Possible role of endoplasmic reticulum stress in the pathogenesis of chronic adenoiditis and adenoid hypertrophy: A prospective, parallel-group study

Background

Adenoid tissue is a first-line host defense secondary lymphoid organ, especially in childhood. The endoplasmic reticulum (ER) is required to maintain balanced cellular activity. With impaired ER functions, protein accumulation occurs, resulting in ER stress, which plays a role in the etiopathogenesis of many diseases.

Objective

We aimed to investigate the relationship between ER stress and adenoid tissue disorders, thereby elucidating the mechanisms of immunity-related diseases.

Methods

Fifty-four pediatric patients (>3 years old) who underwent adenoidectomy for chronic adenoiditis (CA) or adenoid hypertrophy (AH) were enrolled in this prospective, parallel-group clinical study. Adenoids were divided into two groups (CA or AH) based on their size and evaluated for ER stress pathway and apoptosis pathway markers by Real-time PCR and Western blot analysis.

Results

ER stress pathway markers significantly differed between the CA and AH groups. Children with CA had higher ER stress marker levels than the AH group (p < .001 for ATF-4, ATF-6, and GRP78, and p < .05 for EDEM1, CHOP, EIF2AK3, ERNI, and GRP94). Apoptosis pathway marker levels (BAX and BCL-2) were not different between groups.

Conclusions

ER stress contributes to the etiopathogenesis of adenoid tissue diseases and the pathogenesis of adenoid tissue disorders, which are part of the immune response. These results may guide the development of new and alternative treatments for immune system disorders.

Sigma-1 Receptor Activation Improves Oligodendrogenesis and Promotes White-Matter Integrity after Stroke in Mice with Diabetic Mellitus

Diabetes mellitus (DM) is a major risk factor for stroke and exacerbates white-matter damage in focal cerebral ischemia. Our previous study showed that the sigma-1 receptor agonist PRE084 ameliorates bilateral common-carotid-artery occlusion-induced brain damage in mice. However, whether this protective effect can extend to white matter remains unclear. In this study, C57BL/6 mice were treated with high-fat diets (HFDs) combined with streptozotocin (STZ) injection to mimic type 2 diabetes mellitus (T2DM). Focal cerebral ischemia in T2DM mice was established via injection of the vasoconstrictor peptide endothelin-1 (ET-1) into the hippocampus. Three different treatment plans were used in this study. In one plan, 1 mg/kg of PRE084 (intraperitoneally) was administered for 7 d before ET-1 injection; the mice were sacrificed 24 h after ET-1 injection. In another plan, PRE084 treatment was initiated 24 h after ET-1 injection and lasted for 7 d. In the third plan, PRE084 treatment was initiated 24 h after ET-1 injection and lasted for 21 d. The Y-maze, novel object recognition, and passive avoidance tests were used to assess neurobehavioral outcomes. We found no cognitive dysfunction or white-matter damage 24 h after ET-1 injection. However, 7 and 21 d after ET-1 injection, the mice showed significant cognitive impairment and white-matter damage. Only PRE084 treatment for 21 d could improve this white-matter injury; increase axon and myelin density; decrease demyelination; and increase the expressions of myelin regulator 2'-3'-cyclic nucleotide 3'-phosphodiesterase (CNpase) and myelin oligodendrocyte protein (MOG) (which was expressed by mature oligodendrocytes), the number of nerve/glial-antigen 2 (NG2)-positive cells, and the expression of platelet-derived growth factor receptor-alpha (PDGFRα), all of which were expressed by oligodendrocyte progenitor cells in mice with diabetes and focal cerebral ischemia. These results indicate that maybe there was more severe white-matter damage in the focal cerebral ischemia of the diabetic mice than in the mice with normal blood glucose levels. Long-term sigma-1 receptor activation may promote oligodendrogenesis and white-matter functional recovery in patients with stroke and with diabetes.

Cerebral Glucose Metabolism and Potential Effects on Endoplasmic Reticulum Stress in Stroke

Ischemic stroke is an extremely common pathology with strikingly high morbidity and mortality rates. The endoplasmic reticulum (ER) is the primary organelle responsible for conducting protein synthesis and trafficking as well as preserving intracellular Ca2⁺ homeostasis. Mounting evidence shows that ER stress contributes to stroke pathophysiology. Moreover, insufficient circulation to the brain after stroke causes suppression of ATP production. Glucose metabolism disorder is an important pathological process after stroke. Here, we discuss the relationship between ER stress and stroke and treatment and intervention of ER stress after stroke. We also discuss the role of glucose metabolism, particularly glycolysis and gluconeogenesis, post-stroke. Based on recent studies, we speculate about the potential relationship and crosstalk between glucose metabolism and ER stress. In conclusion, we describe ER stress, glycolysis, and gluconeogenesis in the context of stroke and explore how the interplay between ER stress and glucose metabolism contributes to the pathophysiology of stroke.

Ischemic brain injury in diabetes and endoplasmic reticulum stress

Diabetes is a widespread disease characterized by high blood glucose levels due to abnormal insulin activity, production, or both. Chronic diabetes causes many secondary complications including cardiovascular disease: a life-threatening complication. Cerebral ischemia-related mortality, morbidity, and the extent of brain injury are high in diabetes. However, the mechanism of increase in ischemic brain injury during diabetes is not well understood. Multiple mechanisms mediate diabetic hyperglycemia and hypoglycemia-induced increase in ischemic brain injury. Endoplasmic reticulum (ER) stress mediates both brain injury as well as brain protection after ischemia-reperfusion injury. The pathways of ER stress are modulated during diabetes. Free radical generation and mitochondrial dysfunction, two of the prominent mechanisms that mediate diabetic increase in ischemic brain injury, are known to stimulate the pathways of ER stress. Increased ischemic brain injury in diabetes is accompanied by a further increase in the activation of ER stress. As there are many metabolic changes associated with diabetes, differential activation of the pathways of ER stress may mediate pronounced ischemic brain injury in subjects suffering from diabetes. We presently discuss the literature on the significance of ER stress in mediating increased ischemia-reperfusion injury in diabetes.

Exacerbated VEGF up-regulation accompanies diabetes-aggravated hemorrhage in mice after experimental cerebral ischemia and delayed reperfusion

Reperfusion therapy is the preferred treatment for ischemic stroke, but is hindered by its short treatment window, especially in patients with diabetes whose reperfusion after prolonged ischemia is often accompanied by exacerbated hemorrhage. The mechanisms underlying exacerbated hemorrhage are not fully understood. This study aimed to identify this mechanism by inducing prolonged 2-hour transient intraluminal middle cerebral artery occlusion in diabetic Ins2^Akita/+ mice to mimic patients with diabetes undergoing delayed mechanical thrombectomy. The results showed that at as early as 2 hours after reperfusion, Ins2^Akita/+ mice exhibited rapid development of neurological deficits, increased infarct and hemorrhagic transformation, together with exacerbated down-regulation of tight-junction protein ZO-1 and up-regulation of blood-brain barrier-disrupting matrix metallopeptidase 2 and matrix metallopeptidase 9 when compared with normoglycemic Ins2^+/+ mice. This indicated that diabetes led to the rapid compromise of vessel integrity immediately after reperfusion, and consequently earlier death and further aggravation of hemorrhagic transformation 22 hours after reperfusion. This observation was associated with earlier and stronger up-regulation of pro-angiogenic vascular endothelial growth factor (VEGF) and its downstream phospho-Erk1/2 at 2 hours after reperfusion, which was suggestive of premature angiogenesis induced by early VEGF up-regulation, resulting in rapid vessel disintegration in diabetic stroke. Endoplasmic reticulum stress-related pro-apoptotic C/EBP homologous protein was overexpressed in challenged Ins2^Akita/+ mice, which suggests that the exacerbated VEGF up-regulation may be caused by overwhelming endoplasmic reticulum stress under diabetic conditions. In conclusion, the results mimicked complications in patients with diabetes undergoing delayed mechanical thrombectomy, and diabetes-induced accelerated VEGF up-regulation is likely to underlie exacerbated hemorrhagic transformation. Thus, suppression of the VEGF pathway could be a potential approach to allow reperfusion therapy in patients with diabetic stroke beyond the current treatment window. Experiments were approved by the Committee on the Use of Live Animals in Teaching and Research of the University of Hong Kong [CULATR 3834-15 (approval date January 5, 2016); 3977-16 (approval date April 13, 2016); and 4666-18 (approval date March 29, 2018)].

Gangliosides in the Brain: Physiology, Pathophysiology and Therapeutic Applications

Gangliosides are glycosphingolipids highly abundant in the nervous system, and carry most of the sialic acid residues in the brain. Gangliosides are enriched in cell membrane microdomains ("lipid rafts") and play important roles in the modulation of membrane proteins and ion channels, in cell signaling and in the communication among cells. The importance of gangliosides in the brain is highlighted by the fact that loss of function mutations in ganglioside biosynthetic enzymes result in severe neurodegenerative disorders, often characterized by very early or childhood onset. In addition, changes in the ganglioside profile (i.e., in the relative abundance of specific gangliosides) were reported in healthy aging and in common neurological conditions, including Huntington's disease (HD), Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), stroke, multiple sclerosis and epilepsy. At least in HD, PD and in some forms of epilepsy, experimental evidence strongly suggests a potential role of gangliosides in disease pathogenesis and potential treatment. In this review, we will summarize ganglioside functions that are crucial to maintain brain health, we will review changes in ganglioside levels that occur in major neurological conditions and we will discuss their contribution to cellular dysfunctions and disease pathogenesis. Finally, we will review evidence of the beneficial roles exerted by gangliosides, GM1 in particular, in disease models and in clinical trials.

Pioglitazone Attenuates Reoxygenation Injury in Renal Tubular NRK-52E Cells Exposed to High Glucose via Inhibiting Oxidative Stress and Endoplasmic Reticulum Stress

Renal ischemia-reperfusion injury is a major cause of acute kidney injury. In the present study, we investigated the effects of pioglitazone on hypoxia/reoxygenation (H/R) injury in rat renal tubular epithelial cells (RTECs) under normal- (NG) or high-glucose (HG) culture conditions via evaluating oxidative stress and endoplasmic reticulum stress (ERS). The RTECs (NRK-52E cells) were divided into six groups as follows: NG group, HG group, NG + H/R group, HG + H/R group, NG + Pio + H/R group, and HG + Pio + H/R group, among which cells in H/R groups were subjected to 4 h of hypoxia followed by 12 h of reoxygenation. After that, the cells were evaluated using the Cell Counting Kit-8 assay for the determination of their viability and flow cytometry assay for the detection of apoptosis. The levels of superoxide dismutase (SOD), glutathione reductase (GSH), catalase (CAT), and malondialdehyde (MDA) were determined via colorimetric chemical assays. In addition, the expression of ERS-associated proteins, i.e. ATF4, ATF6, GRP78, and CHOP, was determined via western blotting. A HG environment could reduce the viability and increase the apoptotic rate of NRK-52E cells with increased MDA levels and decreased SOD, CAT, and GSH levels, and upregulate the expression of ERS-associated proteins, i.e. ATF4, ATF6, and GRP78. H/R injury could further aggravate changes in the above indicators, but pioglitazone could significantly reverse such changes and alleviate cell injury. Thus, Pioglitazone exhibits a cytoprotective effect on RTECs against H/R injury under NG or HG culture conditions by inhibiting oxidative stress and ERS.

Gangliosides: Treatment Avenues in Neurodegenerative Disease

Gangliosides are cell membrane components, most abundantly in the central nervous system (CNS) where they exert among others neuro-protective and -restorative functions. Clinical development of ganglioside replacement therapy for several neurodegenerative diseases was impeded by the BSE crisis in Europe during the 1990s. Nowadays, gangliosides are produced bovine-free and new pre-clinical and clinical data justify a reevaluation of their therapeutic potential in neurodegenerative diseases. Clinical experience is greatest with monosialo-tetrahexosyl-ganglioside (GM1) in the treatment of stroke. Fourteen randomized controlled trials (RCTs) in overall >2,000 patients revealed no difference in survival, but consistently superior neurological outcomes vs. placebo. GM1 was shown to attenuate ischemic neuronal injuries in diabetes patients by suppression of ERK1/2 phosphorylation and reduction of stress to the endoplasmic reticulum. There is level-I evidence from 5 RCTs of a significantly faster recovery with GM1 vs. placebo in patients with acute and chronic spinal cord injury (SCI), disturbance of consciousness after subarachnoid hemorrhage, or craniocerebral injuries due to closed head trauma. In Parkinson's disease (PD), two RCTs provided evidence of GM1 to be superior to placebo in improving motor symptoms and long-term to result in a slower than expected symptom progression, suggesting disease-modifying potential. In Alzheimer's disease (AD), the role of gangliosides has been controversial, with some studies suggesting a "seeding" role for GM1 in amyloid β polymerization into toxic forms, and others more recently suggesting a rather protective role in vivo. In Huntington's disease (HD), no clinical trials have been conducted yet. However, low GM1 levels observed in HD cells were shown to increase cell susceptibility to apoptosis. Accordingly, treatment with GM1 increased survival of HD cells in vitro and consistently ameliorated pathological phenotypes in several murine HD models, with effects seen at molecular, cellular, and behavioral level. Given that in none of the clinical trials using GM1 any clinically relevant safety issues have occurred to date, current data supports expanding GM1 clinical research, particularly to conditions with high, unmet medical need.

Relationship between CHOP/GADD153 and unstable human carotid atherosclerotic plaque

BACKGROUND AND AIMS

The signaling protein C/EBP homologous protein (CHOP) and corresponding growth-arrest-and-DNA-damage-inducible gene 153 (GADD153) is associated with endoplasmic reticulum stress (ERS), which can lead to apoptosis. Our study aims to elucidate the role of CHOP/GADD153 in unstable atherosclerotic (AS) plaque formation isolated from confounding factors such as diabetes mellitus, primary hyperlipidemia, autoimmune deficiencies/abnormalities, essential hypertension, chronic heart failure, chronic kidney disease, and smoking.

MATERIAL AND METHODS

We collected carotid artery tissue samples from patients aged 50-80 years-old who received carotid endarterectomies (CEA) at our institution. We obtained fresh AS plaque samples during CEA and preserved the specimens immediately in the operating room with liquid nitrogen. Samples were categorized as stable or unstable AS plaques according to a six-stage histologic classification. CHOP/GADD153 expression was then examined with immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

A total of 32 patients met our inclusion and exclusion criteria, with 24 (75.0%) classified as unstable lesions. The mean optical density ratio normalized to GAPDH for CHOP/GADD153 in stable and unstable groups was 0.357 ± 0.025 and 0.490 ± 0.027, respectively (p < .05). Positive immunostaining of CHOP/GADD153 was found in macrophages and smooth muscle cells of unstable AS plaques with a mean integrated optical density of 0.63 ± 0.03, compared to 0.17 ± 0.05 in the stable group (p < .05).

CONCLUSIONS

In conclusion, we were able to show significant elevation of CHOP/GADD153 in unstable plaques independent of other confounding factors that induce ERS.

Acute Hyperglycemia Does Not Affect Brain Swelling or Infarction Volume After Middle Cerebral Artery Occlusion in Rats

Stroke disproportionally affects diabetic and hyperglycemic patients with increased incidence and is associated with higher morbidity and mortality due to brain swelling. In this study, the intraluminal suture middle cerebral artery occlusion (MCAO) model was used to examine the effects of blood glucose on brain swelling and infarct volume in acutely hyperglycemic rats and normo-glycemic controls. Fifty-four rats were distributed into normo-glycemic sham surgery, hyperglycemic sham surgery, normo-glycemic MCAO, and hyperglycemic MCAO. To induce hyperglycemia, 15 min before MCAO surgery, animals were injected with 50 % dextrose. Animals were subjected to 90 min of MCAO and sacrificed 24 h after reperfusion for hemispheric brain swelling and infarct volume calculations using standard equations. While normo-glycemic and hyperglycemic animals after MCAO presented with significantly higher brain swelling and larger infarcts than their respective controls, no statistical difference was observed for either brain swelling or infarct volume between normo-glycemic shams and hyperglycemic shams or normo-glycemic MCAO animals and hyperglycemic MCAO animals. The findings of this study suggest that blood glucose does not have any significant effect on hemispheric brain swelling or infarct volume after MCAO in rats.

Calreticulin Binds to Fas Ligand and Inhibits Neuronal Cell Apoptosis Induced by Ischemia-Reperfusion Injury

Background. Calreticulin (CRT) can bind to Fas ligand (FasL) and inhibit Fas/FasL-mediated apoptosis of Jurkat T cells. However, its effect on neuronal cell apoptosis has not been investigated. Purpose. We aimed to evaluate the neuroprotective effect of CRT following ischemia-reperfusion injury (IRI). Methods. Mice underwent middle cerebral artery occlusion (MCAO) and SH-SY5Y cells subjected to oxygen glucose deprivation (OGD) were used as models for IRI. The CRT protein level was detected by Western blotting, and mRNA expression of CRT, caspase-3, and caspase-8 was measured by real-time PCR. Immunofluorescence was used to assess the localization of CRT and FasL. The interaction of CRT with FasL was verified by coimmunoprecipitation. SH-SY5Y cell viability was determined by MTT assay, and cell apoptosis was assessed by flow cytometry. The measurement of caspase-8 and caspase-3 activity was carried out using caspase activity assay kits. Results. After IRI, CRT was upregulated on the neuron surface and bound to FasL, leading to increased viability of OGD-exposed SH-SY5Y cells and decreased activity of caspase-8 and caspase-3. Conclusions. This study for the first time revealed that increased CRT inhibited Fas/FasL-mediated neuronal cell apoptosis during the early stage of ischemic stroke, suggesting it to be a potential protector activated soon after IRI.

Poor outcome of experimental ischemic stroke in type 2 diabetic rats: impaired circulating endothelial progenitor cells mobilization

BACKGROUND

It is well accepted that type 2 diabetic mellitus (T2DM) results in the poor outcome of ischemic stroke. However, the mechanisms by which T2DM causes aggravated cerebral ischemic/reperfusion (I/R) injury are not clear. Recently, endothelial progenitor cells (EPCs) are considered to be related with the outcome of ischemic stroke. More importantly, T2DM can affect the function of circulating EPCs. This study tried to investigate whether T2DM worsens the cerebral I/R injury via affecting circulating EPCs.

METHODS

We used high-fat diet-fed and low-dose streptozotocin-treated male rats receiving middle cerebral artery occlusion surgery as animal model of focal cerebral I/R injury with T2DM (diabetic operated). And the rats were divided into 4 groups: normal sham, diabetic sham, normal operated, and diabetic operated. We measured the circulating EPCs counts and the levels of vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) in peripheral plasma of 4 groups.

RESULTS

We found that diabetic rats subjected to I/R exhibited significantly severe deterioration in neurologic deficits compared with nondiabetic counterparts, which manifested higher infarct volume and cell apoptosis as well as lower neurologic defective score. There was no significant difference on the plasma glucose of groups before cerebral I/R injury compared with that of the groups posterior to cerebral I/R injury despite cerebral I/R injury had the tendency to increase the plasma glucose no matter in the presence or the absence of T2DM. In addition, there were the marked downregulation of circulating EPCs counts and the levels of VEGF and eNOS in diabetic rats before the cerebral I/R injury. Despite I/R injury without T2DM, there was a significant increase in the circulating EPCs counts, the circulating EPCs counts in I/R injury with T2DM group were significantly decreased compared with those in the other 3 groups. We also observed that the level of eNOS was significantly improved by I/R injury without considering the presence of T2DM.

CONCLUSIONS

Thus, our present study suggested that it might be the impaired EPCs mobilization into the blood that contributed to the worse outcome of cerebral I/R injury with T2DM.

Hypothyroidism affects astrocyte and microglial morphology in type 2 diabetes

In the present study, we investigated the effects of hypothyroidism on the morphology of astrocytes and microglia in the hippocampus of Zucker diabetic fatty rats and Zucker lean control rats. To induce hypothyroidism, Zucker lean control and Zucker diabetic fatty rats at 7 weeks of age orally received the vehicle or methimazole, an anti-thyroid drug, treatment for 5 weeks and were sacrificed at 12 weeks of age in all groups for blood chemistry and immunohistochemical staining. In the methimazole-treated Zucker lean control and Zucker diabetic fatty rats, the serum circulating thyronine (T₃) and thyroxine (T₄) levels were significantly decreased compared to levels observed in the vehicle-treated Zucker lean control or Zucker diabetic fatty rats. This reduction was more prominent in the methimazole-treated Zucker diabetic fatty group. Glial fibrillary acidic protein immunoreactive astrocytes and ionized calcium-binding adapter molecule 1 (Iba-1)-immunoreactive microglia in the Zucker lean control and Zucker diabetic fatty group were diffusely detected in the hippocampal CA1 region and dentate gyrus. There were no significant differences in the glial fibrillary acidic protein and Iba-1 immunoreactivity in the CA1 region and dentate gyrus between Zucker lean control and Zucker diabetic fatty groups. However, in the methimazole-treated Zucker lean control and Zucker diabetic fatty groups, the processes of glial fibrillary acidic protein tive astrocytes and Iba-1 immunoreactive microglia, were significantly decreased in both the CA1 region and dentate gyrus compared to that in the vehicle-treated Zucker lean control and Zucker diabetic fatty groups. These results suggest that diabetes has no effect on the morphology of astrocytes and microglia and that hypothyroidism during the onset of diabetes prominently reduces the processes of astrocytes and microglia.

New insights into the roles of CHOP-induced apoptosis in ER stress

Endoplasmic reticulum stress (ER stress) is triggered due to a loss of homeostasis in the ER, resulting in accumulation of misfolded proteins in the ER lumen. ER stress activates a series of adaptive mechanisms known as the unfolded protein response. Perturbation of the ER is a powerful inducer of the transcription factor C/EBP homologous protein (CHOP). Although it has been proved that excessive or adverse stress to the ER triggers apoptosis, the specific mechanisms underlying these processes induced by CHOP remain unclear. By now, CHOP-induced apoptosis in ER stress has been implicated in numerous human diseases, such as neurodegenerative diseases, diabetes, ischemic diseases, tumor, and so on. In this review, we summarized the current understanding of the roles of CHOP in the development of several diseases from the laboratory to the clinic.

Endoplasmic reticulum stress: relevance and therapeutics in central nervous system diseases

Endoplasmic reticulum (ER) stress plays an important role in a range of neurological disorders, such as neurodegenation diseases, cerebral ischemia, spinal cord injury, sclerosis, and diabetic neuropathy. Protein misfolding and accumulation in the ER lumen initiate unfolded protein response in energy-starved neurons which are relevant to toxic effects. In neurological disorders, such as Alzheimer's disease, Parkinson's disease, and Huntington's disease, ER dysfunction is well recognized, but the mechanisms remain unclear. In stroke and ischemia, spinal cord injury, and amyotrophic lateral sclerosis, chronic activation of ER stress is considered as main pathogeny which causes neuronal disorders. By targeting components of these ER signaling responses, to explore clinical treatment strategies or new drugs in CNS neurological diseases might become possible and valuable in the future.

Ginsenoside Rb1 protects hippocampal neurons from high glucose-induced neurotoxicity by inhibiting GSK3β-mediated CHOP induction

Ginsenoside Rb1 is generally recognized as one of the principal bioactive ingredients in ginseng and shows neuroprotective effects in various neurons. Endoplasmic reticulum (ER) stress is considered to play an important role in numerous neurodegenerative disorders. Recently, glucogen synthase kinase 3β (GSK3β) was reported to regulate ER stress-induced C/EBP homologous protein (CHOP) in neuronal cells. Therefore, in this study, we investigated the effects of ginsenoside Rb1 on GSK3β-mediated ER stress in high glucose-treated hippocampal neurons. Results from the MTT assay showed that treatment with 1 µM Rb1 for 72 h protected neurons from high glucose-induced cell injury. Using western blot analysis, we found that treatment with Rb1 effectively inhibited the phosphorylation of the high glucose-induced protein kinase RNA-like ER kinase (PERK) and of GSK3β, and reduced the level of the CHOP protein. The levels of these proteins were also decreased by treatment with the GSK3β inhibitor Licl. Rb1 also significantly decreased the mRNA expression of the gene CHOP, as shown by quantitative RT-PCR analysis. Taken together, the present results suggested that Rb1 may protect neurons from high glucose-induced cell damage by inhibiting GSK3β‑mediated CHOP induction, providing a potentially new strategy for preventing and treating cognitive impairment caused by diabetes.

Neuroprotection for ischemic stroke: moving past shortcomings and identifying promising directions

The translation of neuroprotective agents for ischemic stroke from bench-to-bedside has largely failed to produce improved treatments since the development of tissue plasminogen activator (tPA). One possible reason for lack of translation is the failure to acknowledge the greatest risk factor for stroke, age, and other common comorbidities such as hypertension, obesity, and diabetes that are associated with stroke. In this review, we highlight both mechanisms of studying these factors and results of those that have been addressed. We also discuss the potential role of other lifestyle factors associated with an increased stroke risk such as sleep fragmentation and/or deprivation. Furthermore, many proposed therapeutic agents have targeted molecular mechanisms occurring soon after the onset of ischemia despite data indicating delayed patient presentation following ischemic stroke. Modulating inflammation has been identified as a promising therapeutic avenue consistent with preliminary success of ongoing clinical trials for anti-inflammatory compounds such as minocycline. We review the role of inflammation in stroke and in particular, the role of inflammatory cell recruitment and macrophage phenotype in the inflammatory process. Emerging evidence indicates an increasing role of neuro-immune crosstalk, which has led to increased interest in identification of peripheral biomarkers indicative of neural injury. It is our hope that identification and investigation of factors influencing stroke pathophysiology may lead to improved therapeutics.

Role of oxidative stress and Ca²⁺ signaling on molecular pathways of neuropathic pain in diabetes: focus on TRP channels

Diabetes mellitus, a debilitating chronic disease, affects ~100 million people. Peripheral neuropathy is one of the most common early complications of diabetes in ~66 % of these patients. Altered Ca(2+) handling and Ca(2+) signaling were detected in a huge variety of preparations isolated from animals with experimentally induced type 1 and 2 diabetes as well as patients suffering from the disease. We reviewed the role of Ca(2+) signaling through cation channels and oxidative stress on diabetic neuropathic pain in sensory neurons. The pathogenesis of diabetic neuropathy involves the polyol pathway, advanced glycation end products, oxidative stress, protein kinase C activation, neurotrophism, and hypoxia. Experimental studies with respect to oxidative stress and Ca(2+) signaling, inhibitor roles of antioxidants in diabetic neuropathic pain are also summarized in the review. We hypothesize that deficits in insulin, triggers alterations of sensory neurone phenotype that are critical for the development of abnormal Ca(2+) homeostasis and oxidative stress and associated mitochondrial dysfunction. The transient receptor potential channels are a large family of proteins with six main subfamilies. The sheer number of different TRPs with distinct functions supports the statement that these channels are involved in a wide range of processes ranging in diabetic neuropathic pain and it seems that the TRPC, TRPM and TRPV groups are mostly responsible from diabetic neuropathic pain. In conclusion, the accumulating evidence implicating Ca(2+) dysregulation and over production of oxidative stress products in diabetic neuropathic pains, along with recent advances in understanding of genetic variations in cation channels such as TRP channels, makes modulation of neuronal Ca(2+) handling an increasingly viable approach for therapeutic interventions against the painful and degenerative aspects of many diabetic neuropathies.

3-Bromo-7-nitroindazole attenuates brain ischemic injury in diabetic stroke via inhibition of endoplasmic reticulum stress pathway involving CHOP

AIMS

The role of nitric oxide (NO) and endoplasmic reticulum (ER) stress has been implicated in the pathogenesis of cerebral ischemic/reperfusion (I/R) injury and diabetes. The aim of the study was to investigate the neuroprotective potential of 3-bromo-7-nitroindazole (3-BNI), a potent and selective neuronal nitric oxide synthase (nNOS) inhibitor against ER stress and focal cerebral I/R injury associated with comorbid type 2 diabetes in-vivo.

MAIN METHODS

Type 2 diabetes was induced by feeding high-fat diet and streptozotocin (35 mg/kg) treatment in rats. Focal cerebral ischemia was induced by 2h middle cerebral artery occlusion (MCAO) followed by 22 h of reperfusion. Immunohistochemistry and western blotting methods were employed for the detection and expression of ER stress/apoptosis markers [78 kDa glucose regulated protein (GRP78) and CCAAT/enhancer binding protein homologous protein (CHOP)]. TUNEL assay for DNA fragmentation was also performed.

KEY FINDINGS

The diabetic rats subjected to cerebral I/R had prominent neurological damage and functional deficits compared with sham-operated rats. Massive DNA fragmentation was observed in ischemic penumbral region of diabetic brains. Concomitantly, the enhanced immunoreactivity and expression of ER stress/apoptosis markers were noticed. 3-BNI (30 mg/kg, i.p.) treatment significantly inhibited the cerebral infarct, edema volume and improved functional recovery of neurological deficits. The neuroprotection was further evident by lesser DNA fragmentation with a concomitant reduction of GRP78 and CHOP.

SIGNIFICANCE

The study demonstrates the neuroprotective potential of 3-BNI in diabetic stroke model which may be partly due to inhibition of ER stress pathway involving CHOP.