Effects of FK506 on Hippocampal CA1 Cells Following Transient Global Ischemia/Reperfusion in Wistar Rat

The Effect of Prosopis farcta and Its Bioactive Luteolin on the Hippocampus of Mice after Induced Ischemia Reperfusion

Background

Ischemia plays an important role in increasing damage to the nervous system. This study aimed to evaluate the effect of Prosopis farcta (PFE) and its bioactive luteolin (Lu) and forced swimming exercise on the hippocampus of mice after induced ischemia reperfusion.

Methods

The bioactive component of PFE (Lu) was identified by HPLC. Fifty-six male mice were divided into different groups. Ischemia was induced by ligation of the common carotid artery. After mice training (swimming exercise, 8 weeks) and consuming PFE and Lu, the mice's memory ability was evaluated in the shuttle box. Histological examination was performed by Nissel staining and immunohistochemistry.

Results

Results showed that the ischemic mice exercised and treated with PFE and Lu had higher step-through latency (STL) compared with the nonexercised mice, and this was confirmed with time spent in the dark compartment (TDC). The number of dark cells in the ischemic group exercising and receiving PFE and Lu decreased compared to that of the other groups in the hippocampus. DCX protein expression was increased in nonexercised groups compared to that of the exercised groups and those treated with PFE and Lu, while NeuN decreased.

Conclusions

Forced swimming exercise following ischemia, as well as consumption of PFE and Lu, has reduced cell death and increased neurogenesis in the hippocampus and thus may help improve memory in ischemia.

Chlorogenic acid ameliorates memory loss and hippocampal cell death after transient global ischemia

Chlorogenic acid (CGA) is known to have antioxidant potentials, yet the effect of CGA on brain ischemia has not been sufficiently understood. Brain ischemia such as transient global ischemia disrupts many areas of the brain of rats, including the hippocampus. Male Wistar rats were randomly assigned into five groups, that is, sham-operated (SO), bilateral common carotid occlusion (BCCO), and BCCO+ 15, 30, and 60 mg/kg bw CGA groups (CGA15, CGA30, and CGA60, respectively). Brain ischemia was induced in Wistar rats with BCCO for 20 min followed by intraperitoneal injection of CGA. The rats were examined for the spatial memory in a Morris water maze test on the 3rd day and were euthanized on the 10th day after BCCO. The total number of pyramidal cells was estimated, and the mRNA expressions of Bcl2, Bax, caspase-3, SOD2, SOD1, GPx, ET-1, eNOS, CD31, and VEGF-A were measured. The BCCO group spent less time and distance in the target quadrant than any other group in the spatial memory retention test. The CA1 pyramidal cell numbers in the BCCO and CGA15 groups were lower than in the CGA30 and CGA60 groups. The mRNA expressions of Bcl2, SOD2, and CD31 in the BCCO group were lower than in the CGA15, CGA30, and CGA60 groups. The ET-1 expression was higher in the BCCO and CGA15 groups than in the SO, CGA30, and CGA60 groups. CGA improves the spatial memory and prevents the CA1 pyramidal cell death after BCCO by increasing Bcl2, SOD2, and CD31 expressions and decreasing ET-1 expression.

Effect of Different Doses and Times of FK506 on Different Areas of the Hippocampus in the Rat Model of Transient Global Cerebral Ischemia-Reperfusion

Background

Stroke is a major worldwide problem that is leading to a high mortality rate in humans. Ischemia, as the most common type of stroke, is characterized by tissue damage that can occur due to insufficient blood flow to the brain even for a brief duration, leading to the release of inflammatory factors, cytokines, and free radicals. In this study, we investigated the effective dose and injection time of FK506 as an immunophilin ligand for providing a suitable effect on cells of CA2, CA3, and dentate gyrus of the hippocampus.

Methods

In this in vivo study, a total of 48 male Wistar rats were divided into nine groups. The ischemia model was induced by the ligation of bilateral common carotid arteries. The doses of FK506 (3, 6, and 10 mg/kg) were administered intravenously (IV) at the beginning of reperfusion, followed by repeated injections (10 mg/kg) at 6, 24, 48, and 72 hours after ischemia, respectively. Brains were removed and prepared for Nissl staining and the TdT-mediated dUTP Nick End Labeling method.

Results

Data showed that global ischemia did not decrease the number of viable pyramidal cells in CA2 and CA3 regions, but significant differences were observed in the number of viable granular cells and apoptotic bodies in the dentate gyrus between the control and ischemia groups. Repeated doses of 6 mg/kg of FK506 at an interval of 48 hours were deemed to be the suitable dose and best time of injection.

Conclusions

It seems that FK506 can ameliorate the extent of apoptosis and may be a good candidate for the treatment of ischemia-induced brain damage.

Neuroprotective Agents in the Intensive Care Unit: -Neuroprotective Agents in ICU

Neuroprotection or prevention of neuronal loss is a complicated molecular process that is mediated by various cellular pathways. Use of different pharmacological agents as neuroprotectants has been reported especially in the last decades. These neuroprotective agents act through inhibition of inflammatory processes and apoptosis, attenuation of oxidative stress and reduction of free radicals. Control of this injurious molecular process is essential to the reduction of neuronal injuries and is associated with improved functional outcomes and recovery of the patients admitted to the intensive care unit. This study reviews neuroprotective agents and their mechanisms of action against central nervous system damages.

An Elastomeric Polymer Matrix, PEUU-Tac, Delivers Bioactive Tacrolimus Transdurally to the CNS in Rat

Central nervous system (CNS) neurons fail to regrow injured axons, often resulting in permanently lost neurologic function. Tacrolimus is an FDA-approved immunosuppressive drug with known neuroprotective and neuroregenerative properties in the CNS. However, tacrolimus is typically administered systemically and blood levels required to effectively treat CNS injuries can lead to lethal, off-target organ toxicity. Thus, delivering tacrolimus locally to CNS tissues may provide therapeutic control over tacrolimus levels in CNS tissues while minimizing off-target toxicity. Herein we show an electrospun poly(ester urethane) urea and tacrolimus elastomeric matrix (PEUU-Tac) can deliver tacrolimus trans-durally to CNS tissues. In an acute CNS ischemia model in rat, the optic nerve (ON) was clamped for 10s and then PEUU-Tac was used as an ON wrap and sutured around the injury site. Tacrolimus was detected in PEUU-Tac wrapped ONs at 24 h and 14 days, without significant increases in tacrolimus blood levels. Similar to systemically administered tacrolimus, PEUU-Tac locally decreased glial fibrillary acidic protein (GFAP) at the injury site and increased growth associated protein-43 (GAP-43) expression in ischemic ONs from the globe to the chiasm, consistent with decreased astrogliosis and increased retinal ganglion cell (RGC) axon growth signaling pathways. These initial results suggest PEUU-Tac is a biocompatible elastic matrix that delivers bioactive tacrolimus trans-durally to CNS tissues without significantly increasing tacrolimus blood levels and off-target toxicity.

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PEUU-Tac locally delivers tacrolimus to CNS tissues

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PEUU-Tac positively modulates CNS tissue remodeling

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PEUU-Tac minimizes off-target tacrolimus toxicity

Central nervous system (CNS) injury typically results in permanently lost neurological function. Tacrolimus is an FDA-approved drug used during organ transplantation that also has CNS neuroprotective and neuroregenerative properties. However, tacrolimus is typically delivered systemically in the blood and delivering effective concentrations to CNS tissues requires tacrolimus blood levels that can lead to adverse side effects in multiple organs. Herein we show that PEUU-Tac, a tacrolimus-eluting matrix, can locally deliver tacrolimus to injured CNS tissues without increasing blood levels, suggesting PEUU-Tac can be used to treat CNS injuries locally while minimizing adverse side effects.

Early Minocycline and Late FK506 Treatment Improves Survival and Alleviates Neuroinflammation, Neurodegeneration, and Behavioral Deficits in Prion-Infected Hamsters

Prion infections of the central nervous system (CNS) are characterized by initial reactive gliosis followed by overt neuronal death. Gliosis is likely to be caused initially by the deposition of misfolded, proteinase K-resistant, isoforms (termed PrPSc) of the normal cellular prion protein (PrPc) in the brain. Proinflammatory cytokines and chemokines released by PrPSc-activated glia and stressed neurons may also contribute directly or indirectly to the disease development by enhancing gliosis and inducing neurotoxicity. Recent studies have illustrated that early neuroinflammation activates nuclear factor of activated T cells (NFAT) in the calcineurin signaling cascade, resulting in nuclear translocation of nuclear factor kappa B (NF-κB) to promote apoptosis. Hence, useful therapeutic approaches to slow down the course of prion disease development should control early inflammatory responses to suppress NFAT signaling. Here we used a hamster model of prion diseases to test, for the first time, the neuroprotective and NFAT-suppressive effect of a second-generation semisynthetic tetracycline derivative, minocycline, versus a calcineurin inhibitor, FK506, with known NFAT suppressive activity. Our results indicate that prolonged treatment with minocycline, starting from the presymptomatic stage of prion disease was more effective than FK506 given either during the presymptomatic or symptomatic stage of prion disease. Specifically, minocycline treatment reduced the expression of the astrocyte activation marker glial fibrillary acidic protein and of the microglial activation marker ionized calcium-binding adapter molecule-1, subsequently reducing the level of proinflammatory cytokines interleukin 1β and tumor necrosis factor-α. We further found that minocycline and FK506 treatment inhibited mitogen-activated protein kinase p38 phosphorylation and NF-κB nuclear translocation in a caspase-dependent manner, and enhanced phosphorylated cyclic adenosine monophosphate response element-binding protein and phosphorylated Bcl2-associated death promoter levels to reduce cognitive impairment and apoptosis. Taken together, our results indicate that minocycline is a better choice for prolonged use in prion diseases and encourage its further clinical development as a possible treatment for this disease.

Effect of dexmedetomidine on diseased coronary vessel diameter and myocardial protection in percutaneous coronary interventional patients

Introduction:

Dexmedetomidine is an alpha-2 agonist used for conscious sedation. It has also been shown to have a myocardial protective effect in off-pump coronary artery bypass patients. The aim of the study was to assess the effect of dexmedetomidine for myocardial protection in percutaneous coronary interventional patients.

Methodology:

A total of 60 patients (group dexmedetomidine, n = 30 and group normal saline, n = 30) were enrolled in the study. Dexmedetomidine infusion (1 mcg/kg) over 15 min was given as a loading dose after coronary angiography in group dexmedetomidine (D) while normal saline was given in the control group (C) and later maintenance infusion was started at 0.5 mcg/kg/h in both the groups. Coronary vessel diameter was noted before (T0) and after (T1) loading dose of dexmedetomidine/saline in each group. Troponin T (Trop T) values were noted at baseline (T0), 6 h (T2), 12 h (T3) and 24 h (T4) after starting the loading dose. Hemodynamic variables (heart rate [HR] and blood pressure) were monitored at T0, T1, and at regular intervals till 2 h postprocedure.

Results:

Coronary vessel diameter and HR significantly decreased in group D as compared to control group (P < 0.05) whereas the decrease in Trop T at 6 h, 12 h, and 24 h were not statistically significant between the two groups.

Conclusion:

Dexmedetomidine decreases the coronary vessel diameter, but maintains the myocardial oxygen demand-supply ratio by decreasing the HR. The decrease in Trop T is statistically insignificant at the doses used.

Exercise preconditioning exhibits neuroprotective effects on hippocampal CA1 neuronal damage after cerebral ischemia

Recent evidence has suggested the neuroprotective effects of physical exercise on cerebral ischemic injury. However, the role of physical exercise in cerebral ischemia-induced hippocampal damage remains controversial. The aim of the present study was to evaluate the effects of pre-ischemia treadmill training on hippocampal CA1 neuronal damage after cerebral ischemia. Male adult rats were randomly divided into control, ischemia and exercise + ischemia groups. In the exercise + ischemia group, rats were subjected to running on a treadmill in a designated time schedule (5 days per week for 4 weeks). Then rats underwent cerebral ischemia induction through occlusion of common carotids followed by reperfusion. At 4 days after cerebral ischemia, rat learning and memory abilities were evaluated using passive avoidance memory test and rat hippocampal neuronal damage was detected using Nissl and TUNEL staining. Pre-ischemic exercise significantly reduced the number of TUNEL-positive cells and necrotic cell death in the hippocampal CA1 region as compared to the ischemia group. Moreover, pre-ischemic exercise significantly prevented ischemia-induced memory dysfunction. Pre-ischemic exercise mighct prevent memory deficits after cerebral ischemia through rescuing hippocampal CA1 neurons from ischemia-induced degeneration.

Nampt/PBEF/visfatin exerts neuroprotective effects against ischemia/reperfusion injury via modulation of Bax/Bcl-2 ratio and prevention of caspase-3 activation

Nicotinamide phosphoribosyl transferase/pre-B cell colony-enhancing factor/visfatin (Nampt/PBEF/visfatin) is an adipocytokine. By synthesizing nicotinamide adenine dinucleotide (NAD(+)), Nampt/PBEF/visfatin functions to maintain an energy supply that has critical roles in cell survival. Cerebral ischemia leads to energy depletion and eventually neuronal death by apoptosis in specific brain regions specially the hippocampus. However, the role of Nampt/PBEF/visfatin in brain and cerebral ischemia remains to be investigated. This study investigated the role of administration Nampt/PBEF/visfatin in hippocampal CA3 area using a transient global cerebral ischemia model. Both common carotid arteries were occluded for 20 min followed by reperfusion. Saline as a vehicle and Nampt/PBEF/visfatin at a dose of 100 ng were injected intracerebroventricularly (ICV) at the time of cerebral reperfusion. To investigate the underlying mechanisms of Nampt/PBEF/visfatin neuroprotection, levels of expression of apoptosis-related proteins (caspase-3 activation, Bax protein levels, and Bcl-2 protein levels) 96 h after ischemia were determined by immunohistochemical staining. The number of active caspase-3-positive neurons in CA3 was significantly increased in the ischemia group, compared with the sham group (P < 0.001), and treatment with Nampt/PBEF/visfatin significantly reduced the ischemia/reperfusion-induced caspase-3 activation, compared to the ischemia group (P < 0.05). Also, results indicated a significant increase in Bax/Bcl-2 ratio in the ischemia group, compared with the sham group (P < 0.01). However, treatment with Nampt/PBEF/visfatin significantly attenuated the ischemia/reperfusion-induced increase in Bax/Bcl-2 ratio, compared with the ischemia group (P < 0.05). This study has indicated that Nampt/PBEF/visfatin entails neuroprotective effects against ischemia injury when used at the time of cerebral reperfusion. These neuroprotective mechanisms of Nampt/PBEF/visfatin occur through decrease the expression ofproapoptotic proteins (cleaved caspase-3 and Bax) and, on the other hand, increase the expression ofantiapoptotic proteins (Bcl-2). Thus, our findings indicate that Nampt/PBEF/visfatin is a new therapeutic target for cerebral ischemia.

A calcineurin docking motif (LXVP) in dynamin-related protein 1 contributes to mitochondrial fragmentation and ischemic neuronal injury

Fission and fusion events dynamically control the shape and function of mitochondria. The activity of the mitochondrial fission enzyme dynamin-related protein 1 (Drp1) is finely tuned by several post-translational modifications. Phosphorylation of Ser-656 by cAMP-dependent protein kinase (PKA) inhibits Drp1, whereas dephosphorylation by a mitochondrial protein phosphatase 2A isoform and the calcium-calmodulin-dependent phosphatase calcineurin (CaN) activates Drp1. Here, we identify a conserved CaN docking site on Drp1, an LXVP motif, which mediates the interaction between the phosphatase and mechanoenzyme. We mutated the LXVP motif in Drp1 to either increase or decrease similarity to the prototypical LXVP motif in the transcription factor NFAT, and assessed stability of the mutant Drp1-CaN complexes by affinity precipitation and isothermal titration calorimetry. Furthermore, we quantified effects of LXVP mutations on Drp1 dephosphorylation kinetics in vitro and in intact cells. With tools for bidirectional control of the CaN-Drp1 signaling axis in hand, we demonstrate that the Drp1 LXVP motif shapes mitochondria in neuronal and non-neuronal cells, and that CaN-mediated Drp1 dephosphorylation promotes neuronal death following oxygen-glucose deprivation. These results point to the CaN-Drp1 complex as a potential target for neuroprotective therapy of ischemic stroke.

The effects of gallic acid on pain and memory following transient global ischemia/reperfusion in Wistar rats

OBJECTIVE

It is generally agreed that most of the phenomena observed during brain ischemia and reperfusion can be explained by the damage to membrane structure. Oxidative stress is resulted in an imbalance between high consumption of oxygen and low levels of endogenous antioxidants. It is known that gallic acid (GA) is a strong antioxidant. The present study was carried out to evaluate the effect of GA on ischemia/reperfusion (I/R)-induced brain injury in rats.

MATERIALS AND METHODS

Wistar adult male rats weighing 200-250 g were divided into six groups as sham operated (Sh), ischemia/reperfusion (I/R) received normal saline (I+Veh), I/R groups treated with gallic acid (I+GA, 50, 100, or 200 mg/kg, orally, respectively), or with 100 mg /kg phenytoin (I+Phen). The global cerebral I/R injury was induced by occluding bilateral common carotid arteries (BCCA) for 20 min, followed by 5 days reperfusion in adult male rats.

RESULTS

It was found that administration of 100 mg/kg GA for 5 days before and 5 days after I/R induction reversed gait performance, sensorimotor disorders (p<0.01), and hypoalgesia (p<0.001) while dose of 50 mg/kg increased passive avoidance memory significantly (p<0.05).

CONCLUSION

Our findings clearly demonstrate that GA has beneficial effects on behavioral impairments after brain injury induced by I/R. The results of this study show that GA pretreatment ameliorates cerebral ischemia/reperfusion injury and enhances the antioxidant defense against BCCA occlusion-induced I/R in rats, so it exhibits cerebroprotective property.