Neuroprotective mechanism of ischemic postconditioning in mice: a possible relationship between protein kinase C and nitric oxide pathways

Guhong Injection Alleviates Cerebral Ischemia-Reperfusion Injury via the PKC/HIF-1α Pathway in Rats

Guhong injection (GHI) is a drug for ischemic stroke created by combining safflower, a traditional Chinese medicine, and aceglutamide, a Western medicine. In this study, we investigated the curative effect of GHI on cerebral ischemia–reperfusion (I/R) injury via the PKC/HIF-1α pathway in rats. Adult male Sprague Dawley rats were randomly divided into seven groups: sham-operated, middle cerebral artery occlusion (MCAO), GHI, nimodipine injection (NMDP), MCAO + LY317615 (PKC inhibitor), GHI + LY317615, and NMDP + LY317615. After establishing an MCAO rat model, we performed neurological deficit testing, 2,3,5-triphenyltetrazolium chloride staining, hematoxylin and eosin (HE) staining, enzyme-linked immunosorbent assay, Western blotting, and q-PCR to detect the brain damage in rats. Compared with the MCAO group, the GHI and GHI + LY317615 group showed neurological damage amelioration as well as decreases in serum hypoxia-inducible factor-1α (HIF-1α), protein kinase C (PKC), and erythropoietin levels; brain HIF-1α and inducible nitric oxide synthase protein expression; and brain HIF-1α and NOX-4 mRNA expression. These effects were similar to those in the positive control groups NMDP and NMDP + LY317615. Thus, our results confirmed GHI can ameliorate cerebral I/R injury in MCAO rats possibly via the PKC/HIF-1α pathway.

Targeted Metabolomic Profiling Reveals Association Between Altered Amino Acids and Poor Functional Recovery After Stroke

Amino acids have been shown to be among the most important metabolites to be altered following stroke; however, they are a double-edged sword with regard to regulating hemostasis. In this study, we conducted a targeted metabolomic study to examine the association between serum levels of amino acids and functional recovery after stroke. Three hundred and fifty-one patients with stroke admitted to an acute rehabilitation hospital were screened, and 106 patients were selected based on inclusion and exclusion criteria. Recruited patients were stratified using Montebello Rehabilitation Factor Score (MRFS) efficiency. We selected the top (n = 20, 19%) and bottom (n = 20, 19%) of MRFS efficiency for metabolomic analysis. A total of 21 serum amino acids levels were measured using ultra high performance liquid chromatography and mass spectrometry. The normalized data were analyzed by multivariate approaches, and the selected potential biomarkers were combined in different combinations for prediction of stroke functional recovery. The results demonstrated that there were significant differences in leucine-isoleucine, proline, threonine, glutamic acid, and arginine levels between good and poor recovery groups. In the training (0.952) and test (0.835) sets, metabolite biomarker panels composed of proline, glutamic acid, and arginine had the highest sensitivity and specificity in distinguishing good recovery from poor. In particular, arginine was present in the top 10 combinations of the average area under the receiver operating characteristic curve (AUC) test set. Our findings suggest that amino acids related to energy metabolism and excitotoxicity may play an important role in functional recovery after stroke. Therefore, the level of serum arginine has predictive value for the recovery rate after stroke.

Limb remote ischemic postconditioning protects integrity of the blood-brain barrier after stroke

Integrity of the blood-brain barrier structure is essential for maintaining the internal environment of the brain. Development of cerebral infarction and brain edema is strongly associated with blood-brain barrier leakage. Therefore, studies have suggested that protecting the blood-brain barrier may be an effective method for treating acute stroke. To examine this possibility, stroke model rats were established by middle cerebral artery occlusion and reperfusion. Remote ischemic postconditioning was immediately induced by three cycles of 10-minute ischemia/10-minute reperfusion of bilateral hind limbs at the beginning of middle cerebral artery occlusion reperfusion. Neurological function of rat models was evaluated using Zea Longa’s method. Permeability of the blood-brain barrier was assessed by Evans blue leakage. Infarct volume and brain edema were evaluated using 2,3,5-triphenyltetrazolium chloride staining. Expression of matrix metalloproteinase-9 and claudin-5 mRNA was determined by real-time quantitative reverse transcription-polymerase chain reaction. Expression of matrix metalloproteinase-9 and claudin-5 protein was measured by western blot assay. The number of matrix metalloproteinase-9- and claudin-5-positive cells was analyzed using immunohistochemistry. Our results showed that remote ischemic postconditioning alleviated disruption of the blood-brain barrier, reduced infarct volume and edema, decreased expression of matrix metalloproteinase-9 mRNA and protein and the number of positive cells, increased expression of claudin-5 mRNA and protein and the number of positive cells, and remarkably improved neurological function. These findings confirm that by suppressing expression of matrix metalloproteinase-9 and claudin-5 induced by acute ischemia/reperfusion, remote ischemic postconditioning reduces blood-brain barrier injury, mitigates ischemic injury, and exerts protective effects on the brain.

l-Arginine Pathway Metabolites Predict Need for Intra-operative Shunt During Carotid Endarterectomy

OBJECTIVE/BACKGROUND

Asymmetric dimethylarginine (ADMA) inhibits nitric oxide (NO) synthesis and is a marker of atherosclerosis. This study examined the correlation between pre-operative l-arginine and ADMA concentration during carotid endarterectomy (CEA), and jugular lactate indicating anaerobic cerebral metabolism, jugular S100B reflecting blood-brain barrier integrity, and with factors of surgical intervention.

METHODS

The concentration of l-arginine, ADMA, and symmetric dimethylarginine was measured in blood taken under regional anaesthesia from the radial artery of 55 patients prior to CEA. Blood gas parameters, concentration of lactate, and S100B were also serially measured in blood taken from both the radial artery and the jugular bulb before and after carotid clamping, and after release of the clamp. To estimate anaerobic metabolism, the jugulo-arterial ratio of CO₂ gap/oxygen extraction was calculated.

RESULTS

Positive correlation was found between pre-operative ADMA levels and the ratio of jugulo-arterial CO₂ gap/oxygen extraction during clamp and reperfusion (p = .005 and p = .01, respectively). An inverse correlation was found between the pre-operative l-arginine concentration and jugular lactate at each time point (both p = .002). The critical pre-operative level of l-arginine was determined by receiver operator curve analysis. If l-arginine was below the cutoff value of 35 μmol/L, jugular S100B concentration was higher 24 h post-operatively (p = .03), and jugular lactate levels were increased during reperfusion (p = .02). The median pre-operative concentration of l-arginine was lower in patients requiring an intra-operative shunt than in patients without need of shunt (median: 30.3 μmol/L [interquartile range 24.4-34.4 μmol/L] vs. 57.6 μmol/L [interquartile range 42.3-74.5 μmol/L]; p = .002).

CONCLUSION

High pre-operative ADMA concentration predicts poor cerebral perfusion indicated by elevated jugulo-arterial CO₂ gap/oxygen extraction. Low pre-operative l-arginine concentration predicts the need for a shunt. The inverse correlation between pre-operative l-arginine concentration and both jugular lactate and S100B during carotid clamping suggests a protective role of the NO donor l-arginine.

Rodent Gymnastics: Neurobehavioral Assays in Ischemic Stroke

Despite years of research, most preclinical trials on ischemic stroke have remained unsuccessful owing to poor methodological and statistical standards leading to "translational roadblocks." Various behavioral tests have been established to evaluate traits such as sensorimotor function, cognitive and social interactions, and anxiety-like and depression-like behavior. A test's validity is of cardinal importance as it influences the chance of a successful translation of preclinical results to clinical settings. The mission of choosing a behavioral test for a particular project is, therefore, imperative and the present review aims to provide a structured way to evaluate rodent behavioral tests with implications in ischemic stroke.

Neuronal effects of a nickel-piperazine/NO donor complex in rodents

In the brain, NO is a very important molecule in the regulation of cerebral and extra cerebral cranial blood flow and arterial diameters. It is also importantly involved in many neuronal functions and innumerable roles of NO in many brain related disorders including epilepsy, schizophrenia, drug addiction, anxiety, major depression, have been postulated. The present study aimed to explore the neuronal role exerted by the metal-nonoate compound Ni(PipNONO)Cl, a novel NO donor whose vascular protective effects have been recently demonstrated. Ni(PipNONO)Cl showed antidepressant-like properties in the tail suspension test and antiamnesic activity in the passive avoidance test in the absence of any hypernociceptive response to a mechanical stimulus. These effects were related to the NO-releasing properties of the compound within the central nervous system as demonstrated by the increase of iNOS levels in the brain, spinal cord and dura mater. The modulation of neuronal functions appeared after acute and repeated treatment, showing the lack of any tolerance to neuronal effects. At the dose used (10 mg/kg i.p.), Ni(PipNONO)Cl did not induce any visible sign of toxicity and experiments were performed in the absence of locomotor impairments. In addition to the NO-related neuronal activities of Ni(PipNONO)Cl, the decomposition control compound Ni(Pip)Cl2 showed anxiogenic-like and procognitive effects. The present findings showed neuronal modulatory activity of Ni(PipNONO)Cl through a NO-mediated mechanism. The activities of the decomposition compound Ni(Pip)Cl2 attributed to Ni(PipNONO)Cl the capability to modulate additional neuronal functions independently from NO releasing properties extending and improving the therapeutic perspectives of the NO donor.