The possible role of CREB-BDNF signaling pathway in neuroprotective effects of minocycline against alcohol-induced neurodegeneration: molecular and behavioral evidences

DAPK1 mediates cognitive dysfunction and neuronal apoptosis in PSD rats through the ERK/CREB/BDNF signaling pathway

Post-stroke depression (PSD) is one of the most common mental sequelae after a stroke and can damage the brain. Although PSD has garnered increasing attention in recent years, the precise mechanism remains unclear. Studies have indicated that the expression of DAPK1 is elevated in various neurodegenerative conditions, including depression, ischemic stroke, and Alzheimer's disease. However, the specific molecular mechanism of DAPK1-mediated cognitive dysfunction and neuronal apoptosis in PSD rats is unclear. In this study, we established a rat model of PSD, and then assessed depression-like behaviors and cognitive dysfunction in rats using behavioral tests. In addition, we detected neuronal apoptosis and analyzed the expression of DAPK1 protein and proteins related to the ERK/CREB/BDNF signaling pathway. The findings revealed that MCAO combined with CUMS can induce more severe depression-like behaviors and cognitive dysfunction in rats, while overexpression of DAPK1 may hinder the downstream ERK/CREB/BDNF signaling pathways, resulting in neuronal loss and exacerbation of brain tissue damage. In this study, we will focus on DAPK1 and explore its role in PSD.

Neuroprotective potential of trimetazidine against tramadol-induced neurotoxicity: role of PI3K/Akt/mTOR signaling pathways

Tramadol (TRA) causes neurotoxicity whereas trimetazidine (TMZ) is neuroprotective. The potential involvement of the PI3K/Akt/mTOR signaling pathway in the neuroprotection of TMZ against TRA-induced neurotoxicity was evaluated. Seventy male Wistar rats were divided into groups. Groups 1 and 2 received saline or TRA (50 mg/kg). Groups 3, 4, and 5 received TRA (50 mg/kg) and TMZ (40, 80, or 160 mg/kg) for 14 days. Group 6 received TMZ (160 mg/kg). Hippocampal neurodegenerative, mitochondrial quadruple complex enzymes, phosphatidylinositol-3-kinases (PI3Ks)/protein kinase B levels, oxidative stress, inflammatory, apoptosis, autophagy, and histopathology were evaluated. TMZ decreased anxiety and depressive-like behavior induced by TRA. TMZ in tramadol-treated animals inhibited lipid peroxidation, GSSG, TNF-α, and IL-1β while increasing GSH, SOD, GPx, GR, and mitochondrial quadruple complex enzymes in the hippocampus. TRA inhibited Glial fibrillary acidic protein expression and increased pyruvate dehydrogenase levels. TMZ reduced these changes. TRA decreased the level of JNK and increased Beclin-1 and Bax. TMZ decreased phosphorylated Bcl-2 while increasing the unphosphorylated form in tramadol-treated rats. TMZ activated phosphorylated PI3Ks, Akt, and mTOR proteins. TMZ inhibited tramadol-induced neurotoxicity by modulating the PI3K/Akt/mTOR signaling pathways and its downstream inflammatory, apoptosis, and autophagy-related cascades.

Minocycline alleviated scopolamine-induced amnesia by regulating antioxidant and cholinergic function

Background and aim

Minocycline, a tetracycline derivative, has been found to exert neuroprotective properties. The current project aimed to assess the antioxidant status and cholinergic function in the amnesia induced by scopolamine.

Methods

We evaluated the passive avoidance performance, acetylcholine esterase (AChE) enzyme activity, and the oxidative stress indicators in the following groups: Normal control, scopolamine, and the treatment groups (the animals were given minocycline (10-30 mg/kg)).

Results

Scopolamine (intraperitoneal) injection was associated with impairment of passive avoidance performance and neurotoxicity. Minocycline pronouncedly ameliorated scopolamine injury as presented by the increased latency time to darkness and stay time in lightness along with the decreased darkness entry. Moreover, minocycline decreased lipid peroxidation, while it elevated the levels of superoxide dismutase, AChE enzymes, and thiol groups in both the cortex and hippocampus.

Conclusion

Our data suggested that minocycline modulated the antioxidant status and AChE in the brains, which may contribute to its protective effects against scopolamine-induced amnesia.

Minocycline Protects Against Lipopolysaccharide-Induced Cognitive Impairment and Oxidative Stress: Possible Role of the CREB-BDNF Signaling Pathway

The oxidative stress-induced dysregulation of the cyclic AMP response element-binding protein- brain-derived neurotrophic factor (CREB-BDNF) cascade has been linked to cognitive impairment in several studies. This study aimed to investigate the effect of minocycline on the levels of oxidative stress markers, CREB, and BDNF in lipopolysaccharide (LPS)-induced cognitive impairment. Fifty adult male Sprague Dawley rats were divided randomly into five groups. Group 1 was an untreated control group. Groups 2, 3, 4 and 5 were treated concurrently with LPS (5 mg/kg, i.p) once on day 5 and normal saline (0.7 ml/rat, i.p) or minocycline (25 and 50 mg/kg, i.p) or memantine (10 mg/kg, i.p) once daily from day 1 until day 14, respectively. From day 15 to day 22 of the experiment, Morris Water Maze (MWM) was used to evaluate learning and reference memory in rats. The levels of protein carbonyl (PCO), malondialdehyde (MDA), catalase (CAT), and superoxide dismutase (SOD) were determined by enzyme-linked immunosorbent assay (ELISA). CREB and BDNF expression and density were measured by immunohistochemistry and western blot analysis, respectively. LPS administration significantly increased escape latency to the hidden platform with decreased travelled distance, swimming speed, target crossings and time spent in the target quadrant. Besides, the hippocampal tissue of LPS rats showed increased levels of PCO and MDA, decreased levels of CAT and SOD, and reduced expression and density of BDNF and CREB. Treatment with minocycline reversed these effects in a dose-dependent manner, comparable to the effects of memantine. Both doses of minocycline treatment protect against LPS-induced cognitive impairment by reducing oxidative stress and upregulating the CREB-BDNF signalling pathway in the rat hippocampus.

Amyloid β-Peptide Causes the Permanent Activation of CaMKIIα through Its Oxidation

Alzheimer's disease (AD) is characterised by the presence of extracellular amyloid plaques in the brain. They are composed of aggregated amyloid beta-peptide (Aβ) misfolded into beta-sheets which are the cause of the AD memory impairment and dementia. Memory depends on the hippocampal formation and maintenance of synapses by long-term potentiation (LTP), whose main steps are the activation of NMDA receptors, the phosphorylation of CaMKIIα and the nuclear translocation of the transcription factor CREB. It is known that Aβ oligomers (oAβ) induce synaptic loss and impair the formation of new synapses. Here, we have studied the effects of oAβ on CaMKIIα. We found that oAβ produce reactive oxygen species (ROS), that induce CaMKIIα oxidation in human neuroblastoma cells as we assayed by western blot and immunofluorescence. Moreover, this oxidized isoform is significantly present in brain samples from AD patients. We found that the oxidized CaMKIIα is active independently of the binding to calcium/calmodulin, and that CaMKIIα phosphorylation is mutually exclusive with CaMKIIα oxidation as revealed by immunoprecipitation and western blot. An in silico modelling of the enzyme was also performed to demonstrate that oxidation induces an activated state of CaMKIIα. In brains from AD transgenic models of mice and in primary cultures of murine hippocampal neurons, we demonstrated that the oxidation of CaMKIIα induces the phosphorylation of CREB and its translocation to the nucleus to promote the transcription of ARC and BDNF. Our data suggests that CaMKIIα oxidation would be a pro-survival mechanism that is triggered when a noxious stimulus challenges neurons as do oAβ.

Melatonin Protects Against Titanium Oxide-Induced Neurotoxicity: Neurochemical, Neurobehavioral, and Histopathological Evidences

titania (titanium dioxide, TiO₂) is known to induce neurotoxicity and CNS dysfunctions. Numerous studies have explored the neuroprotective effects of melatonin against neurotoxicity. This study evaluates the potential of melatonin to protect against titania-induced neurotoxicity and the role of the Keap1/Nrf2/ARE signaling pathway. One group of animals were treated with Titania (0.045 and 0.075 g/rat) alone while the other with added melatonin (1 mg/kg and 3 mg/kg) and behavioral alterations were assessed using OFT (open field test). Neurochemical and histopathological changes were also studied in the hippocampus by analyzing kelch ECH associating protein 1 (Keap1), nuclear factor erythroid 2-related factor 2 (Nrf2), and antioxidant response element (ARE). It was seen that the animals with added Melatonin had improved behavioral scores in the OFT, like anxiety and motor dysfunction triggered by TiO₂. Melatonin also reduced lipid peroxidation, ROS, GSSG, IL1β, TNFα, Bax, and Keap1 levels, but boosted GSH, GPx, GR, SOD,IL10,IL4, Bcl2, Nrf2, and ARE levels and improved quadruple mitochondrial enzyme complex activity in titania-treated animals. Histopathological examination showed melatonin induced cytoprotection against vacuolization and necrosis in granular cells of DG and pyramidal cells of CA1 area of the hippocampus. In our study, pretreatment with melatonin reduced titania-induced neurotoxicity in the hippocampus through a mechanism potentially mediated by the Keap-1/Nrf2/ARE pathway.

Neuroprotective Properties of Minocycline Against Methylphenidate-Induced Neurodegeneration: Possible Role of CREB/BDNF and Akt/GSK3 Signaling Pathways in Rat Hippocampus

Neurodegeneration is a side effect of methylphenidate (MPH), and minocycline possesses neuroprotective properties. This study aimed to investigate the neuroprotective effects of minocycline against methylphenidate-induced neurodegeneration mediated by signaling pathways of CREB/BDNF and Akt/GSK3. Seven groups of seventy male rats were randomly distributed in seven groups (n = 10). Group 1 received 0.7 ml/rat of normal saline (i.p.), and group 2 was treated with MPH (10 mg/kg, i.p.). Groups 3, 4, 5, and 6 were simultaneously administered MPH (10 mg/kg) and minocycline (10, 20, 30, and 40 mg/kg, i.p.) for 21 days. Minocycline alone (40 mg/kg, i.p.) was administrated to group 7. Open field test (OFT) (on day 22), forced swim test (FST) (on day 24), and elevated plus maze (on day 26) were conducted to analyze the mood-related behaviors; hippocampal oxidative stress, inflammatory, and apoptotic parameters, as well as the levels of protein kinase B (Akt-1), glycogen synthase kinase 3 (GSK3), cAMP response element-binding protein (CREB), and brain-derived neurotrophic factor (BDNF), were also assessed. Furthermore, localization of total CREB, Akt, and GSK3 in the DG and CA1 areas of the hippocampus were measured using immunohistochemistry (IHC). Histological changes in the mentioned areas were also evaluated. Minocycline treatment inhibited MPH-induced mood disorders and decreased lipid peroxidation, oxidized form of glutathione (GSSG), interleukin 1 beta (IL-1β), alpha tumor necrosis factor (TNF-α), Bax, and GSK3 levels. In the contrary, it increased the levels of reduced form of glutathione (GSH), Bcl-2, CREB, BDNF, and Akt-1 and superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR) activities in the experimental animals' hippocampus. IHC data showed that minocycline also improved the localization and expression of CREB and Akt positive cells and decreased the GSK3 positive cells in the DG and CA1 regions of the hippocampus of MPH-treated rats. Minocycline also inhibited MPH-induced changes of hippocampal cells' density and shape in both DG and CA1 areas of the hippocampus. According to obtained data, it can be concluded that minocycline probably via activation of the P-CREB/BDNF or Akt/GSK3 signaling pathway can confer its neuroprotective effects against MPH-induced neurodegeneration.

Moderate blood alcohol and brain neurovulnerability: Selective depletion of calcium-independent phospholipase A2, omega-3 docosahexaenoic acid, and its synaptamide derivative as a potential harbinger of deficits in anti-inflammatory reserve

BACKGROUND

Repetitive, highly elevated blood alcohol (ethanol) concentrations (BACs) of 350 to 450 mg/dl over several days cause brain neurodegeneration and coincident neuroinflammation in adult rats localized in the hippocampus (HC), temporal cortex (especially the entorhinal cortex; ECX), and olfactory bulb (OB). The profuse neuroinflammation involves microgliosis, increased proinflammatory cytokines, and elevations of Ca+2 -dependent phospholipase A2 (cPLA2) and secretory PLA2 (sPLA2), which both mobilize proinflammatory ω-6 arachidonic acid (ARA). In contrast, Ca+2 -independent PLA2 (iPLA2) and anti-inflammatory ω-3 docosahexaenoic acid (DHA), a polyunsaturated fatty acid regulated primarily by iPLA2, are diminished. Furthermore, supplemented DHA exerts neuroprotection. Given uncertainties about the possible effects of lower circulating BACs that are common occurring during short- term binges, we examined how moderate BACs affected the above inflammatory events, and the impact of supplemented DHA.

METHODS AND RESULTS

Young adult male rats sustaining upper-moderate BACs (~150 mg/dl) from once-daily alcohol intubations were sacrificed with appropriate controls after 1 week. The HC, ECX and OB were quantitatively examined using immunoblotting, neurodegeneration staining, and lipidomics assays. Whereas neurodegeneration, increases in cPLA2 IVA, sPLA2 IIA, and ARA, and microglial activation were not detected, the HC and ECX regions demonstrated significantly reduced iPLA2 levels. Levels of DHA and synaptamide, its anti-inflammatory N-docosahexaenoylethanolamide derivative, also were lower in HC, and DHA supplementation prevented the iPLA2 decrements in HC. Additionally, adult mice maintaining upper-moderate BACs from limited alcohol binges had reduced midbrain iPLA2 levels.

CONCLUSIONS

The apparently selective depletion by moderate BACs of the metabolically linked anti-inflammatory triad of hippocampal iPLA2, DHA, and synaptamide, and of iPLA2 in the ECX, potentially indicates an unappreciated deficit in brain anti-inflammatory reserve that may be a harbinger of regional neurovulnerability.

Teratogenic effects of maternal drug abuse on developing brain and underlying neurotransmitter mechanisms

The aim of this review is to highlight our knowledge of the various drugs of abuse that can prove potential teratogens affecting the brain and cognitive development in an individual exposed to maternal consumption of such agents. Among several drugs of abuse in women, we specifically highlighted the commonly used alcohol, nicotine, opioids, cannabis, cocaine and marijuana. These drugs can affect the fetal development and slow the cognitive maturation apart from physical disabilities. However, no known therapy exists to counter the toxic potential of these drugs. Several researchers used animal models of drug abuse to understand the underlying mechanisms affecting brain development and the relevant neurotransmitter system. Identifying such targets can potentially help in drug discovery research. We reported in depth analysis of such mechanisms and discussed the potential targets for drug development research.

The effect of microglial inhibition on the expression of BDNF, KCC2, and GABAA receptor before and after the establishment of CCI-induced neuropathic pain model

Damage to the peripheral or central nervous system results in neuropathic pain. Based on a complicated mechanism, neuropathic pain has no efficient treatment so far. It has been well-known that the expression of some proteins (BDNF, KCC2, GABA-A) during neuropathic pain changes. Microglial cell activation is considered as a trigger to alter the expression of these proteins. In the current study, the effect of minocycline as a potent microglial activation inhibitor on the gene and protein expression of these neuropathic pain mediators was investigated. This experiment was done in two paradigms, preinjury and postinjury administration of minocycline. In each paradigm, male Wistar rats (weight 150-200 g, n = 6) were allocated to sham, control, and drug groups. Minocycline (30 mg/kg, i.p.) was injected 1 h before or at day seven after nerve injury and continued till day 14 in the preemptive or postinjury part of the study, respectively. After the last injection, the animals were decapitated and the lumbar part of the spinal cord was isolated to assess the expression of genes and proteins of interest. In the preventive study, minocycline increased the expression of KCC2 and GABA-A/γ₂ proteins and decreased BDNF expression. On the other hand, the target gene expression and protein expression were not changed when minocycline was administered after nerve injury. It seems that minocycline was able to change the expression of proteins of interest merely when used before nerve damage.

Acupuncture Alleviates Anxiety and 22-kHz Ultrasonic Vocalizations in Rats Subjected to Repeated Alcohol Administration by Modulating the Brain-Derived Neurotrophic Factor/Corticotropin-Releasing Hormone Signaling Pathway

The Shenmen point (acupuncture point heart 7: HT7), located in the heart meridian, is frequently used to treat mental disorders, including drug addiction, anxiety, and depression. This study aimed to determine how HT7 regulates anxiety and negative emotions caused by repeated alcohol administration, focusing on the amygdala and paraventricular nucleus (PVN). Repeated administration of alcohol (ETOH; 2 g/kg, i.p. injection, 16% v/v) for 14 days increased the corticosterone (CORT) levels, and HT7 stimulation reduced the plasma CORT levels. HT7 stimulation mitigated anxiety-like behaviors and reduced 22-kHz ultrasonic vocalizations in rats receiving repeated ETOH injections. HT7 stimulation increased the amygdala expression of mature brain-derived neurotropic factor (mBDNF) and phosphorylated tropomyosin receptor kinase B (pTrkB) and decreased the PVN corticotropin-releasing hormone (CRH) expression. Amygdala microinjections of the TrkB antagonist ANA-12 (0.1 pmol/1 μL) reversed the increase in PVN CRH levels. The reduced PVN CRH levels were regulated by CRH-expressing neurons in the amygdala, and the increased amygdala CRH levels were affected by the HT7-stimulation induced increases in mBDNF. HT7 stimulation alleviates increased stress hormone levels and mitigates anxiety and negative emotions caused by repeated ETOH administration. These results provide scientific support for the clinical use of acupuncture to treat various alcoholism-induced diseases.