Enalapril and moexipril protect from free radical-induced neuronal damage in vitro and reduce ischemic brain injury in mice and rats

Usage of Angiotensin-Converting Enzyme Inhibitor or Angiotensin II Receptor Blocker in Hypertension Intracerebral Hemorrhage

BACKGROUND

Inflammation plays an essential role in secondary brain injury after intracerebral hemorrhage (ICH). Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) have been suggested to suppress neuroinflammation after central nervous system (CNS) damage in animal models. However, the role of ACEIs and ARBs in ICH patients with hypertension remains unresolved in clinic. The aim of the present study is to evaluate the effect of ACEIs/ARBs on ICH patients with hypertension using a retrospective, single-center data analysis.

METHODS

ICH patients diagnosed by computerized tomographic (CT) at Southwest Hospital, Third Military Medical University were included in the present research from January 2015 to December 2019. According to the medical history for the usage of antihypertensive drugs, patients were assigned into either ACEIs/ARBs group or non-ACEIs/ARBs group. Demographics, clinical baseline, radiological documents and treatments were collected and these data were statistically analyzed between the two groups.

RESULTS

A total of 635 ICH patients with hypertension were included and allocated into 2 groups according to the usage of antihypertensive drugs: 281 in the ACEIs/ARBs group and 354 in the non-ACEIs/ARBs group. The results presented that the 3-months mortality and prevalence of ICH-associated pneumonia were lower in ACEIs/ARBs group than that in non-ACEIs/ARBs group (5.0% vs 11.9%, p=0.002; 58.4% vs 66.7%, p=0.031). While, there was no significant difference in favorable outcome (40.2% vs 33.9%, p=0.101) between the two groups. Furthermore, patients in ACEIs/ARBs group exhibited significantly less perihematomal edema volume on days 3 (23.5 ± 14.4 versus 28.7 ± 20.1 mL, p=0.045) and 7 (21.0 ± 13.7 versus 25.7 ± 17.6 mL, p=0.044), compared to that in non- ACEIs/ARBs group.

CONCLUSION

The usage of ACEIs/ARBs helps decrease mortality, perihematomal edema volume, and prevalence of ICH-associated pneumonia in ICH patients with hypertension.

A microscopy-based small molecule screen in primary neurons reveals neuroprotective properties of the FDA-approved anti-viral drug Elvitegravir

Glutamate toxicity is a pathomechanism that contributes to neuronal cell death in a wide range of acute and chronic neurodegenerative and neuroinflammatory diseases. Activation of the N-methyl-D-aspartate (NMDA)-type glutamate receptor and breakdown of the mitochondrial membrane potential are key events during glutamate toxicity. Due to its manifold functions in nervous system physiology, however, the NMDA receptor is not well suited as a drug target. To identify novel compounds that act downstream of toxic NMDA receptor signaling and can protect mitochondria from glutamate toxicity, we developed a cell viability screening assay in primary mouse cortical neurons. In a proof-of-principle screen we tested 146 natural products and 424 FDA-approved drugs for their ability to protect neurons against NMDA-induced cell death. We confirmed several known neuroprotective drugs that include Dutasteride, Enalapril, Finasteride, Haloperidol, and Oxybutynin, and we identified neuroprotective properties of Elvitegravir. Using live imaging of tetramethylrhodamine ethyl ester-labelled primary cortical neurons, we found that Elvitegravir, Dutasteride, and Oxybutynin attenuated the NMDA-induced breakdown of the mitochondrial membrane potential. Patch clamp electrophysiological recordings in NMDA receptor-expressing HEK293 cell lines and primary mouse hippocampal neurons revealed that Elvitegravir does not act at the NMDA receptor and does not affect the function of glutamatergic synapses. In summary, we have developed a cost-effective and easy-to-implement screening assay in primary neurons and identified Elvitegravir as a neuro- and mitoprotective drug that acts downstream of the NMDA receptor.

Protective effects of Althaea officinalis L. extract in 6-hydroxydopamine-induced hemi-Parkinsonism model: behavioral, biochemical and histochemical evidence

It is well known that Parkinson's disease (PD) is the second most common neurodegenerative disorder in humans. In this regard, the neuroprotective effect of Althaea officinalis (AO) has already been reported. Therefore, this study examined whether administration of AO extract would improve behavioral, biochemical and structural abnormalities in an experimental animal model of PD in rats. For this purpose, we induced hemi-Parkinsonism by unilateral intranigral injection of 6-hydroxydopamine (6-OHDA, 8 μg/5 μl saline-ascorbate). The rats were pretreated i.p. with AO extract (10 mg/kg) started 6 days before surgery and continued until the 3rd day post-surgery. Regarding oxidative stress, brain MDA concentration (as a lipid peroxidation marker) increased significantly in the 6-OHDA-administered group in comparison with rats pretreated with AO extract. It was found that AO treatment attenuated rotational behavior in the 6-OHDA-administered group and protected the neurons of substantia nigra pars compacta against 6-OHDA toxicity. Overall, AO extract administration indicated neuroprotective effects against 6-OHDA-induced hemi-Parkinsonism in rats.

Angiotensin II potentiates zinc-induced cortical neuronal death by acting on angiotensin II type 2 receptor

Background

The angiotensin system has several non-vascular functions in the central nervous system. For instance, inhibition of the brain angiotensin system results in a reduction in neuronal death following acute brain injury such as ischemia and intracerebral hemorrhage, even under conditions of constant blood pressure. Since endogenous zinc has been implicated as a key mediator of ischemic neuronal death, we investigated the possibility that the angiotensin system affects the outcome of zinc-triggered neuronal death in cortical cell cultures.

Results

Exposure of cortical cultures containing neurons and astrocytes to 300 μM zinc for 15 min induced submaximal death in both types of cells. Interestingly, addition of angiotensin II significantly enhanced the zinc-triggered neuronal death, while leaving astrocytic cell death relatively unchanged. Both type 1 and 2 angiotensin II receptors (AT1R and AT2R, respectively) were expressed in neurons as well as astrocytes. Zinc neurotoxicity was substantially attenuated by PD123319, a specific inhibitor of AT2R, and augmented by CGP42112, a selective activator of AT2R, indicating a critical role for this receptor subtype in the augmentation of neuronal cell death.

Because zinc toxicity occurs largely through oxidative stress, the levels of superoxides in zinc-treated neurons were assessed by DCF fluorescence microscopy. Combined treatment with zinc and angiotensin II substantially increased the levels of superoxides in neurons compared to those induced by zinc alone. This increase in oxidative stress by angiotensin II was completely blocked by the addition of PD123319. Finally, since zinc-induced oxidative stress may be caused by induction and/or activation of NADPH oxidase, the activation status of Rac and the level of the NADPH oxidase subunit p67^phox were measured. Angiotensin II markedly increased Rac activity and the levels of p67^phox in zinc-treated neurons and astrocytes in a PD123319-dependent manner.

Conclusion

The present study shows that the angiotensin system, especially that involving AT2R, may have an oxidative injury-potentiating effect via augmentation of the activity of NADPH oxidase. Hence, blockade of angiotensin signaling cascades in the brain may prove useful in protecting against the oxidative neuronal death that is likely to occur in acute brain injury.

Attenuation of focal cerebral ischemic injury following post-ischemic inhibition of angiotensin converting enzyme (ACE) activity in normotensive rat

BACKGROUND

Central renin angiotensin system has an important role on the cerebral microcirculation and metabolism. Our previous work showed that inhibition of angiotensin converting enzyme (ACE) activity prior to induction of ischemia protected the brain from severe ischemia/reperfusion (I/R) injuries. This study evaluated the impacts of post-ischemic inhibition of ACE, enalapril, on brain infarction in normotensive rats.

METHODS

Rats were anesthetized with chloral hydrate (400 mg/kg). Focal cerebral ischemia was induced by 60-min intraluminal occlusion of right middle cerebral artery (MCA). Intraperitoneal injection of enalapril (0.03 or 0.1 mg/kg) was done after MCA reopening (reperfusion). Neurological deficit score (NDS) was evaluated after 24 h and the animals randomly assigned for the assessments of infarction, absolute brain water content (ABWC) and index of brain edema.

RESULTS

Severe impaired motor functions (NDS = 2.78 ± 0.28), massive infarction (cortex = 214 ± 19 mm3, striatum = 86 ± 5 mm3) and edema (ABWC = 83.1 ± 0.46%) were observed in non-treated ischemic rats. Non-hypotensive dose of enalapril (0.03 mg/kg) significantly reduced NDS (1.5 ± 0.22), infarction (cortex = 102 ± 16 mm3, striatum = 38 ± 5 mm3) and edema (ABWC = 80.9 ± 0.81%). Enalapril at dose of 0.1 mg/kg significantly lowered arterial pressure could not improve NDS (2.0 ± 0.45) and reduce infarction (cortex = 166 ± 26 mm3, striatum = 71 ± 11 mm3).

CONCLUSION

Post-ischemic ACE inhibition in the normotensive rats without affecting arterial pressure protects the brain from reperfusion injuries; however, this beneficial action is masked by hypotension.

Potential antifibrotic effects of AT1 receptor antagonist, losartan, and/or praziquantel on acute and chronic experimental liver fibrosis induced by Schistosoma mansoni

1. This study investigates the potential antifibrotic effect of losartan, AT-1 receptor antagonist, and/or praziquantel (PZQ) on acute and chronic hepatic fibrosis induced by Schistosoma mansoni (S. mansoni). 2. Schistosoma mansoni-infected mice were in two batches (I & II), each in four groups: (i) Infected untreated; (ii) treated with losartan, starting from the 4th or 12th weeks post-infection (PI); (iii) treated with PZQ in the 7th week PI; and (iv) treated with losartan, as group (ii) plus PZQ as group (iii). Comparable groups of uninfected mice were run in parallel with infected groups. Mice of batches I and II were killed 10 and 18 weeks PI, respectively. Hepatic content of hydroxyproline (HYP), serum levels and tissue expression of matrix metalloproteinase-2 (MMP-2), and transforming growth factor-β1 (TGF-β1) were determined. Parasitological, biochemical and histological parameters, which reflect disease severity and morbidity, were examined. 3. Losartan alone caused a considerable decrease in worm burden, hepatic tissue egg load with an increase in percentage of dead eggs, modulation of granuloma size and regression of inflammatory reactions, which was less obvious in the chronic stage. The best results were obtained when losartan was co-administered with PZQ, especially in the acute stage. This was revealed by a remarkable reduction in serum levels and tissue expression of MMP-2, TGF-β1 and HYP content, accompanied by conservation of hepatic reduced glutathione (GSH) versus the PZQ-treated group. 4. In conclusion, losartan has a promising antifibrotic action and could be introduced as a therapeutic tool with PZQ especially in acute schistosomal hepatic fibrosis.

Prevention and intervention studies with telmisartan, ramipril and their combination in different rat stroke models

Objectives

The effects of AT1 receptor blocker, telmisartan, and the ACE inhibitor, ramipril, were tested head-to head and in combination on stroke prevention in hypertensive rats and on potential neuroprotection in acute cerebral ischemia in normotensive rats.

Methods

Prevention study: Stroke-prone spontaneously hypertensive rats (SHR-SP) were subjected to high salt and randomly assigned to 4 groups: (1) untreated (NaCl, n = 24), (2) telmisartan (T; n = 27), (3) ramipril (R; n = 27) and (4) telmisartan +ramipril (T+R; n = 26). Drug doses were selected to keep blood pressure (BP) at 150 mmHg in all groups. Neurological signs and stroke incidence at 50% mortality of untreated SHR-SP were investigated.

Intervention study: Normotensive Wistar rats were treated s.c. 5 days prior to middle cerebral artery occlusion (MCAO) for 90 min with reperfusion. Groups (n = 10 each): (1) sham, (2) vehicle (V; 0,9% NaCl), (3) T (0,5 mg/kg once daily), (4) R (0,01 mg/kg twice daily), (5) R (0,1 mg/kg twice daily) or (6) T (0,5 mg/kg once daily) plus R (0,01 mg/kg twice daily). Twenty-four and 48 h after MCAO, neurological outcome (NO) was determined. Forty-eight h after MCAO, infarct volume by MRI, neuronal survival, inflammation factors and neurotrophin receptor (TrkB) were analysed.

Results

Stroke incidence was reduced, survival was prolonged and neurological outcome was improved in all treated SHR-SP with no differences between treated groups. In the acute intervention study, T and T+R, but not R alone, improved NO, reduced infarct volume, inflammation (TNFα), and induced TrkB receptor and neuronal survival in comparison to V.

Conclusions

T, R or T+R had similar beneficial effects on stroke incidence and NO in hypertensive rats, confirming BP reduction as determinant factor in stroke prevention. In contrast, T and T+R provided superior neuroprotection in comparison to R alone in normotensive rats with induced cerebral ischemia.

ACE inhibition reduces infarction in normotensive but not hypertensive rats: correlation with cortical ACE activity

Angiotensin-converting enzyme (ACE) inhibition can reduce stroke risk by up to 43% in humans and reduce the associated disability, and hence understanding the mechanism of improvement is important. In animals and humans, these effects may be independent of the blood pressure-lowering effects of ACE inhibition. Normotensive (Wistar-Kyoto (WKY)) and hypertensive (spontaneously hypertensive rat (SHR)) animals were treated with the ACE inhibitors ramipril or lisinopril for 7 or 42 days before 2 hours of transient middle cerebral artery occlusion (MCAo). Blood pressure, serum ACE, and blood glucose levels were measured and stroke infarct volume was recorded 24 hours after stroke. Despite greater reductions in blood pressure, infarct size was not improved by ACE inhibition in hypertensive animals. Short-term ACE inhibition produced only a modest reduction in blood pressure, but WKY rats showed marked reductions in infarct volume. Long-term ACE inhibition had additional reductions in blood pressure; however, infarct volumes in WKY rats did not improve further but worsened. WKY rats differed from SHR in having marked cortical ACE activity that was highly sensitive to ACE inhibition. The beneficial effects of ACE inhibition on infarct volume in normotensive rats do not correlate with changes in blood pressure. However, WKY rats have ACE inhibitor-sensitive cortical ACE activity that is lacking in the SHR.

Prior use of angiotensin-converting enzyme inhibitors does not affect outcome in patients with intracerebral hemorrhage

BACKGROUND AND OBJECTIVES

Angiotensin-converting enzyme inhibitors (ACEI) exert protective effects in patients with stroke but their effects remain unknown in patients with intracerebral hemorrhage (ICH).

METHODS

We recruited consecutive patients with acute ICH and analysed pre-admission demographic variables and drug therapy as well as clinical and radiological parameters. Functional and neurological outcomes were determined with the modified Rankin score (mRS) and the NIH Stroke Scale (NIHSS) score administered 90 days after ICH.

RESULTS

Three hundred and ninety-nine patients were included over 6 years with a mortality rate of 47.3%. Before ICH, 130 patients (32.6%) used ACEI. ACEI-treated patients more often had vascular co-morbidities and were more frequently treated with anti-platelets. Admission NIHSS scores were significantly higher in ACEI-treated patients but 90 days NIHSS scores were not. Improvement from baseline NIHSS scores was significantly larger in ACEI-treated patients. Pre-ICH use of ACEI was not associated with lower mortality or better functional outcome on univariate analysis. On multivariable logistic regression analysis, controlling for possible confounding variables, ACEI use was not associated with increased chances for good outcome and failed to show an influence on mortality.

DISCUSSION

In conclusion, our study does not support a possible neuroprotective effect for ACEI use prior to the occurrence of ICH.

Candesartan but not ramipril pretreatment improves outcome after stroke and stimulates neurotrophin BNDF/TrkB system in rats

OBJECTIVES

Drugs interfering with the renin-angiotensin system (RAS) have been shown to reduce the incidence of stroke in patients at risk and to afford neuroprotection in experimental brain ischemia. This study aimed to compare potential neuroprotective effects of systemic pretreatment with the angiotensin receptor blocker, candesartan, and the angiotensin-converting enzyme (ACE)-inhibitor, ramipril, in normotensive Wistar rats after focal cerebral ischemia, with special emphasis on the regulation of neurotrophins.

METHODS

Equipotent subcutaneous doses of candesartan and ramipril were determined via inhibition of pressor responses to intravenously injected angiotensin II (Ang II) or angiotensin I (Ang I), respectively. Accordingly, animals were treated with candesartan (0.1 mg/kg body weight, twice daily), ramipril (0.01 and 0.1 mg/kg body weight, twice daily) or vehicle (0.9% saline, twice daily), respectively, 5 days prior to middle cerebral artery occlusion (MCAO) with reperfusion. Severity of stroke was estimated via infarct size [magnetic resonance imaging (MRI) 48 h after MCAO] and neurological outcome (24 h, 48 h after MCAO). Measurements of neurotrophins/receptors in brain tissue were performed 48 h after MCAO.

RESULTS

Pretreatment with candesartan and ramipril (low dose) did not reduce blood pressure during MCAO, whereas ramipril high dose did. Candesartan, but not ramipril at any dose, significantly reduced stroke volume and improved neurological outcome. Poststroke mRNA and protein of the neurotrophin receptor, TrkB, were significantly elevated in animals treated with candesartan, but not ramipril.

CONCLUSIONS

Systemic pretreatment with a sub-hypotensive, RAS-blocking dose of candesartan affords neuroprotection after focal ischemia, associated with increased activity of the neurotrophin BDNF/TrkB system. Ramipril at sub-hypotensive and hypotensive, RAS-blocking doses showed no significant neuroprotective effects.

Pattern of time-dependent reduction of histologically determined infarct volume after focal ischaemia in mice

The mouse model of transcranial permanent occlusion of the middle cerebral artery (tpMCAO) is widely used in stroke research. Here we quantified infarct size using a conventional histological method at several post-ischaemic times, going beyond the commonly analysed period of up to 2 days, following artery occlusion. Two different mouse strains, which are widely used for pharmacological studies of neuroprotection and for genetic engineering, were used. A drill whole was made into the skull of anaesthetised mice and ischaemia was induced by electrocoagulation of the middle cerebral artery. In both mouse strains tested (C57Black/6 and NMRI), the measured infarct volumes decreased significantly during the first days after tpMCAO. Notably, 13 days after surgery, ischaemic and sham-operated animals had indistinguishably small lesions, which where in the range of only 5% of the infarct size on day 2 post-ischaemia. The standard method of calculating oedema and shrinkage correction provided no sufficient explanation for this significant decrease in infarct volume. There was, however, evidence that structural changes in the residual ipsilateral hemisphere may compromise the significance of results arising from the method of calculating oedema and shrinkage correction. In conclusion, our study indicates that the pronounced and fast, time-dependent decrease in histologically defined infarct volume can compromise results when studying the lasting neuroprotective effects of potential drugs.

Ramipril protects from free radical induced white matter damage in chronic hypoperfusion in the rat

We investigated whether the angiotensin converting enzyme inhibitor, ramipril, could attenuate white matter lesions caused by chronic hypoperfusion in the rat, and whether suppression of oxidative stress is involved in the resulting neuroprotection. The ramipril treatment group showed significant protection from development of white matter lesions in the optic tract, the anterior commissure, the corpus callosum, the internal capsule and the caudoputamen. The level of malondialdehyde (MDA) and the oxidized glutathione (GSSG)/total glutathione (GSH t) ratio was also significantly decreased in the ramipril group compared to the vehicle-treated group. These results suggest that ramipril can protect against white matter lesions that result from chronic ischemia due to its effects on free radical scavenging. Further efficacy should be studied in the treatment of cerebrovascular insufficiency states and vascular dementia.

Inhibition of the renin-angiotensin system attenuates the development of liver fibrosis and oxidative stress in rats

1. The present study was designed to investigate the potential antifibrotic and anti-oxidant effects of lisinopril, fosinopril and losartan in an experimental rat model of liver injury using carbon tetrachloride (CCl(4)). 2. First, the potential hepatoprotective dose of each drug was screened against CCl(4)-induced acute hepatotoxicity. Then, we chose the minimum hepatoprotective dose of each drug to further investigate the mechanisms involved in the hepatoprotection using a chronic model of hepatotoxicity induced by CCl(4). 3. Liver function was assessed in addition to histopathological examination. Furthermore, oxidative stress markers (reduced glutathione (GSH) and lipid peroxides levels) and markers of fibrosis (hydroxyproline content and liver fibrosis area) were assessed. 4. It was found that treatment of animals with different drugs concomitantly with CCl(4) significantly counteracted the changes in liver function induced by CCl(4) (except fosinopril). In addition, the drugs ameliorated the histopathological changes induced by CCl(4). All drugs significantly counteracted lipid peroxidation and GSH depletion (except fosinopril) compared with the CCl(4)-intoxicated group. Moreover, the drugs studied significantly reduced liver hydroxyproline levels and the area of fibrosis compared with the CCl(4)-intoxicated group. 5. In conclusion, the present study provides evidence for the hepatoprotective effect of lisinopril, fosinopril and losartan. Both lisinopril and losartan was found to have better hepatoprotective potential than fosinopril against CCl(4)-induced hepatotoxicity. These hepatoprotective effects can be explained on the basis of anti-oxidant and antifibrotic mechanisms, mainly enhancement of GSH and reduction of lipid peroxidation and fibrosis.

Angiotensin-converting enzyme inhibition reduces oxidative stress and protects dopaminergic neurons in a 6-hydroxydopamine rat model of Parkinsonism

It is now established that the brain possesses a local renin-angiotensin system and that angiotensin II exerts multiple actions in the nervous system, including regulation of striatal dopamine release. Furthermore, angiotensin activates NADPH-dependent oxidases, which are a major source of superoxide, and angiotensin-converting enzyme inhibitors, commonly used in the treatment of hypertension and chronic heart failure, have shown antioxidant properties in several tissues. Oxidative stress is a key contributor to the pathogenesis and progression of Parkinson's disease. In the present study, we treated rats with intraventricular injections of the dopaminergic neurotoxin 6-hydroxydopamine and subcutaneous injections of the angiotensin-converting enzyme inhibitor Captopril to study the possible neuroprotective effect of the latter on the dopaminergic system and on 6-hydroxydopamine-induced oxidative stress. Rats treated with Captopril and 6-hydroxydopamine showed significantly less reduction in the number of dopaminergic neurons (i.e., immunoreactive to tyrosine hydroxylase) in the substantia nigra and in the density of striatal dopaminergic terminals than 6-hydroxydopamine-lesioned rats not treated with Captopril. In addition, Captopril reduced the levels of major oxidative stress indicators (i.e., lipid peroxidation and protein oxidation) in the ventral midbrain and the striatum of 6-hydroxydopamine-lesioned rats. Our results suggest that angiotensin-converting enzyme inhibitors may be useful for treatment of Parkinson's disease and that further investigation should focus on the neuroprotective capacity of these compounds.

Does angiotensin-1 converting enzyme genotype influence motor or cognitive development after pre-term birth?

Background

Raised activity of the renin-angiotensin system (RAS) may both amplify inflammatory and free radical responses and decrease tissue metabolic efficiency and thus enhance cerebral injury in the preterm infant. The angiotensin-converting enzyme (ACE) DD genotype is associated with raised ACE and RAS activity as well as potentially adverse stimuli such as inflammation. The DD genotype has been associated with neurological impairments in the elderly, and thus may be also associated with poorer motor or cognitive development amongst children born preterm prematurely.

Methods

The association of DD genotype with developmental progress amongst 176 Caucasian children born at less than 33 weeks gestation (median birthweight 1475 g, range 645–2480 g; gestation 30 weeks, range 22–32; 108 male) was examined at 2 and 5 1/2 years of age. Measured neuro-cognitive outcomes were cranial ultrasound abnormalities, cerebral palsy, disability, Griffiths Developmental Quotient [DQ] at 2 yrs, and General Cognitive Ability [British Ability Scales-11] and motor performance [ABC Movement], both performed at 5 1/2 yrs. All outcomes were correlated with ACE genotype.

Results

The DD genotype was not associated with lower developmental quotients even after accounting for important social variables.

Conclusion

These data do not support either a role for ACE in the development of cognitive or motor function in surviving infants born preterm or inhibition of ACE as a neuroprotective therapy.

Exogenous erythropoietin protects against dorsal root ganglion apoptosis and pain following peripheral nerve injury

Erythropoietin (Epo) has been shown to have potent anti-apoptotic activity in central nervous system neurons in animal models of ischaemic injury. Recently, Epo and its receptor (EpoR) have been identified in the peripheral nervous system [Campana & Myers (2001), FASEB J., 15, 1804-1806]. Herein, we demonstrate that in painful neuropathy caused by L5 spinal nerve crush (SNC), therapy with recombinant human Epo (rhEpo) reduced dorsal root ganglion (DRG) apoptosis and pain behaviours. Quantification of both DRG neurons and satellite cells revealed that vehicle-treated, crush-injured DRGs had 35.5 +/- 8.3% apoptotic neurons and 23.5 +/- 2.36% satellite cells compared with 7.5 +/- 6.3% apoptotic neurons and 6.4 +/- 3.94% satellite cells in rhEpo-treated, crush-injured DRGs (P < 0.05). While rhEpo-treated animals were not initially protected from mechanical allodynia associated with L5 SNC, rhEpo did significantly improve recovery rates compared to vehicle-treated animals (P < 0.01). Systemic rhEpo therapy increased JAK2 phosphorylation, a key anti-apoptotic signalling molecule for Epo-induced neuroprotection, in DRGs after crush. Dual immunofluorescence demonstrated Epo-induced JAK2-p was associated with both neuronal and glial cells. JAK2-p was associated with NF200-positive large neurons and with smaller neurons. This population of small neurons did not colocalize with IB4, a marker of nonpeptidergic, glial derived growth factor-responsive neurons. The findings link anti-apoptosis activities of Epo/EpoR/JAK2 in DRG neurons capable of inducing protracted pain states with reductions in pain behaviours, and therefore support a role for Epo therapy in the treatment of neuropathic pain.

Influence of temocapril on cultured ventral spinal cord neurons

Temocapril, a angiotensin-converting enzyme (ACE) inhibitor, was tested for neurotrophic activity in primary explant cultures of ventral spinal cord of fetal rats (VSCC). Temocapril had a remarkable effect on neurite outgrowth with a 4.2- to 5.1-fold increased over that of control VSCC at their effective concentrations. In temocapril-treated VSCC, choline acetyltransferase (ChAT) activity was also increased 2.4-3.2 times over that of control at 10(-9) and 10(-8) M, respectively. Our data suggest that temocapril is a candidate for neurotrophic factors on spinal motor neurons in vitro. A possible therapeutic role for temocapril in damaged motor neurons, such as in motor neuropathy and amyotrophic lateral sclerosis, remains to be defined.

ACE Inhibition with moexipril: a review of potential effects beyond blood pressure control

ACE inhibitors induce metabolic changes and exert cardioprotective and vasoprotective properties, some of which cannot be attributed to their antihypertensive effect per se. Moexipril is an ACE inhibitor with a lipophilicity in the same range as quinapril, benazepril or ramipril, and so can readily penetrate lipid membranes and thus target tissue ACE in addition to plasma ACE. Evidence from animal studies shows similar and significant (p < 0.05) reductions in tissue ACE activity for moexipril and quinapril. Moexipril may improve endothelial dysfunction; moexiprilat and ramiprilat have demonstrated greater activity than captopril, enalaprilat and quinaprilat in isolated endothelium-denuded segments of the rabbit jugular vein where bradykinin elicits a constrictor response, mediated by activation of the bradykinin B(2) receptor. ACE inhibitors, including moexipril, may exert neuroprotective effects. Moexipril promoted neuronal survival in vitro and it is thought that this neuroprotective effect is due to free radical scavenging properties of the drug. ACE inhibitors can also decrease progression of renal insufficiency in patients with various underlying renal diseases. Moexipril may also have a renoprotective effect as it increased the ultrafiltration coefficient and normalized urinary protein excretion in rat models. Preclinical studies indicate that the renin-angiotensin-aldosterone system may play a role in the regulation of bone resorption and moexipril had no adverse effects on bone metabolism in animal models and the drug did not hamper the osteoprotective effects of estrogen. Reduction in left ventricular mass with moexipril in patients with hypertension was similar in magnitude to the effect of other ACE inhibitors. When investigated in hypertensive patients with an elevated cardiovascular risk, moexipril increased arterial distensibility and demonstrated antioxidative properties in addition to efficiently controlling blood pressure. Moexipril does not adversely affect serum levels of uric acid, lipids, blood glucose levels and plasma insulin levels and can be co-administered with hormone replacement therapy. Moreover, quality-of-life data suggest favorable effects of moexipril treatment in a patient population at high cardiovascular risk.

Inhibiting renin-angiotensin in the brain: the possible therapeutic implications

The renin-angiotensin system (RAS) within the brain is involved in central blood pressure regulation. Biochemical and neurophysiological studies suggest that the brain system is regulated independently of the peripheral RAS and that the system may also contribute to blood pressure control and body fluid homeostasis. In addition, circulating angiotensin II can exert some of its actions through the stimulation of angiotensin subtype 1 (AT1) and subtype 2 (AT2) receptors within the brain. As in peripheral tissues, the AT1 receptor mediates the central actions of angiotensin II on osmotic control and blood pressure regulation. The AT2 receptor appears to be involved in brain development and neuronal regeneration, but may also modulate some effects of central AT1 receptor stimulation. Selective non-peptide antagonists of the AT1 receptor have been shown to inhibit not only peripheral, but also central AT1 receptors after systemic application. In animal models, treatment with AT1 receptor antagonists proved to be beneficial with respect to stroke incidence and outcome. Other animal studies have shown that the AT1 receptor antagonists enable endogenous angiotensin II to stimulate nerve generation via AT2 receptors.

Functional decline in aging and disease: a role for apoptosis

The process of aging and senescence is associated with a decline in several organ functions and ultimately takes away independence and reduces quality of life. The precariously marginal functional reserves of the immune, pulmonary, and cardiovascular systems are among the most important causes of increased hospitalization in the older population. When complicated by chronic diseases, as is often the case, the problem is magnified. Apoptosis, or programmed cell death, is a process that goes on continuously throughout life. It is involved in embryogenesis for proper organ and tissue development. After birth and through adulthood, it helps eliminate unneeded and damaged cells. There is evidence that advanced age is associated with dysregulation of apoptosis. Several studies have shown age-related changes in the levels of proteins and factors that regulate apoptosis. This could explain the age-associated increased prevalence of cancers, certain autoimmune diseases, and neurodegenerative disorders in older people. More studies are needed to further elucidate the process of apoptosis. With this knowledge, the use of gene therapy and apoptosis modulators may someday have therapeutic value in preventing the functional decline we see in the older population.

Preconditioning-induced neuroprotection is mediated by reactive oxygen species and activation of the transcription factor nuclear factor-kappaB

Preconditioning by a sublethal stimulus induces tolerance to a subsequent, otherwise lethal insult and it has been suggested that reactive oxygen species (ROS) are involved in this phenomenon. In the present study, we determined whether preconditioning activates the transcription factor nuclear factor-kappaB (NF-kappaB) and how this activation contributes to preconditioning-induced inhibition of neuronal apoptosis. Preconditioning was performed by incubating mixed cultures of neurons and astrocytes from neonatal rat hippocampus with xanthine/xanthine oxidase or FeSO4 for 15 min followed by 24 h of recovery which protected the neurons against subsequent staurosporine-induced (200 nM, 24 h) apoptosis. The cellular ROS content increased during preconditioning, but returned to basal levels after removal of xanthine/xanthine oxidase or FeSO4. We detected a transient activation of NF-kappaB 4 h after preconditioning as shown by immunocytochemistry, by a decrease in the protein level of IkappaBalpha as well as by electrophoretic mobility shift assay. Preconditioning-mediated neuroprotection was abolished by antioxidants, inhibitors of NF-kappaB activation and cycloheximide suggesting the involvement of ROS, an activation of NF-kappaB and de novo protein synthesis in preconditioning-mediated rescue pathways. Furthermore, preconditioning increased the protein level of Mn-superoxide dismutase which could be blocked by antioxidants, cycloheximide and kappaB decoy DNA. Our data suggest that inhibition of staurosporine-induced neuronal apoptosis by preconditioning with xanthine/xanthine oxidase or FeSO4 involves an activation of NF-kappaB and an increase in the protein level of Mn-superoxide dismutase.

Preconditioning-induced neuroprotection is mediated by reactive oxygen species

The current study was performed to determine the role of reactive oxygen species (ROS) in preconditioning against different forms of neuronal damage. Primary cultures of chick embryonic neurons were treated with either FeSO(4) (100 microM; 15 min) to generate hydroxyl radicals or xanthine/xanthinoxidase (10 microM/0.5 mU ml(-1); 15 min; =X/XO (pre)) to produce superoxide radicals. Both stimuli moderately enhanced ROS formation as measured by fluorescence microscopy. This preconditioning significantly protected the neurons against subsequent glutamate (1 mM)-induced excitotoxic damage, staurosporine (200 nM)-induced neuronal apoptosis and oxidative damage caused by exposure to xanthine/xanthinoxidase (500 microM/5 mU ml(-1); 1 h; =X/XO (dam)). The antioxidants vitamin E (10 microM) and 2-OH-estradiol (1 microM), present during the 15-min preconditioning period, completely abolished the protective effect of X/XO (pre). Furthermore, glutamate, staurosporine or X/XO (dam) markedly enhanced oxygen radical formation. Preceding preconditioning by mild ROS stimulation with X/XO (pre) or Fe(2+) reduced this oxygen radical burst. Again, the effect of X/XO (pre) could be blocked by coadministration of vitamin E or 2-OH-estradiol. However, the FeSO(4)-mediated preconditioning was not abolished by the radical scavengers. To address this phenomenon, the effect of vitamin E and 2-OH-estradiol on Fe(2+)- and X/XO (pre)-induced ROS formation kinetics within the 15 min of preconditioning was monitored. The moderate rise of intracellular ROS content during preconditioning was only reduced permanently by the antioxidants, when the neurons were treated with X/XO (pre), but not when Fe(2+) was used. Thus, an immediate and constant radical scavenging seems to be indispensable to abolish the ROS-induced neuronal preconditioning. The current results indicate that preconditioning by moderate ROS-stimulation protects cultured neurons against different damaging agents and prevents against the subsequent massive oxygen radical formation.

Apoptosis and necrosis in cerebrovascular disease

Neuronal death following ischemic insults has been thought to reflect necrosis. However, recent evidence from several labs suggests that programmed cell death, leading to apoptosis, might additionally contribute to this death. We have used both in vitro and in vivo models to study the role of apoptosis in ischemic cell death. Some features of apoptosis (TUNEL staining, internucleosomal DNA fragmentation, sensitivity to cycloheximide) were observed following transient focal ischemia in rats. Brief transient focal ischemia was followed by delayed infarction more than 3 days later; this delayed infarction was sensitive to cycloheximide. A cycloheximide-sensitive component of neuronal cell death was also observed in cultured murine neocortical neurons deprived of oxygen-glucose in the presence of glutamate receptor antagonists. This presumed ischemic apoptosis was attenuated by caspase inhibitors, or by homozygous deletion of the bax gene. Neurons may undergo both apoptosis and necrosis after ischemic insults, and thus it may be therapeutically desirable to block both processes.

Neuroprotection by estrogens in a mouse model of focal cerebral ischemia and in cultured neurons: evidence for a receptor-independent antioxidative mechanism

Estrogens have been suggested for the treatment of neurodegenerative disorders, including stroke, because of their neuroprotective activities against various neurotoxic stimuli such as glutamate, glucose deprivation, iron, or beta-amyloid. Here, the authors report that 17beta-estradiol (0.3 to 30 mg/kg) and 2-OH-estradiol (0.003 to 30 mg/kg) reduced brain tissue damage after permanent occlusion of the middle cerebral artery in male NMRI mice. In vitro, 17beta-estradiol (1 to 10 micromol/L) and 2-OH-estradiol (0.01 to 1 micromol/L) reduced the percentage of damaged chick embryonic neurons treated with FeSO4. In these primary neurons exposed to FeSO4, the authors also found reactive oxygen species to be diminished after treatment with 17beta-estradiol (1 to 10 micromol/L) or 2-OH-estradiol (0.01 to 10 micromol/L), suggesting a strong antioxidant activity of the estrogens that were used. Neither the neuroprotective effect nor the free radical scavenging properties of the estrogens were influenced by the estrogen receptor antagonist tamoxifen. The authors conclude that estrogens protect neurons against damage by radical scavenging rather than through estrogen receptor activation.