Carnosine Protects against Cerebral Ischemic Injury by Inhibiting Matrix-Metalloproteinases

The protective role of carnosine against type 2 diabetes-induced cognitive impairment

The morbidity and mortality associated with type 2 diabetes mellitus (T2DM) have grown exponentially over the last 30 years. Together with its associated complications, the mortality rates have increased. One important complication in those living with T2DM is the acceleration of age-related cognitive decline. T2DM-induced cognitive impairment seriously affects memory, executive function, and quality of life. However, there is a lack of effective treatment for both diabetes and cognitive decline. Thus, finding novel treatments which are cheap, effective in both diabetes and cognitive impairment, are easily accessible, are needed to reduce impact on patients with diabetes and health-care systems. Carnosine, a histidine containing dipeptide, plays a protective role in cognitive diseases due to its antioxidant, anti-inflammation, and anti-glycation properties, all of which may slow the development of neurodegenerative diseases and ischemic injury. Furthermore, carnosine is also involved in regulating glucose and insulin in diabetes. Herein, we discuss the neuroprotective role of carnosine and its mechanisms in T2DM-induced cognitive impairment, which may provide a theoretical basis and evidence base to evaluate whether carnosine has therapeutic effects in alleviating cognitive dysfunction in T2DM patients.

Blood-brain barrier permeability in the ischemic stroke: An update

Stroke is the second leading cause of death globally and the major cause of long-term disability. Among the types of strokes, ischemic stroke, which occurs due to obstruction of blood vessels responsible for cerebral irrigation, is considered the most prevalent, accounting for approximately 86 % of all stroke cases. This interruption of blood supply leads to a critical pathophysiological mechanism, including oxidative stress and neuroinflammation which are responsible for structural alterations of the blood-brain barrier (BBB). The increased BBB permeability associated with cerebral ischemia-reperfusion may contribute to a worse outcome after stroke. Thus, this narrative review aims to update the pathophysiological mechanisms involved in the increase in BBB permeability and to list the possible therapeutic strategies.

Dual Effect of Carnosine on ROS Formation in Rat Cultured Cortical Astrocytes

Carnosine is composed of β-alanine and L-histidine and is considered to be an important neuroprotective agent with antioxidant, metal chelating, and antisenescence properties. However, children with serum carnosinase deficiency present increased circulating carnosine and severe neurological symptoms. We here investigated the in vitro effects of carnosine on redox and mitochondrial parameters in cultured cortical astrocytes from neonatal rats. Carnosine did not alter mitochondrial content or mitochondrial membrane potential. On the other hand, carnosine increased mitochondrial superoxide anion formation, levels of thiobarbituric acid reactive substances and oxidation of 2',7'-dichlorofluorescin diacetate (DCF-DA), indicating that carnosine per se acts as a pro-oxidant agent. Nonetheless, carnosine prevented DCF-DA oxidation induced by H2O2 in cultured cortical astrocytes. Since alterations on mitochondrial membrane potential are not likely to be involved in these effects of carnosine, the involvement of N-Methyl-D-aspartate (NMDA) receptors in the pro-oxidant actions of carnosine was investigated. MK-801, an antagonist of NMDA receptors, prevented DCF-DA oxidation induced by carnosine in cultured cortical astrocytes. Astrocyte reactivity induced by carnosine was also prevented by the coincubation with MK-801. The present study shows for the very first time the pro-oxidant effects of carnosine per se in astrocytes. The data raise awareness on the importance of a better understanding of the biological actions of carnosine, a nutraceutical otherwise widely reported as devoid of side effects.

The neuroprotective role of prolonged normobaric oxygenation applied during ischemia and in the early stage of reperfusion in cerebral ischemic rats

BACKGROUND

Recanalization is the main treatment option for ischemic stroke. However, prognosis remains poor for about half of patients after recanalization, possibly due to the "no-reflow" phenomenon at the early phase of recanalization. Normobaric oxygenation (NBO) during ischemia can reportedly maintain the partial pressure of oxygen and exert a protective effect in ischemic brain tissue.

OBJECTIVES AND METHODS

This study investigated whether prolonged NBO treatment during ischemia and the early phase of reperfusion (i/rNBO) has neuroprotective effects and to elucidate the underlying mechanisms in rats with middle cerebral artery occlusion plus reperfusion.

RESULTS

NBO treatment significantly elevated the level of O2 in the atmosphere and arterial blood without altering the level of CO2. The infarcted cerebral volume was significantly reduced by application of i/rNBO as compared to iNBO (applied during ischemia) or rNBO (applied at the early phase of reperfusion), indicating better protective effects of i/rNBO. i/rNBO more effectively suppressed s-nitrosylation of MMP-2 (amplifying inflammation) as compared to iNBO and rNBO, dramatically downregulated the cleavage of poly(ADP-ribose)polymerase-1 (PARP-1, acting as the substrate of MMP-2), and suppressed neuronal apoptosis, as determined by the TUNEL assay and staining for NeuN. These results demonstrated that application of i/rNBO in the early stage of reperfusion significantly alleviated neuronal apoptosis via suppression of the MMP-2/PARP-1 pathway.

CONCLUSIONS

The mechanism underlying the neuroprotective role of i/rNBO involved prolonged NBO treatment for cerebral ischemia, suggesting that i/rNBO may allow expansion of the time window for NBO application in stroke patients following vascular recanalization.

Biomarkers and the outcomes of ischemic stroke

Biomarkers are measurable substances that could be used as objective indicators for disease diagnosis, responses to treatments, and outcomes predictions. In this review, we summarized the data on a number of important biomarkers including glutamate, S100B, glial fibrillary acidic protein, receptor for advanced glycation end-products, intercellular adhesion molecule-1, von willebrand factor, matrix metalloproteinase-9, interleukin-6, tumor necrosis factor-a, activated protein C, copeptin, neuron-specific enolase, tau protein, gamma aminobutyric acid, blood glucose, endothelial progenitor cells, and circulating CD34-positive cells that could be potentially used to indicate the disease burden and/or predict clinical outcome of ischemic stroke. We examined the relationship between specific biomarkers and disease burden and outcomes and discussed the potential mechanisms underlying the relationship. The clinical significance and implications of these biomarkers were also discussed.

Anethole Pretreatment Modulates Cerebral Ischemia/Reperfusion: The Role of JNK, p38, MMP-2 and MMP-9 Pathways

Anethole (AN) is one of the major constituents of several plant oils, demonstrating plentiful pharmacological actions. Ischemic stroke is the main cause of morbidity and death worldwide, particularly since ischemic stroke therapeutic choices are inadequate and limited; thus, the development of new therapeutic options is indispensable. This study was planned to explore the preventive actions of AN in ameliorating cerebral ischemia/reperfusion-induced brain damage and BBB permeability leakage, as well as to explore anethole’s potential mechanisms of action. The proposed mechanisms included modulating JNK and p38 as well as MMP-2 and MMP-9 pathways. Sprague–Dawley male rats were randomly assigned into four groups: sham, middle cerebral artery occlusion (MCAO), AN125 + MCAO, and AN250 + MCAO. Animals in the third and fourth groups were pretreated with AN 125 or 250 mg/kg orally, respectively, for two weeks before performing middle cerebral artery occlusion (MCAO)-induced cerebral ischemic/reperfusion surgery. Animals that experienced cerebral ischemia/reperfusion exhibited amplified infarct volume, Evans blue intensity, brain water content, Fluoro-Jade B-positive cells, severe neurological deficits, and numerous histopathological alterations. MCAO animals exhibited elevated MMP-9 and MMP-2 gene expressions, enzyme activities, augmented JNK, and p38 phosphorylation. On the other hand, pretreatment with AN diminished the infarct volume, Evans blue dye intensity, brain water content, and Fluoro-Jade B-positive cells, improved the neurological score and enhanced histopathological examination. AN effectively lowered MMP-9 and MMP-2 gene expression and enzyme activities and diminished phosphorylated JNK, p38. AN decreased MDA content, amplified GSH/GSSG ratio, SOD, and CAT, decreased the serum and brain tissue homogenate inflammatory cytokines (TNF-α, IL-6, IL-1β), NF-κB, and deterred the apoptotic status. This study revealed the neuroprotective ability of AN against cerebral ischemia/reperfusion in rats. AN boosted blood–brain barrier integrity via modulating MMPs and diminished oxidative stress, inflammation, and apoptosis through the JNK/p38 pathway.

Matrix Metalloproteinases in Cardioembolic Stroke: From Background to Complications

Matrix metalloproteinases (MMPs) are endopeptidases participating in physiological processes of the brain, maintaining the blood-brain barrier integrity and playing a critical role in cerebral ischemia. In the acute phase of stroke activity, the expression of MMPs increase and is associated with adverse effects, but in the post-stroke phase, MMPs contribute to the process of healing by remodeling tissue lesions. The imbalance between MMPs and their inhibitors results in excessive fibrosis associated with the enhanced risk of atrial fibrillation (AF), which is the main cause of cardioembolic strokes. MMPs activity disturbances were observed in the development of hypertension, diabetes, heart failure and vascular disease enclosed in CHA₂DS₂VASc score, the scale commonly used to evaluate the risk of thromboembolic complications risk in AF patients. MMPs involved in hemorrhagic complications of stroke and activated by reperfusion therapy may also worsen the stroke outcome. In the present review, we briefly summarize the role of MMPs in the ischemic stroke with particular consideration of the cardioembolic stroke and its complications. Moreover, we discuss the genetic background, regulation pathways, clinical risk factors and impact of MMPs on the clinical outcome.

Effect of Carnosine on the Activity of Matrix Metalloproteinase-2 and Oxidative Stress in the Kidneys in Experimental Urate Nephrolithiasis

The effect of carnosine on MMP-2 activity and oxidative stress in the kidneys in experimental urate nephrolithiasis was studied. Urate nephrolithiasis was modeled in Wistar rats by intragastric administration of a mixture of oxonic and uric acids. Carnosine was administered intragastrically through a tube in a dose of 15 mg/kg. In rats treated with carnosine, the concentration of MMP-2 in the urine decreased by 3.7 times, and the excretion of MMP-2 with urine decreased by 4.3 times. In the homogenate of the kidneys from rats treated with carnosine, the concentration of TBA-reactive substances decreased by 5 times and the concentration of MMP-2 decreased by 12.7%. After treatment with carnosine, the number of histologically confirmed cases of urate nephrolithiasis decreased by 2 times, while the mean size of urate deposits decreased by 2.7 times. Thus, carnosine inhibits MMP-2 and reduces the intensity of oxidative stress in the kidneys, which prevents the development of urate nephrolithiasis.

DIA-based technology explores hub pathways and biomarkers of neurological recovery in ischemic stroke after rehabilitation

Objective

Ischemic stroke (IS) is a common disease that causes severe and long-term neurological disability in people worldwide. Although rehabilitation is indispensable to promote neurological recovery in ischemic stroke, it is limited to providing a timely and efficient reference for developing and adjusting treatment strategies because neurological assessment after stroke treatment is mostly performed using scales and imaging. Therefore, there is an urgent need to find biomarkers that can help us evaluate and optimize the treatment plan.

Methods

We used data-independent acquisition (DIA) technology to screen differentially expressed proteins (DEPs) before and after ischemic stroke rehabilitation treatment, and then performed Gene Ontology (GO) and pathway enrichment analysis of DEPs using bioinformatics tools such as KEGG pathway and Reactome. In addition, the protein-protein interaction (PPI) network and modularity analysis of DEPs were integrated to identify the hub proteins (genes) and hub signaling pathways for neurological recovery in ischemic stroke. PRM-targeted proteomics was also used to validate some of the screened proteins of interest.

Results

Analyzing the serum protein expression profiles before and after rehabilitation, we identified 22 DEPs that were upregulated and downregulated each. Through GO and pathway enrichment analysis and subsequent PPI network analysis constructed using STRING data and subsequent Cytoscape MCODE analysis, we identified that complement-related pathways, lipoprotein-related functions and effects, thrombosis and hemostasis, coronavirus disease (COVID-19), and inflammatory and immune pathways are the major pathways involved in the improvement of neurological function after stroke rehabilitation.

Conclusion

Complement-related pathways, lipoprotein-related functions and effects, thrombosis and hemostasis, coronavirus disease (COVID-19), and inflammation and immunity pathways are not only key pathways in the pathogenesis of ischemic stroke but also the main pathways of action of rehabilitation therapy. In addition, IGHA1, LRG1, IGHV3-64D, and CP are upregulated in patients with ischemic stroke and downregulated after rehabilitation, which may be used as biomarkers to monitor neurological impairment and recovery after stroke.

[Astragalus polysaccharide protects against blood-brain barrier damage in MCAO rats by inhibiting P2X7R channel]

OBJECTIVE

To investigate the protective effect of astragalus polysaccharide (APS) against blood-brain barrier in a rat model of middle cerebral artery occlusion (MCAO) and the role of P2X7R channel in the protective mechanism.

METHODS

In rat microglial cell models of oxygen and glucose deprivation (OGD) or ATP treatment, the formation of blood-brain barrier in vitro was assessed using the leak test, and the effect of APS on the permeability of the blood-brain barrier was determined using LC-MS. In 12 SD rats, MCAO model was established followed by treatment with intraperitoneal injection of normal saline (n= 6) or APS (45 mg/kg, n=6) for 3 consecutive days, with another 6 rats without MCAO receiving saline injections as the control group. The permeability of the blood-brain barrier of the rats was evaluated by determining Evans blue (EB) extravasation, and ATP content in the brain tissue was detected using ELISA; the expression levels of matrix metalloproteinase-9 (MMP-9) and P2X7R in the brain tissue were detected with Western blot.

RESULTS

In the in vitro cell model of OGD or ATP treatment, APS treatment obviously promoted the repair of blood-brain barrier integrity. In the rat models, the EB content in the brain tissue and the blood-brain barrier permeability increased significantly in MCAO+saline group and MCAO+APS group as compared with those in the control group (P < 0.01). Compared with saline treatment, APS treatment significantly decreased EB content in the brain tissue and improved the blood-brain barrier permeability in the MCAO rats (P < 0.05). MCAO caused a significant reduction of ATP content and obviously increased the expression levels of MMP-9 and P2X7R in the brain tissue of the rats (P < 0.01), and these changes were significantly alleviated after APS treatment (P < 0.01 or 0.05).

CONCLUSION

APS can protect the brain tissue of MCAO rats by stabilizing the internal environment, down-regulating the expression of MMP-9 and improving the permeability of blood-brain barrier under cerebral ischemia and hypoxia, and its mechanism may involve the inhibition of P2X7R channel.

Neuroprotective efficacy of N-t-butylhydroxylamine (NtBHA) in transient focal ischemia in rats

The pharmacological or toxicological activities of the degradation products of drug candidates have been unaddressed during the drug development process. Ischemic stroke accounts for 80% of all strokes and is responsible for considerable mortality and disability worldwide. Despite decades of research on neuroprotective agents, tissue plasminogen activators (t-PA), a thrombolytic agent, remains the only approved acute stroke pharmacological therapy. NXY-059, a free radical scavenger, exhibited striking neuroprotective properties in preclinical models and met all the criteria established by the Stroke Academic Industry Roundtable (STAIR) for a neuroprotective agent. In phase 3 clinical trials, NXY-059 exhibited significant neuroprotective effects in one trial (SAINT-I), but not in the second (SAINT-II). Some have hypothesized that N-t-butyl hydroxylamine (NtBHA), a breakdown product of NXY-059 was the actual neuroprotective agent in SAINT-I and that changes to the formulation of NXY-059 to prevent its breakdown to NtBHA in SAINT -II was the reason for the lack of efficacy. We evaluated the neuroprotective effect of NtBHA in N-methyl-D-aspartate (NMDA)-treated primary neurons and in rat focal cerebral ischemia. NtBHA significantly attenuated infarct volume in rat transient focal ischemia, and attenuated NMDA-induced cytotoxicity in primary cortical neurons. NtBHA also reduced free radical generation and exhibited mitochondrial protection.

Cerebral edema after ischemic stroke: Pathophysiology and underlying mechanisms

Ischemic stroke is associated with increasing morbidity and has become the main cause of death and disability worldwide. Cerebral edema is a serious complication arising from ischemic stroke. It causes an increase in intracranial pressure, rapid deterioration of neurological symptoms, and formation of cerebral hernia, and is an important risk factor for adverse outcomes after stroke. To date, the detailed mechanism of cerebral edema after stroke remains unclear. This limits advances in prevention and treatment strategies as well as drug development. This review discusses the classification and pathological characteristics of cerebral edema, the possible relationship of the development of cerebral edema after ischemic stroke with aquaporin 4, the SUR1-TRPM4 channel, matrix metalloproteinase 9, microRNA, cerebral venous reflux, inflammatory reactions, and cerebral ischemia/reperfusion injury. It also summarizes research on new therapeutic drugs for post-stroke cerebral edema. Thus, this review provides a reference for further studies and for clinical treatment of cerebral edema after ischemic stroke.

Impact of MMP2 rs243849 and rs14070 genetic polymorphisms on the ischemic stroke susceptibility in Chinese Shaanxi population

Background

Ischemic stroke (IS) is a complex neurological disease affected by genetics and environment. Matrix metalloproteinase-2 (MMP2) is involved in extracellular matrix (ECM) degradation, inflammation and angiogenesis to regulate the development and recovery of IS.

Purposes

The aim of this study was to explore the association of rs1053605, rs243849 and rs14070 in MMP2 with the risk of IS in Chinese Shaanxi population.

Methods

In this study, 677 IS patients and 681 normal controls were recruited. Rs1053605, rs243849 and rs14070 in MMP2 were genotyped. Logistic regression analysis was applied to evaluate the association of rs1053605, rs243849 and rs14070 in MMP2 with IS susceptibility and the association of environmental factors with MMP2 genetic susceptibility to IS.

Results

The results of the overall analysis demonstrated that rs14070 in MMP2 significantly reduced the risk of IS in Chinese Shaanxi population (OR = 0.767, 95% CI = 0.619–0.952, P = 0.016). Subgroup analysis illustrated that rs243849 in MMP2 evidently increased the risk of IS among drinkers, while rs14070 in MMP2 apparently reduced IS susceptibility among females, participants with aged >55, smokers and drinkers.

Conclusions

Collectively, rs243849 and rs14070 in MMP2 were significantly associated with the risk of IS in Chinese Shaanxi population, and the effect of MMP2 to IS may be associated with its genetic susceptibility.

Carnosine Alleviates Knee Osteoarthritis and Promotes Synoviocyte Protection via Activating the Nrf2/HO-1 Signaling Pathway: An In-Vivo and In-Vitro Study

The most common joint disease in the elderly is knee osteoarthritis (OA). It is distinguished by cartilage degradation, subchondral bone loss, and a decrease in joint space. We studied the effects of carnosine (CA) on knee OA in male Wistar rats. OA is induced by anterior cruciate ligament transection combined with medial meniscectomy (ACLT+MMx) method and in vitro studies are conducted in fibroblast-like synoviocyte cells (FLS). The pain was assessed using weight-bearing and paw-withdrawal tests. CA supplementation significantly reduced pain. The enzyme-linked immunosorbent assay (ELISA) method was used to detect inflammatory proteins in the blood and intra-articular synovial fluid (IASF), and CA reduced the levels of inflammatory proteins. Histopathological studies were performed on knee-tissue samples using toluidine blue and hematoxylin and eosin (H and E) assays. CA treatment improved synovial protection and decreased cartilage degradation while decreasing zonal depth lesions. Furthermore, Western blotting studies revealed that the CA-treated group activated nuclear factor erythroid 2-related factor (Nrf2) and heme oxygenase (HO-1) and reduced the expression of cyclooxygenase-2 (COX-2). FLS cells were isolated from the knee joints and treated with IL-1β to stimulate the inflammatory response and increase reactive oxygen species (ROS). The matrix metalloproteinase protein (MMP's) levels (MMP-3, and MMP-13) were determined using the reverse transcription-polymerase chain reaction (RT-PCR), and CA treatment reduced the MMP's expression levels. When tested using the 2',7'-dicholorodihydrofluroscene diacetate (DCFDA) assay and the 5,5',6,6'-tetracholoro-1,1',3,3'-tertraethylbenzimidazolcarboc janine iodide (JC-1) assay in augmented ROS FLS cells, CA reduced the ROS levels and improved the mitochondrial membrane permeability. This study's investigation suggests that CA significantly alleviates knee OA both in vitro and in vivo.

MMP2 and MMP9 contribute to lung ischemia-reperfusion injury via promoting pyroptosis in mice

BACKGROUND

Lung ischemia-reperfusion injury (LIRI) is a cause of poor prognosis in several lung diseases and after lung transplantation. In LIRI, matrix metalloproteinases and pyroptosis indicators change in parallel, both of them involvement of inflammatory modulation, but it is unclear whether they are related to each other.

METHODS

We analyzed the matrix metalloproteinases (MMPs) changes from RNA sequencing (RNA-Seq) data of human transplantation and rat ischemia-reperfusion lung tissues in the Group on Earth Observations (GEO) database. Then established the mouse LIRI model to validate the changes. Further, the severity of lung injury was measured after intervening the matrix metalloproteinases changes with their selective inhibitor during Lung ischemia-reperfusion. Meanwhile, lung, pyroptosis was assessed by assaying the activity of Caspase-1 and interleukin 1β (IL-1β) before and after intervening the matrix metalloproteinases changes.

RESULTS

The RNA-Seq data revealed that matrix metallopeptidase 2 (MMP2), matrix metallopeptidase 9 (MMP9) mRNA expression was elevated both in human lung transplantation and rat lung ischemia-reperfusion tissues, consistent with the change in our mouse model. At the same time, the activity of Caspase-1 and IL-1β were increased after LIRI. While, the lung injury was attenuated for the use of MMP2 and MMP9 selective inhibitor SB-3CT. Likewise, lung pyroptosis alleviated when treatment the mice with SB-3CT in LIRI.

CONCLUSION

We conclude that MMP2 and MMP9 are involved in the process of LIRI, the mechanism of which is related to the promotion of lung pyroptosis.