Overexpression of rat heat shock protein 70 is associated with reduction of early mitochondrial cytochrome C release and subsequent DNA fragmentation after permanent focal ischemia

Loss of Gucy1a3 causes poor post-stroke recovery by reducing angiogenesis via the HIF-1α/VEGFA signaling pathway in mice

OBJECTIVES

Ischemic stroke is a common and debilitating disease that can cause permanent neurological damage. Gucy1a3, which encodes the α1 subunit of soluble guanylyl cyclase, has been reported to be associated with functional recovery after ischemic stroke. However, the mechanism is still not well understood. In the present study, we investigated the effects of Gucy1a3 on (i) post-stroke recovery; (ii) vascular endothelial growth factor A (VEGFA) and hypoxia inducible factor 1 alpha (HIF-1α) expression; and (iii) angiogenesis after ischemic stroke.

MATERIALS AND METHODS

Wild-type and Gucy1a3 knockout C57BL/6J male mice were respectively used to establish the models of permanent middle cerebral artery occlusion (pMCAO). Neurological deficit scores were evaluated at 24 h and 96 h after pMCAO. Cerebral infarct volume was measured by 2,3,5-triphenyltetrazolium chloride (TTC) staining. For determining microvessel density, immunohistochemical analysis was performed with CD31. The expression of VEGFA and HIF-1α was detected by western blotting.

RESULTS

Our results suggest that loss of Gucy1a3 increased the infarct volume and aggravated neurological deficits after pMCAO. In addition, the Gucy1a3 knockout brains exhibited significantly lower microvessel densities and VEGFA and HIF-1α expression levels than the wild-type brains at 96 h post-pMCAO.

CONCLUSIONS

Our study indicates that GUCY1A3 might be involved in angiogenesis after ischemic stroke. Further investigation of GUCY1A3 will provide a new therapeutic target for stroke.

Palmatine, a natural alkaloid, attenuates memory deficits and neuroinflammation in mice submitted to permanent focal cerebral ischemia

Ischemic stroke is one of the major causes of human morbidity and mortality. The pathophysiology of ischemic stroke involves complex events, including oxidative stress and inflammation, that lead to neuronal loss and cognitive deficits. Palmatine (PAL) is a naturally occurring (Coptidis rhizome) isoquinoline alkaloid that belongs to the class of protoberberines and has a wide spectrum of pharmacological and biological effects. In the present study, we evaluated the impact of Palmatine on neuronal damage, memory deficits, and inflammatory response in mice submitted to permanent focal cerebral ischemia induced by middle cerebral artery (pMCAO) occlusion. The animals were treated with Palmatine (0.2, 2 and 20 mg/kg/day, orally) or vehicle (3% Tween + saline solution) 2 h after pMCAO once daily for 3 days. Cerebral ischemia was confirmed by evaluating the infarct area (TTC staining) and neurological deficit score 24 h after pMCAO. Treatment with palmatine (2 and 20 mg/kg) reduced infarct size and neurological deficits and prevented working and aversive memory deficits in ischemic mice. Palmatine, at a dose of 2 mg/kg, had a similar effect of reducing neuroinflammation 24 h after cerebral ischemia, decreasing TNF-, iNOS, COX-2, and NF- κB immunoreactivities and preventing the activation of microglia and astrocytes. Moreover, palmatine (2 mg/kg) reduced COX-2, iNOS, and IL-1β immunoreactivity 96 h after pMCAO. The neuroprotective properties of palmatine make it an excellent adjuvant treatment for strokes due to its inhibition of neuroinflammation.

Induction of ischemic tolerance by remote perconditioning or postconditioning as neuroprotective strategy for spinal cord motor neurons

AIMS

The study is focused on the investigation of the mechanisms leading to ischemic tolerance acquisition in the spinal cord neurons via application of non-invasive method of remote conditioning.

MATERIAL AND METHODS

We have verified the possibility of neuroprotection of spinal cord in rabbit by using remote perconditioning (PerC) applied during last 12 min of spinal cord ischemia (SC-ischemia) or postconditioning (PostC) applied after 1st (early) or 3rd (late) h of reperfusion. Spinal cord ischemia was induced by occlusion of the aorta below the left renal artery for 20 min. Reperfusion period was 24 or 72 h. Remote conditioning was induced by compression of left forelimb with a tourniquet in 3 cycles of 2 min of ischemia, each followed by 2 min of reperfusion. Damaged neurons were detected by Fluoro Jade B method and the modified Tarlov score was used for functional assessment.

KEY FINDINGS

The remote conditioning significantly attenuated degeneration of motor neurons in all remote conditioned groups versus both SC-ischemia groups. We detected significant changes in number of Hsp70 positive motor neurons. At 72time point, in the group with remote late PostC we observed significant increase (p < 0.001) of Hsp70 positive motor neurons versus SC- ischemia group and sham control. There was a trend towards improvement of hindlimbs movement.

SIGNIFICANCE

This study showed the effectiveness of remote conditioning as a neuroprotective strategy, evidenced by induction of ischemic tolerance leading to decrease of motor neuron degeneration.

The role of the brain renin-angiotensin system (RAS) in mild traumatic brain injury (TBI)

There is considerable interest in traumatic brain injury (TBI) induced by repeated concussions suffered by athletes in sports, military personnel from combat-and non-combat related activities, and civilian populations who suffer head injuries from accidents and domestic violence. Although the renin-angiotensin system (RAS) is primarily a systemic cardiovascular regulatory system that, when dysregulated, causes hypertension and cardiovascular pathology, the brain contains a local RAS that plays a critical role in the pathophysiology of several neurodegenerative diseases. This local RAS includes receptors for angiotensin (Ang) II within the brain parenchyma, as well as on circumventricular organs outside the blood-brain-barrier. The brain RAS acts primarily via the type 1 Ang II receptor (AT₁R), exacerbating insults and pathology. With TBI, the brain RAS may contribute to permanent brain damage, especially when a second TBI occurs before the brain recovers from an initial injury. Agents are needed that minimize the extent of injury from an acute TBI, reducing TBI-mediated permanent brain damage. This review discusses how activation of the brain RAS following TBI contributes to this damage, and how drugs that counteract activation of the AT₁R including AT₁R blockers (ARBs), renin inhibitors, angiotensin-converting enzyme (ACE) inhibitors, and agonists at type 2 Ang II receptors (AT₂) and at Ang (1-7) receptors (Mas) can potentially ameliorate TBI-induced brain damage.

Ferulic Acid Exerts Anti-apoptotic Effects against Ischemic Injury by Activating HSP70/Bcl-2- and HSP70/Autophagy-Mediated Signaling after Permanent Focal Cerebral Ischemia in Rats

This study assessed the anti-apoptotic effects of the administration of ferulic acid (FrA) in rats 30 min before middle cerebral artery occlusion (MCAo) followed by 3 d of ischemia and the involvement of 70 kDa heat shock protein (HSP70)-mediated signaling in the penumbral cortex. Our results demonstrated that FrA pretreatment at doses of 80 mg/kg (FrA-80 mg) and 100 mg/kg (FrA-100 mg) effectively ameliorated neurological functions and reduced the numbers of cytochrome c-, cleaved caspase-3-, and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive cells in the penumbral cortex 3 d after ischemia. Moreover, FrA-80 mg and FrA-100 mg pretreatment markedly upregulated cytosolic HSP70, Beclin-1, microtubule-associated protein 1 light chain 3 (LC3) A/B-II and autophagy-related protein 5 (Atg5) expression; cytosolic and mitochondrial X-linked inhibitor of apoptosis (XIAP) expression and the Bcl-2/Bax ratio. FrA pretreatment downregulated cytosolic cytochrome c, apoptosis-inducing factor (AIF), procathepsin B, and cathepsin B expression and mitochondrial and cytosolic second mitochondria-derived activator of caspase/direct inhibitor of apoptosis protein-binding protein with a low isoelectric point (Smac/DIABLO) expression in the penumbral cortex. Pretreatment with VER155008, a HSP70 family inhibitor, significantly inhibited the effects of FrA-100 mg on the expression of the aforementioned proteins expression in the penumbral cortex. FrA-80 mg and FrA-100 mg pretreatment exerts neuroprotective effects against caspase-dependent and -independent apoptosis through activating HSP70/Bcl-2- and HSP70/autophagy-induced signaling pathways. Furthermore, the HSP70/Bcl-2- and HSP70/autophagy-induced anti-apoptotic effects of FrA pretreatment can be attributed to the regulation of Bax/cytochrome c/Smac/DIABLO/XIAP/ caspase-3- (or Bax/AIF-) and Beclin-1/LC3A/B-II/Atg5-mediated signaling, respectively, in the penumbral cortex 3 d after permanent MCAo.

Anastasis: recovery from the brink of cell death

Anastasis is a natural cell recovery phenomenon that rescues cells from the brink of death. Programmed cell death such as apoptosis has been traditionally assumed to be an intrinsically irreversible cascade that commits cells to a rapid and massive demolition. Interestingly, recent studies have demonstrated recovery of dying cells even at the late stages generally considered immutable. Here, we examine the evidence for anastasis in cultured cells and in animals, review findings illuminating the potential mechanisms of action, discuss the challenges of studying anastasis and explore new strategies to uncover the function and regulation of anastasis, the identification of which has wide-ranging physiological, pathological and therapeutic implications.

Up-regulation of miR-122 protects against neuronal cell death in ischemic stroke through the heat shock protein 70-dependent NF-κB pathway by targeting FOXO3

Dysfunction of the microRNA (miRNA) network has been emerging as a main regulator in ischemic stroke. Recently, studies have linked the deregulation of miR-122 to ischemic stroke. However, the specific role and molecular mechanism of miR-122 in ischemic stroke remain to be further investigated. Here, we found that miR-122 was decreased in mouse N2A neuroblastoma (N2A) cells after oxygen-glucose deprivation (OGD) and mouse brain after transient middle cerebral artery occlusion (MCAO). OGD treatment significantly increased N2A cell death and Caspase-3 activity, and decreased Bcl-2 protein expression. In addition, MCAO treatment induced severe mouse brain infarction, mitochondrial reactive oxygen species (ROS) production, and long-term neurological deficit. Gain-of-miR-122 function significantly suppressed OGD- and MCAO-induced injures in vitro and in vivo. Subsequently, miR-122 was validated to directly bind to the predicted 3'-untranslated region (3'-UTR) of FOXO3 gene, and the inhibitory effects of miR-122 on ischemic injury in vitro and in vivo were overturned by FOXO3 overexpression. Moreover, our results further revealed that miR-122-FOXO3 axis functioned via the heat shock protein 70 (HSP-70)-mediated NF-κB pathway. Collectively, our data suggest that miR-122 inhibits ischemic neuronal death through the HSP-70-dependent NF-κB pathway by targeting FOXO3. These findings raise the possibility that this regulatory net may contribute to the pathogenesis of the ischemic brain injury in stroke.

Hypothermia decreased the expression of heat shock proteins in neonatal rat model of hypoxic ischemic encephalopathy

Hypothermia (HT) is a well-established neuroprotective strategy against neonatal hypoxic ischemic encephalopathy (HIE). The overexpression of heat shock proteins (HSP) has been shown to provide neuroprotection in animal models of stroke. We aimed to investigate the effect of HT on HSP70 and HSP27 expression in a neonatal rat model of HIE. Seven-day-old rat pups were exposed to hypoxia for 90 min to establish the Rice-Vannucci model and were assigned to the following four groups: hypoxic injury (HI)-normothermia (NT, 36 °C), HI-HT (30 °C), sham-NT, and sham-HT. After temperature intervention for 24 h, the mRNA and protein expression of HSP70 and HSP27 were measured. The association between HSP expression and brain injury severity was also evaluated. The brain infarct size was significantly smaller in the HI-HT group than in the HI-NT group. The mRNA and protein expression of both HSPs were significantly greater in the two HI groups, compared to those in the two sham groups. Moreover, among the rat pups subjected to HI, HT significantly reduced the mRNA and protein expression of both HSPs. The mRNA expression level of the HSPs was proportional to the brain injury severity. Post-ischemic HT, i.e., a cold shock attenuated the expression of HSP70 and HSP27 in a neonatal rat model of HIE. Our study suggests that neither HSP70 nor HSP27 expression is involved in the neuroprotective mechanism through which prolonged HT protects against neonatal HIE.

Baicalin attenuates lipopolysaccharide induced inflammation and apoptosis of cow mammary epithelial cells by regulating NF-κB and HSP72

Baicalin is the main ingredient of traditional Chinese herbal medicine, Scutellaria baicalensis, which has been widely used clinically as an anti-inflammatory agent. However, molecular mechanism of action of this drug is not yet clear. In the present study, the protective mechanism of baicalin against lipopolysaccharide (LPS) induced inflammatory injury in cow mammary epithelial cells (CMECs) was explored. For this purpose, in vitro cultured CMECs were treated with baicalin (10μg/mL) and LPS (10μg/mL) for 24 and 12h, respectively, and the cell viability was measured by using cell counting kit-8 (CCK-8). The results revealed that LPS induced inflammatory responses, as p-p65/p65 and p-IκBα/IκBα ratios and TNF-α and IL-1β production was increased in the CMECs. Both Bcl-2/Bax ratio and cell viability were decreased and caspase-3 cleaved following LPS treatment, indicating apoptosis of CMECs. Moreover, both LPS and baicalin increased HSP72 expression of the CMECs. However, cellular inflammatory responses and apoptosis were significantly reduced in baicalin treated CMECs. In conclusion, baicalin ameliorated inflammation and apoptosis of the CMECs induced by LPS via inhibiting NF-κB activation and up regulation of HSP72.

Overexpression of mitochondrial Hsp75 protects neural stem cells against microglia-derived soluble factor-induced neurotoxicity by regulating mitochondrial permeability transition pore opening in vitro

Microglia (MG)-induced neurotoxicity, a major determinant of Alzheimer's disease, is closely related to the survival of neural stem cells (NSCs). Heat shock protein 75 (Hsp75) has been reported to exert protective effects against environmental stresses; however, whether or not it protects NSCs against MG-derived soluble factor-induced neurotoxicity remains unclear. In the present study, we constructed NSCs that overexpressed human Hsp75 protein and established a co-culture system in order to elucidate the role of Hsp75 in NSC-MG interactions. The results obtained indicated that Hsp75 expression increased after 12 h of soluble factor induction and continued to increase for up to 36 h of treatment. The overexpression of Hsp75 decreased NSC apoptosis and preserved mitochondrial membrane potential. Further experiments revealed that the overexpression of Hsp75 inhibited the formation of cyclophilin D (CypD)-dependent mitochondrial permeability transition pore (mPTP) involvement in neurotoxicity-mediated mitochondrial dysfunction and suppressed the activation of the mitochondrial apoptotic cascade, as demonstrated by the inhibition of the release of cytochrome c (Cytc) and the activation of caspase-3. The findings of this study demonstrate that Hsp75 overexpression prevents the impairment of NSCs induced by MG-derived soluble factors by regulating the opening of mPTP. Thus, Hsp75 warrants further investigation as a potential candidate for protection against neurotoxicity.

Oxidative stress-dependent phosphorylation activates ZNRF1 to induce neuronal/axonal degeneration

Oxidative stress is a well-known inducer of neuronal apoptosis and axonal degeneration. We previously showed that the E3 ubiquitin ligase ZNRF1 promotes Wallerian degeneration by degrading AKT to induce GSK3B activation. We now demonstrate that oxidative stress serves as an activator of the ubiquitin ligase activity of ZNRF1 by inducing epidermal growth factor receptor (EGFR)-mediated phosphorylation at the 103rd tyrosine residue and that the up-regulation of ZNRF1 activity by oxidative stress leads to neuronal apoptosis and Wallerian degeneration. We also show that nicotinamide adenine dinucleotide phosphate-reduced oxidase activity is required for the EGFR-dependent phosphorylation-induced activation of ZNRF1 and resultant AKT degradation via the ubiquitin proteasome system to induce Wallerian degeneration. These results indicate the pathophysiological significance of the EGFR-ZNRF1 pathway induced by oxidative stress in the regulation of neuronal apoptosis and Wallerian degeneration. A deeper understanding of the regulatory mechanism for ZNRF1 catalytic activity via phosphorylation will provide a potential therapeutic avenue for neurodegeneration.

Anti-fibrotic effect of Holothuria arenicola extract against bile duct ligation in rats

BACKGROUND

Holothuria arenicola is the most important and abundant sea cucumber species in the Mediterranean Sea on the Egyptian coast. The present study aims to assess the anti-oxidative and anticholestatic effects of the sea cucumber Holothuria arenicola extract (HaE) in a model of bile duct ligation in male albino rats.

METHODS

Fifty four male Wistar albino rats were assigned into two main groups, the Sham-operated control and bile duct ligated (BDL) group. After 14 days of surgery, the animals of the group I (Sham control) received distilled water only for 7, 14 and 28 days. Second group (BDL group) was divided into 2 subgroups, animals of these subgroups treated for 7, 14 and 28 consecutive days as follow: subgroup I (BDL), rats of this subgroup administered distilled water orally. Subgroup II (HaE), animals of this subgroup treated orally with HaE (200 mg/kg body weight).

RESULTS

The HaE revealed significant antifibrotic effect as evident by decreasing the levels of total conjugated and unconjugated bilirubin and the activities of serum aminotransferases (ASAT and ALAT) and alkaline phosphatase (ALP) as well as malondialdehyde (MDA) level, and increasing the serum albumin, glutathione reduced (GSH) levels. Treatment with HaE normalized the antioxidant enzyme, glutathione-S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT) activities activities.

CONCLUSION

The present prospective study correlated the antifibrotic effect of HaE to its direct antioxidant effect that can be related to its contents of phenolic compounds specially chlorogenic acid, pyrogallol, rutin and coumaric acid.

Ginseng: a promising neuroprotective strategy in stroke

Ginseng is one of the most widely used herbal medicines in the world. It has been used in the treatment of various ailments and to boost immunity for centuries; especially in Asian countries. The most common ginseng variant in traditional herbal medicine is ginseng, which is made from the peeled and dried root of Panax Ginseng. Ginseng has been suggested as an effective treatment for a vast array of neurological disorders, including stroke and other acute and chronic neurodegenerative disorders. Ginseng’s neuroprotective effects are focused on the maintenance of homeostasis. This review involves a comprehensive literature search that highlights aspects of ginseng’s putative neuroprotective effectiveness, focusing on stroke. Attenuation of inflammation through inhibition of various proinflammatory mediators, along with suppression of oxidative stress by various mechanisms, including activation of the cytoprotective transcriptional factor Nrf2, which results in decrease in reactive oxygen species, could account for its neuroprotective efficacy. It can also prevent neuronal death as a result of stroke, thus decreasing anatomical and functional stroke damage. Although there are diverse studies that have investigated the mechanisms involved in the efficacy of ginseng in treating disorders, there is still much that needs to be clarified. Both in vitro and in vivo studies including randomized controlled clinical trials are necessary to develop in-depth knowledge of ginseng and its practical applications.

Attenuation of Streptomycin Ototoxicity by Tetramethylpyrazine in Guinea Pig Cochlea

Objective

Tetramethylpyrazine has been suggested to have a therapeutic effect on impaired hearing that is induced by aminoglycoside antibiotics. However, its effectiveness on streptomycin ototoxicity and its cellular mechanisms are relatively unknown. Here we investigate the protective effect of tetramethylpyrazine on streptomycin-induced ototoxicity in guinea pig cochlea.

Study Design

Prospective randomized laboratory study.

Setting

Hearing Research Laboratory of China Medical University.

Subjects and Methods

Adult guinea pigs were randomized to 4 groups. Hearing sensitivity of guinea pigs was tested by auditory brainstem response measurements before streptomycin exposure and again 10 days later. The cochlear tissues were prepared for electron microscopy and immunohistochemical staining of heat shock protein 70 (HSP70). The effect of tetramethylpyrazine on streptomycin-induced activation of caspase-3 was evaluated by Western blotting.

Results

Co-therapy with tetramethylpyrazine reduced a profound streptomycin-induced auditory threshold shift compared with streptomycin treatment alone ( P = .0002 or P = .00008). Tetramethylpyrazine also attenuated the structural disruption in streptomycin-treated outer hair cells and marginal cells of vascular stria by transmission electronic microscopy and scanning electronic microscopy, respectively. Moreover, tetramethylpyrazine decreased the streptomycin-stimulated expressions of HSP70 and caspase-3. The correlation analysis demonstrated that HSP70 expression had a positive correlation with auditory brainstem response thresholds (|R| = 0.6-0.9, P = .0073 or P = .0169).

Conclusions

Our data suggest that the protective effect of tetramethylpyrazine on hearing function is associated with the reduction of stress response and inhibition of apoptosis. Tetramethylpyrazine may have therapeutic potential for patients with ototoxicity diseases.

Heat shock protein-mediated protection against Cisplatin-induced hair cell death

Cisplatin is a highly successful and widely used chemotherapy for the treatment of various solid malignancies in both adult and pediatric patients. Side effects of cisplatin treatment include nephrotoxicity and ototoxicity. Cisplatin ototoxicity results from damage to and death of cells in the inner ear, including sensory hair cells. We showed previously that heat shock inhibits cisplatin-induced hair cell death in whole-organ cultures of utricles from adult mice. Since heat shock protein 70 (HSP70) is the most upregulated HSP in response to heat shock, we investigated the role of HSP70 as a potential protectant against cisplatin-induced hair cell death. Our data using utricles from HSP70 (-/-) mice indicate that HSP70 is necessary for the protective effect of heat shock against cisplatin-induced hair cell death. In addition, constitutive expression of inducible HSP70 offered modest protection against cisplatin-induced hair cell death. We also examined a second heat-inducible protein, heme oxygenase-1 (HO-1, also called HSP32). HO-1 is an enzyme responsible for the catabolism of free heme. We previously showed that induction of HO-1 using cobalt protoporphyrin IX (CoPPIX) inhibits aminoglycoside-induced hair cell death. Here, we show that HO-1 also offers significant protection against cisplatin-induced hair cell death. HO-1 induction occurred primarily in resident macrophages, with no detectable expression in hair cells or supporting cells. Depletion of macrophages from utricles abolished the protective effect of HO-1 induction. Together, our data indicate that HSP induction protects against cisplatin-induced hair cell death, and they suggest that resident macrophages mediate the protective effect of HO-1 induction.

Upregulation of Hsp72 mediates anoxia/reoxygenation neuroprotection in the freshwater turtle via modulation of ROS

The neuroprotective role of Hsp72 has been demonstrated in several ischemic/stroke models to occur primarily through mediation of apoptotic pathways, and a number of heat shock proteins are upregulated in animal models capable of extended anoxic survival. In the present study, we investigated the role of Hsp72 on cell death and apoptotic regulators in one anoxia tolerant model system, the freshwater turtle Trachemys scripta. Since Hsp72 is known to regulate apoptosis through interactions with Bcl-2, we manipulated the levels of Hsp72 and Bcl-2 with siRNA in neuronally enriched primary cell cultures and examined downstream effects. The knockdown of either Hsp72 or Bcl-2 induced cell death during anoxia and reoxygenation. Knockdown of Bcl-2 resulted in increases in apoptotic markers and increased ROS levels 2-fold. However, significant knockdown of Hsp72 did not have any effect on the expression of key mitochondrial apoptotic regulators such as Cytochrome c and caspase-3. Hsp72 knockdown however significantly increased apoptosis inducing factor in both anoxia and reoxygenation and resulted in a six-fold induction of hydrogen peroxide levels. These findings suggest that the neuroprotection offered by Hsp72 in the anoxia/reoxygenation tolerant turtle is through the mediation of ROS levels and not through modulation of caspase-dependent pathways.

Presence of heat shock protein 70 in secondary lymphoid tissue correlates with stroke prognosis

Heat shock protein 70 (Hsp-70) can act as a danger signal and activate immune responses. We studied the presence of Hsp-70 in lymphoid tissue and plasma of acute stroke patients and asymptomatic controls free of neurological disease. Immunofluorescence, Western blotting, qRT-PCR and flow cytometry studies were performed. Plasma Hsp-70 concentration at day 7 was similar in patients and controls, whereas patients disclosed stronger immunoreactivity to Hsp-70 in lymphoid tissue than controls. Most Hsp-70+ cells were antigen presenting cells located in T cell zones. Stronger immunoreactivity to Hsp-70 was associated with smaller infarctions and better functional outcome.

Oxygen glucose deprivation post-conditioning protects cortical neurons against oxygen-glucose deprivation injury: role of HSP70 and inhibition of apoptosis

In the present study, we examined the effect of oxygen glucose deprivation (OGD) post-conditioning (PostC) on neural cell apoptosis in OGD-PostC model and the protective effect on primary cortical neurons against OGD injury in vitro. Four-h OGD was induced by OGD by using a specialized and humidified chamber. To initiate OGD, culture medium was replaced with de-oxygenated and glucose-free extracellular solution-Locke's medium. After OGD treatment for 4 h, cells were then allowed to recover for 6 h or 20 h. Then lactate dehydrogenase (LDH) release assay, Western blotting and flow cytometry were used to detect cell death, protein levels and apoptotic cells, respectively. For the PostC treatment, three cycles of 15-min OGD, followed by 15 min normal cultivation, were applied immediately after injurious 4-h OGD. Cells were then allowed to recover for 6 h or 20 h, and cell death was assessed by LDH release assay. Apoptotic cells were flow cytometrically evaluated after 4-h OGD, followed by re-oxygenation for 20 h (O4/R20). In addition, Western blotting was used to examine the expression of heat-shock protein 70 (HSP70), Bcl-2 and Bax. The ratio of Bcl-2 expression was (0.44±0.08)% and (0.76±0.10)%, and that of Bax expression was (0.51±0.05)% and (0.39±0.04)%, and that of HSP70 was (0.42±0.031)% and (0.72±0.045)% respectively in OGD group and PostC group. After O4/R6, the rate of neuron death in PostC group and OGD groups was (28.96±3.03)% and (37.02±4.47)%, respectively. Therefore, the PostC treatment could up-regulate the expression of HSP70 and Bcl-2, but down-regulate Bax expression. As compared with OGD group, OGD-induced neuron death and apoptosis were significantly decreased in PostC group (P<0.05). These findings suggest that PostC inhibited OGD-induced neuron death. This neuro-protective effect is likely achieved by anti-apoptotic mechanisms and is associated with over-expression of HSP70.

Neuroprotective effects of geranylgeranylacetone in experimental traumatic brain injury

Geranylgeranylacetone (GGA) is an inducer of heat-shock protein 70 (HSP70) that has been used clinically for many years as an antiulcer treatment. It is centrally active after oral administration and is neuroprotective in experimental brain ischemia/stroke models. We examined the effects of single oral GGA before treatment (800 mg/kg, 48 hours before trauma) or after treatment (800 mg/kg, 3 hours after trauma) on long-term functional recovery and histologic outcomes after moderate-level controlled cortical impact, an experimental traumatic brain injury (TBI) model in mice. The GGA pretreatment increased the number of HSP70(+) cells and attenuated posttraumatic α-fodrin cleavage, a marker of apoptotic cell death. It also improved sensorimotor performance on a beam walk task; enhanced recovery of cognitive/affective function in the Morris water maze, novel object recognition, and tail-suspension tests; and improved outcomes using a composite neuroscore. Furthermore, GGA pretreatment reduced the lesion size and neuronal loss in the hippocampus, cortex, and thalamus, and decreased microglial activation in the cortex when compared with vehicle-treated TBI controls. Notably, GGA was also effective in a posttreatment paradigm, showing significant improvements in sensorimotor function, and reducing cortical neuronal loss. Given these neuroprotective actions and considering its longstanding clinical use, GGA should be considered for the clinical treatment of TBI.

Exploring molecular mechanism underlying Chinese medicine syndrome: a study on correlation between Chinese medicine syndrome and biomarkers for ischemic stroke

OBJECTIVE

To investigate whether Chinese medicine (CM) syndrome is associated with particular molecular mechanism, we explored the correlation between CM syndrome and changes of intercellular adhesion molecule-1 (ICAM-1), matrix metalloproteinase 9 (MMP-9) and heat shock protein 70 (HSP70) in patients with ischemic stroke, which were reported to play an important role in the inflammatory and apoptosis cascade.

METHODS

CM syndrome factors of 175 patients with ischemic stroke were assessed using Ischemic Stroke CM Syndrome Factor Diagnostic Scale (ISTSFDS). The patients were grouped according to the main syndrome factor combinations at different time points based on distribution probability of syndrome factor combinations. Blood levels of ICAM-1, MMP-9 and HSP70 were quantified by enzyme-linked immunosorbent assay.

RESULTS

ICAM-1 expression was significantly higher in the internal-wind+phlegm-dampness+blood-stasis, phlegmdampness+ blood-stasis, internal-fire+phlegm-dampness+blood-stasis group than that in the blood-stasis+qideficiency group within 72 h from stroke onset (P <0.05); HSP70 expression was significantly lower in the phlegm-dampness+blood-stasis, internal-fire+phlegm-dampness+blood-stasis, blood-stasis group than that in the phlegm-dampness+blood-stasis+qi-deficiency group on the 7th day from stroke onset (P<0.05).

CONCLUSIONS

Phlegm-dampness and blood-stasis exist through the whole process of ischemic stroke. An increased level of ICAM-1 and a reduced level of HSP70 reflect the pathological state of phlegm-stasis mutual binding. These results suggest that inflammation and apoptosis induced by cerebral vascular injury in the pathological processes of ischemic stroke are more prominent in the excess syndrome state like phlegm-dampness and blood-stasis.

Ras family small GTPase-mediated neuroprotective signaling in stroke

Selective neuronal cell death is one of the major causes of neuronal damage following stroke, and cerebral cells naturally mobilize diverse survival signaling pathways to protect against ischemia. Importantly, therapeutic strategies designed to improve endogenous anti-apoptotic signaling appear to hold great promise in stroke treatment. While a variety of complex mechanisms have been implicated in the pathogenesis of stroke, the overall mechanisms governing the balance between cell survival and death are not well-defined. Ras family small GTPases are activated following ischemic insults, and in turn, serve as intrinsic switches to regulate neuronal survival and regeneration. Their ability to integrate diverse intracellular signal transduction pathways makes them critical regulators and potential therapeutic targets for neuronal recovery after stroke. This article highlights the contribution of Ras family GTPases to neuroprotective signaling cascades, including mitogen-activated protein kinase (MAPK) family protein kinase- and AKT/PKB-dependent signaling pathways as well as the regulation of cAMP response element binding (CREB), Forkhead box O (FoxO) and hypoxiainducible factor 1(HIF1) transcription factors, in stroke.

Iptakalim, an ATP-sensitive potassium channel opener, confers neuroprotection against cerebral ischemia/reperfusion injury in rats by protecting neurovascular unit cells

OBJECTIVE

To investigate the role of iptakalim, an ATP-sensitive potassium channel opener, in transient cerebral ischemia/reperfusion (I/R) injury and its involved mechanisms.

METHODS

Intraluminal occlusion of middle cerebral artery (MCAO) in a rat model was used to investigate the effect of iptakalim at different time points. Infarct volume was measured by staining with 2,3,5-triphenyltetrazolium chloride, and immunohistochemistry was used to evaluate the expressions of Bcl-2 and Bax. In vitro, neurovascular unit (NVU) cells, including rat primary cortical neurons, astrocytes, and cerebral microvascular endothelial cells, were cultured and underwent oxygen-glucose deprivation (OGD). The protective effect of iptakalim on NVU cells was investigated by cell viability and injury assessments, which were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and release of lactate dehydrogenase. Caspase-3, Bcl-2 and Bax mRNA expressions were evaluated by real-time polymerase chain reaction (PCR).

RESULTS

Administration of iptakalim 0 or 1 h after reperfusion significantly reduced infarct volumes, improved neurological scores, and attenuated brain edema after cerebral I/R injury. Iptakalim treatment (0 h after reperfusion) also reduced caspase-3 expression and increased the ratio of Bcl-2 to Bax by immunohistochemistry. Iptakalim inhibited OGD-induced cell death in cultured neurons and astrocytes, and lactate dehydrogenase release from cerebral microvascular endothelial cells. Iptakalim reduced mRNA expression of caspase-3 and increased the ratio of Bcl-2 to Bax in NVU cells.

CONCLUSIONS

Iptakalim confers neuroprotection against cerebral I/R injury by protecting NVU cells via inhibiting of apoptosis.

Antioxidant and anti-inflammatory effects of exercise in diabetic patients

Diabetes is a chronic metabolic disease which is characterized by absolute or relative deficiencies in insulin secretion and/or insulin action. The key roles of oxidative stress and inflammation in the progression of vascular complications of this disease are well recognized. Accumulating epidemiologic evidence confirms that physical inactivity is an independent risk factor for insulin resistance and type II diabetes. This paper briefly reviews the pathophysiological pathways associated with oxidative stress and inflammation in diabetes mellitus and then discusses the impact of exercise on these systems. In this regard, we discuss exercise induced activation of cellular antioxidant systems through “nuclear factor erythroid 2-related factor.” We also discuss anti-inflammatory myokines, which are produced and released by contracting muscle fibers. Antiapoptotic, anti-inflammatory and chaperon effects of exercise-induced heat shock proteins are also reviewed.

Identification of a NF-κB cardioprotective gene program: NF-κB regulation of Hsp70.1 contributes to cardioprotection after permanent coronary occlusion

The transcription factor Nuclear Factor Kappa B (NF-κB) has been shown to be cardioprotective after permanent coronary occlusion (PO) and late ischemic preconditioning (IPC), and yet it is cell injurious after ischemia/reperfusion (I/R) in the heart. There is limited information regarding NF-κB-dependent cardioprotection, and the NF-κB-dependent genes that contribute to the cardioprotection after PO are completely unknown. The objective of the study was to identify NF-κB-dependent genes that contribute to cardioprotection after PO. Microarray analysis was used to delineate genes that potentially contribute to the NF-κB-dependent cardioprotection by determining the overlap between the set of PO regulated genes and genes regulated by NF-κB, using mice with genetic abrogation of NF-κB activation in the heart. This analysis identified 16 genes as candidates for NF-κB-dependent effects after PO. This set of genes overlaps with, but is significantly different from the set of genes we previously identified as regulated by NF-κB after IPC. The genes encoding heat shock protein 70.3 (hspa1a) and heat shock protein 70.1 (hspa1b) were the most significantly regulated genes after PO and were up-regulated by NF-κB. Results using knockout mice show that Hsp70.1 contributes to NF-κB-dependent cardioprotection after PO and likely underlies, at least in part, the NF-κΒ-dependent cardioprotective effect. Our previous results show that Hsp70.1 is injurious after I/R injury. This demonstrates that, like NF-κB itself, Hsp70.1 has antithetical effects on myocardial survival and suggests that this may underlie the similar antithetical effects of NF-κB after different ischemic stimuli. The significance of the research is that understanding the gene network regulated by NF-κB after ischemic insult may lead to identification of therapeutic targets more appropriate for clinical development.

Combined prostaglandin E1 and lithium exert potent neuroprotection in a rat model of cerebral ischemia

AIM

To examine the effects of a mixed formulation composed of prostaglandin E1 and lithium (PGE1+Li mixture) on brain damage after cerebral ischemia. The effects of the mixture on protein expression of heat shock proteins (HSPs), p53, and Bcl-2 were also determined.

METHODS

Brain ischemia was induced with a permanent middle cerebral artery occlusion (pMCAO) in rats. Rats were treated with a single intravenous administration of PGE1, lithium or a PGE1+Li mixture immediately after the ischemic insult. The infarct volume and motor behavior deficits were analyzed 24 h after the ischemic insult. The protein levels of HSP70, glucose-regulated protein 78 (GRP78), HSP60, Bcl-2, and p53 in the striatum of the ipsilateral hemisphere were examined using immunoblotting.

RESULTS

The mixture (PGE1 22.6 nmol/kg+Li 0.5 mmol/kg) reduced infarct volume and neurological deficits induced by focal cerebral ischemia. Moreover, the mixture had a greater neuroprotective effect against cerebral ischemia compared with PGE1 or lithium alone. The mixture was effective even if it was administered 3 h after ischemia. PGE1+Li also significantly upregulated cytoprotective HSP70, GRP78, HSP60, and Bcl-2 protein levels, while decreasing p53 expression.

CONCLUSION

These results demonstrated a PGE1+Li mixture with a therapeutic window of up to 3 h for clinical treatment of cerebral ischemia. The PGE1+Li mixture potentially exerts a protective effect after stroke through the induction of HSPs and Bcl-2 proteins.

Geldanamycin reduced brain injury in mouse model of intracerebral hemorrhage

We investigated the effect of the heat shock protein inducer geldanamycin on the development of secondary brain injury after ICH in mice. The effect of the drug at two different concentrations was evaluated at two time points: 24 and 72 h after ICH induction. In the first part of this study, a total of 30 male CD-1 mice were randomly divided into four groups: one sham group and three ICH groups. ICH animals received either an intraperitoneal injection of vehicle or geldanamycin (1 or 10 mg/kg). Neurological deficits and brain water content were evaluated 24 h after ICH. In the second part of this study, the effect of a high concentration of geldanamycin was evaluated 72 h after ICH. Neurological deficits were evaluated by the Garcia neuroscoring, wire hanging and beam balance tests. For estimation of brain water content, the "wet/dry weight" method was used. We demonstrated that administration of geldanamycin (10 mg/kg) ameliorated ICH-induced increase of brain water content significantly in both parts of the study. Geldanamycin improved the neurological outcome according to performance on Garcia and beam balance tests in the 72 h part of this study. Geldanamycin-induced induction of heat shock protein after ICH has a neuroprotective effect and may be a therapeutic target for ICH.

Molecular actions and therapeutic potential of lithium in preclinical and clinical studies of CNS disorders

Lithium has been used clinically to treat bipolar disorder for over half a century, and remains a fundamental pharmacological therapy for patients with this illness. Although lithium's therapeutic mechanisms are not fully understood, substantial in vitro and in vivo evidence suggests that it has neuroprotective/neurotrophic properties against various insults, and considerable clinical potential for the treatment of several neurodegenerative conditions. Evidence from pharmacological and gene manipulation studies support the notion that glycogen synthase kinase-3 inhibition and induction of brain-derived neurotrophic factor-mediated signaling are lithium's main mechanisms of action, leading to enhanced cell survival pathways and alteration of a wide variety of downstream effectors. By inhibiting N-methyl-D-aspartate receptor-mediated calcium influx, lithium also contributes to calcium homeostasis and suppresses calcium-dependent activation of pro-apoptotic signaling pathways. In addition, lithium decreases inositol 1,4,5-trisphosphate by inhibiting phosphoinositol phosphatases, a process recently identified as a novel mechanism for inducing autophagy. Through these mechanisms, therapeutic doses of lithium have been demonstrated to defend neuronal cells against diverse forms of death insults and to improve behavioral as well as cognitive deficits in various animal models of neurodegenerative diseases, including stroke, amyotrophic lateral sclerosis, fragile X syndrome, as well as Huntington's, Alzheimer's, and Parkinson's diseases, among others. Several clinical trials are also underway to assess the therapeutic effects of lithium for treating these disorders. This article reviews the most recent findings regarding the potential targets involved in lithium's neuroprotective effects, and the implication of these findings for the treatment of a variety of diseases.

Heat shock protein 70 upregulation by geldanamycin reduces brain injury in a mouse model of intracerebral hemorrhage

This study investigated the effect of geldanamycin post-treatment on the development of secondary brain injury and neurological deficits in a mouse model of intracerebral hemorrhage. CD-1 mice received stereotactic injection of collagenase type VII into the right basal ganglia. Treatment groups were administered 1 mg/kg (low dose) or 10 mg/kg (high dose) of geldanamycin. Mice were euthanized at two time-points: 24 h or 72 h. Blood-brain-barrier permeability, brain edema, and neurobehavioral deficits were assessed. Additionally, the effects of geldanamycin on heat shock protein 27 and 72; tumor necrosis factor-alpha and interleukin 1 beta expressions were evaluated. High dose geldanamycin significantly attenuated blood-brain barrier disruption and brain edema after intracerebral hemorrhage. Neurobehavioral outcomes were significantly improved in some parameters by high dose treatment. Molecular results showed a marked increase in heat shock protein 72 expression in ipsilateral brain of geldanamycin treated groups with a reduction in the pro-inflammatory tumor necrosis factor-alpha.

CONCLUSION

Geldanamycin post-treatment is neuroprotective in the mouse model of intracerebral hemorrhage. Geldanamycin administration results in reduction of inflammation, preservation of blood-brain-barrier and amelioration of neurobehavioral deficits after an insult possibly by upregulation of heat shock protein 72.

Combined effect of tumor necrosis factor (TNF)-alpha and heat shock protein (HSP)-70 in reducing apoptotic injury in hypoxia: a cell culture study

Studies have demonstrated neuroprotective effects of either TNF-alpha or HSP-70 in ischemia/reperfusion injury following exercise. However, the protective mechanisms involving combined effect of the two proteins, particularly in neuronal apoptosis, remain unclear. This study aims to elucidate the beneficial role of TNF-alpha and HSP-70 in the regulation of apoptotic proteins and ERK signaling in hypoxic injury. Cortical neurons from 20 Sprague-Dawley rat embryos were isolated and cultured in five groups with or without pretreatment with recombinant TNF-alpha, HSP-70 protein or both prior to hypoxic conditions: (1) control; (2) control/hypoxia; (3) TNF-alpha/hypoxia; (4) HSP-70/hypoxia and (5) TNF-alpha/HSP-70/hypoxia. Western blotting was used to detect pro- and anti-apoptotic proteins, including Bax, AIF, Bcl-xL, Bcl-2, and pERK1/2 protein. TNF-alpha and HSP-70 significantly (p<0.05) reduced the levels of pro-apoptotic proteins, Bax and AIF. Also, pretreatment of hypoxic brain tissue with TNF-alpha and HSP-70 significantly (p<0.05) enhanced the levels of anti-apoptotic protein, Bcl-xL. TNF-alpha and HSP-70 together increased Bcl-2 levels by 70%. Hypoxia caused a significant (p<0.05) increase in ERK1/2 phosphorylation levels by 224%. The most effective inhibition of ERK levels was obtained by the combined administration of TNF-alpha and HSP-70. This study suggested that TNF-alpha and HSP-70 together enhance the decrease in pro-apoptotic protein levels and the increase in anti-apoptotic protein levels in the event of neuronal hypoxia through ERK1/2 signal transduction.

HSP70 protects intestinal epithelial cells from hypoxia/reoxygenation injury via a mechanism that involves the mitochondrial pathways

Though recent studies have reported the importance of several endogenous cytoprotective factors including heat shock protein 70 (HSP70) that protect intestinal epithelial cells (IECs) from the effects of stress and injury, the exact mechanism of HSP70 underlying cytoprotection against hypoxia/reoxygenation induced IEC injury remains unclear. The present study was designed to investigate the possible mechanisms by which HSP70 protected IECs against hypoxia/reoxygenation injury and focused on the effects of HSP70 on IEC apoptosis induced by hypoxia/reoxygenation injury. Recombinant adenoviruses (Ad-HSP70) were transfected into the intestinal epithelial cell line in vitro and then suffered from 90 min of hypoxia followed by 60 min of reoxygenation. The LDH leaking, apoptosis, and mitochondrial membrane potential (Psi(m)) were evaluated after hypoxia/reoxygenation. The expression of HSP70, cytochrome c and Bcl-2 protein was determined by Western blot or immunofluorescence analysis. The results show that HSP70 protein was highly expressed in the IECs at 48h following Ad-HSP70 transfection. HSP70 overexpression could reduce LDH leakage and cell apoptosis in IECs following hypoxia/reoxygenation injury. Furthermore, the overexpression of HSP70 significantly reversed the decrease of mitochondrial membrane potential and the release of mitochondrial cytochrome c in IECs during hypoxia/reoxygenation. HSP70 overexpression was also associated with the increasing expression of Bcl-2 protein in IECs during hypoxia/reoxygenation. We conclude that HSP70 protects IECs against hypoxia/reoxygenation induced apoptosis through increasing Bcl-2 expression, which in turn could inhibit the mitochondria-related apoptotic pathway that involves the disruption of the Psi(m) and release of cytochrome c from mitochondria.

Heat shock proteins: cellular and molecular mechanisms in the central nervous system

Emerging evidence indicates that heat shock proteins (HSPs) are critical regulators in normal neural physiological function as well as in cell stress responses. The functions of HSPs represent an enormous and diverse range of cellular activities, far beyond the originally identified roles in protein folding and chaperoning. HSPs are now understood to be involved in processes such as synaptic transmission, autophagy, ER stress response, protein kinase and cell death signaling. In addition, manipulation of HSPs has robust effects on the fate of cells in neurological injury and disease states. The ongoing exploration of multiple HSP superfamilies has underscored the pluripotent nature of HSPs in the cellular context, and has demanded the recent revamping of the nomenclature referring to these families to reflect a re-organization based on structure and function. In keeping with this re-organization, we first discuss the HSP superfamilies in terms of protein structure, regulation, expression and distribution in the brain. We then explore major cellular functions of HSPs that are relevant to neural physiological states, and from there we discuss known and proposed HSP impacts on major neurological disease states. This review article presents a three-part discussion on the array of HSP families relevant to neuronal tissue, their cellular functions, and the exploration of therapeutic targets of these proteins in the context of neurological diseases.

Proteomic profiling of proteins in rat spinal cord induced by contusion injury

It is widely accepted that mechanical injury to spinal cord can cause nervous system dysfunction, which leads to the loss of movement and sensation. However, the exact molecular mechanism is currently unclear. In this study, contused rat spinal cords were collected at 8h, 1 day, 3, and 5 days after injury and the expression patterns of the proteins were monitored and quantified with two-dimensional gel electrophoresis-based proteomics. Fifty-one protein spots showed significant regulation at least at one time point. Of the 39 proteins, identified by mass spectrometry analysis and clustered into three down-regulation profiles and two up-regulation profiles, eight contusion-related proteins have been reported in previous proteomic studies of spinal cord whereas 31 proteins were described for the first time. For example, apoptosis-related protein of heat shock 70 kDa protein 1B increased after contusion, reaching the peak at 1 day; septin 7, a protein involved in cytoskeleton organization, maintained a steady increase for the first 5 days after injury; metabolism-related protein of 3-hydroxy-3-methylglutaryl-Coenzyme A synthase 1 was constantly down-regulated during the whole time course observed; tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein, epsilon polypeptide, associated with cell cycle progression, showed a gradual increase after contusion. To our knowledge, this is the first case of detailed and dynamic proteomic snapshots of contusion-induced spinal cord injury. Most of the identified proteins were found for the first time to be differentially expressed after spinal cord contusion, which may help explore the complex molecular cascades underlying the progressive pathologic changes in the contused spinal cord.

Ischemic postconditioning may not influence early brain injury induced by focal cerebral ischemia/reperfusion in rats

Background

Experimental studies have shown that ischemic postconditioning can reduce neuronal injury in the setting of cerebral ischemia, but the mechanisms are not yet clearly elucidated. This study was conducted to determine whether ischemic postconditioning can alter expression of heat shock protein 70 and reduce acute phase neuronal injury in rats subjected to transient focal cerebral ischemia/reperfusion.

Methods

Focal cerebral ischemia was induced by intraluminal middle cerebral artery occlusion for 60 min in twenty male Sprague-Dawley rats (250-300 g). Rats were randomized into control group and an ischemic postconditioning group (10 rats per group). The animals of control group had no intervention either before or after MCA occlusion. Ischemic postconditioning was elicited by 3 cycles of 30 s reperfusion interspersed by 10 s ischemia immediately after onset of reperfusion. The infarct ratios, brain edema ratios and motor behavior deficits were analyzed 24 hrs after ischemic insult. Caspase-3 reactive cells and cells showing heat shock protein 70 activity were counted in the caudoputamen and frontoparietal cortex.

Results

Ischemic postconditiong did not reduce infarct size and brain edema ratios compared to control group. Neurologic scores were not significantly different between groups. The number of caspase-3 reactive cells in the ischemic postconditioning group was not significantly different than the value of the control group in the caudoputamen and frontoparietal cortex. The number of cells showing heat shock protein 70 activity was not significantly different than the control group, as well.

Conclusions

These results suggest that ischemic postconditioning may not influence the early brain damage induced by focal cerebral ischemia in rats.

Geldanamycin induces production of heat shock protein 70 and partially attenuates ototoxicity caused by gentamicin in the organ of Corti explants

Background

Heat shock protein 70 (HSP70) protects inner ear cells from damage and death induced by e.g. heat or toxins. Benzoquinone ansamycin antibiotic geldanamycin (GA) was demonstrated to induce the expression of HSP70 in various animal cell types. The aim of our study was to investigate whether GA induces HSP70 in the organ of Corti (OC), which contains the auditory sensory cells, and whether GA can protect these cells from toxicity caused by a common aminoglycoside antibiotic gentamicin.

Methods

To address these questions, we used the OC explants isolated from p3-p5 rats. As a read-out, we used RT-PCR, ELISA and immunofluorescence.

Results

We found that GA at the concentration of 2 μM efficiently induced HSP70 expression on mRNA and protein level in the OC explants. Confocal microscopy revealed that HSP70 induced by GA is expressed by hair cells and interdental cells of spiral limbus. Preincubation of explants with 2 μM GA prior to adding gentamicin (500 μM) significantly reduced the loss of outer but not inner hair cells, suggesting different mechanisms of otoprotection needed for these two cell types.

Conclusion

GA induced HSP70 in the auditory sensory cells and partially protected them from toxicity of gentamicin. Understanding the molecular mechanisms of GA otoprotection may provide insights for preventative therapy of the hearing loss caused by aminoglycoside antibiotics.

Melatonin provides neuroprotection by reducing oxidative stress and HSP70 expression during chronic cerebral hypoperfusion in ovariectomized rats

Oxidative stress is believed to contribute to functional and histopathologic disturbances associated with chronic cerebral hypoperfusion (CCH) in rats. Melatonin has protective effects against cerebral ischemia/reperfusion injury. This effect has mainly been attributed to its antioxidant properties. In the present study, we evaluate the effects of melatonin on chronic cerebral hypoperfused rats and examined its possible influence on oxidative stress, superoxide dismutase (SOD) activity, reduced glutathione (GSH) levels, and heat shock protein (HSP) 70 induction. CCH was induced by permanent bilateral common carotid artery occlusion in ovariectomized female rats. Extensive neuronal loss in the hippocampus at day 14 following CCH was observed. The ischemic changes were preceded by increases in malondialdehyde (MDA) concentration and HSP70 induction as well as reductions in GSH and SOD. Melatonin treatment restored the levels of MDA, SOD, GSH, and HSP70 induction as compared to the ischemic group. Histopathologic analysis confirmed the protective effect of melatonin against CCH-induced morphologic alterations. Taken together, our results document that melatonin provides neuroprotective effects in CCH by attenuating oxidative stress and stress protein expression in neurons. This suggests melatonin may be helpful for the treatment of vascular dementia and cerebrovascular insufficiency.

Hsp70 inhibits aminoglycoside-induced hearing loss and cochlear hair cell death

Sensory hair cells of the inner ear are sensitive to death from aging, noise trauma, and ototoxic drugs. Ototoxic drugs include the aminoglycoside antibiotics and the antineoplastic agent cisplatin. Exposure to aminoglycosides results in hair cell death that is mediated by specific apoptotic proteins, including c-Jun N-terminal kinase (JNK) and caspases. Induction of heat shock proteins (Hsps) can inhibit JNK- and caspase-dependent apoptosis in a variety of systems. We have previously shown that heat shock results in robust upregulation of Hsps in the hair cells of the adult mouse utricle in vitro. In addition, heat shock results in significant inhibition of both cisplatin- and aminoglycoside-induced hair cell death. In this system, Hsp70 is the most strongly induced Hsp, which is upregulated over 250-fold at the level of mRNA 2 h after heat shock. Hsp70 overexpression inhibits aminoglycoside-induced hair cell death in vitro. In this study, we utilized Hsp70-overexpressing mice to determine whether Hsp70 is protective in vivo. Both Hsp70-overexpressing mice and their wild-type littermates were treated with systemic kanamycin (700 mg/kg body weight) twice daily for 14 days. While kanamycin treatment resulted in significant hearing loss and hair cell death in wild-type mice, Hsp70-overexpressing mice were significantly protected against aminoglycoside-induced hearing loss and hair cell death. These data indicate that Hsp70 is protective against aminoglycoside-induced ototoxicity in vivo.

Multiple apoptogenic proteins are involved in the nuclear translocation of Apoptosis Inducing Factor during transient focal cerebral ischemia in rat

Apoptosis Inducing Factor is a mitochondrial protein which upon translocation to nucleus causes large scale DNA fragmentation. The stimulus for the cytosolic release and nuclear translocation for this protein still remains to be understood. The role of calpains, cathepsin-b, Poly ADP (ribose) Polymerase and granzyme-b in the nuclear translocation of AIF has been investigated in the pathology of cerebral ischemia. Calpains, cathepsin-b and PARP-1 which were mostly confined to cytosol, lysosomes and nucleus respectively were found to be elevated in the mitochondrial fraction interacting with AIF in the western blot analysis and double immunofluorescence analysis. Western blot and immunohistochemical analysis revealed elevated levels of granzyme-b secreted by cytotoxic T lymphocytes and natural killer cells in the infarct of ischemic mouse brain. Co-immunoprecipitation revealed and western blot analysis the interaction and break down of Heat Shock Protein-70 an endogenous inhibitor of AIF into signature fragments by granzyme-b facilitating the nuclear translocation of AIF. Break down of HSP-70 correlated with the nuclear translocation of AIF observed in western and immunohistochemical analysis. These results indicate that multiple proteases were involved in the nuclear translocation of AIF during the pathology of cerebral ischemia.

Synergistic effects of prostaglandin E1 and lithium in a rat model of cerebral ischemia

AIM

Heat shock proteins (HSPs) are important regulators of cellular survival and exert neuroprotective effects against cerebral ischemia. Both prostaglandin E1 (PGE1) and lithium have been reported to protect neurons against ischemic injury. The present study was undertaken to examine if lithium could potentiate the neuroprotection of PGE1 against cerebral ischemia, and if the synergetic effects take place at the level of HSPs.

METHODS

Brain ischemia was induced by a permanent middle cerebral artery occlusion (pMCAO) in rats. Rats were pretreated with subcutaneous injection of lithium for 2 d and a single intravenous administration of PGE1 immediately after ischemic insult. Cerebrocortical blood flow of each group was closely monitored prior to onset of ischemia, 5 min, 15 min, 30 min and 60 min after surgical operation. Body temperature was measured before, 5 min, 2 h and 24 h after the onset of pMCAO. The infarct volume, brain edema and motor behavior deficits were analyzed 24 h after ischemic insult. Cytoprotective HSP70 and heme oxygenase-1 (HO-1) in the striatum of the ipsilateral hemisphere were detected by immunoblotting. Brain sections from the striatum of the ipsilateral hemisphere were double-labeled with the anti-HSP70 antibody and 4,6-diamidino-2-phenylindole (DAPI).

RESULTS

Treatment with PGE1 (8 and 16 microg/kg, iv) or lithium (0.5 mEq/kg, sc) alone reduced infarct volume, neurological deficits and brain edema induced by focal cerebral ischemia in rats. Moreover, a greater neuroprotection was observed when PGE1 and lithium were given together. Co-administration of PGE1 and lithium significantly upregulated cytoprotective HSP70 and HO-1 protein levels.

CONCLUSION

Lithium and PGE1 may exert synergistic effects in treatment of cerebral ischemia and thus may have potential clinical value for the treatment of stroke.

Hsp70 inhibits aminoglycoside-induced hair cell death and is necessary for the protective effect of heat shock

Sensory hair cells of the inner ear are sensitive to death from aging, noise trauma, and ototoxic drugs. Ototoxic drugs include the aminoglycoside antibiotics and the antineoplastic agent cisplatin. Exposure to aminoglycosides results in hair cell death that is mediated by specific apoptotic proteins, including c-Jun N-terminal kinase (JNK) and caspases. Induction of heat shock proteins (Hsps) is a highly conserved stress response that can inhibit JNK- and caspase-dependent apoptosis in a variety of systems. We have previously shown that heat shock results in a robust upregulation of Hsps in the hair cells of the adult mouse utricle in vitro. In addition, heat shock results in significant inhibition of both cisplatin- and aminoglycoside-induced hair cell death. In our system, Hsp70 is the most strongly induced Hsp, which is upregulated over 250-fold at the level of mRNA 2 h after heat shock. Therefore, we have begun to examine the role of Hsp70 in mediating the protective effect of heat shock. To determine whether Hsp70 is necessary for the protective effect of heat shock against aminoglycoside-induced hair cell death, we utilized utricles from Hsp70.1/3 (-/-) mice. While heat shock inhibited gentamicin-induced hair cell death in wild-type utricles, utricles from Hsp70.1/3 (-/-) mice were not protected. In addition, we have examined the role of the major heat shock transcription factor, Hsf1, in mediating the protective effect of heat shock. Utricles from Hsf1 (-/-) mice and wild-type littermates were exposed to heat shock followed by gentamicin. The protective effect of heat shock on aminoglycoside-induced hair cell death was only observed in wild-type mice and not in Hsf1 (-/-) mice. To determine whether Hsp70 is sufficient to protect hair cells, we have utilized transgenic mice that constitutively overexpress Hsp70. Utricles from Hsp70-overexpressing mice and wild-type littermates were cultured in the presence of varying neomycin concentrations for 24 h. The Hsp70-overexpressing utricles were significantly protected against neomycin-induced hair cell death at moderate to high doses of neomycin. This protective effect was achieved without a heat shock. Taken together, these data indicate that Hsp70 and Hsf1 are each necessary for the protective effect of heat shock against aminoglycoside-induced death. Furthermore, overexpression of Hsp70 alone significantly inhibits aminoglycoside-induced hair cell death.

Regulation of apoptotic and inflammatory cell signaling in cerebral ischemia: the complex roles of heat shock protein 70

Although heat shock proteins have been studied for decades, new intracellular and extracellular functions in a variety of diseases continue to be discovered. Heat shock proteins function within networks of interacting proteins; they can alter cellular physiology rapidly in response to stress without requiring new protein synthesis. This review focuses on the heat shock protein 70 family and considers especially the functions of the inducible member, heat shock protein 72, in the setting of cerebral ischemia. In general, inhibiting apoptotic signaling at multiple points and up-regulating survival signaling, heat shock protein 70 has a net prosurvival effect. Heat shock protein 70 has both antiinflammatory and proinflammatory effects depending on the cell type, context, and intracellular or extracellular location. Intracellular effects are often antiinflammatory with inhibition of nuclear factor-kappaB signaling. Extracellular effects can lead to inflammatory cytokine production or induction of regulatory immune cells and reduced inflammation.