The benefits of neuroinflammation for the repair of the injured central nervous system

Modulation of MicroRNAs as a Potential Molecular Mechanism Involved in the Beneficial Actions of Physical Exercise in Alzheimer Disease

Alzheimer disease (AD) is one of the most common neurodegenerative diseases, affecting middle-aged and elderly individuals worldwide. AD pathophysiology involves the accumulation of beta-amyloid plaques and neurofibrillary tangles in the brain, along with chronic neuroinflammation and neurodegeneration. Physical exercise (PE) is a beneficial non-pharmacological strategy and has been described as an ally to combat cognitive decline in individuals with AD. However, the molecular mechanisms that govern the beneficial adaptations induced by PE in AD are not fully elucidated. MicroRNAs are small non-coding RNAs involved in the post-transcriptional regulation of gene expression, inhibiting or degrading their target mRNAs. MicroRNAs are involved in physiological processes that govern normal brain function and deregulated microRNA profiles are associated with the development and progression of AD. It is also known that PE changes microRNA expression profile in the circulation and in target tissues and organs. Thus, this review aimed to identify the role of deregulated microRNAs in the pathophysiology of AD and explore the possible role of the modulation of microRNAs as a molecular mechanism involved in the beneficial actions of PE in AD.

Astrocyte- and Neuron-Derived Extracellular Vesicles from Alzheimer's Disease Patients Effect Complement-Mediated Neurotoxicity

We have previously shown that blood astrocytic-origin extracellular vesicles (AEVs) from Alzheimer’s disease (AD) patients contain high complement levels. To test the hypothesis that circulating EVs from AD patients can induce complement-mediated neurotoxicity involving Membrane Attack Complex (MAC) formation, we assessed the effects of immunocaptured AEVs (using anti-GLAST antibody), in comparison with neuronal-origin (N)EVs (using anti-L1CAM antibody), and nonspecific CD81+ EVs (using anti-CD81 antibody), from the plasma of AD, frontotemporal lobar degeneration (FTLD), and control participants. AEVs (and, less effectively, NEVs) of AD participants induced Membrane Attack Complex (MAC) expression on recipient neurons (by immunohistochemistry), membrane disruption (by EthD-1 assay), reduced neurite density (by Tuj-1 immunohistochemistry), and decreased cell viability (by MTT assay) in rat cortical neurons and human iPSC-derived neurons. Demonstration of decreased cell viability was replicated in a separate cohort of autopsy-confirmed AD patients. These effects were not produced by CD81+ EVs from AD participants or AEVs/NEVs from FTLD or control participants, and were suppressed by the MAC inhibitor CD59 and other complement inhibitors. Our results support the stated hypothesis and should motivate future studies on the roles of neuronal MAC deposition and AEV/NEV uptake, as effectors of neurodegeneration in AD.

Neuroprotective and Anti-Neuroinflammatory Effects of a Poisonous Plant Croton Tiglium Linn. Extract

Neuroinflammation is involved in various neurological diseases. Activated microglia secrete many pro-inflammatory factors and induce neuronal cell death. Thus, the inhibition of excessive proinflammatory activity of microglia leads to a therapeutic effect that alleviates the progression of neuronal degeneration. In this study, we investigated the effect of Croton tiglium (C. tiglium) Linn. extract (CTE) on the production of pro- and anti-inflammatory mediators in microglia and astrocytes via RT-PCR, Western blot, and nitric oxide assay. Neurotoxicity was measured by cell viability assay and GFP image analysis. Phagocytosis of microglia was measured using fluorescent zymosan particles. CTE significantly inhibited the production of neurotoxic inflammatory factors, including nitric oxide and tumor necrosis factor-α. In addition, CTE increased the production of the neurotrophic factor, brain-derived neurotrophic factor, and the M2 phenotype of microglia. The culture medium retained after CTE treatment increased the survival of neurons, thereby indicating the neuroprotective effect of CTE. Our findings indicated that CTE inhibited pro-inflammatory response and increased the neuroprotective ability of microglia. In conclusion, although CTE is known to be a poisonous plant and listed on the FDA poisonous plant database, it can be used as a medicine if the amount is properly controlled. Our results suggested the potential benefits of CTE as a therapeutic agent for different neurodegenerative disorders involving neuroinflammation.

L-Type Amino Acid Transporter 1-Utilizing Prodrugs of Ketoprofen Can Efficiently Reduce Brain Prostaglandin Levels

In order to efficiently combat neuroinflammation, it is essential to deliver the anti-inflammatory drugs to their target sites in the brain. Pro-drugs utilizing the L-type amino acid transporter 1 (LAT1) can be transported across the blood-brain barrier (BBB) and the cellular barriers of the brain’s parenchymal cells. In this study, we evaluated, for the first time, the efficacy of LAT1-utilizing prodrugs of ketoprofen (KPF) on cyclooxygenase (COX) enzymes in vitro and prostaglandin E2 production in vivo by using an enzymatic assay and liquid chromatography- tandem mass spectrometry method, respectively. Aliphatic amino acid-conjugated pro-drugs inhibited the peroxidase activity of COX in vitro in their intact form (85% inhibition, IC50 ≈ 1.1 µM and 79%, IC50 ≈ 2.3 µM), which was comparable to KPF (90%, IC50 ≈ 0.9). Thus, these compounds acted more as KPF derivatives rather than pro-drugs. In turn, aromatic amino acid-conjugated pro-drugs behaved differently. The ester pro-drug inhibited the COX peroxidase activity in vitro (90%, IC50 ≈ 0.6 µM) due to its bioconversion to KPF, whereas the amide pro-drug was inactive toward COX enzymes in vitro. However, the amide pro-drug released KPF in the mouse brain in sufficient and effective amounts measured as reduced PGE2 levels.

Neuroinflammation: An overview of neurodegenerative and metabolic diseases and of biotechnological studies

Neuroinflammation is an important factor contributing to cognitive impairment and neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), Amyotrophic lateral sclerosis (ALS), ischemic injury, and multiple sclerosis (MS). These diseases are characterized by inexorable progressive injury of neuron cells, and loss of motor or cognitive functions. Microglia, which are the resident macrophages in the brain, play an important role in both physiological and pathological conditions. In this review, we provide an updated discussion on the role of ROS and metabolic disease in the pathological mechanisms of activation of the microglial cells and release of cytotoxins, leading to the neurodegenerative process. In addition, we also discuss in vivo models, such as zebrafish and Caenorhabditis elegans, and provide new insights into therapeutics bioinspired by neuropeptides from venomous animals, supporting high throughput drug screening in the near future, searching for a complementary approach to elucidating crucial mechanisms associated with neurodegenerative disorders.

Microglia and macrophage phenotypes in intracerebral haemorrhage injury: therapeutic opportunities

The prognosis of intracerebral haemorrhage continues to be devastating despite much research into this condition. A prominent feature of intracerebral haemorrhage is neuroinflammation, particularly the excessive representation of pro-inflammatory CNS-intrinsic microglia and monocyte-derived macrophages that infiltrate from the circulation. The pro-inflammatory microglia/macrophages produce injury-enhancing factors, including inflammatory cytokines, matrix metalloproteinases and reactive oxygen species. Conversely, the regulatory microglia/macrophages with potential reparative and anti-inflammatory roles are outcompeted in the early stages after intracerebral haemorrhage, and their beneficial roles appear to be overwhelmed by pro-inflammatory microglia/macrophages. In this review, we describe the activation of microglia/macrophages following intracerebral haemorrhage in animal models and clinical subjects, and consider their multiple mechanisms of cellular injury after haemorrhage. We review strategies and medications aimed at suppressing the pro-inflammatory activities of microglia/macrophages, and those directed at elevating the regulatory properties of these myeloid cells after intracerebral haemorrhage. We consider the translational potential of these medications from preclinical models to clinical use after intracerebral haemorrhage injury, and suggest that several approaches still lack the experimental support necessary for use in humans. Nonetheless, the preclinical data support the use of deactivator or inhibitor of pro-inflammatory microglia/macrophages, whilst enhancing the regulatory phenotype, as part of the therapeutic approach to improve the prognosis of intracerebral haemorrhage.

The lncRNA Malat1 functions as a ceRNA to contribute to berberine-mediated inhibition of HMGB1 by sponging miR-181c-5p in poststroke inflammation

Long non-coding RNAs (lncRNAs) have been identified as essential mediators in neurological dysfunction. Our previous study shows that berberine (BBR) hampers the nuclear-to-cytosolic translocation of high-mobility group box 1 (HMGB1) in the process of poststroke inflammation. In this study, we explored the role of lncRNA metastasis-associated lung adenocarcinoma transcript 1 (Malat1) in the process of BBR-induced inhibition of HMGB1 in ischemic brain. Before the 60-min MCAO surgery, the mice were pretreated with BBR (50 mg· kg^-1 per day, ig) for 14 days or ICV injected with specific lentiviral vector or shRNA. We showed that MCAO caused marked increase in the expression Malat1 and HMGB1 in the ipsilateral cortex, which was significantly attenuated by pretreatment with BBR. Knockdown of Malat1 attenuated the inflammatory injury after brain ischemia, whereas overexpression of Malat1 exacerbated ischemic brain inflammation. Overexpression of Malat1 also reversed BBR-induced reduction of HMGB1 and proinflammatory cytokines. The above results suggested a potential correlation between Malat1 and stroke inflammation. Based on informatics analysis we predicted that HMGB1 was a direct downstream target of miR-181c-5p, whereas Malat1 acted as a competitive endogenous RNA (ceRNA) for miR-181c-5p targeted the 3'-UTR of HMGB1 to promote inflammation after ischemic stroke. Knockdown of Malat1 significantly decreased HMGB1 level, which could be abrogated by transfection with miR-181c-5p inhibitors. Taken together, our results demonstrate for the first time that Malat1/miR-181c-5p/HMGB1 axis may be a key pathway of BBR-induced antiinflammation effects in stroke, and they may provide a novel avenue for targeted therapy.

Acute Spinal Cord Injury: A Systematic Review Investigating miRNA Families Involved

Acute traumatic spinal cord injury (SCI) involves primary and secondary injury mechanisms. The primary mechanism is related to the initial traumatic damage caused by the damaging impact and this damage is irreversible. Secondary mechanisms, which begin as early as a few minutes after the initial trauma, include processes such as spinal cord ischemia, cellular excitotoxicity, ionic dysregulation, and free radical-mediated peroxidation. SCI is featured by different forms of injury, investigating the pathology and degree of clinical diagnosis and treatment strategies, the animal models that have allowed us to better understand this entity and, finally, the role of new diagnostic and prognostic tools such as miRNA could improve our ability to manage this pathological entity. Autopsy could benefit from improvements in miRNA research: the specificity and sensitivity of miRNAs could help physicians in determining the cause of death, besides the time of death.