Suppressing inflammatory cascade by cyclo-oxygenase inhibitors attenuates quinolinic acid induced Huntington's disease-like alterations in rats

Bacillus calmette gaurine vaccine ameliorates the neurotoxicity of quinolinic acid in rats via the modulation of antioxidant, inflammatory and apoptotic markers

A mutation in the Huntingtin gene causes 'Huntington's disease, which presents as a motor and behavioral impairment. Due to the limited drug therapy for this disease, scientists are constantly searching for newer and alternative drugs that may either retard or prevent the progress of the disease. This study aims to explore the neuroprotective potential of Bacillus Calmette Gaurine (BCG) vaccine against quinolinic acid-induced (QA) neurotoxicity in rats. QA (200 nmol/2 µl, i.s) was injected bilaterally into the rat striatum, after which a single dose of BCG (2 × 10^7, cfu) was given to the rats. Animals were assessed for behavioral parameters on the 14th and 21st days. On the 22nd day, animals were sacrificed, brains were harvested, and striatum was separated to evaluate biochemical, inflammatory, and apoptotic mediators. Histopathological studies were performed using Hematoxyline and Eosin staining to assess neuronal morphology. BCG treatment reversed motor abnormalities, reduced oxidative stress and neuroinflammatory markers, apoptotic mediators and striatal lesions induced by QA treatment. In conclusion, treat' 'ing rats with BCG vaccine (2 × 10^7, cfu) mitigated the quinolinic acid-induced Huntington's disease-like symptoms. Hence, BCG vaccine (2 ×10^7, cfu) could be used as an adjuvant in managing HD.

Meloxicam Targets COX-2/NOX1/NOX4/Nrf2 Axis to Ameliorate the Depression-like Neuropathology Induced by Chronic Restraint Stress in Rats

Meloxicam has shown significant neuroprotection in experimental models of stroke, Alzheimer's disease, and Parkinson's disease. However, the potential of meloxicam to treat depression-like neuropathology in a chronic restraint stress (CRS) model and the associated molecular changes has been insufficiently explored. The current work aimed to explore the potential neuroprotective actions of meloxicam against CRS-evoked depression in rats. In the current experiments, animals received meloxicam (10 mg/kg/day; i.p.) for 21 days, and CRS was instigated by restraining the animals for 6 h/day during the same period. The sucrose preference test and the forced swimming test were used to explore the depression-linked anhedonia/despair, whereas the open-field test examined the animals' locomotor activity. The current findings revealed that CRS elicited typical depression behavioral anomalies in the animals, including anhedonia, despair, and diminished locomotor activity; these findings were reinforced with Z-normalization scores. These observations were corroborated by brain histopathological changes and increased damage scores. In CRS-exposed animals, serum corticosterone spiked, and the hippocampi revealed decreased monoamine neurotransmitter levels (norepinephrine, serotonin, and dopamine). Mechanistically, neuroinflammation was evident in stressed animals, as shown by elevated hippocampal TNF-α and IL-1β cytokines. Moreover, the hippocampal COX-2/PGE₂ axis was activated in the rats, confirming the escalation of neuroinflammatory events. In tandem, the pro-oxidant milieu was augmented, as seen by increased hippocampal 8-hydroxy-2'-deoxyguanosine alongside increased protein expression of the pro-oxidants NOX1 and NOX4 in the hippocampi of stressed animals. In addition, the antioxidant/cytoprotective Nrf2/HO-1 cascade was dampened, as evidenced by the lowered hippocampal protein expression of Nrf2 and HO-1 signals. Interestingly, meloxicam administration mitigated depression manifestations and brain histopathological anomalies in the rats. These beneficial effects were elicited by meloxicam's ability to counteract the corticosterone spike and hippocampal neurotransmitter decrease while also inhibiting COX-2/NOX1/NOX4 axis and stimulating Nrf2/HO-1 antioxidant pathway. Together, the present findings prove the neuroprotective/antidepressant actions of meloxicam in CRS-induced depression by ameliorating hippocampal neuroinflammation and pro-oxidant changes, likely by modulating COX-2/NOX1/NOX4/Nrf2 axis.

Significance of Brain Glucose Hypometabolism, Altered Insulin Signal Transduction, and Insulin Resistance in Several Neurological Diseases

Several neurological diseases share pathological alterations, even though they differ in their etiology. Neuroinflammation, altered brain glucose metabolism, oxidative stress, mitochondrial dysfunction and amyloidosis are biological events found in those neurological disorders. Altered insulin-mediated signaling and brain glucose hypometabolism are characteristic signs observed in the brains of patients with certain neurological diseases, but also others such as type 2 diabetes mellitus and vascular diseases. Thus, significant reductions in insulin receptor autophosphorylation and Akt kinase activity, and increased GSK-3 activity and insulin resistance, have been reported in these neurological diseases as contributing to the decline in cognitive function. Supporting this relationship is the fact that nasal and hippocampal insulin administration has been found to improve cognitive function. Additionally, brain glucose hypometabolism precedes the unmistakable clinical manifestations of some of these diseases by years, which may become a useful early biomarker. Deficiencies in the major pathways of oxidative energy metabolism have been reported in patients with several of these neurological diseases, which supports the hypothesis of their metabolic background. This review remarks on the significance of insulin and brain glucose metabolism alterations as keystone common pathogenic substrates for certain neurological diseases, highlighting new potential targets.

Ginsenoside Rg1 exerts neuroprotective effects in 3-nitropronpionic acid-induced mouse model of Huntington's disease via suppressing MAPKs and NF-κB pathways in the striatum

Huntington's disease (HD) is one of main neurodegenerative diseases, characterized by striatal atrophy, involuntary movements, and motor incoordination. Ginsenoside Rg1 (Rg1), an active ingredient in ginseng, possesses a variety of neuroprotective effects with low toxicity and side effects. In this study, we investigated the potential therapeutic effects of Rg1 in a mouse model of HD and explored the underlying mechanisms. HD was induced in mice by injection of 3-nitropropionic acid (3-NP, i.p.) for 4 days. From the first day of 3-NP injection, the mice were administered Rg1 (10, 20, 40 mg·kg^-1, p.o.) for 5 days. We showed that oral pretreatment with Rg1 alleviated 3-NP-induced body weight loss and behavioral defects. Furthermore, pretreatment with Rg1 ameliorated 3-NP-induced neuronal loss and ultrastructural morphological damage in the striatum. Moreover, pretreatment with Rg1 reduced 3-NP-induced apoptosis and inhibited the activation of microglia, inflammatory mediators in the striatum. We revealed that Rg1 exerted neuroprotective effects by suppressing 3-NP-induced activation of the MAPKs and NF-κΒ signaling pathways in the striatum. Thus, our results suggest that Rg1 exerts therapeutic effects on 3-NP-induced HD mouse model via suppressing MAPKs and NF-κΒ signaling pathways. Rg1 may be served as a novel therapeutic option for HD.

Bioactive lipids, inflammation and chronic diseases

Endogenous bioactive lipids are part of a complex network that modulates a plethora of cellular and molecular processes involved in health and disease, of which inflammation represents one of the most prominent examples. Inflammation serves as a well-conserved defence mechanism, triggered in the event of chemical, mechanical or microbial damage, that is meant to eradicate the source of damage and restore tissue function. However, excessive inflammatory signals, or impairment of pro-resolving/anti-inflammatory pathways leads to chronic inflammation, which is a hallmark of chronic pathologies. All main classes of endogenous bioactive lipids - namely eicosanoids, specialized pro-resolving lipid mediators, lysoglycerophopsholipids and endocannabinoids - have been consistently involved in the chronic inflammation that characterises pathologies such as cancer, diabetes, atherosclerosis, asthma, as well as autoimmune and neurodegenerative disorders and inflammatory bowel diseases. This review gathers the current knowledge concerning the involvement of endogenous bioactive lipids in the pathogenic processes of chronic inflammatory pathologies.

Cyclic GMP-AMP synthase promotes the inflammatory and autophagy responses in Huntington disease

Huntington disease (HD) is a genetic disorder caused by glutamine-expansion in the huntingtin (mHTT) protein, which affects motor, psychiatric, and cognitive function, but the mechanisms remain unclear. mHTT is known to induce DNA damage and affect autophagy, both associated with inflammatory responses, but what mediates all these were unknown. Here we report that cGAS, a DNA damage sensor, is highly upregulated in the striatum of a mouse model and HD human patient’s tissue. We found ribosomes, which make proteins, are robustly accumulated on the cGAS mRNA in HD cells. cGAS depletion decreases—and cGAS expression increases—both inflammatory and autophagy responses in HD striatal cells. Thus, cGAS is a therapeutic target for HD. Blocking cGAS will prevent/slow down HD symptoms.

Huntington disease (HD) is caused by an expansion mutation of the N-terminal polyglutamine of huntingtin (mHTT). mHTT is ubiquitously present, but it induces noticeable damage to the brain’s striatum, thereby affecting motor, psychiatric, and cognitive functions. The striatal damage and progression of HD are associated with the inflammatory response; however, the underlying molecular mechanisms remain unclear. Here, we report that cGMP-AMP synthase (cGAS), a DNA sensor, is a critical regulator of inflammatory and autophagy responses in HD. Ribosome profiling revealed that the cGAS mRNA has high ribosome occupancy at exon 1 and codon-specific pauses at positions 171 (CCG) and 172 (CGT) in HD striatal cells. Moreover, the protein levels and activity of cGAS (based on the phosphorylated STING and phosphorylated TBK1 levels), and the expression and ribosome occupancy of cGAS-dependent inflammatory genes (Ccl5 and Cxcl10) are increased in HD striatum. Depletion of cGAS diminishes cGAS activity and decreases the expression of inflammatory genes while suppressing the up-regulation of autophagy in HD cells. In contrast, reinstating cGAS in cGAS-depleted HD cells activates cGAS activity and promotes inflammatory and autophagy responses. Ribosome profiling also revealed that LC3A and LC3B, the two major autophagy initiators, show altered ribosome occupancy in HD cells. We also detected the presence of numerous micronuclei, which are known to induce cGAS, in the cytoplasm of neurons derived from human HD embryonic stem cells. Collectively, our results indicate that cGAS is up-regulated in HD and mediates inflammatory and autophagy responses. Thus, targeting the cGAS pathway may offer therapeutic benefits in HD.

Design of selective COX-2 inhibitors in the (aza)indazole series. Chemistry, in vitro studies, radiochemistry and evaluations in rats of a [18F] PET tracer

A series of novel derivatives exhibiting high affinity and selectivity towards the COX-2 enzyme in the (aza) indazole series was developed. A short synthetic route involving a bromination/arylation sequence under microwave irradiation and direct C–H activation were established in the indazole and azaindazole series respectively. In vitro assays were conducted and structural modifications were carried out on these scaffolds to furnish compound 16 which exhibited effective COX-2 inhibitory activity, with IC₅₀ values of 0.409 µM and an excellent selectivity versus COX-1. Radiolabeling of this most potent derivative [¹⁸F]16 was achieved after boron ester release and the tracer was evaluated in vivo in a rat model of neuroinflammation. All chemistry, radiochemistry and biological experimental data are discussed.

Promises and pitfalls of immune-based strategies for Huntington's disease

Huntington's disease (HD) is an autosomal-dominant neurodegenerative disease characterized by the selective loss of neurons in the striatum and cortex, leading to progressive motor dysfunction, cognitive decline and behavioral symptoms. HD is caused by a trinucleotide (CAG) repeat expansion in the gene encoding for huntingtin. Several studies have suggested that inflammation is an important feature of HD and it is already observed in the early stages of the disease. Recently, new molecules presenting anti-inflammatory and/or immunomodulatory have been investigated for HD. The objective of this review is to discuss the data obtained so far on the immune-based therapeutic strategies for HD.

Quinolinic acid neurotoxicity: Differential roles of astrocytes and microglia via FGF-2-mediated signaling in redox-linked cytoskeletal changes

QUIN is a glutamate agonist playing a role in the misregulation of the cytoskeleton, which is associated with neurodegeneration in rats. In this study, we focused on microglial activation, FGF2/Erk signaling, gap junctions (GJs), inflammatory parameters and redox imbalance acting on cytoskeletal dynamics of the in QUIN-treated neural cells of rat striatum. FGF-2/Erk signaling was not altered in QUIN-treated primary astrocytes or neurons, however cytoskeleton was disrupted. In co-cultured astrocytes and neurons, QUIN-activated FGF2/Erk signaling prevented the cytoskeleton from remodeling. In mixed cultures (astrocyte, neuron, microglia), QUIN-induced FGF-2 increased level failed to activate Erk and promoted cytoskeletal destabilization. The effects of QUIN in mixed cultures involved redox imbalance upstream of Erk activation. Decreased connexin 43 (Cx43) immunocontent and functional GJs, was also coincident with disruption of the cytoskeleton in primary astrocytes and mixed cultures. We postulate that in interacting astrocytes and neurons the cytoskeleton is preserved against the insult of QUIN by activation of FGF-2/Erk signaling and proper cell-cell interaction through GJs. In mixed cultures, the FGF-2/Erk signaling is blocked by the redox imbalance associated with microglial activation and disturbed cell communication, disrupting the cytoskeleton. Thus, QUIN signal activates differential mechanisms that could stabilize or destabilize the cytoskeleton of striatal astrocytes and neurons in culture, and glial cells play a pivotal role in these responses preserving or disrupting a combination of signaling pathways and cell-cell interactions. Taken together, our findings shed light into the complex role of the active interaction of astrocytes, neurons and microglia in the neurotoxicity of QUIN.

Neuroimmunology of Huntington's Disease: Revisiting Evidence from Human Studies

Huntington's disease (HD) is a neurodegenerative disorder characterized by selective loss of neurons in the striatum and cortex, which leads to progressive motor dysfunction, cognitive decline, and psychiatric disorders. Although the cause of HD is well described—HD is a genetic disorder caused by a trinucleotide (CAG) repeat expansion in the gene encoding for huntingtin (HTT) on chromosome 4p16.3—the ultimate cause of neuronal death is still uncertain. Apart from impairment in systems for handling abnormal proteins, other metabolic pathways and mechanisms might contribute to neurodegeneration and progression of HD. Among these, inflammation seems to play a role in HD pathogenesis. The current review summarizes the available evidence about immune and/or inflammatory changes in HD. HD is associated with increased inflammatory mediators in both the central nervous system and periphery. Accordingly, there have been some attempts to slow HD progression targeting the immune system.

Inhibition of soluble tumor necrosis factor is therapeutic in Huntington's disease

Neuroinflammation is a common feature of many neurodegenerative diseases, including Huntington's disease (HD). HD is an autosomal dominant genetic disease caused by an expanded CAG repeat in exon 1 of the huntingtin (HTT) gene. Previous studies demonstrated that levels of several proinflammatory cytokines, including tumor necrosis factor (TNF)-α, were higher in the plasma and brain tissues of mice and patients with HD, suggesting that inflammation may contribute to HD progression. To evaluate the pathological role of TNF-α in HD pathogenesis, we blocked TNF-α signaling using a dominant negative inhibitor of soluble TNF-α (XPro1595). XPro1595 effectively suppressed the inflammatory responses of primary astrocytes-enriched culture isolated from a transgenic mouse model (R6/2) and human astrocytes-enriched culture derived from induced pluripotent stem cells (iPSCs) of HD patients evoked by lipopolysaccharide and cytokines, respectively. Moreover, XPro1595 protected the cytokine-induced toxicity of primary R6/2 neurons and human neurons derived from iPSCs of HD patients. To assess the beneficial effect of XPro1595 in vivo, an intracerebroventricular (i.c.v.) infusion was provided with an osmotic minipump. ELISA analyses showed that i.c.v. infusion of XPro1595 decreased elevated levels of TNFα in the cortex and striatum, improved motor function, reduced caspase activation, diminished the amount of mutant HTT aggregates, increased neuronal density and decreased gliosis in brains of R6/2 mice. Moreover, reducing the peripheral inflammatory response by a systemic injection of XPro1595 improved the impaired motor function of R6/2 mice but did not affect caspase activation. Collectively, our findings suggest that an effective and selective anti-inflammatory treatment targeting the abnormal brain inflammatory response is a potential therapeutic strategy for HD.

Minocycline modulates neuroprotective effect of hesperidin against quinolinic acid induced Huntington's disease like symptoms in rats: behavioral, biochemical, cellular and histological evidences

Emerging evidences indicate hesperidin, a citrus flavanone, attenuates neurodegenerative processes and related complications. Besides its anti-oxidant properties, the other probable mechanisms which underpin its neuroprotective potential are still not clear. In light of emerging role of flavonoids in modulating oxidative stress and neuro-inflammation, the study has been designed to explore the possible neuroprotective effect of hesperidin and its combination with minocycline (microglial inhibitor), against quinolinic acid (QA) induced Huntington's disease (HD) like symptoms in rats. Unilateral intrastriatal administration of QA (300 nmol/4 µl) significantly reduced body weight, impaired behavior (locomotor activity, beam balance and memory performance), caused oxidative damage (increased lipid peroxidation, nitrite concentration, depleted super oxide dismutase and reduced glutathione), demonstrated mitochondrial dysfunction (decreased Complex-I, II, III, and IV activities), increased striatal lesion volume and altered the levels of TNF-α, caspase-3 as well as BDNF expression, as compared to sham group. Meanwhile, chronic hesperidin (100mg/kg, p.o.) and minocycline (25mg/kg, p.o.) treatment for 21 days significantly attenuated the behavioral, biochemical and cellular alterations as compared to QA treated (control) animals, whereas hesperidin (50mg/kg, p.o.) treatment was found to be non-significant. However, treatment of hesperidin (50mg/kg) in combination with minocycline (25mg/kg) potentiated their neuroprotective effect, which was significant as compared to their effects per se in QA treated animals. Taken altogether, the results of the present study suggest a possible interplay of microglial modulation and anti-oxidant effect in neuroprotective potential of hesperidin against QA induced HD like symptoms in rats.

Quinolinic acid: an endogenous neurotoxin with multiple targets

Quinolinic acid (QUIN), a neuroactive metabolite of the kynurenine pathway, is normally presented in nanomolar concentrations in human brain and cerebrospinal fluid (CSF) and is often implicated in the pathogenesis of a variety of human neurological diseases. QUIN is an agonist of N-methyl-D-aspartate (NMDA) receptor, and it has a high in vivo potency as an excitotoxin. In fact, although QUIN has an uptake system, its neuronal degradation enzyme is rapidly saturated, and the rest of extracellular QUIN can continue stimulating the NMDA receptor. However, its toxicity cannot be fully explained by its activation of NMDA receptors it is likely that additional mechanisms may also be involved. In this review we describe some of the most relevant targets of QUIN neurotoxicity which involves presynaptic receptors, energetic dysfunction, oxidative stress, transcription factors, cytoskeletal disruption, behavior alterations, and cell death.

Brain insulin dysregulation: implication for neurological and neuropsychiatric disorders

Arduous efforts have been made in the last three decades to elucidate the role of insulin in the brain. A growing number of evidences show that insulin is involved in several physiological function of the brain such as food intake and weight control, reproduction, learning and memory, neuromodulation and neuroprotection. In addition, it is now clear that insulin and insulin disturbances particularly diabetes mellitus may contribute or in some cases play the main role in development and progression of neurodegenerative and neuropsychiatric disorders. Focusing on the molecular mechanisms, this review summarizes the recent findings on the involvement of insulin dysfunction in neurological disorders like Alzheimer's disease, Parkinson's disease and Huntington's disease and also mental disorders like depression and psychosis sharing features of neuroinflammation and neurodegeneration.

Role of prostaglandins in neuroinflammatory and neurodegenerative diseases

Increasing data demonstrates that inflammation participates in the pathophysiology of neurodegenerative diseases. Among the different inflammatory mediators involved, prostaglandins play an important role. The effects induced by prostaglandins might be mediated by activation of their known receptors or by nonclassical mechanisms. In the present paper, we discuss the evidences that link prostaglandins, as well as the enzymes that produce them, to some neurological diseases.

Meloxicam Modulates Oxidative Stress Status, Inhibits Prostaglandin E2, and Abrogates Apoptosis in Carbon Tetrachloride–Induced Rat Hepatic Injury

The current study aimed at investigating the potential hepatoprotective property and mechanism of meloxicam (MEL) against carbon tetrachloride (CCl4)-induced hepatocellular damage in rats. Subcutaneous administration of CCl4 (2 mL/kg, twice/week for 8 weeks) induced hepatocellular damage substantiated by hematoxylin and eosin staining and significant elevation in serum aspartate transaminase, alanine transaminase, and total bilirubin. In addition, CCL4 treatment led to elevation in liver contents of lipid peroxidation marker (malondialdehyde), prostaglandin E2, active caspase 3, and Terminal deoxynucleotidyl transferase dUTP nick end labeling–positive cells and reduction in the activities of superoxide dismutase, catalase, glutathione- S-transferase, and reduced glutathione in the liver tissue. Prior oral treatment with MEL (5 mg/kg, twice/week) retained the normal liver histology and significantly restored all of these parameters close to normal values. These results demonstrated the hepatoprotective utility of MEL against the CCl4-induced liver injury which might ascribe to its antioxidant, free radical scavenging, antiapoptotic and anti-inflammatory effects.