Bcl-2 and Bax proteins are increased in neocortical but not in thalamic apoptosis following devascularizing lesion of the cerebral cortex in the rat: an immunohistochemical study

Posttreatment with Ospemifene Attenuates Hypoxia- and Ischemia-Induced Apoptosis in Primary Neuronal Cells via Selective Modulation of Estrogen Receptors

Stroke and perinatal asphyxia have detrimental effects on neuronal cells, causing millions of deaths worldwide each year. Since currently available therapies are insufficient, there is an urgent need for novel neuroprotective strategies to address the effects of cerebrovascular accidents. One such recent approach is based on the neuroprotective properties of estrogen receptors (ERs). However, activation of ERs by estrogens may contribute to the development of endometriosis or hormone-dependent cancers. Therefore, in this study, we utilized ospemifene, a novel selective estrogen receptor modulator (SERM) already used in dyspareunia treatment. Here, we demonstrated that posttreatment with ospemifene in primary neocortical cell cultures subjected to 18 h of hypoxia and/or ischemia followed by 6 h of reoxygenation has robust neuroprotective potential. Ospemifene partially reverses hypoxia- and ischemia-induced changes in LDH release, the degree of neurodegeneration, and metabolic activity. The mechanism of the neuroprotective actions of ospemifene involves the inhibition of apoptosis since the compound decreases caspase-3 overactivity during hypoxia and enhances mitochondrial membrane potential during ischemia. Moreover, in both models, ospemifene decreased the levels of the proapoptotic proteins BAX, FAS, FASL, and GSK3β while increasing the level of the antiapoptotic protein BCL2. Silencing of specific ERs showed that the neuroprotective actions of ospemifene are mediated mainly via ESR1 (during hypoxia and ischemia) and GPER1 (during hypoxia), which is supported by ospemifene-evoked increases in ESR1 protein levels in hypoxic and ischemic neurons. The results identify ospemifene as a promising neuroprotectant, which in the future may be used to treat injuries due to brain hypoxia/ischemia.

Curcumin Efficacy in a Serum/Glucose Deprivation-Induced Neuronal PC12 Injury Model

BACKGROUND

Glucose/serum deprivation (GSD), has been used for understanding molecular mechanisms of neuronal damage during ischemia. It has been suggested that curcumin may improve neurodegenerative diseases.

AIM

In this study, the protective effects of curcumin and its underlying mechanisms were investigated in PC12 cells upon GSD-induced stress.

METHODS

PC12 cells were cultured in DMEM overnight and then incubated in GSD condition for either 6 or 12h. GSD-treated cells were pretreated with various concentrations of curcumin (10, 20, and 40 μM) for 5h. The cell viability, apoptosis, reactive oxygen species (ROS) level, oxidative stress, expression of apoptosis-related genes, and IL-6 were determined.

RESULTS

Curcumin increased cell viability and caused an anti-apoptotic effect in PC12 cells exposed for 12h to GSD . Curcumin also increased antioxidant enzyme expression, suppressed lipid peroxidation, and decreased interleukin-6 secretion in PC12 cells subjected to GSD. In addition, pretreatment with curcumin down-regulated pro-apoptotic (Bax), and up-regulated antiapoptotic (Bcl2) mediators.

CONCLUSION

Curcumin mitigates many of the adverse effects of ischemia, and therefore, should be considered as an adjunct therapy in ischemic patients.

Role of peroxisome proliferator-activated receptors in stroke prevention and therapy-The best is yet to come?

Role of peroxisome proliferator-activated receptors (PPARs) in the pathophysiology of stroke and protective effects of PPAR ligands have been widely investigated in the last 20 years. Activation of all three PPAR isoforms, but especially PPAR-γ, was documented to limit postischemic injury in the numerous in vivo, as well as in in vitro studies. PPARs have been demonstrated to act on multiple mechanisms and were shown to activate multiple protective pathways related to inflammation, apoptosis, BBB protection, neurogenesis, and oxidative stress. The aim of this review was to summarize two decades of PPAR research in stroke with emphasis on in vivo animal studies. We focus on each PPAR receptor separately and detail their implication in stroke. This review also discusses recent clinical efforts in the field and the epidemiological data with regard to role of PPAR polymorphisms in susceptibility to stroke, and tries to draw conclusions and describe future perspectives.

Evaluation of combined developmental neurological toxicity of di (n-butyl) phthalates and lead using immature mice

In this study, the immature mice were taken to assess the potential neurological toxicity of lead (Pb) and di (n-butyl) phthalates (DBP) combination exposure. Mouse administration with DBP combination with Pb exhibited longer escape latency and lower average number of crossing of the platform. Pb content in the tissues was increased, especially in the brain, after Pb exposure as compared to those without Pb exposure. The alterations of oxidative damages in tissues (MDA and SOD) and biochemical indicators in the brain (AChE, TNOS, and iNOS) were observed, as well as the synergistic effect of joint exposure. Expressions of apoptosis-related protein (bax/bcl-2 ratio and caspase-3) were significantly increased in the hippocampus, while the bcl-2 was remarkably decreased and no significant differences were observed on the bax. The results suggested that the possible mechanisms for the learning and memory ability impairments were as follows: Firstly, the combination exposure induced the occurrence of lipid peroxidation in the brain, leading to damage to the brain cells. Secondly, it destroyed the normal metabolic balance of ACh, causing nerve damage in mice. Thirdly, it induced apoptosis in mouse hippocampal cells. The overall findings revealed that Pb and DBP co-exposure greatly influenced the developmental nervous system and accompanied with synergistic toxic effect.

2-(2-Benzofuranyl)-2-imidazoline treatment within 5 hours after cerebral ischemia/reperfusion protects the brain

We previously demonstrated that administering 2-(2-benzofuranyl)-2-imidazolin (2-BFI), an imidazoline I2 receptor agonist, immediately after ischemia onset can protect the brain from ischemic insult. However, immediate administration after stroke is difficult to realize in the clinic. Thus, the therapeutic time window of 2-BFI should be determined. Sprague-Dawley rats provided by Wenzhou Medical University in China received right middle cerebral artery occlusion for 120 minutes, and were treated with 2-BFI (3 mg/kg) through the caudal vein at 0, 1, 3, 5, 7, and 9 hours after reperfusion. Neurological function was assessed using the Longa's method. Infarct volume was measured by 2,3,5-triphenyltetrazolium chloride assay. Morphological changes in the cortical penumbra were observed by hematoxylin-eosin staining under transmission electron microscopy . The apoptosis levels in the ipsilateral cortex were examined with terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay. The protein expression of Bcl-2 and BAX was detected using immunohistochemistry. We found the following: Treatment with 2-BFI within 5 hours after reperfusion obviously improved neurological function. Administering 2-BFI within 9 hours after ischemia/reperfusion decreased infarct volume and alleviated apoptosis. 2-BFI administration at different time points after reperfusion alleviated the pathological damage of the ischemic penumbra and reduced the number of apoptotic neurons, but the protective effect was more obvious when administered within 5 hours. Administration of 2-BFI within 5 hours after reperfusion remarkably increased Bcl-2 expression and decreased BAX expression. To conclude, 2-BFI shows potent neuroprotective effects when administered within 5 hours after reperfusion, seemingly by up-regulating Bcl-2 and down-regulating BAX expression. The time window provided clinical potential for ischemic stroke by 2-BFI.

Ginkgolide K protects SH‑SY5Y cells against oxygen‑glucose deprivation‑induced injury by inhibiting the p38 and JNK signaling pathways

The purpose of the present study was to explore the protective effect and functional mechanism of ginkgolide K (GK: C₂₀H₂₂O₉) on cerebral ischemia. SH-SY5Y cells were exposed to oxygen-glucose deprivation (OGD) to simulate an ischemic model in vitro. Cell viability, reactive oxygen species (ROS), nuclear staining with Hoechst 33258 and mitochondrial membrane potential were detected following 4 h of exposure to OGD. Subsequently, the expression levels of the apoptosis-related proteins, caspase-9, caspase-3, Bcl-2, Bax, p53 and c-Jun, as well as the mitogen-activated protein kinases (MAPKs) signaling molecules were detected by western blot analysis. GK significantly elevated the cell viability and decreased the generation of ROS and the number of apoptotic cells in a dose-dependent manner. Furthermore, GK markedly decreased the protein expression levels of p-p38, p-JNK, p-p53, p-c-Jun and the expression levels of Bcl-2, Bax, cleaved caspase-9 and caspase-3. In conclusion, GK demonstrated a neuroprotective effect on the simulated cerebral ischemia in vitro, and this effect was mediated through the inhibition of the mitochondria-mediated apoptosis pathway triggered by ROS-evoked p38 and JNK activation.

Mechanism underlying the protective effect of Kaixin Jieyu Fang on vascular depression following cerebral white matter damage

The Chinese compound Kaixin Jieyu Fang can be used to treat vascular depression; however, the underlying mechanism remains unclear. This study established a rat model of chronic cerebral ischemia-caused white matter damage by ligation of the bilateral common carotid arteries. Rats received daily intragastric administration of a suspension of Kaixin Jieyu Fang powder. After 3, 7 and 21 days of treatment, the degree of white matter damage in the cerebral ischemia rat model was alleviated, Bcl-2 protein and mRNA expression in brain tissue increased, and Bax protein and mRNA expression decreased. These results indicate that Kaixin Jieyu Fang can alleviate cerebral white matter damage, and the underlying mechanism is associated with regulation of Bcl-2/Bax protein and mRNA expression, which is one of possible mechanism behind the protective effect of Kaixin Jieyu Fang against vascular depression.

Human neural stem cell transplantation attenuates apoptosis and improves neurological functions after cerebral ischemia in rats

BACKGROUND

Neuroprotection is a major therapeutic approach for ischemic brain injury. We investigated the neuroprotective effects induced by transplantation of human embryonic neural stem cells (NSCs) into the cortical penumbra 24 h after focal cerebral ischemia.

METHODS

NSCs were prepared from human embryonic brains obtained at 8 weeks of gestation. Focal cerebral ischemia was induced in adult rats by permanent occlusion of the middle cerebral artery. Animals were randomly divided into two groups: NSCs-grafted group and medium-grafted group (control). Infarct size was assessed 28 days after transplantation by hematoxylin and eosin staining. Neurological severity scores were evaluated before ischemia and at 1, 7, 14, and 28 days after transplantation. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay and immunohistochemical analysis of Bcl-2 and Bax were performed at 7, 14, and 28 days after transplantation.

RESULTS

Physiological parameters of the two groups were comparable, but not significantly different. NSC transplantation significantly improved neurological function (P<0.05) but did not reduce the infarct size significantly (P>0.05). Compared with the control, NSC transplantation significantly reduced the number of TUNEL- and Bax-positive cells in the penumbra at 7 days. Interestingly, the number of Bcl-2-positive cells in the penumbra after NSC transplantation was significantly higher than that after medium transplantation (P<0.05).

CONCLUSIONS

The results indicate that NSC transplantation has anti-apoptotic activity and can improve the neurological function; these effects are mediated by the up-regulation of Bcl-2 expression in the penumbra.

PPARs as new therapeutic targets for the treatment of cerebral ischemia/reperfusion injury

Stroke is a leading cause of death and long-term disability in industrialized countries. Despite advances in understanding its pathophysiology, little progress has been made in the treatment of stroke. The currently available therapies have proven to be highly unsatisfactory (except thrombolysis) and attempts are being made to identify and characterize signaling proteins which could be exploited to design novel therapeutic modalities. The peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that control lipid and glucose metabolism. PPARs regulate gene expression by binding with the retinoid X receptor (RXR) as a heterodimeric partner to specific DNA sequences, termed PPAR response elements. In addition, PPARs may modulate gene transcription also by directly interfering with other transcription factor pathways in a DNA-binding independent manner. To date, three different PPAR isoforms, designated alpha, beta/delta, and gamma, have been identified. Recently, they have been found to play an important role for the pathogenesis of various disorders of the central nervous system and accumulating data suggest that PPARs may serve as potential targets for treating ischemic stroke. Activation of all PPAR isoforms, but especially of PPARgamma, was shown to prevent post-ischemic inflammation and neuronal damage in several in vitro and in vivo models, negatively regulating the expression of genes induced by ischemia/ reperfusion (I/R). This paper reviews the evidence and recent developments relating to the potential therapeutic effects of PPAR-agonists in the treatment of cerebral I/R injury.

Therapeutic Potential of PPARγ Activation in Stroke

Stroke (focal cerebral ischemia) is a leading cause of death and disability among adult population. Many pathological events including inflammation and oxidative stress during the acute period contributes to the secondary neuronal death leading the neurological dysfunction after stroke. Transcriptional regulation of genes that promote these pathophysiological mechanisms can be an effective strategy to minimize the poststroke neuronal death. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors known to be upstream to many inflammatory and antioxidant genes. The goal of this review is to discuss the therapeutic potential and putative mechanisms of neuroprotection following PPAR activation after stroke.

Molecular mechanisms of apoptosis in cerebral ischemia: multiple neuroprotective opportunities

Cerebral ischemia/reperfusion (I/R) injury triggers multiple and distinct but overlapping cell signaling pathways, which may lead to cell survival or cell damage. There is overwhelming evidence to suggest that besides necrosis, apoptosis do contributes significantly to the cell death subsequent to I/R injury. Both extrinsic and intrinsic apoptotic pathways play a vital role, and upon initiation, these pathways recruit downstream apoptotic molecules to execute cell death. Caspases and Bcl-2 family members appear to be crucial in regulating multiple apoptotic cell death pathways initiated during I/R. Similarly, inhibitor of apoptosis family of proteins (IAPs), mitogen-activated protein kinases, and newly identified apoptogenic molecules, like second mitochondrial-activated factor/direct IAP-binding protein with low pI (Smac/Diablo), omi/high-temperature requirement serine protease A2 (Omi/HtrA2), X-linked mammalian inhibitor of apoptosis protein-associated factor 1, and apoptosis-inducing factor, have emerged as potent regulators of cellular apoptotic/antiapoptotic machinery. All instances of cell survival/death mechanisms triggered during I/R are multifaceted and interlinked, which ultimately decide the fate of brain cells. Moreover, apoptotic cross-talk between major subcellular organelles suggests that therapeutic strategies should be optimally directed at multiple targets/mechanisms for better therapeutic outcome. Based on the current knowledge, this review briefly focuses I/R injury-induced multiple mechanisms of apoptosis, involving key apoptotic regulators and their emerging roles in orchestrating cell death programme. In addition, we have also highlighted the role of autophagy in modulating cell survival/death during cerebral ischemia. Furthermore, an attempt has been made to provide an encouraging outlook on emerging therapeutic approaches for cerebral ischemia.

Mechanisms of anti-inflammatory and neuroprotective actions of PPAR-gamma agonists

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors of the nuclear hormone receptor superfamily. The 3 PPAR isoforms (alpha, delta/beta and gamma) are known to control many physiological functions including glucose absorption, lipid balance, and cell growth and differentiation. Of interest, PPAR-gamma activation was recently shown to mitigate the inflammation associated with chronic and acute neurological insults. Particular attention was paid to test the therapeutic potential of PPAR agonists in acute conditions like stroke, spinal cord injury (SCI) and traumatic brain injury (TBI), in which massive inflammation plays a detrimental role. While 15d-prostaglandin J2 (15d PGJ2) is the natural ligand of PPAR-gamma, the thiazolidinediones (TZDs) are potent exogenous agonists. Due to their insulin-sensitizing properties, 2 TZDs rosiglitazone and pioglitazone are currently FDA-approved for type-2 diabetes treatment. Recent studies from our laboratory and other groups have shown that TZDs induce significant neuroprotection in animal models of focal ischemia and SCI by multiple mechanisms. The beneficial actions of TZDs were observed to be both PPAR-gamma-dependent as well as -independent. The major mechanism of TZD-induced neuroprotection seems to be prevention of microglial activation and inflammatory cytokine and chemokine expression. TZDs were also shown to prevent the activation of pro-inflammatory transcription factors at the same time promoting the anti-oxidant mechanisms in the injured CNS. This review article discusses the multiple mechanisms of TZD-induced neuroprotection in various animal models of CNS injury with an emphasis on stroke.

Differential response of apoptosis-regulatory Bcl-2 and Bax proteins to an inflammatory challenge in the cerebral cortex and hippocampus of aging mice

Apoptosis plays a key role in normal aging and neurodegeneration. It is now known that normal aging implies low-grade inflammation and increases susceptibility to neurodegenerative diseases, which, in turn, include a neuroinflammatory component. We here investigated, using mice of 2-3 months, 10-11 months, or 18-21 months of age, the expression of apoptosis-regulatory proteins in cortical brain regions in response to intracerebroventricular administration of pro-inflammatory cytokines. A mixture of interferon-gamma and tumor necrosis factor-alpha was injected, using vehicle (phosphate-buffered saline) as control. At 4 days, levels of the anti-apoptotic Bcl-2 and pro-apoptotic Bax proteins in the cerebral cortex and hippocampus, examined with Western blotting, were markedly upregulated by cytokine exposure in mice of all age groups with respect to controls. Interestingly, cytokine-elicited Bcl-2 upregulation was aging-dependent, with significant enhancement paralleling the animals' age. Cytokine-elicited Bax expression did not exhibit instead significant aging-related variation. Using the same paradigm and 1 or 2 day survival, Bcl-2 immunoreactivity was observed mainly in neurons of cortex and hippocampus of both control and cytokine-treated mice of all age groups. Furthermore, immunohistochemistry confirmed the enhancement of cytokine-elicited Bcl-2 expression in the cerebral cortex and hippocampus of old mice, and showed that this finding was already evident in the second day after cytokine exposure. The data point out the novel finding that Bcl-2 and Bax expression in cortical brain regions is differentially regulated during senescence in response to an acute inflammatory challenge. Aging-related Bcl-2 increases in neurons after cytokine exposure could contribute to amplify neuroprotective mechanisms in the old brain.

Focal Photothrombotic Lesion of the Rat Motor Cortex Increases BDNF Levels in Motor-Sensory Cortical Areas Not Accompanied by Recovery of Forelimb Motor Skills

Brain infarct triggers neurodegeneration that often shades spontaneous plasticity, occurring in the areas related anatomically and functionally to the infarcted structures. Neurotrophins which promote neuronal survival and plasticity, may protect neurons and enhance remodeling of the remaining circuits, leading to restoration of function. In particular, the crucial role of brain-derived neurotrophic factor (BDNF) in cortical function is well documented. Since BDNF was implicated in the mechanism of postinfarct recovery, we investigated whether focal photothrombosis in the motor cortex of adult rats modifies cortical BDNF protein levels in a time- and region-dependent fashion. In parallel, we aimed to establish, which cortical cells respond with altered BDNF expression and whether these alterations are reflected by forelimb motor skill impairment and recovery, evaluated up to 1 month postinfarct. The distribution of BDNF protein was visualized immunohistochemically and BDNF tissue levels were evaluated with enzyme-linked immunosorbent assay (ELISA). Ipsilateral to the infarct, an increase in BDNF levels occurred both in injured and neighboring regions already 24 h after photothrombosis. This increase was sustained up to postlesion day 7 in the motor cortex and reduced at 28 days. No BDNF changes were detected in homotopic regions of the contralateral cortex. The time-course of enhanced neurotrophic expression was paralleled by bilateral deficits in skilled reaching, which was the only clear and measurable motor impairment observed in the study. We conclude that the spontaneous increase of BDNF is not sufficient to protect neurons from degeneration in the lesion proximity whereas plasticity reported in the adjacent regions may be attributable to enhanced BDNF-related stimuli, which do not counteract the impairment of skilled reaching but might be, at least in part, responsible for the absence of deficits in other functional/behavioral tests.

Beneficial effect of recombinant human growth hormone on the intestinal mucosa barrier of septic rats

The objective of the present study was to investigate the effects of recombinant human growth hormone (rhGH) on the intestinal mucosa barrier of septic rats and explore its possible mechanism. Female Sprague-Dawley rats were randomized into three groups: control, Escherichia coli-induced sepsis (S) and treatment (T) groups. Groups S and T were subdivided into subgroups 1d and 3d, respectively. Expression of liver insulin-like growth factor-1 (IGF-1) mRNA, Bcl-2 and Bax protein levels and the intestinal Bax/Bcl-2 ratio, and plasma GH and IGF-1 levels were determined. Histological examination of the intestine was performed and bacterial translocation was determined. rhGH significantly attenuated intestinal mucosal injuries and bacterial translocation in septic rats, markedly decreased Bax protein levels, inhibited the decrease of Bcl-2 protein expression and maintained the Bax/Bcl-2 ratio in the intestine. rhGH given after sepsis significantly improved levels of plasma GH (T1d: 1.28 +/- 0.24; T3d: 2.14 +/- 0.48 microg/L vs S1d: 0.74 +/- 0.12; S3d: 0.60 +/- 0.18 microg/L; P < 0.05) and IGF-1 (T1d: 168.94 +/- 65.67; T3d: 201.56 +/- 64.98 microg/L vs S1d: 116.72 +/- 13.96; S3d: 107.50 +/- 23.53 microg/L; P < 0.05) and expression of liver IGF-1 mRNA (T1d: 0.98 +/- 0.20; T3d: 1.76 +/- 0.17 vs S1d: 0.38 +/- 0.09; S3d: 0.46 +/- 0.10; P < 0.05). These findings indicate that treatment with rhGH had beneficial effects on the maintenance of the integrity of the intestinal mucosa barrier in septic rats.

Neuronal cell death due to glutamate excitotocity is mediated by P38 activation in the rat cerebral cortex

Excitotoxic neuronal death occurs through the activation of NMDA and non-NMDA glutamatergic receptors in the CNS. Glutamate also induces strong activation of p38 and indeed, cell death can be prevented by inhibitors of the p38 pathway. Furthermore, intracellular signals generated by AMPA receptors activate the stress sensitive MAP kinases implicated in apoptotic neuronal death, such as JNK and p38. To investigate the relationship between these elements, we have used immunohistochemistry to analyze the expression of GluR2 in the cerebral cortex of postnatal rats (postnatal Day [PD] 8 and 14) after administering them with monosodium glutamate (MSG; 4 mg/g body weight on PD1, 3, 5, and 7). Similarly, the expression of REST, Fas-L and Bcl-2 mRNA transcripts in animals exposed to a p38 inhibitor, SB203580 (0.42 microg/g body weight, administered subcutaneously) was determined by reverse transcriptase-PCR. The enhanced GluR2-expression in the cerebral cortex at PD8 and the down regulation of this receptor at PD14 was correlated with neuronal damage induced by excitotoxicity. In addition, the enhanced expression of REST at PD8 and PD14 suggests that the induction of REST transcription contributes to glutamate-induced excitotoxic neurodegeneration, possibly by modulating GluR2 expression. Fas-L and Bcl-2 over expression at PD8 and their subsequent down regulation at PD14 also suggests that Fas-L could be the direct effector of apoptosis in the cerebral cortex. On the other hand, the presence of Bcl-2 at PD8 could attenuate certain survival signals in neurons under these neurotoxic conditions. Thus, a change in glutamate receptor composition, and enhanced Fas-L and Bcl-2 expression, coupled with activation of the p38/SAPK pathway appear to be events involved in the neuronal apoptosis induced under neurotoxic conditions.

Peroxisome proliferator-activated receptor-γ-agonist, rosiglitazone, promotes angiogenesis after focal cerebral ischemia

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist, rosiglitazone, not only improves insulin resistance in patients with type II diabetes but also exerts a broad spectrum protective effects in variable animal models of neurologic or cardiovascular diseases. We studied the effect of rosiglitazone on angiogenesis and neurological recovery after focal cerebral ischemia. Rosiglitazone (3 mg/kg or 0.3 mg/kg, p.o.) was administered for 7 days prior to and 3 days after the induction of focal ischemia (total 10 days) in adult rats. The rosiglitazone-treated group showed the enhanced neurologic improvement, the reduced infarction volume compared to the ischemia-vehicle group with dose dependency, and the reduced hemispheric atrophy. Rosiglitazone treatment reduced TUNEL(+)/activated caspase-3(+) cells, MPO(+)/Ox-42(+) inflammatory cell infiltrations, caspase-3 activity, and Bax(+) cells, as compared to the ischemia-vehicle group. The vascular surface area, the vascular branch points, the vascular length, and the number of BrdU(+) endothelial cells were significantly increased in the rosiglitazone group compared with the ischemia-vehicle group. Rosiglitazone increased eNOS expression around the ischemic margin with downregulation of FasL. Here, we show that rosiglitazone treatment enhances angiogenesis and functional recovery with dose-dependent induction of ischemic tolerance.

Adriamycin-induced oxidative stress, activation of MAP kinases and apoptosis in isolated cardiomyocytes

BACKGROUND

Adriamycin (ADR) induced heart failure is associated with an increase in oxidative stress and apoptosis. Changes due to ADR in mitogen-activated protein kinases (ERK1/2 and p38 MAPKs), pro- and anti-apoptotic proteins (Bax and Bcl-xl) and apoptosis were examined in isolated adult rat cardiomyocytes.

METHODS

Isolated adult rat cardiomyocytes were exposed to different concentrations of ADR (0.1, 1 and 10mumol/L) and analyzed at different post-treatment durations. Antioxidant, trolox (20mumol/L) was used to determine involvement of oxidative stress on these changes.

RESULTS

Total ERK1/2 and p38 did not show any significant change. However, phosphorylated ERK1/2 showed a rapid increase (497%) after 5min of ADR treatment, peaking (610%) at 10min followed by a decline to submaximal levels at 30min (280%) and 60min (247%). Phosphorylated p38 showed no changes until after 30min, peaking (284%) at 1h, followed by a small decline at 2h. These changes were found to be dose-dependent (0.1, 1 and 10mumol/L of ADR). Adriamycin induced apoptosis was confirmed by Hoechst staining. The ratio of Bax/Bcl-xl increased in a dose-dependent manner. At 10mumol/L, this ratio increased to a maximum at 1h, remained steady at the level for up to 12h, followed by a decline below the base line at 24h. Antioxidant, trolox modulated the ADR-induced increase in phosphorylation of ERK1/2 and p38 MAPKs as well as in the ratio of Bax/Bcl-xl.

CONCLUSION

It is suggested that ADR activates MAP kinases, followed by an activation of pro-apoptotic protein Bax which results in cardiomyocyte apoptosis and these effects appear to be mediated by ADR-induced oxidative stress.

Effect of subchronic exposure to acrylamide induced on the expression of bcl-2, bax and caspase-3 in the rat nervous system

Occupational exposure and experimental intoxication with acrylamide (ACR) produce a neuropathy characterized by nerve degeneration. We hypothesize that ACR differentially affects the expression of bcl-2, bax and caspase-3 in the central nervous system (CNS) and the peripheral nervous system (PNS) tissue. Male adult Wistar rats were given ACR (20, 40 mg/kg i.p. 3 days/week) for 8 weeks. Samples of the cerebral cortex, cerebellum, spinal cord and sciatic nerves were collected and examined for bcl-2, bax and caspase-3 expression using Western blotting. Subchronic exposure to ACR reduced cortical bcl-2 expression in the low dose, increased it in the high dose; the change of bcl-2 expression in the spinal cord and cerebellum followed the same pattern as that described in the cerebral cortex; there was no significant change in the expression of bax in the cerebral cortex and the spinal cord, however, in the cerebellum the change of bax expression and bcl-2 expression is just the reverse. Thus, the bcl-2/bax ratio of the CNS tissue was affected by exposure to ACR, it decreased in the low dose group and increased in the high group. Compared to control, densitometric analysis showed that in the sciatic nerves the expression of bcl-2 and bax expression was markedly increased following ACR administration. The expression of inactive isoforms (32 kDa) of caspase-3 was not altered in the cortices of ACR-treated rats, but increased in their spinal cords and sciatic nerves. Thus, subchronic exposure to ACR affected the expression of death-related proteins in the CNS and PNS tissue, which indicate there is the early molecular regulatory mechanism of apoptosis in the neuropathy induced by ACR.

Pro- and anti-apoptotic evidence for cholinergic denervation and hippocampal sympathetic ingrowth in rat dorsal hippocampus

In rat, injection of the specific cholinotoxin, 192 IgG-saporin, into the medial septum results not only in a selective cholinergic denervation of hippocampus, but in an ingrowth of peripheral sympathetic fibers, originating from the superior cervical ganglion, into the hippocampus. A similar process, in which peripheral noradrenergic axons invade hippocampus, may also occur in Alzheimer's disease. Since apoptotic cell death has been demonstrated in the selective neuronal loss found in Alzheimer's disease, the aim of this study was to measure apoptotic protein expression and DNA fragmentation in hippocampal sympathetic ingrowth and cholinergic denervation. Western blot, TdT-mediated dUTP nick end labeling, and oligo ligation techniques were used. Choline acetyltransferase activity and norepinephrine concentrations were also measured. As seen in our previous results, an increase in apoptotic markers was induced by cholinergic denervation alone (medial septum lesion + ganglionectomy), while hippocampal sympathetic ingrowth (medial septum + sham ganglionectomy) reduced or normalized apoptotic effects to control group levels. A decrease in choline acetyltransferase activity was also found in the dorsal hippocampus of hippocampal sympathetic ingrowth and cholinergic denervation groups. An increase in norepinephrine concentration was found in hippocampal sympathetic ingrowth but not in cholinergic denervation group. Results of this study suggest that cholinergic denervation is responsible for most of the proapoptotic responses, while hippocampal sympathetic ingrowth produces a protective effect in the process of programmed cell death in rat dorsal hippocampus. This effect may be a secondary to an altered relationship between norepinephrine-acetylcholine.