The protective effect of dopamine against OGD/R injury-induced cell death in HT22 mouse hippocampal cells

Dopamine receptor agonist pramipexole exerts neuroprotection on global cerebral ischemia/reperfusion injury by inhibiting ferroptosis

OBJECTIVE

To explore the mechanism of dopamine receptor agonist pramipexole in exerting neuroprotection on global cerebral ischemia/reperfusion injury (GCI/R).

MATERIAL AND METHOD

Male Sprague-Dawley rats were randomly divided into four groups (n = 36 in each group), and the Pulsinelli's four-vessel occlusion method was used to establish the rat model of GCI/R injury. Pramipexole administration group was intraperitoneally injected with pramipexole 0.5 mg kg-1 once a day for 14 days. Pramipexole combined with levodopa administration group was intraperitoneally injected with pramipexole 0.5 mg kg-1 and levodopa 50 mg kg-1 once a day for 14 days. The mNSS scores and Y maze test were used to evaluate neurological behaviors. Nissl staining and transmission electron microscopy were used to respectively observe hippocampal neurons and mitochondrial ultrastructure. Molecular biological tests including tissue iron concentration, GSH, MDA were used to detect the degree of ferroptosis. Western blotting was used to detect the expression levels of Nrf2, GPX4, X-CT and p53 proteins at 3 days, 7 days and 14 days after GCI/R injury.

RESULTS

Pramipexole alone or combined with levodopa for 14 days improved neurological behaviors, improved the morphology of neurons, increased the number of surviving neurons in the hippocampal CA1 region of GCI/R rats, which showed similar neuroprotective effects. Pramipexole alone or combined with levodopa for 14 days restored mitochondrial ultrastructure, decreased tissue iron concentration and MDA concentration, increased GSH concentration in the brain of GCI/R rats, which also induced the relative expressions of Nrf2, GPX4 and X-CT proteins and reduced p53 protein.

CONCLUSION

Pramipexole alone or combined with levodopa exert neuroprotection by inhibiting ferroptosis after GCI/R injury via Nrf2/GPX4/SLC7A11 pathway, and long-term intervention could be applied as an effective therapeutic strategy for neuroprotection against GCI/R injury.

Efficacy of a Novel Nanohydrogel Formulation Containing Dopamine, Chitosan Nanoparticles, and Tridax procumbens Extract for Enhanced Wound Healing in Human Gingival Fibroblast Cells: An In Vitro Study

Background Natural compounds and biomaterials, such as nanohydrogels, have gained interest due to their biocompatibility and tissue regeneration potential. A novel nanohydrogel was prepared by employing Tridax procumbens, a traditional plant with anti-inflammatory properties and chitosan nanoparticles and a natural bioadhesive with potent antimicrobial and antioxidant effects and dopamine, which has been shown to regulate angiogenesis and influence cell growth. The objective of this study was to examine how human gingival fibroblast (HGF) cells respond to a nanohydrogel formulation containing dopamine, chitosan nanoparticles, and T. procumbens extract in terms of cell viability and cell migration. Methods From human gingival tissue, fibroblasts were cultured. A nanohydrogel formulation was prepared by combining dopamine, chitosan nanoparticles, and T. procumbens extract. Three groups were evaluated: Group 1 (nanohydrogel containing dopamine, chitosan nanoparticles, and T. procumbens extract (DnCTP)), Group 2 (chitosan nanoparticles and T. procumbens extract (nCTP)), and Group 3(T. procumbens extract (TP)). The MTT assay was used to measure the percentage of cell viability and a scratch assay to observe cell migration in the wounded area at different concentrations. The data were tabulated in Microsoft Excel (Microsoft Corporation, USA) and imported to IBM SPSS Statistics for Windows, version 23.0 (released 2015, IBM Corp., Armonk, NY), and the Mann-Whitney U test was conducted to statistically analyze the cell viability for different concentrations within the three groups. Results The nanohydrogel formulation (DnCTP) showed dose-dependent effects on cell viability with the highest cell viability at 40 µL/mL concentration, and higher concentrations of 80 µL/mL exhibited cytotoxic effects. nCTP and TP showed decreased cell viability at 80 µL/mL concentration (p < 0.05), indicating potential cytotoxicity at higher concentrations. DnCTP showed improved cell migration in the scratch assay as compared to other groups (nCTP and TP), indicating its potential for facilitating wound healing. Conclusion Dopamine, chitosan nanoparticles, and T. procumbens worked together synergistically to create a nanohydrogel formulation (DnCTP) that showed promise for improving wound healing in human gingival fibroblast cells at a dose-dependent concentration, which may therefore work as an excellent wound-healing agent in periodontal and peri-implant therapy.

L-DOPA ameliorates hippocampus-based mitochondria respiratory dysfunction caused by GCI/R injury

Mitochondrial dysmorphology/dysfunction follow global cerebral ischemia-reperfusion (GCI/R) injury, leading to neuronal death. Our previous researches demonstrated that Levodopa (L-DOPA) improves learning and memory impairment in GCI/R rats by increasing synaptic plasticity of hippocampal neurons. This study investigates if L-DOPA, used in Parkinson's disease treatment, alleviates GCI/R-induced cell death by enhancing mitochondrial quality. Metabolomics and transcriptomic results showed that GCI/R damage affected the Tricarboxylic acid (TCA) cycle in the hippocampus. The results of this study show that L-DOPA stabilized mitochondrial membrane potential and ultrastructure in hippocampus of GCI/R rats, increased dopamine level in hippocampus, decreased succinic acid level, and stabilized Ca2+ level in CA1 subregion of hippocampus. As a precursor of dopamine, L-DOPA is presumed to improves mitochondrial function in hippocampus of GCI/R rats. However, dopamine cannot cross the blood-brain barrier, so L-DOPA is used in clinical therapy to supplement dopamine. In this investigation, OGD/R models were established in isolated mouse hippocampal neurons (HT22) and primary rat hippocampal neurons. Notably, dopamine exhibited a multifaceted impact, demonstrating inhibition of mitochondrial reactive oxygen species (mitoROS) production, stabilization of mitochondrial membrane potential and Ca2+ level, facilitation of TCA circulation, promotion of aerobic respiratory metabolism, and downregulation of succinic acid-related gene expression. Consistency between in vitro and in vivo results underscores dopamine's significant neuroprotective role in mitigating mitochondrial dysfunction following global cerebral hypoxia and ischemia injury. Supplement dopamine may represent a promising therapy to the cognitive impairment caused by GCI/R injury.

Effects of different doses of dopamine receptor agonist pramipexole on neurobehaviors and changes of mitochondrial membrane potentials in rats with global cerebral ischemia-reperfusion injury

OBJECTIVE

To explore the effects of different doses of dopamine receptor agonist pramipexole on neurobehaviors and changes of mitochondrial membrane potential in rats with global cerebral ischemia-reperfusion injury.

METHODS

A total of 75 SPF Sprague-Dawley male rats were randomly divided into sham group (n=20), model group (n=20), pramipexole administration group (n=35). The rat model of global cerebral ischemia-reperfusion injury was prepared by the modified Pulsinelli's four-vessel occlusion method. Pramipexole administration group was administered intraperitoneally in rats with global cerebral ischemia-reperfusion injury at different doses of pramipexole 0.25 mg/kg, 0.5 mg/kg, 1 mg/kg, 2 mg/kg, once a day for 14 consecutive days. Based on the results of modified neurological severity scores, open field test and morphology by Nissl's staining to determine the optimal dose of pramipexole. Mitochondrial membrane potential in the optimal dose of pramipexole administration group were measured by the JC-1 fluorescent probe staining method.

RESULTS

1. Different doses of pramipexole 0.25 mg/kg, 0.5 mg/kg, 1 mg/kg, and 2 mg/kg, were used as drug administration in rats with global cerebral ischemia-reperfusion injury for 14 consecutive days, and we found that all four doses of pramipexole could improve the modified neurological severity scores of rats with global cerebral ischemia-reperfusion injury to varying degrees, but only 0.5 mg/kg pramipexole at 1, 3, 7 and 14 days consistently reduced modified neurological severity scores and improved neurological function in rats with global cerebral ischemia-reperfusion injury. In the open-field test, only 0.5 mg/kg pramipexole increased the number of entries into the central zone, duration spent in the central zone, total distance travelled in the open field and average velocity, which improved the spontaneous activities and reduced anxiety and depression of rats with global cerebral ischemia-reperfusion injury. 2. Different doses of pramipexole 0.25 mg/kg, 0.5 mg/kg, 1 mg/kg, and 2 mg/kg for 14 consecutive days significantly increased the number of surviving neurons in the hippocampal CA1 subfield in rats with global cerebral ischemia-reperfusion injury to varying degrees. Based on these results, we tentatively found that 0.5 mg/kg pramipexole may be the optimal dose in all of the above. 3. We found that 0.5 mg/kg pramipexole significantly increased the mitochondrial membrane potential in rats after global cerebral ischemia-reperfusion injury.

CONCLUSION

Different doses of dopamine receptor agonist pramipexole improved neurological function of rats with global cerebral ischemia-reperfusion injury to varying degrees, and 0.5 mg/kg pramipexole may be the optimal dose in all of the above. Pramipexole may produce neuroprotective effects by protecting neurons in the hippocampus and improving the mitochondrial membrane potential after global cerebral ischemia-reperfusion injury.

Neuroprotective effects of Chrysanthemum morifolium on cerebral ischemia- reperfusion injury contributes to the oxidative stress suppression and related Keap1/Nrf2 pathway

BACKGROUND

Ischemic stroke, the cause of death and disability worldwide, is closely related to oxidative stress damage. Chrysanthemum has profound antiantioxidant activity. We aimed to verify whether Chrysanthemum morifolium extract (CME) influences brain injury in cerebral ischemia-reperfusion injury (CR/RI) model.

METHODS

In vitro, rat hippocampal H19-7 neurons were pretreated with CME, CR/RI was simulated with oxygen glucose deprivation/reoxygenation (OGD/R). The cell viability, apoptosis, lactate dehydrogenase release, reactive oxygen species (ROS) generation, malonaldehyde (MDA) content and superoxide dismutase（SOD） activity were detected. In vivo, middle cerebral artery occlusion (MCAO) model rats were pre-administered with CME, and then behavioral test, triphenyltetrazolium chloride (TTC), hematoxylin-eosin staining (HE), terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL), ROS immunofluorescence, MDA and SOD activity were tested. Furthermore, Keap1/Nrf2 signaling of CME in CI/RI was investigated.

RESULTS

In OGD/R induced in H19-7 cells, CME increased OGD/R-induced cell viability and reduced cell apoptosis, which was reversed by siNrf2 transfection . In MCAO rats, CME improved the neurological deficits and alleviated brain injury. However, co-treatment with MLK385 counteracted these neuroprotective effects of CME on MCAO rats.

CONCLUSION

CME could significantly reduce oxidative stress and nerve injury in vitro and in vivo models of CI/RI by regulating the Keap1/Nrf2 pathway.

Analysis of Three-Dimensional Cell Migration in Dopamine-Modified Poly(aspartic acid)-Based Hydrogels

Several types of promising cell-based therapies for tissue regeneration have been developing worldwide. However, for successful therapeutical application of cells in this field, appropriate scaffolds are also required. Recently, the research for suitable scaffolds has been focusing on polymer hydrogels due to their similarity to the extracellular matrix. The main limitation regarding amino acid-based hydrogels is their difficult and expensive preparation, which can be avoided by using poly(aspartamide) (PASP)-based hydrogels. PASP-based materials can be chemically modified with various bioactive molecules for the final application purpose. In this study, dopamine containing PASP-based scaffolds is investigated, since dopamine influences several cell biological processes, such as adhesion, migration, proliferation, and differentiation, according to the literature. Periodontal ligament cells (PDLCs) of neuroectodermal origin and SH-SY5Y neuroblastoma cell line were used for the in vitro experiments. The chemical structure of the polymers and hydrogels was proved by ¹H-NMR and FTIR spectroscopy. Scanning electron microscopical (SEM) images confirmed the suitable pore size range of the hydrogels for cell migration. Cell viability assay was carried out according to a standardized protocol using the WST-1 reagent. To visualize three-dimensional cell distribution in the hydrogel matrix, two-photon microscopy was used. According to our results, dopamine containing PASP gels can facilitate vertical cell penetration from the top of the hydrogel in the depth of around 4 cell layers (~150 μm). To quantify these observations, a detailed image analysis process was developed and firstly introduced in this paper.

Melatonin reshapes the mitochondrial network and promotes intercellular mitochondrial transfer via tunneling nanotubes after ischemic-like injury in hippocampal HT22 cells

Mitochondrial dysfunction is considered one of the hallmarks of ischemia/reperfusion injury. Mitochondria are plastic organelles that undergo continuous biogenesis, fusion, and fission. They can be transferred between cells through tunneling nanotubes (TNTs), dynamic structures that allow the exchange of proteins, soluble molecules, and organelles. Maintaining mitochondrial dynamics is crucial to cell function and survival. The present study aimed to assess the effects of melatonin on mitochondrial dynamics, TNT formation, and mitochondria transfer in HT22 cells exposed to oxygen/glucose deprivation followed by reoxygenation (OGD/R). The results showed that melatonin treatment during the reoxygenation phase reduced mitochondrial reactive oxygen species (ROS) production, improved cell viability, and increased the expression of PGC1α and SIRT3. Melatonin also preserved the expression of the membrane translocase proteins TOM20 and TIM23, and of the matrix protein HSP60, which are involved in mitochondrial biogenesis. Moreover, it promoted mitochondrial fusion and enhanced the expression of MFN2 and OPA1. Remarkably, melatonin also fostered mitochondrial transfer between injured HT22 cells through TNT connections. These results provide new insights into the effect of melatonin on mitochondrial network reshaping and cell survival. Fostering TNTs formation represents a novel mechanism mediating the protective effect of melatonin in ischemia/reperfusion injury.

Levodopa Improves Cognitive Function and the Deficits of Structural Synaptic Plasticity in Hippocampus Induced by Global Cerebral Ischemia/Reperfusion Injury in Rats

The cognitive impairment caused by cerebral ischemia/reperfusion is an unsolved problem in the field of international neural rehabilitation. Not only ameliorates the consciousness level of certain patients who suffered from ischemia-reperfusion injury and were comatose for a long time period after cerebral resuscitation treatment, but levodopa also improves the symptoms of neurological deficits in rats with global cerebral ischemia-reperfusion injury. However, Levodopa has not been widely used as a brain protection drug after cardiopulmonary resuscitation, because of its unclear repair mechanism. Levodopa was used to study the neuroplasticity in the hippocampus of global cerebral ischemia/reperfusion injury rat model, established by Pulsinelli's four-vessel occlusion method. Levodopa was injected intraperitoneally at 50 mg/kg/d for 7 consecutive days after 1st day of surgery. The modified neurological function score, Morris water maze, magnetic resonance imaging, Nissl and TH staining, electron microscopy and western blot were used in the present study. The results showed that levodopa improved the neurological function and learning and memory of rats after global cerebral ischemia/reperfusion injury, improved the integrity of white matter, and density of gray matter in the hippocampus, increased the number of synapses, reduced the delayed neuronal death, and increased the expression of synaptic plasticity-related proteins (BDNF, TrkB, PSD95, and Drebrin) in the hippocampus. In conclusion, levodopa can improve cognitive function after global cerebral ischemia/reperfusion injury by enhancing the synaptic plasticity in the hippocampus.

Possible involvement of D2/D3 receptor activation in ischemic preconditioning mediated protection of the brain

Ischemic stroke is a medical condition that arises because of poor blood supply to the brain. Reperfusion being salvage to the brain further causes, exacerbation of tissue injury, known as reperfusion injury. Ischemic preconditioning (IPC) has been known to provide benefits against ischemia reperfusion (I/R) injury. Dopamine D2/D3 receptor mediated several pathways are also reported as mediators in the IPC mediated neuroprotection. This study investigates the possible involvement of D2/D3 receptor activation in IPC mediated neuroprotection in the I/R brain. Global cerebral ischemia/reperfusion (GCI/R) injury in swiss albino mice was induced by occluding the common carotid arteries for 17 min, followed by 24 h reperfusion. IPC was provided by giving 3 episodes of I/R prior to Ischemia (17 min). Morris water maze (MWM) was used to assess the spatial learning, memory and Rota rod, lateral push test as well as inclined beam test were conducted to assess the motor functions in animals. Cerebral oxidative markers (thiobarbituric acid reactive species-TBARS, reduced glutathione-GSH, superoxide dismutase-SOD, and catalase-CAT), inflammatory markers (IL-6, IL-10, TNF-α, and myeloperoxidase-MPO), acetylcholinesterase activity-AChE, infarct size (% weight and % volume), and histopathological changes were also assessed. Haloperidol (0.05 mg/kg, i.p) was used to antagonize the effects of D2/D3 receptor activation. I/R animals showed reduction in memory, motor function, increase in cerebral oxidative stress, inflammation, AChE activity, infarct size and histopathological changes. Episodes of IPC prior to ischemia, attenuated the deleterious effects of I/R injury. Administration of haloperidol abolished the protective effects of IPC. Hence, it may be concluded that IPC mediated neuroprotection may involves dopamine D2/D3 receptor activation in mice.

Neuroprotective Mitochondrial Remodeling by AKAP121/PKA Protects HT22 Cell from Glutamate-Induced Oxidative Stress

Protein kinase A (PKA) is a ser/thr kinase that is critical for maintaining essential neuronal functions including mitochondrial homeostasis, bioenergetics, neuronal development, and neurotransmission. The endogenous pool of PKA is targeted to the mitochondrion by forming a complex with the mitochondrial scaffold A-kinase anchoring protein 121 (AKAP121). Enhanced PKA signaling via AKAP121 leads to PKA-mediated phosphorylation of the fission modulator Drp1, leading to enhanced mitochondrial networks and thereby blocking apoptosis against different toxic insults. In this study, we show for the first time that AKAP121/PKA confers neuroprotection in an in vitro model of oxidative stress induced by exposure to excess glutamate. Unexpectedly, treating mouse hippocampal progenitor neuronal HT22 cells with an acute dose or chronic exposure of glutamate robustly elevates PKA signaling, a beneficial compensatory response that is phenocopied in HT22 cells conditioned to thrive in the presence of excess glutamate but not in parental HT22 cells. Secondly, redirecting the endogenous pool of PKA by transiently transfecting AKAP121 or transfecting a constitutively active mutant of PKA targeted to the mitochondrion (OMM-PKA) or of an isoform of AKAP121 that lacks the KH and Tudor domains (S-AKAP84) are sufficient to significantly block cell death induced by glutamate toxicity but not in an oxygen deprivation/reperfusion model. Conversely, transient transfection of HT22 neuronal cells with a PKA-binding-deficient mutant of AKAP121 is unable to protect against oxidative stress induced by glutamate toxicity suggesting that the catalytic activity of PKA is required for AKAP121's protective effects. Mechanistically, AKAP121 promotes neuroprotection by enhancing PKA-mediated phosphorylation of Drp1 to increase mitochondrial fusion, elevates ATP levels, and elicits an increase in the levels of antioxidants GSH and superoxide dismutase 2 leading to a reduction in the level of mitochondrial superoxide. Overall, our data supports AKAP121/PKA as a new molecular target that confers neuroprotection against glutamate toxicity by phosphorylating Drp1, to stabilize mitochondrial networks and mitochondrial function and to elicit antioxidant responses.

miR-29b affects neurocyte apoptosis by targeting MCL-1 during cerebral ischemia/reperfusion injury

The present study aimed to determine whether an miRNA (miR)-29b inhibitor protected against cerebral ischemia/reperfusion (I/R) injury in vitro and to investigate the underlying mechanisms. As a model for induced cerebral IR injury, N2a cells were exposed to an oxygen-glucose deprivation/reoxygenation (OGD/R) environment. Using this model, it was demonstrated that miR-29b was significantly upregulated compared with cells in a normal environment. The interactions between miR-29b and myeloid cell leukemia sequence (MCL)-1 were then investigated using dual-luciferase assays, revealing a strong regulation of MCL-1 through the 3'untranslated region. Using the OGD/R model, the present study additionally examined the effects of miR-29b and miR-29b inhibitor on cell viability and apoptosis using Cell Counting kit 8 and flow cytometry assays, respectively. miR-29b transfection led to increased N2a cell apoptosis and reduced cell viability under an OGD/R environment. However, this effect was reversed by the miR-29b inhibitor. Finally, the effects of miR-29b on the expression of several Wnt-associating proteins were examined. It was observed that B cell lymphoma-2 was inhibited by miR-29b, as was MCL-1, whereas caspase-3 expression was promoted. The miR-29b inhibitor demonstrated the opposite effect. Overall, miR-29b promoted neurocyte apoptosis by targeting MCL-1 during cerebral I/R injury. The results of the present study suggest a potential novel therapeutic target for the treatment of ischemic stroke.

Expression profiles of long noncoding RNAs and mRNAs in post-cardiac arrest rat brains

To investigate long noncoding (lnc)-RNA and mRNA expression profiles in post-cardiac arrest (CA) brains, an external transthoracic electrical current was applied for 8 min to induce CA (the CA group). A total of 4 rats received sham-operations and served as the blank control (BC) group. Upon return of spontaneous circulation (ROSC), lncRNA and mRNA expression in the rat cerebral cortex was assayed with high-throughput Agilent lncRNA and mRNA microarrays. In total, 37 lncRNAs were upregulated and 21 lncRNAs were downregulated in the CA group, and 258 mRNA transcripts were differentially expressed with 177 mRNAs upregulated and 81 mRNAs downregulated in the CA group. The differentially expressed lncRNAs in the CA group were co-expressed with thousands of mRNAs. The differentially expressed lncRNAs could be clustered into >100 signaling pathways and processes according to Gene Ontology, and Kyoto Encyclopedia of Genes and Genomes analyses. The most common predicted functions involved metabolic pathways, protein synthesis, transport and degradation during CA-ROSC. CA-ROSC led to significant alterations in cerebral lncRNA and mRNA expression profiles. Thus, lncRNA-mRNA network interactions have the potential to regulate vital metabolic pathways and processes involved in CA-ROSC.

Levodopa improves learning and memory ability on global cerebral ischemia-reperfusion injured rats in the Morris water maze test

Previous studies have shown that levodopa (L-dopa) for 1-7days improved the consciousness level of certain patients who suffered from ischemia-reperfusion injury and were comatose for a long time period after cerebral resuscitation treatment. It also has an awakening effect on patients with disorders of consciousness. This study aimed to investigate whether L-dopa, which is used clinically to treat Parkinson's disease, might also ameliorate the behavior of rats following global cerebral ischemia-reperfusion injury. Fifty-six healthy adult male Sprague-Dawley rats were randomly divided into four groups: shamoperated, global cerebral ischemia mode, 25mg/kg/d L-dopa intervention, and 50mg/kg/d L-dopa intervention. The level of consciousness and modified neurological severity score (NSS) of the rats in each group were measured before reperfusion and 6, 24, and 72h and 1-4 weeks after reperfusion. The Morris water maze test was used to assess behavior of rats 1 week after reperfusion and 2 weeks after reperfusion in each group. The results showed that after global cerebral ischemiareperfusion injury, neurological deficits of rats are severe, and space exploration capacity and learning and memory capacity are significantly decreased. L-dopa can shorten the duration of coma in rats following global cerebral ischemia-reperfusion injury and improve the symptoms of neurological deficits and advanced learning and memory. In the range of the selected doses, the relationship between L-dopa and improvement of the neurological behavior in rats was not dose-dependent. Dopamine may be useful for treating severe ischemia-reperfusion brain injury.