical exercise on adult neurogenesis, but not cognition, in a MCT2-dependent manner.