Insulin renders diabetic rats resistant to acute ischemic stroke by arresting nitric oxide reaction with superoxide to form peroxynitrite

Prospects for the Use of Intranasally Administered Insulin and Insulin-Like Growth Factor-1 in Cerebral Ischemia

Current approaches to the treatment of stroke have significant limitations, and neuroprotective therapy is ineffective. In view of this, searching for effective neuroprotectors and developing new neuroprotective strategies remain a pressing topic in research of cerebral ischemia. Insulin and insulin-like growth factor-1 (IGF-1) play a key role in the brain functioning by regulating the growth, differentiation, and survival of neurons, neuronal plasticity, food intake, peripheral metabolism, and endocrine functions. Insulin and IGF-1 produce multiple effects in the brain, including neuroprotective action in cerebral ischemia and stroke. Experiments in animals and cell cultures have shown that under hypoxic conditions, insulin and IGF-1 improve energy metabolism in neurons and glial cells, promote blood microcirculation in the brain, restore nerve cell functions and neurotransmission, and produce the anti-inflammatory and antiapoptotic effects on brain cells. The intranasal route of insulin and IGF-1 administration is of particular interest in the clinical practice, since it allows controlled delivery of these hormones directly to the brain, bypassing the blood-brain barrier. Intranasally administered insulin alleviated cognitive impairments in elderly people with neurodegenerative and metabolic disorders; intranasally administered insulin and IGF-1 promoted survival of animals with ischemic stroke. The review discusses the published data and results of our own studies on the mechanisms of neuroprotective action of intranasally administered insulin and IGF-1 in cerebral ischemia, as well as the prospects of using these hormones for normalization of CNS functions and reduction of neurodegenerative changes in this pathology.

Hot Spots for the Use of Intranasal Insulin: Cerebral Ischemia, Brain Injury, Diabetes Mellitus, Endocrine Disorders and Postoperative Delirium

A decrease in the activity of the insulin signaling system of the brain, due to both central insulin resistance and insulin deficiency, leads to neurodegeneration and impaired regulation of appetite, metabolism, endocrine functions. This is due to the neuroprotective properties of brain insulin and its leading role in maintaining glucose homeostasis in the brain, as well as in the regulation of the brain signaling network responsible for the functioning of the nervous, endocrine, and other systems. One of the approaches to restore the activity of the insulin system of the brain is the use of intranasally administered insulin (INI). Currently, INI is being considered as a promising drug to treat Alzheimer's disease and mild cognitive impairment. The clinical application of INI is being developed for the treatment of other neurodegenerative diseases and improve cognitive abilities in stress, overwork, and depression. At the same time, much attention has recently been paid to the prospects of using INI for the treatment of cerebral ischemia, traumatic brain injuries, and postoperative delirium (after anesthesia), as well as diabetes mellitus and its complications, including dysfunctions in the gonadal and thyroid axes. This review is devoted to the prospects and current trends in the use of INI for the treatment of these diseases, which, although differing in etiology and pathogenesis, are characterized by impaired insulin signaling in the brain.

A review of stress-induced hyperglycaemia in the context of acute ischaemic stroke: Definition, underlying mechanisms, and the status of insulin therapy

The transient elevation of blood glucose produced following acute ischaemic stroke (AIS) has been described as stress-induced hyperglycaemia (SIH). SIH is common even in patients with AIS who have no previous diagnosis of diabetes mellitus. Elevated blood glucose levels during admission and hospitalization are strongly associated with enlarged infarct size and adverse prognosis in AIS patients. However, insulin-intensive glucose control therapy defined by admission blood glucose for SIH has not achieved the desired results, and new treatment ideas are urgently required. First, we explore the various definitions of SIH in the context of AIS and their predictive value in adverse outcomes. Then, we briefly discuss the mechanisms by which SIH arises, describing the dual effects of elevated glucose levels on the central nervous system. Finally, although preclinical studies support lowering blood glucose levels using insulin, the clinical outcomes of intensive glucose control are not promising. We discuss the reasons for this phenomenon.

The novel GLP-1/GIP dual agonist DA3-CH is more effective than liraglutide in reducing endoplasmic reticulum stress in diabetic rats with cerebral ischemia-reperfusion injury

BACKGROUND AND AIMS

Diabetes is one of the most important risk factors and comorbidities of ischemic stroke. Endoplasmic reticulum stress (ERS) is considered to be the major injury mechanism of ischemic stroke with diabetes. Studies have found that incretin can inhibit ERS in ischemia-reperfusion injury of the liver and heart. We aimed to explore the effects of GLP-1/GIP double agonist DA3-CH and GLP-1 single agonist liraglutide on ERS and apoptosis in diabetic rats with cerebral ischemia-reperfusion injury.

METHODS AND RESULTS

72 Sprague-Dawley (SD) male rats were randomly divided into 4 groups: ① blank group (Sham group, n = 18); model group (Saline group, n = 18); DA3 treatment group (DA3 group, n = 18); liraglutide treatment group (Lir group, n = 18). The Sham group was not given any treatment and was only raised in the same environment as the other groups. The remaining 3 groups used STZ-induced diabetes models. After the successful membrane formation of diabetes, DA3-CH and liraglutide (10 mmol/kg, once-daily for 14 days) were injected intraperitoneally. Thereafter, rats were subjected to middle cerebral artery occlusion followed by 24-h reperfusion. Animals were evaluated for neurologic deficit score, infarct volume, and biomarker analyses of the brain after ischemia. The DA3-CH-treated and liraglutide-treated groups showed significantly reduced scores of neurological dysfunction and cerebral infarction size, and reduced the expression of ERS markers GRP78, CHOP and Caspase-12, and the expression of apoptosis marker bax. Anti-apoptotic markers bcl-2 and neuronal numbers increased significantly.

CONCLUSIONS

DA3-CH and liraglutide have obvious neuroprotective effects in a rat model of cerebral ischemia-reperfusion injury with diabetes, which can reduce the infarct size and the neurological deficit score. Their exert neuroprotective effects in a rat model of cerebral ischemia-reperfusion injury with diabetes by inhibiting endoplasmic reticulum stress and thereby reducing apoptosis. DA3 is better than liraglutide.

Stanniocalcin-1 ameliorates cerebral ischemia by decrease oxidative stress and blood brain barrier permeability

Blood brain barrier (BBB) permeability and oxidative stress have been reported to be important mechanisms for brain damage following ischemic stroke and stanniocalcin-1 (STC-1), a neuroprotective protein, has anti-inflammatory and anti-oxidative stress properties. Herein, we report the effect of STC-1 on BBB permeability and brain oxidative stress after stroke in an animal model. Male Wistar received an intracerebroventricularly injection of human recombinant STC-1 (100 ng/kg) or saline and were subjected to sham procedure or global cerebral ischemia/reperfusion (I/R) model. Six and 24 h after I/R, neurological evaluation was performed; at 24 h brain water content was evaluated in the total brain, and BBB permeability, nitrite/nitrate (N/N) concentration, lipid peroxidation, protein carbonyls formation, superoxide dismutase (SOD) and catalase (CAT) activity were determined in the hippocampus, cortex, prefrontal cortex, striatum and cerebellum. Rats exhibited neurological deficit at 6 and 24 h after I/R and STC-1 reduction at 24 h. After I/R there were an increase of brain water content, BBB permeability in the hippocampus, cortex and pre-frontal cortex and N/N in the hippocampus, and STC-1 decreased this level only in the hippocampus. STC-1 decreased lipid peroxidation in the hippocampus, cortex and prefrontal cortex and protein oxidative damage in the hippocampus and cortex. SOD activity decreased in the hippocampus, cortex and prefrontal cortex after I/R and STC-1 reestablished these levels in the hippocampus and cortex. CAT activity decreased only in the hippocampus and cortex and STC-1 increased the CAT activity in the hippocampus. Our data provide the first experimental demonstration that STC-1 reduced brain dysfunction associated with cerebral I/R in rats, by decreasing BBB permeability and oxidative stress parameters.

Diabetes, a Contemporary Risk for Parkinson's Disease: Epidemiological and Cellular Evidences

Diabetes mellitus (DM), a group of diseases characterized by defective glucose metabolism, is the most widespread metabolic disorder affecting over 400 million adults worldwide. This pathological condition has been implicated in the pathogenesis of a number of central encephalopathies and peripheral neuropathies. In further support of this notion, recent epidemiological evidence suggests a link between DM and Parkinson’s disease (PD), with hyperglycemia emerging as one of the culprits in neurodegeneration involving the nigrostriatal pathway, the neuroanatomical substrate of the motor symptoms affecting parkinsonian patients. Indeed, dopaminergic neurons located in the mesencephalic substantia nigra appear to be particularly vulnerable to oxidative stress and degeneration, likely because of their intrinsic susceptibility to mitochondrial dysfunction, which may represent a direct consequence of hyperglycemia and hyperglycemia-induced oxidative stress. Other pathological pathways induced by increased intracellular glucose levels, including the polyol and the hexosamine pathway as well as the formation of advanced glycation end-products, may all play a pivotal role in mediating the detrimental effects of hyperglycemia on nigral dopaminergic neurons. In this review article, we will examine the epidemiological as well as the molecular and cellular clues supporting the potential susceptibility of nigrostriatal dopaminergic neurons to hyperglycemia.

Liposomal Curcumin is Better than Curcumin to Alleviate Complications in Experimental Diabetic Mellitus

Curcumin (CC) is known to have anti-inflammatory and anti-oxidative properties and has already been tested for its efficiency in different diseases including diabetes mellitus (DM). New formulations and route administration were designed to obtain products with higher bioavailability. Our study aimed to test the effect of intraperitoneal (i.p.) administration of liposomal curcumin (lCC) as pre-treatment in streptozotocin(STZ)-induced DM in rats on oxidative stress, liver, and pancreatic functional parameters. Forty-two Wistar-Bratislava rats were randomly divided into six groups (seven animals/group): control (no diabetes), control-STZ (STZ-induced DM —60 mg/100g body weight a single dose intraperitoneal administration, and no CC pre-treatment), two groups with DM and CC pre-treatment (1mg/100g bw—STZ + CC1, 2 mg/100g bw—STZ + CC2), and two groups with DM and lCC pre-treatment (1 mg/100g bw—STZ + lCC1, 2 mg/100g bw—STZ + lCC1). Intraperitoneal administration of Curcumin in diabetic rats showed a significant reduction of nitric oxide, malondialdehyde, total oxidative stress, and catalase for both evaluated formulations (CC and lCC) compared to control group (p < 0.005), with higher efficacy of lCC formulation compared to CC solution (p < 0.002, excepting catalase for STZ + CC2vs. STZ + lCC1when p = 0.0845). The CC and lCC showed hepatoprotective and hypoglycemic effects, a decrease in oxidative stress and improvement in anti-oxidative capacity status against STZ-induced DM in rats (p < 0.002). The lCC also proved better efficacy on MMP-2, and -9 plasma levels as compared to CC (p < 0.003, excepting STZ + CC2 vs. STZ + lCC1 comparison with p = 0.0553). The lCC demonstrated significantly better efficacy as compared to curcumin solution on all serum levels of the investigated markers, sustaining its possible use as adjuvant therapy in DM.

A comparative proteomic study of secretomes in kaempferitrin-treated CTX TNA2 astrocytic cells

ETHNOPHARMACOLOGICAL RELEVANCE

Kaempferitrin is extracted in significantly high quantities from the leaves of Cinnamomum osmophloeum (C.O) and Bauhinia forficata, and are used as an antidiabetic herbal remedy in China and Brazil. Commercial product using dry Cinnamomum osmophloeum leaves has been sold locally in Taiwan. Oral administration of kaempferitrin reduced blood sugar in diabetic rats.

AIM OF THE STUDY

Though previously demonstrated to activate the classical insulin signaling pathways, a mechanism for kaempferitrin is still not fully understood. Also, studies on kaempferitrin on immune related cells have been inconclusive, and people consuming extract containing kaempferitrin often happen to be at high risk of diabetes and neurodegenerative diseases. Therefore, for kaempferitrin to be used every day, a comprehensive study is needed.

MATERIALS AND METHODS

Astrocytic cell line was used as a model to test the differentially regulated secretomes, to test kaempferitrin effect on CNS glia, on pro-inflammatory cytokines, and to test how different the mechanism of kaempferitrin is from that of insulin. CTX TNA2 astrocytic cells were differentially treated with and without 10 µM kaempferitrin for 24 h, and the conditioned medium was collected. For the proteomic study, protein in conditioned medium was trypsin digested, and resulting peptides in kaempferitrin/non-treated sample pair were differentially dimethyl labeled. The labeled peptides were further fractionated by StageTip-based strong-exchange method before LC-MS/MS analyses. Levels of interesting proteins were verified using Western or Eliza. C.O. leaf crude extract treated samples were included for a comparison of effects of purified kaempferitrin vs. kaempferitrin containing crude extract.

RESULTS AND CONCLUSIONS

Data were obtained via ProteomeXchange with identifier PXD002814. It was found that no pro-inflammatory cytokines or inhibitory ECM were elevated upon treatment of kaempferitrin or a crude extract of C.O. leaves. This suggests that prolonged use of kaempferitrin containing herbs may not increase pro-inflammatory reaction. LDL-R trafficking between the cell membrane and the extracellular niche was regulated by kaempferitrin toward reduced secretion. Our proteomic study also demonstrated that molecules related to plasma membrane recycling were regulated by kaempferitrin. Our discoveries provide evidence that link kaempferitrin regulation for LDL-R and membrane recycling to the blood lipid regulation by the C.O. leaves extract. However, these proteins were differently regulated when cells were treated with crude extract. This demonstrates that the molecular interactions within crude extract of herbs are complex and may not act similar to the compound purified from the crude extract.

Cerebral Ischemia-Reperfusion Injuries in Vanadyl-Treated Diabetic Rats

BACKGROUND

Ischemic stroke recovery is poor in diabetic mellitus (DM). Vanadium compounds (vanadium) relieve DM signs, but their influences on cerebral ischemia/reperfusion injury (I/RI) are inconclusive. Herein, the intensity of I/RI was inspected in vanadium-treated DM rats.

METHODS

Rats made diabetic with a single intravenous dose of streptozocin (39 mg/kg). Normal and DM rats used water or vanadyl solution for 45 days. Under isoflurane anesthesia, right middle cerebral artery occlusion was performed for 60 minutes and 12 hours reperfusion. Ischemic rats were divided into untreated-control normal (ICN) and diabetic (ICD), vanadium-treated normal (IVTN) and diabetic (IVTD) groups (n=14 each). After neurological deficit score (NDS) test, the rats were sacrificed and their brain removed and stained with triphenyltetrazolium chloride (TTC) to measure cerebral infarct volume (CIV, mm³) or Evans blue extravasation (EBE, μg/g wet-tissue). Data analysis was performed using one-way ANOVA and Tukey's test (SPSS software, version 21.0) and P values <0.05 were considered statistically significant.

RESULTS

Blood glucose (BG, mg/dL) was similar in ICN and IVTN, elevated in IVTD and ICD (245±6 vs. 344±2, P<0.001). The increased CIV in ICN and IVTN was similar (48±2 and 34±5), very high in ICD but lower in IVTD (249±37 vs. 110±16, P<0.001). EBE was absent in non-lesioned hemispheres, similarly increased in lesioned hemispheres of ICN and IVTN (14±1 and 13±1). EBE in IVTD was significantly lower than ICD (21±2 vs. 33±5, P=0.01).

CONCLUSION

I/RI was moderate in normoglycemia and did not change with vanadium. Hyperglycemia robustly intensified I/RI. Vanadium ameliorated hyperglycemia and reduced I/RI. Nonetheless, more investigations are required to link the mechanisms of vanadium on DM and stroke injuries.

Improving the regenerative potential of olfactory ensheathing cells by overexpressing prostacyclin synthetase and its application in spinal cord repair

Background

Olfactory ensheathing cells (OEC), specialized glia that ensheathe bundles of olfactory nerves, have been reported as a favorable substrate for axonal regeneration. Grafting OEC to injured spinal cord appears to facilitate axonal regeneration although the functional recovery is limited. In an attempt to improve the growth-promoting properties of OEC, we transduced prostacyclin synthase (PGIS) to OEC via adenoviral (Ad) gene transfer and examined the effect of OEC with enhanced prostacyclin synthesis in co-culture and in vivo. Prostacyclin is a vasodilator, platelet anti-aggregatory and cytoprotective agent.

Results

Cultured OEC expressed high level of cyclooxygneases, but not PGIS. Infection of AdPGIS to OEC could selectively augument prostacyclin synthesis. When cocultured with either OEC or AdPGIS-OEC, neuronal cells were resistant to OGD-induced damage. The resulted OEC were further transplanted to the transected cavity of thoracic spinal cord injured (SCI) rats. By 6 weeks post-surgery, significant functional recovery in hind limbs occurred in OEC or AdPGIS-OEC transplanted SCI rats compared with nontreated SCI rats. At 10–12 weeks postgraft, AdPGIS-OEC transplanted SCI rats showed significantly better motor restoration than OEC transplanted SCI rats. Futhermore, regenerating fiber tracts in the distal spinal cord stump were found in 40–60% of AdPGIS-OEC transplanted SCI rats.

Conclusions

Enhanced synthesis of prostacyclin in grafted OEC improved fiber tract regeneration and functional restoration in spinal cord injured rats. These results suggest an important potential of prostacyclin in stimulating OEC therapeutic properties that are relevant for neural transplant therapies.

Impact of glucose-lowering therapies on risk of stroke in type 2 diabetes

Patients with type 2 diabetes (T2D) have an increased risk of stroke compared with people without diabetes. However, the effects of glucose-lowering drugs on risk of ischaemic stroke in T2D have been less extensively investigated than in coronary heart disease. Some evidence, including the UKPDS, has suggested a reduced risk of stroke with metformin, although the number of studies is limited. Inhibition of the K_ATP channels increases ischaemic brain lesions in animals. This is in agreement with a recent meta-analysis showing an increased risk of stroke with sulphonylureas vs. various comparators as both mono- and combination therapy. Pioglitazone can prevent recurrence of stroke in patients with previous stroke, as already shown in PROactive, although results are less clear for first strokes. As for DPP-4 inhibitors, there was a non-significant trend towards benefit for stroke, whereas a possible increased risk of stroke with SGLT2 inhibitors-and in particular, empagliflozin in the EMPA-REG OUTCOME trial-has been suggested and requires clarification. Experimental results support a potential protective effect of GLP-1 receptor agonists against stroke that has, at least in part, been translated to clinical benefits in T2D patients in the LEADER and SUSTAIN-6 trials. Further interventional studies are now warranted to confirm the effects of glucose-lowering agents on risk of stroke in patients with T2D. In summary, the effects of antidiabetic drugs on risk of stroke appear to be heterogeneous, with some therapies (pioglitazone, GLP-1 receptor agonists) conferring possible protection against ischaemic stroke, other classes showing a neutral impact (DPP-4 inhibitors, insulin) and some glucose-lowering agents being associated with an increased risk of stroke (sulphonylureas, possibly SGLT2 inhibitors, high-dose insulin in the presence of insulin resistance).

Direct Measurement of Free Radical Levels in the Brain After Cortical Ischemia Induced by Photothrombosis

Tissue ischemia is connected with the production of free radicals (FR). This study was designed to directly measure of the amount of FR in rat brains related to a photothrombotic ischemic event shortly after establishing the lesion. A model of left hemisphere photothrombosis ischemia was used in the experiment. Brains of animals from the experimental group were removed and placed in liquid N2 for 60 min after the green laser exposure, the control group brains, exposed to the photosensitive dye Rose Bengal (RB), were placed in liquid N2 for 80 min after RB application, naïve control brains were also briefly stored in liquid N2. Spectroscopy of electron paramagnetic (spin) resonance was used to directly measure FR (hydroxyl (OH●) and nitroxyl (NO●). Compared to naïve controls, both the ischemia and RB groups had significantly higher levels of OH●, however, there were no differences between them. Comparison of hemispheres, i.e. with and without ischemia, in the experimental group did not show any significant difference in OH●. NO● were elevated in the ischemia and RB groups compare to naïve controls. Higher levels of NO● were found in hemispheres with ischemia compared to unexposed hemispheres. Increases in OH● were probably associated with the action of RB itself in this model of ischemia. Increases in NO● were closely related to the pathogenesis of photothrombotic ischemia and could be related to the activity of nitric oxide synthases.

Lipoic Acid Use and Functional Outcomes after Thrombolysis in Patients with Acute Ischemic Stroke and Diabetes

Background

Alpha-lipoic acid (aLA) is a strong antioxidant commonly used for treating diabetic polyneuropathy. Previously, we demonstrated the neurorestorative effects of aLA after cerebral ischemia in rats. However, its effects on patients with stroke remain unknown. We investigated whether patients treated with aLA have better functional outcomes after acute ischemic stroke (AIS) and reperfusion therapy than patients not receiving aLA.

Methods

In this retrospective study of 172 prospectively registered patients with diabetes and AIS treated with tissue plasminogen activator (tPA), we investigated the relationship between aLA use and functional outcome both after 3 months and after 1 year. The functional outcomes included occurrence of hemorrhagic transformation (HT), early neurological deterioration (END), and early clinical improvement (ECI). Favorable outcomes were defined as modified Rankin Scale (mRS) scores of 0–2.

Results

Of the 172 patients with AIS and diabetes, 47 (27.3%) used aLA. In the entire cohort, favorable outcomes occurred at significantly higher rates both at 3 months and at 1 year in those treated with aLA. The risks for END and HT were lower and the occurrence of ECI was higher in patients treated with aLA. In multivariable analysis, aLA use was associated with favorable outcomes both at 3 months and at 1 year. Age, HT, and increased National Institutes of Health Stroke Scale scores were negative predictors of a favorable outcome.

Conclusions

The use of aLA in patients with AIS and diabetes who are treated with tPA is associated with favorable outcomes. These results indicate that aLA could be a useful intervention for the treatment of AIS after reperfusion therapy.

Notch signaling in cerebrovascular diseases (Review)

The Notch signaling pathway is a crucial regulator of numerous fundamental cellular processes. Increasing evidence suggests that Notch signaling is involved in inflammation and oxidative stress, and thus in the progress of cerebrovascular diseases. In addition, Notch signaling in cerebrovascular diseases is associated with apoptosis, angiogenesis and the function of blood-brain barrier. Despite the contradictory results obtained to date as to whether Notch signaling is harmful or beneficial, the regulation of Notch signaling may provide a novel strategy for the treatment of cerebrovascular diseases.

Hyperglycemic Stress and Carbon Stress in Diabetic Glucotoxicity

Diabetes and its complications are caused by chronic glucotoxicity driven by persistent hyperglycemia. In this article, we review the mechanisms of diabetic glucotoxicity by focusing mainly on hyperglycemic stress and carbon stress. Mechanisms of hyperglycemic stress include reductive stress or pseudohypoxic stress caused by redox imbalance between NADH and NAD(+) driven by activation of both the polyol pathway and poly ADP ribose polymerase; the hexosamine pathway; the advanced glycation end products pathway; the protein kinase C activation pathway; and the enediol formation pathway. Mechanisms of carbon stress include excess production of acetyl-CoA that can over-acetylate a proteome and excess production of fumarate that can over-succinate a proteome; both of which can increase glucotoxicity in diabetes. For hyperglycemia stress, we also discuss the possible role of mitochondrial complex I in diabetes as this complex, in charge of NAD(+) regeneration, can make more reactive oxygen species (ROS) in the presence of excess NADH. For carbon stress, we also discuss the role of sirtuins in diabetes as they are deacetylases that can reverse protein acetylation thereby attenuating diabetic glucotoxicity and improving glucose metabolism. It is our belief that targeting some of the stress pathways discussed in this article may provide new therapeutic strategies for treatment of diabetes and its complications.

GPER inhibits diabetes-mediated RhoA activation to prevent vascular endothelial dysfunction

The effect of estrogen receptors on diabetes-induced vascular dysfunction is critical, but ambiguous. Individuals with diabetic vascular disease may require estrogen receptor-specific targeted therapy in the future. The G protein-coupled estrogen receptor (GPER) has beneficial effects on vascular function. However, its fundamental mechanisms are unclear. The RhoA/Rho-kinase pathway contributes to diabetic vascular complications, whereas estrogen can suppress Rho-kinase function. Thus, we assumed that GPER inhibits diabetes-mediated RhoA activation to prevent vascular dysfunction. We further investigated the underlying mechanisms involved in this process. Vascular endothelial cells and ex vivo cultured ovariectomized (OVX) C57BL/6 mouse aortae were treated with high glucose (HG) alone or in combination with GPER agonist (G1). G1 treatment was also administered to OVX db/db mice for 8 weeks. An ex-vivo isovolumic myograph was used to analyze the endothelium-dependent vasodilation and endothelium-independent contraction of mouse aortae. Apoptosis, oxidative stress, and inflammation were attenuated in G1-pretreated vascular endothelial cells. G1 significantly decreased the phosphorylation of inhibitory endothelial nitric oxide (NO) synthase residue threonine 495 (eNOS Thr495), inhibited RhoA expression, and increased NO production. Additionally, G1 rescued the impaired endothelium-dependent relaxation and inhibited RhoA activation in the thoracic aorta of OVX db/db mice and ex-vivo cultured OVX C57BL/6 mouse aortae treated with HG. Estrogens acting via GPER could protect vascular endothelium, and GPER activation might elicit ERα-independent effect to inhibit RhoA/Rho-kinase pathway. Additionally, GPER activation might reduce vascular smooth muscle contraction by inhibiting RhoA activation. Thus, the results of the present study suggest a new therapeutic paradigm for end-stage vascular dysfunction by inhibiting RhoA/Rho-kinase pathway via GPER activation.

Acidic FGF promotes neurite outgrowth of cortical neurons and improves neuroprotective effect in a cerebral ischemic rat model

Acidic fibroblast growth factor (aFGF) is a neurotrophic factor which is a powerful neuroprotective and neuroregenerative factor of the nervous system. Prior study had shown that levels of FGFs significantly increase following ischemic injury, reflecting a physiological protection mechanism. However, few reports demonstrated the efficacy of applying aFGF in cerebral ischemia. A recent report showed that the intranasal aFGF treatment improved neurological functional recovery; however, it did not significantly reduce the lesion size in ischemic rats. The present study examines the neuroprotective effect of aFGF on cortical neuron-glial cultures under oxygen glucose deprivation (OGD)-induced cell damage and investigates whether epidural application of slow-released aFGF could improve benefit on ischemic stroke injury in conscious rats. We used a topical application of aFGF mixed in fibrin glue, a slow-release carrier, over the peri-ischemic cortex and examined such treatment on cerebral infarction and behavioral impairments of rats subjected to focal cerebral ischemia (FCI). Results demonstrate that aFGF effectively protected cortical neuron-glial cultures from OGD-induced neuronal damage. Neurite extension from cortical neurons was significantly enhanced by aFGF, mediated through activation of AKT and ERK. In addition, topical application of fibrin glue-mixed aFGF dose-dependently reduced ischemia-induced brain infarction and improved functional restoration in ischemic stroke rats. Slow-released aFGF not only protected hippocampal and cortical cell loss but reduced microglial infiltration in FCI rats. Our results suggest that aFGF mixed in fibrin glue could prolong the protective/regenerative efficacy of aFGF to the damaged brain tissue and thus improve the functional restorative effect of aFGF.

Alpha-lipoic acid treatment is neurorestorative and promotes functional recovery after stroke in rats

The antioxidant properties of alpha-lipoic acid (aLA) correlate with its ability to promote neuroproliferation. However, there have been no comprehensive studies examining the neurorestorative effects of aLA administration after the onset of ischemia. The middle cerebral artery (MCA) of adult rats was occluded for 2 hours and then reperfused. aLA (20 mg/kg) was administered in 71 animals (aLA group) through the left external jugular vein immediately after reperfusion. An equivalent volume of vehicle was administered to 71 animals (control group). Functional outcome, levels of endogenous neural precursors with neurogenesis, glial cell activation, and brain metabolism were evaluated. Immediate aLA administration after reperfusion resulted in significantly reduced mortality, infarct size, and neurological deficit score (NDS) in the test group compared to the control group. Long-term functional outcomes, measured by the rotarod test, were markedly improved by aLA treatment. There was a significant increase in the number of cells expressing nestin and GFAP in the boundary zone and infarct core regions after aLA treatment. Furthermore, significantly more BrdU/GFAP, BrdU/DCX, and BrdU/NeuN double-labeled cells were observed along the boundary zone of the aLA group on days 7, 14, and 28 days, respectively. And brain metabolism using ¹⁸F-FDG microPET imaging was markedly improved in aLA group. The effects of aLA was blocked by insulin receptor inhibitor, HNMPA (AM)3. These results indicate that immediate treatment with aLA after ischemic injury may have significant neurorestorative effects mediated at least partially via insulin receptor activation. Thus, aLA may be useful for the treatment of acute ischemic stroke.