Melatonin and zinc supplements with physical and mental activities subside neurodegeneration and hepatorenal injury induced by aluminum chloride in rats: Inclusion of GSK-3β-Wnt/β-catenin signaling pathway

Melatonin ameliorates inflammation-induced developmental defects of enamel by upregulating regulator of G protein signaling 2

Background/purpose

Developmental defects of enamel (DDE) is a dental disease with a high prevalence and no effective means of prevention. One of the major causes of DDE is infection, but the pathogenesis is still unclear. Melatonin is known for its anti-inflammatory and mineralization-promoting activities. However, the effects of melatonin on inflammation-induced DDE remain unknown. Here, we investigated the pathogenesis and potential therapeutic targets of inflammation-induced DDE.

Materials and methods

First, the effect of lipopolysaccharide-induced inflammation in pregnant mice on the enamel mineralization of the offspring was detected by 3D X-ray microscope analysis, immunohistochemical assays, and quantitative real-time polymerase chain reaction (qRT-PCR). Then, the ameloblastic differentiation ability of ameloblast lineage cells (ALCs) in macrophage conditioned medium (CM) was detected. Subsequently, ameloblastic mineralization after melatonin administration was studied both in vivo and in vitro. The underlying mechanism of melatonin was investigated by RNA sequencing and small interfering RNA transfection.

Results

Enamel mineralization was decreased in the inflammatory environment both in vivo and in vitro. Furthermore, melatonin treatment ameliorated these defects. RNA sequencing analysis revealed that regulator of G protein signaling 2 (Rgs2) was downregulated in the inflammation group, whereas it was upregulated after the addition of melatonin. Further studies showed that Rgs2 knockdown resulted in decreased ameloblastic mineralization in ALCs. After Rgs2 knockdown of ALCs in M1-CM with melatonin, the effect of melatonin-mediated attenuation of DDE was greatly reduced.

Conclusion

Our results demonstrate that melatonin ameliorates inflammation-induced DDE by upregulating RGS2, suggesting that RGS2 is a potential therapeutic target for inflammation-induced DDE.

Coenzyme Q10 ameliorates cyclophosphamide-induced chemobrain by repressing neuronal apoptosis and preserving hippocampal neurogenesis: Mechanistic roles of Wnt/ β-catenin signaling pathway

Deterioration in the neurocognitive function of cancer patients referred to as "Chemobrain" is a devastating obstacle associated with cyclophosphamide (CYP). CYP is an alkylating agent, clinically utilized as an efficient anticancer and immunosuppressant. Coenzyme Q10 (CoQ10) is a worthwhile micronutrient with diverse biological activities embracing antioxidant, anti-apoptotic, and neuroprotective effects. The current experiment was designed for investigating the neuroprotective capability of CoQ10 versus CYP-elicited chemobrain in rats besides elucidating the causal molecular mechanisms. Male Sprague Dawley rats received CoQ10 (10 mg/kg, orally, once daily, for 10 days) and/or a single dose of CYP (200 mg/kg i.p. on day 7). CoQ10 counteracted CYP-induced cognitive and motor dysfunction as demonstrated by the findings of neurobehavioral tests (passive avoidance, Y maze, locomotion, and rotarod tests). Histopathological analysis further affirmed the neuroprotective abilities of CoQ10. CoQ10 effectually diminished CYP-provoked oxidative injury by restoring the antioxidant activity of catalase (CAT) enzyme while reducing malondialdehyde (MDA) levels. Besides, CoQ10 efficiently repressed CYP-induced neuronal apoptosis by downregulating the expression of Bax and caspase-3 while upregulating the Bcl-2 expression. Moreover, CoQ10 hampered CYP-provoked upregulation in acetylcholinesterase (AChE) activity. Furthermore, CoQ10 considerably augmented hippocampal neurogenesis by elevating the expressions of brain-derived neurotrophic factor (BDNF) and Ki-67. These promising neuroprotective effects can be credited to upregulating Wnt/β-catenin pathway as evidenced by the elevated expressions of Wnt-3a, β-catenin, and Phoshpo-glycogen synthase kinase-3 β (p-GSK-3β). Collectively, these findings proved the neuroprotective capabilities of CoQ10 against CYP-induced chemobrain through combating oxidative injury, repressing intrinsic apoptosis, boosting neurogenesis, and eventually upregulating the Wnt/β-catenin pathway.

Classic Famous Prescription Kai-Xin-San Ameliorates Alzheimer's Disease via the Wnt/β-Catenin Signaling Pathway

Kai-Xin-San (KXS) is a classic famous prescription composed of Polygalae Radix, Ginseng Radix et Rhizoma, Acori Tatarinowii Rhizoma, and Poria. Clinically, KXS is effective in treating amnesia and regulating cognitive dysfunction of Alzheimer's disease (AD), whereas its mechanism of action is still unclear. In this study, the AD model rats were established by combining intraperitoneal injection of D-galactose (150 mg/kg/day) and intracerebral injection of Aβ25-35 (10 μL) to investigate the meliorative effect of KXS on AD and explore its mechanism. After 1-month KXS treatment, Morris water maze test showed that different doses of KXS all improved the cognitive impairment of AD rats. The results of hematoxylin and eosin staining, Nissl staining, and Tunnel staining showed that the neuron injury in the hippocampal CA1 region of the AD rats was markedly improved after KXS treatment. Concurrently, KXS reversed the levels of biochemical indexes of AD rats. Furthermore, the protein expressions of Wnt1 and β-catenin in KXS groups were remarkably increased, while the expressions of Bax and caspase-3 were significantly decreased. Besides, KXS-medicated serum reduced the levels of tumor necrosis factor-α, interleukin-1β, and reactive oxygen species and regulated the protein expressions of β-catenin, glycogen synthase kinase-3β (GSK-3β), p-GSK-3β, Bax, and caspase-3 in Aβ25-35-induced pheochromocytoma cells. Most importantly, this effect was attenuated by the Wnt inhibitor IWR-1. Our results suggest that KXS improves cognitive and memory function of AD rats, and its neuroprotective mechanism may be mediated through the Wnt/β-catenin signaling pathway.

Adipose tissue-derived mesenchymal stem cells ameliorate cognitive impairment in Alzheimer's disease rat model: Emerging role of SIRT1

Alzheimer's disease (AD) is a complex form of neurodegenerative dementia. Growing body of evidence supports the cardinal role of sirtuin1 (SIRT1) in neurodegeneration and AD development. Recently, adipose tissue-derived mesenchymal stem cells (Ad-MSCs) have made their mark for a wide array of regenerative medicine applications, including neurodegenerative disorders. Therefore, the present study aimed to investigate the therapeutic potential of Ad-MSCs in AD rat model, and to explore the possible implication of SIRT1. Ad-MSCs were isolated from rat epididymal fat pads and properly characterized. Aluminum chloride was used to induce AD in rats, and afterward, a group of AD-induced rats received a single dose of Ad-MSCs (2 × 106 cell, I.V per rat). One month after Ad-MSCs transplantation, behavioral tests were done, brain tissues were collected, then histopathological and biochemical assessments were performed. Amyloid beta and SIRT1 levels were determined by enzyme-linked immunosorbent assay. Whereas expression levels of neprilysin, BCL2 associated X protein, B-cell lymphoma-2, interleukin-1β, interleukin-6, and nerve growth factor in hippocampus and frontal cortex brain tissues were assessed using reverse transcriptase quantitative polymerase chain reaction. Our data demonstrated that transplantation of Ad-MSCs alleviated cognitive impairment in AD rats. Additionally, they exhibited anti-amyloidogenic, antiapoptotic, anti-inflammatory, as well as neurogenic effects. Furthermore, Ad-MSCs were found to possibly mediate their therapeutic effects, at least partially, via modulating both central and systemic SIRT1 levels. Hence, the current study portrays Ad-MSCs as an effective therapeutic approach for AD management and opens the door for future investigations to further elucidate the role of SIRT1 and its interrelated molecular mediators in AD.

Role of Autophagy and Apoptosis in Aluminum Exposure-Induced Liver Injury in Rats

Aluminum (Al) exposure can lead to different degrees of damage to various organ systems of the body. It has been previously revealed that Al exposure can damage the liver, causing liver dysfunction. However, the specific mechanism remains unclear. This research aims to uncover the damaging effect of Al exposure on rat liver and to demonstrate the role of autophagy and apoptosis in this effect. Thirty-two Wistar rats were randomly divided into the control group (C group), low-dose Al exposure group (L group), middle-dose Al exposure group (M group), and high-dose Al exposure group (H group) (n = 8). The rats, respectively, received intraperitoneal injections of 0, 5, 10, and 20 mg/kg·day AlCl₃ solution for 4 weeks (5 times/week). After the experiment, changes in the ultrastructure and autolysosome in rat liver were observed; the liver function, apoptosis rate, as well as levels of apoptosis-associated proteins and autophagy-associated proteins were detected. The results indicated that Al exposure damaged rat liver function and structure and resulted in an increase in autolysosomes. TUNEL staining revealed an elevated number of apoptotic hepatocytes after Al exposure. Moreover, we found from Western blotting that the levels of autophagy-associated proteins Beclin1 and LC3-II were increased; apoptotic protein Caspase-3 level was elevated and the Bcl-2/Bax ratio was reduced. Our research suggested that Al exposure can lead to high autophagy and apoptosis levels of rat hepatocytes, accompanied by hepatocyte injury and impaired liver function. This study shows that autophagy and apoptosis pathways participate in Al toxication-induced hepatocyte injury.

Zinc Ameliorates Nogo-A Receptor and Osteocalcin Gene Expression in Memory-Sensitive Rat Hippocampus Impaired by Intracerebroventricular Injection of Streptozotocin

Metabolic dysfunction is a critical step in the etiopathogenesis of Alzheimer's disease. In this progressive neurological disorder, impaired zinc homeostasis has a key role that needs to be clarified. The aim of this study was to investigate the effect of zinc deficiency and administration on hippocampal Nogo-A receptor and osteocalcin gene expression in rats injected with intracerebroventricular streptozotocin (icv-STZ). Forty male Wistar rats were divided into 5 groups in equal numbers: Sham 1 group received icv artificial cerebrospinal fluid (aCSF); Sham 2 group received icv a CSF and i.p. saline; STZ group received 3 mg/kg icv STZ; STZ-Zn-deficient group received 3 mg/kg icv STZ and fed a zinc-deprived diet; STZ-Zn-supplemented group received 3 mg/kg icv STZ and i.p. zinc sulfate (5 mg/kg/day). Hippocampus tissue samples were taken following the cervical dislocation of the animals under general anesthesia. Nogo-A receptor and osteocalcin gene expression levels were determined by real-time-PCR method. Zinc supplementation attenuated the increase in hippocampal Nogo-A receptor gene expression, which was significantly increased in zinc deficiency. Again, zinc supplementation upregulated the intrinsic protective mechanisms of the brain by activating osteocalcin-expressing cells in the brain. The results of the study show that zinc has critical effects on Nogo-A receptor gene expression and hippocampal osteocalcin gene expression levels in the memory-sensitive rat hippocampus that is impaired by icv-STZ injection. These results are the first to examine the effect of zinc deficiency and supplementation on hippocampal Nogo-A receptor and osteocalcin gene expression in icv-STZ injection in rats.

Microglial infiltration mediates cognitive dysfunction in rat models of hypothalamic obesity via a hypothalamic-hippocampal circuit involving the lateral hypothalamic area

This study aimed to explore the mechanism underlying cognitive dysfunction mediated by the lateral hypothalamic area (LHA) in a hypothalamic-hippocampal circuit in rats with lesion-induced hypothalamic obesity (HO). The HO model was established by electrically lesioning the hypothalamic nuclei. The open field (OP) test, Morris water maze (MWM), novel object recognition (NOR), and novel object location memory (NLM) tests were used to evaluate changes in cognition due to alterations in the hypothalamic-hippocampal circuit. Western blotting, immunohistochemical staining, and cholera toxin subunit B conjugated with Alexa Fluor 488 (CTB488) reverse tracer technology were used to determine synaptophysin (SYN), postsynaptic density protein 95 (PSD95), ionized calcium binding adaptor molecule 1 (Iba1), neuronal nuclear protein (NeuN), and Caspase3 expression levels and the hypothalamic-hippocampal circuit. In HO rats, severe obesity was associated with cognitive dysfunction after the lesion of the hypothalamus. Furthermore, neuronal apoptosis and activated microglia in the downstream of the lesion area (the LHA) induced microglial infiltration into the intact hippocampus via the LHA-hippocampal circuit, and the synapses engulfment in the hippocampus may be the underlying mechanism by which the remodeled microglial mediates memory impairments in HO rats. The HO rats exhibited microglial infiltration and synapse loss into the hippocampus from the lesioned LHA via the hypothalamic-hippocampal circuit. The underlying mechanisms of memory function may be related to the circuit.

Neuroprotective Effects of Phytochemicals against Aluminum Chloride-Induced Alzheimer’s Disease through ApoE4/LRP1, Wnt3/β-Catenin/GSK3β, and TLR4/NLRP3 Pathways with Physical and Mental Activities in a Rat Model

Background: Alzheimer’s disease (AD) is a neurodegenerative disorder that is associated with abnormal cognition. AD is aided in its initiation and progression by hereditary and environmental factors. Aluminum (Al) is a neurotoxic agent that causes oxidative stress, which is linked to AD progression. Additionally, Nrf2/HO-1, APOE4/LRP1, Wnt3/β-catenin, and TLR4/NLRP3 are the main signaling pathways involved in AD pathogenesis. Several phytochemicals are promising options in delaying AD evolution. Objectives: This study aimed at studying the neuroprotective effects of some phytochemicals as morin (MOR), thymol (TML), and thymoquinone (TMQ) on physical and mental activities (PhM) in Al chloride (AlCl₃)-induced AD rat model. Another objective was to determine the specificity of phytochemicals to AD signaling pathways using molecular docking. Methods: Eighty male Dawley rats were divided into eight groups. Each group received: saline (control group), AlCl₃, (ALAD), PhM, either alone or with a combination of MOR, TML, and/or TMQ for five weeks. Animals were then subjected to behavioral evaluation. Brain tissues were used for histopathological and biochemical analyses to determine the extent of neurodegeneration. The effect of phytochemicals on AlCl₃-induced oxidative stress and the main signaling pathways involved in AD progression were also investigated. Results: AlCl₃ caused a decline in spatial learning and memory, as well as histopathological changes in the brains of rats. Phytochemicals combined with PhM restored antioxidant activities, increased HO-1 and Nrf2 levels, blocked inflammasome activation, apoptosis, TLR4 expression, amyloide-β generation, and tau hyperphophorylation. They also brought ApoE4 and LRP1 levels back to normal and regulated Wnt3/β-catenin/GSK3β signaling pathway. Conclusions: The use of phytochemicals with PhM is a promising strategy for reducing AD by modulating Nrf2/HO-1, TLR4/NLRP3, APOE4/LRP1, and Wnt3/β-catenin/GSK-3β signaling pathways.