Carvacrol Protects Against 6-Hydroxydopamine-Induced Neurotoxicity in In Vivo and In Vitro Models of Parkinson's Disease

Neuroprotective role of Carvacrol via Nrf2/HO-1/NLRP3 axis in Rotenone-induced PD mice model

Parkinson's disease (PD) is a multifactorial neurodegenerative disorder whose cause is unclear. Neuroinflammation is recognized as one of the major pathogenic mechanisms involved in the development and progression of PD. NLRP3 inflammasome is the most widely studied inflammatory mediator in various diseases including PD. Several phytoconstituents have shown neuroprotective role in PD. Carvacrol is a phenolic monoterpene commonly found in the essential oils derived from plants belonging to Lamiaceae family. It is well known for its anti-inflammatory and antioxidant properties and has been widely explored in several diseases. In this study, we explored the role of Carvacrol in suppressing neuroinflammation by regulating NLRP3 inflammasome through Nrf2/HO-1 axis and subsequently, inflammatory cytokines like IL-1β, IL-18 in Rotenone induced PD mice model. Three doses (25 mg/kg, 50 mg/kg, 100 mg/kg p.o.) of Carvacrol were administered to, respectively, three groups (LD, MD, HD), one hour after administration of Rotenone (1.5 mg/kg, i.p.), every day, for 21 days. Treatment with Carvacrol ameliorated the motor impairment caused by Rotenone. It alleviated neurotoxicity and reduced inflammatory cytokines. Further, Carvacrol also alleviated oxidative stress and increased antioxidant enzymes. From these results, we show that Carvacrol exerts neuroprotective effects in PD via anti-inflammatory and antioxidant mechanisms and could be a potential therapeutic option in PD.

Antimicrobial drugs for Parkinson's disease: Existing therapeutic strategies and novel drugs exploration

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by loss of dopaminergic neurons in the substantia nigra, as well as the abnormal accumulation of misfolded α-synuclein. Clinically, PD is featured by typical motor symptoms and some non-motor symptoms. Up to now, although considerable progress has been made in understanding the pathogenesis of PD, there is still no effective therapeutic treatment for the disease. Thus, exploring new therapeutic strategies has been a topic that needs to be addressed urgently. Noteworthy, with the proposal of the microbiota-gut-brain axis theory, antimicrobial drugs have received significant attention due to their effects on regulating the intestinal microbiota. Nowadays, there is growing evidence showing that some antimicrobial drugs may be promising drugs for the treatment of PD. Data from pre-clinical and clinical studies have shown that some antimicrobial drugs may play neuroprotective roles in PD by modulating multiple biochemical and molecular pathways, including reducing α-synuclein aggregation, inhibiting neuroinflammation, regulating mitochondrial structure and function, as well as suppressing oxidative stress. In this paper, we summarized the effects of some antimicrobial drugs on PD treatment from recent pre-clinical and clinical studies. Then, we further discussed the potential of a few antimicrobial drugs for treating PD based on molecular docking and molecular dynamics simulation. Importantly, we highlighted the potential of clorobiocin as the therapeutic strategy for PD owing to its ability to inhibit α-synuclein aggregation. These results will help us to better understand the potential of antimicrobial drugs in treating PD and how antimicrobial drugs may alleviate or reverse the pathological symptoms of PD.

Fumaria vaillantii extract protects PC12 cells against neurotoxicity induced by 6-OHDA

BACKGROUND

Parkinson's disease is a neurological disorder caused by the loss of dopaminergic neurons in the midbrain. Various mechanisms are involved in the incidence of the disease including oxidative stress. Several herbs and natural products may interfere with the oxidative-stress pathway due to their antioxidant effects.

OBJECTIVE

Herein, we aimed to investigate the neuroprotective role of F. vaillantii extract on Parkinson's in vitro and in vivo model owing to the presence of the bioactive agents with antioxidant properties.

METHODS

In vitro experments showed that 6-hydroxydopamine could induce toxicity in PC12 cells. The impact of F. vaillantii extract on cell viability was measured by using MTT assay. Nuclear morphological changes were qualitatively evaluated employing Hoechst staining. The antioxidant activity of the extract was determined by ROS and lipid peroxidation assays. Tyrosine hydroxylase protein expression was measured by western blotting in PC12 cells. For in vivo study, movement parameters were evaluated.

RESULTS

The results indicated that 75 µΜ of 6-OHDA induced 50% toxicity in PC12 cells for 24 h. Following post-treatment with F. vaillantii extract (0.1 mg/ml) for 72 h, we observed that the extract effectively prevented cell toxicity induced by 6-OHDA and reduced the apoptotic cell population. Furthermore, the extract attenuated the ROS level, lipid peroxidation and increased protein expression of TH after 72 h of treatment. In addition, oral administration of 300 mg/kg of F. vaillantii extract for 14 days improved locomotor activity, catalepsy, bradykinesia, motor coordination and reduced the apomorphine-caused rotation in 6-OHDA- induced Parkinson's disease-like symptoms in male rats.

CONCLUSION

The present study suggests a protective role for the extract of F. vaillantii against oxidative stress-induced cell damage in the PC12 cells exposed to neurotoxin 6-OHDA which was verified in in vivo model by reducing the motor defects induced by 6-OHDA. This extract could be a promising therapeutic agent for the prevention of PD progression.

Trachyspermum ammi Bioactives Promote Neuroprotection by Inhibiting Acetylcholinesterase, Aβ-Oligomerization/Fibrilization, and Mitigating Oxidative Stress In Vitro

Neurodegenerative diseases (NDs) are a large category of progressive neurological disorders with diverse clinical and pathological characteristics. Among the NDs, Alzheimer's disease (AD) is the most widespread disease, which affects more than 400 million people globally. Oxidative stress is evident in the pathophysiology of nearly all NDs by affecting several pathways in neurodegeneration. No single drug can manage multi-faceted diseases like NDs. Therefore, an alternative therapeutic strategy is required, which can affect several pathophysiological pathways at a time. To achieve this aim, hexane and ethyl acetate extract from Trachyspermum ammi (Carom) were prepared, and GC/MS identified the bioactive compounds. For the cell-based assays, oxidative stress was induced in SH-SY5Y neuroblastoma cells using hydrogen peroxide to evaluate the neuroprotective potential of the Carom extracts/bioactives. The extracts/bioactives provided neuroprotection in the cells by modulating multiple pathways involved in neurodegeneration, such as alleviating oxidative stress and mitochondrial membrane potential. They were potent inhibitors of acetylcholine esterase enzymes and displayed competitive/mixed-type inhibition. Additionally, anti-Aβ1-42 fibrilization/oligomerization and anti-glycation activities were also analyzed. The multi-faceted neuroprotection shown via Carom/Carvacrol makes it a prospective contender in drug development for NDs.

Essential Oil Molecules Can Break the Loop of Oxidative Stress in Neurodegenerative Diseases

Essential oils (EOs) are mixtures of volatile compounds, extracted from aromatic plants, with multiple activities including antioxidant and anti-inflammatory ones. EOs are complex mixtures easy to find on the market and with low costs. In this mini narrative review, we have collected the results of in vitro and in vivo studies, which tested these EOs on validated models of neurodegeneration and in particular of the two main neurodegenerative diseases (NDs) that afflict humans: Alzheimer's and Parkinson's. Since EO compositions can vary greatly, depending on the environmental conditions, plant cultivar, and extraction methods, we focused our attention to studies involving single EO molecules, and in particular those that have demonstrated the ability to cross the blood-brain barrier. These single EO molecules, alone or in defined mixtures, could be interesting new therapies to prevent or slow down oxidative and inflammatory processes which are common mechanisms that contribute to neuronal death in all NDs.

The Effects of Carvacrol on Transient Receptor Potential (TRP) Channels in an Animal Model of Parkinson's Disease

In this study, we aimed to investigate the effects of carvacrol (CA), a widely used phytochemical having anti-oxidant and neuroprotective effects, on transient receptor potential (TRP) channels in an animal model of Parkinson's disease (PD). A total of 64 adult male Spraque-Dawley rats were divided into four groups: sham-operated, PD animal model (unilateral intrastriatal injections of 6-hydroxydopamine (6-OHDA), 6 µg/µl), PD + vehicle (dimethyl sulfoxide (DMSO)) treatment, and PD + CA treatment (10 mg/kg, every other day, for 14 days). Half of the brain samples of substantia nigra pars compacta (SNpc) and striatum (CPu) were collected for immunohistochemistry and the remaining half were used for molecular analyses. CA treatment significantly increased the density of dopaminergic neurons immunolabeled with tyrosine hydroxylase and transient receptor potential canonical 1 (TRPC1) channel in the SNpc of PD animals. In contrast, the density of astrocytes immunolabeled with glial fibrillary acetic acid and transient receptor potential ankyrin 1 (TRPA1) channel significantly decreased following CA treatment in the CPu of PD animals. RT-PCR and western blot analyses showed that 6-OHDA administration significantly reduced TRPA1 and TPRPC1 mRNA expression and protein levels in both SNpc and CPu. CA treatment significantly upregulated TRPA1 expression in PD group, while TRPC1 levels did not display an alteration. Based on this data it was concluded that CA treatment might protect the number of dopaminergic neurons by reducing the reactive astrogliosis and modulating the expression of TRP channels in both neurons and astrocytes in an animal model of PD.

A New Stereoselective Approach to the Substitution of Allyl Hydroxy Group in para-Mentha-1,2-diol in the Search for New Antiparkinsonian Agents

Two approaches to the synthesis of para-menthene epoxide ((1S,5S,6R)-4) are developed. The first approach includes a reaction between chlorohydrin 7 and NaH in THF. The second involves the formation of epoxide in the reaction of corresponding diacetate 6 with sodium tert-butoxide. One possible mechanism of this reaction is proposed to explain unexpected outcomes in the regio- and stereospecificity of epoxide (1S,5S,6R)-4 formation. The epoxide ring in (1S,5S,6R)-4 is then opened by various S- and O-nucleophiles. This series of reactions allows for the stereoselective synthesis of diverse derivatives of the monoterpenoid Prottremine 1, a compound known for its antiparkinsonian activity, including promising antiparkinsonian properties.

Carvacrol decreases blood-brain barrier permeability post-diffuse traumatic brain injury in rats

Previously, we showed that Satureja Khuzestanica Jamzad essential oil (SKEO) and its major component, carvacrol (CAR), 5-isopropyl-2-methylphenol, has anti-inflammatory, anti-apoptotic, and anti-edematous properties after experimental traumatic brain injury (TBI) in rats. CAR, predominantly found in Lamiaceae family (Satureja and Oregano), is lipophilic, allowing diffusion across the blood-brain barrier (BBB). These experiments test the hypothesis that acute treatment with CAR after TBI can attenuate oxidative stress and BBB permeability associated with CAR's anti-edematous traits. Rats were divided into six groups and injured using Marmarou weight drop: Sham, TBI, TBI + Vehicle, TBI + CAR (100 and 200 mg/kg) and CAR200-naive treated rats. Intraperitoneal injection of vehicle or CAR was administered thirty minutes after TBI induction. 24 h post-injury, brain edema, BBB permeability, BBB-related protein levels, and oxidative capacity were measured. Data showed CAR 200 mg/kg treatment decreased brain edema and prevented BBB permeability. CAR200 decreased malondialdehyde (MDA) and reactive oxygen species (ROS) and increased superoxide dismutase (SOD) and total antioxidative capacity (T-AOC), indicating the mechanism of BBB protection is, in part, through antioxidant activity. Also, CAR 200 mg/kg treatment suppressed matrix metalloproteinase-9 (MMP-9) expression and increased ZO-1, occludin, and claudin-5 levels. These data indicate that CAR can promote antioxidant activity and decrease post-injury BBB permeability, further supporting CAR as a potential early therapeutic intervention that is inexpensive and more readily available worldwide. However, more experiments are required to determine CAR's long-term impact on TBI pathophysiology.

Carvacrol enhances anti-tumor activity and mitigates cardiotoxicity of sorafenib in thioacetamide-induced hepatocellular carcinoma model through inhibiting TRPM7

AIMS

Sorafenib (Sora) represents one of the few effective drugs for the treatment of advanced hepatocellular carcinoma (HCC), while resistance and cardiotoxicity limit its therapeutic efficacy. This study investigated the effect of transient receptor potential melastatin 7 (TRPM7) inhibitor, carvacrol (CARV), on overcoming Sora resistance and cardiotoxicity in thioacetamide (TAA) induced HCC in rats.

MATERIALS AND METHODS

TAA (200 mg/kg/twice weekly, intraperitoneal) was administered for 16 weeks to induce HCC. Rats were treated with Sora (10 mg/Kg/day; orally) and CARV (15 mg/kg/day; orally) alone or in combination, for six weeks after HCC induction. Liver and heart functions, antioxidant capacity, and histopathology were performed. Apoptosis, proliferation, angiogenesis, metastasis, and drug resistance were assessed by quantitative real time polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemistry.

KEY FINDINGS

CARV/Sora combination significantly improved survival rate, and liver functions, reduced Alpha-Fetoprotein level, and attenuated HCC progression compared with Sora group. CARV coadministration almost obviated Sora-induced changes in cardiac and hepatic tissues. The CARV/Sora combination suppressed drug resistance and stemness by downregulating ATP-binding cassette subfamily G member 2, NOTCH1, Spalt like transcription factor 4, and CD133. CARV boosted Sora antiproliferative and apoptotic activities by decreasing cyclin D1 and B-cell leukemia/lymphoma 2 and increasing BCL2-Associated X and caspase-3.

SIGNIFICANCE

CARV/Sora is a promising combination for tumor suppression and overcoming Sora resistance and cardiotoxicity in HCC by modulating TRPM7. To our best knowledge, this study represents the first study to investigate the efficiency of CARV/ Sora on the HCC rat model. Moreover, no previous studies have reported the effect of inhibiting TRPM7 on HCC.

Carvacrol protects against λ-Cyhalothrin-induced hepatotoxicity and nephrotoxicity by modulating oxidative stress, inflammation, apoptosis, endoplasmic reticulum stress, and autophagy

λ-Cyhalothrin, a type II synthetic pyrethroid, has been widely used in households, agriculture, public health, and gardening to control insect pests. Despite its widespread usage, it is known to induce a variety of adverse effects, including hepatotoxicity and nephrotoxicity. The goal of this study was to investigate the protective effect of carvacrol, which has antioxidant, anti-inflammatory, anti-apoptotic, and some other properties, on λ-Cyhalothrin-induced hepatotoxicity and nephrotoxicity 35 male Sprague-Dawley rats were randomly divided into five groups for this purpose: I-Control group: II-CRV group (50 mg/kg carvacrol), III-LCT group (6.23 mg/kg LCT), IV-LCT + CRV 25 group (6.23 mg/kg LCT + 25 mg/kg carvacrol), and V-LCT + CRV 50 group (6.23 mg/kg LCT + 50 mg/kg carvacrol). Using biochemical, real-time PCR, and western blotting methods, the collected tissues were analyzed. While λ-Cyhalothrin treatment increased MDA levels, which are indicated of lipid peroxidation, but reduced SOD, CAT, GPx activities, and GSH levels. After receiving carvacrol therapy, the degree of oxidative stress reduced as the values of these parameters approached those of the control group. Increased inflammation, apoptosis, endoplasmic reticulum stress, and autophagy with λ-Cyhalothrin administration reduced with carvacrol co-administration, and liver and kidney tissues were protected from damage, depending on the degree of oxidative stress. After considering all of these data, it was discovered that λ-Cyhalothrin-induced oxidative stress, inflammation, apoptosis, endoplasmic reticulum stress, and autophagy in the liver and kidneys; however, carvacrol protected the tissues from damage. Our findings indicate that carvacrol may be a promising protective agent in λ-Cyhalothrin-induced hepatotoxicity and nephrotoxicity.

Neuroprotective Potential and Underlying Pharmacological Mechanism of Carvacrol for Alzheimer's and Parkinson's Diseases

The phytochemicals have antioxidant properties to counter the deleterious effects of oxidative stress in the central nervous system and can be a promising drug candidate for neurodegenerative diseases. Among various phytochemicals, constituents of spice origin have recently received special attention for neurodegenerative diseases owing to their health benefits, therapeutic potential, edible nature, and dietary accessibility and availability. Carvacrol, a phenolic monoterpenoid, has garnered attention in treating and managing various human diseases. It possesses diverse pharmacological effects, including antioxidant, anti-inflammatory, antimicrobial and anticancer. Alzheimer's disease (AD) and Parkinson's disease (PD) are major public health concerns that place a significant financial burden on healthcare systems worldwide. The global burden of these diseases is expected to increase in the next few decades owing to increasing life expectancies. Currently, there is no cure for neurodegenerative diseases, such as AD and PD, and the available drugs only give symptomatic relief. For a long time, oxidative stress has been recognized as a primary contributor to neurodegeneration. Carvacrol enhances memory and cognition by modulating the effects of oxidative stress, inflammation, and Aβ25-35- induced neurotoxicity in AD. Moreover, it also reduces the production of reactive oxygen species and proinflammatory cytokine levels in PD, which further prevents the loss of dopaminergic neurons in the substantia nigra and improves motor functions. This review highlights carvacrol's potential antioxidant and anti-inflammatory properties in managing and treating AD and PD.

Therapeutic application of carvacrol: A comprehensive review

Carvacrol is a major natural constituent and is significantly present as an essential oil in aromatic plants and is well known for its numerous biological activities. Therapeutic properties of carvacrol have been demonstrated as anti-oxidant, anticancer, diabetes prevention, cardioprotective, anti-obesity, hepatoprotective and reproductive role, antiaging, antimicrobial, and immunomodulatory properties. The carvacrol biosynthesis has been mediated through mevalonate pathway. Carvacrol has the anticancer ability against malignant cells via decreasing the expressions of matrix metalloprotease 2 and 9, inducing apoptosis, enhancing the expression of pro-apoptotic proteins, disrupting mitochondrial membrane, suppressing extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase signal transduction, and also decreasing the phosphoinositide 3-kinase/protein kinase B. It also decreased the concentrations of alanine aminotransferase, alkaline phosphatase and aspartate aminotransferase, and gamma-glutamyl transpeptidase as well as also restored liver function, insulin level, and plasma glucose level. Carvacrol also has been found to exert antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, Coagulase-negative staphylococcus, Salmonella spp., Enterococcus sp. Shigella, and Escherichia coli. The current review article summarizes the health-promoting perspectives of carvacrol through various pathways.

Eugenol and carvacrol attenuate brain D-galactose-induced aging-related oxidative alterations in rats

Aging represents the accumulation of progressive changes in a human being over time and can cover physical, psychological, and social changes. It is an oxidative stress-associated process that progresses with age. The antioxidant activity of either eugenol (EU) or carvacrol (CAR) for aging in rats induced by D-gal for 42 days was investigated in the current study using 10 and 20 mg of EU/kg/day/orally, while CAR was supplemented by 40 and 80 mg /kg/day/orally. Biochemical, mRNA expression, and histopathological assessments of brain samples evaluated the oxidative alterations induced by D-gal and the protective role of EU and CAR. Results showed that D-gal was causing oxidative alternation of the brain that was recognized via upregulation of p53 and p21 mRNA expression levels, as aging markers and Bax mRNA expression level, as an apoptotic marker. Also, the results observed alterations in the levels of biochemical markers as creatine phosphokinase (CPK) and triacylglycerol (TAG), besides, enhancement of brain antioxidant capacity. Finally, these results compared with the groups treated with EU and CAR to observe that the EU and CAR potentially attenuate these aging-related oxidative alterations in a dose-dependent manner. Finally, we can conclude that EU and CAR supplementations are considered promising natural protective compounds that could delay aging and maintain health.

Terpenoid analogues as putative therapeutic agents towards glutathione peroxidase (GPX4) in neurodegenerative disorders: a dynamic computational approach

Carvacrol, a monoterpenoid phenolic phytochemical, a potent antioxidant, and neuroprotective agent is an emerging neuroprotective agent for neurodegenerative diseases (NDDs). Considering scarce information on carvacrol analogues, we hypothesized an in silico investigation emphasizing their preferential binding towards glutathione peroxidase (GPX4) as a target across different species for evaluating through preclinical to clinical studies (2OBI and 6HN3 for Homo sapiens; 5L71 for Mus musculus). Enrichment analysis suggests that ROC (0.59) and AUC (0.61) values have higher sensitivity and significant number of ranked actives. Extra Precision (XP) of 59 compounds was conducted, followed by molecular dynamics and trajectory analysis. Top three hits were chosen for each target i.e., 101203408, 101419546, 59294 (2OBI); 101419546, 100938426, and 28092 (6HN3); and 12059, 52434, 335 (5L71) implying high docking score. 101419546 is common among 2OBI and 6HN3 targets, indicating a multi-target approach. Trajectory analysis of hits provides a permissible range of RMSD, RMSF, Rgyr (∼1.3-2 Å, ∼0.84-1.09 Å, ∼15.05-15.29 Å). Overlapped dynamically simulated 3D-structures of Apo and complexes display significant conformational changes in RMSD of the complexes (∼1.40-2.0 Å) in contrast to Apo (∼1.3-1.8 Å), suggesting structural stability and compactness of the complexes within 45-90 ns. DCCM and PCA analysis shows positive correlation and residual clustering among residues of complexes. The establishment of firm H-bonding, favorable aromaticity and ADMET profile makes them promising drugs across various GPX4 targets among the species. Studies considering the targets across different species aids in anticipating and discovering a common compound for future NDDs therapeutics from bench to bedside.Communicated by Ramaswamy H. Sarma.

Protein Kinase C Involvement in Neuroprotective Effects of Thymol and Carvacrol Against Toxicity Induced by Amyloid-β in Rat Hippocampal Neurons

INTRODUCTION

We have reported that thymol and carvacrol can improve cognitive abilities in Alzheimer Disease (AD) rat models. However, the mechanism of their action is not yet fully understood. Recently, our in vitro results suggested that PC12 cell death induced by Aβ25-35 can be protected by thymol and carvacrol via Protein Kinase C (PKC) and Reactive Oxygen Species (ROS) pathways. So, we hypothesize that the mechanisms of thymol and carvacrol in improving the learning impairment in the AD rat model may be related to their effects on PKC. So, the activity of PKC and protein expression levels of PKCα were examined in the hippocampal cells of the AD rat model.

METHODS

To examine the thymol and carvacrol effects, we performed a behavioral test in AD rat models induced by Aβ_25-35 neurotoxicity. To access the underlying mechanism of the protective effects, western blotting was performed with antibodies against PKCα. We also measured the PKC activity assay by Elisa. Histopathological studies were carried out in the hippocampus with Hematoxylin and Eosin (H&E) staining.

RESULTS

The escape latency increased in Aβ-received rats compared to the control group, and thymol and carvacrol reversed this deficit. Furthermore, these compounds could enhance the PKC activity and increase the PKCα expression ratio. Moreover, H&E staining showed that Aβ caused shrinkage of the CA1 pyramidal neurons. However, thymol and carvacrol treatments could prevent this effect of Aβ peptides.

CONCLUSION

This study suggests that Amyloid-Beta (Aβ) results in memory decline and histochemical disturbances in the hippocampus. Moreover, these results revealed that thymol and carvacrol could have protective effects on cognition in AD-like models via PKC activation.

HIGHLIGHTS

Rat's ability to find the invisible platform in the Morris Water Maze (MWM) was impaired by Amyloid-Beta (Aβ) infusion in the hippocampus, while this effect was reversed by thymol or carvacrol administration.Aβ significantly downregulated the Protein Kinase C (PKC) activity in rats' hippocampus.Western blot analysis demonstrated that Aβ significantly reduced PKCα protein expression in AD rat model hippocampal cells.The expression ratio of PKCα was upregulated following the injection of thymol and carvacrol in rats.Injection of Aβ in the hippocampus resulted in histochemical disturbances in CA1 pyramidal neurons.Carvacrol and thymol can prevent several histological changes induced by Aβ.

PLAIN LANGUAGE SUMMARY

Alzheimer's disease is one of the most important brain diseases in which the learning and memory are impaired. One of the main causes of Alzheimer's disease is the presence of amyloid beta plaques in the neurons. Protein kinase C enzyme reduces amyloid production and accumulation in the brain. In the present study, we tested the possible effects of carvacrol and thymol in a rat model of Alzheimer's disease. Memory impairment was induced in adult rats by intra-cerebral infusion of amyloid β. One week later, the memory-impaired animals were treated with carvacrol and thymol. Finally, we tested their memory in a Morris water maze apparatus. Furthermore, their hippocampus was dissected and PKC activity and the neuronal injury was evaluated. Our findings exhibited that thymol and carvacrol improved rats' memory performance. In addition, thymol and carvacrol significantly increased PKC activity and prevented neuronal cell loss in the rat hippocampus. This study shows that thymol and carvacrol have beneficial effects on memory and cognitive function via PKC activation.

Neuroprotective effects of carvacrol against cadmium-induced neurotoxicity in rats: role of oxidative stress, inflammation and apoptosis

Cadmium (Cd), is a heavy metal reported to be associated with oxidative stress and inflammation. In this paper, we investigated the possible protective effects of carvacrol against Cd-induced neurotoxicity in rats. Adult male Sprague Dawley rats were treated orally with Cd (25 mg/kg body weight) and with carvacrol (25 and 50 mg/kg body weight) for 7 days. Carvacrol decreased the levels of malondialdehyde (MDA), glial fibrillary acidic protein (GFAP) and monoamine oxidase (MAO), and significantly increased the levels of glutathione (GSH) and activities of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) in brain tissue. Additionally, carvacrol alleviated the in levels of inflammation and apoptosis related proteins involving p38 mitogen-activated protein kinase (p38 MAPK), cyclooxygenase-2 (COX-2), nuclear factor kappa B (NF-κB), B-cell lymphoma-3 (Bcl-3), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), myeloperoxidase (MPO), prostaglandin E2 (PGE2), neuronal nitric oxide synthase (nNOS), inducible nitric oxide synthase (iNOS), cysteine aspartate specific protease-3 (caspase-3) and Bcl-2 associated X protein (Bax) in the Cd-induced neurotoxicity. Carvacrol also decreased the mRNA expression of matrix metalloproteinases (MMP9 and MMP13), as well as 8-hydroxy-2'-deoxyguanosine (8 - OHdG) level, a marker of oxidative DNA damage. Collectively, our findings indicated that carvacrol has a beneficial effect in ameliorating the Cd-induced neurotoxicity in the brain of rats.

Thymol protects against 6-hydroxydopamine-induced neurotoxicity in in vivo and in vitro model of Parkinson's disease via inhibiting oxidative stress

Background

Parkinson’s disease (PD) is a multifactorial movement disorder with the progressive degeneration of the nigrostriatal system that impairs patients’ movement ability. Oxidative stress has been found to affect the etiology and pathogenesis of PD. Thymol, a monoterpenic phenol, is one of the most important dietary constituents in thyme species. It has been used in traditional medicine and possesses some properties including antioxidant, free radical scavenging, anti-inflammatory. In this study, in vitro and in vivo experiments were performed with the thymol in order to investigate its potential neuroprotective effects in models of PD.

Methods

The present study aimed to evaluate the therapeutic potential of thymol in 6-hydroxydopamine (6-OHDA)-induced cellular and animal models of PD. 

Results

Post-treatment with thymol in vitro was found to protect PC12 cells from toxicity induced by 6-OHDA administration in a dose-dependent manner by (1) increasing cell viability and (2) reduction in intracellular reactive oxygen species, intracellular lipid peroxidation, and annexin-positive cells. In vivo, post-treatment with thymol was protective against neurodegenerative phenotypes associated with systemic administration of 6-OHDA. Results indicated that thymol improved the locomotor activity, catalepsy, akinesia, bradykinesia, and motor coordination and reduced the apomorphine-caused rotation in 6-OHDA-stimulated rats. Increased level of reduced glutathione content and a decreased level of MDA (malondialdehyde) in striatum were observed in the 6-OHDA rats post-treated with thymol.

Conclusions

Collectively, our findings suggest that thymol exerts protective effects, possibly related to an anti-oxidation mechanism, in these in vitro and in vivo models of Parkinson’s disease.

Neuroprotective evaluation of novel substituted 1,3,4-oxadiazole and aroylhydrazone derivatives

The paper reports on the facile and convenient synthesis of a series of novel 2,5-substituted 1,3,4-oxadiazoles 3a-f and that of aroylhydrazone-based molecular hybrids 5a-g from readily available starting materials. The structure of the compounds was confirmed by IR, ¹H-NMR, ¹³C-NMR and HRESI-MS spectral data. The toxicological potential of the compounds was evaluated by monitoring the synaptosomal viability and the levels of reduced glutathione in rat brain synaptosomes, isolated by Percoll gradient. The neuroprotective effects were assessed in vitro in a model of 6-hydroxydopamine-induced neurotoxicity. Administered alone, at a concentration of 40 µM, most of the 1,3,4-oxadiazole derivatives and all of the hydrazone derivatives exhibited weak statistically significant neurotoxic effects, compared to the control. Two of the compounds from the novel oxadiazoles 3a and 3d did not have any toxicity. In a model of 6-OHDA-induced oxidative stress, again 3a and 3d and all aroylhydrazone derivatives 5a-g revealed statistically significant neuroprotective effect by preserving the synaptosomal viability and the level of reduced glutathione, against the toxic agent. Some of the compounds may have neuroprotective effects due to possible stabilization of the synaptosomal membrane and/or because of the preserved reduced glutathione. Additionally, all the compounds display a good predicted ADME profile.

Neurogenesis in the rat neonate's hippocampus with maternal short-term REM sleep deprivation restores by royal jelly treatment

BACKGROUND

Numerous studies have shown the effects of rapid eye movement sleep deprivation (REM-SD) on behavior and brain structures. The impact of REM-SD on learning and memory, thus neurogenesis, has been reported in previous studies. Royal jelly (RJ) is known as the wealthiest biological nutrient with various physiological properties. This study aimed to study the possible effect of RJ on neurogenesis of the rat hippocampus neonates following exposure of mother to REM-SD during pregnancy.

METHODS

Thirty neonate rats from 15 pregnant Wistar rats were used. To induce REM-SD, the flowerpot method was used. The pregnant rats were divided into five groups (n = 3): group 1, no treatment; group 2, REM-SD; groups 3, 4, and 5, REM-SD +RJ. The former group received 72 h REM-SD during pregnancy (days 7, 14, 21), and the latter group received REM-SD + RJ (three trial groups). At week 4, the rat neonates of all groups were sacrificed (n = 6 each group). Their brains were fixed, removed, and prepared for Nissl and Hoechst 33342 staining. By using real time polymerase chain reaction methode the brain-derived neurotrophic factor BDNF gene expression was studied (RT-PCR), brain-derived neurotrophic factor (BDNF) gene expression was studied. The results were analyzed statistically, and the Pv  < .05 was considered significant.

RESULTS

The results showed a significant decrease in the number of neurons in the hippocampus of neonatal rats of REM-SD mothers compared to the neonates of the mother with REM-SD + RJ. REM-SD also led to an increase in apoptosis reaching the neonates from the REM-SD + RJ animals. High expression of BDNF was observed in the hippocampus of the neonates from REM-SD + RJ treated mothers.

CONCLUSION

RJ acts as a neuroprotective agent that could compensate for the effects of REM-SD on learning and memory via restoring neurogenesis.

Evaluation of oxidative stress, inflammation, apoptosis, oxidative DNA damage and metalloproteinases in the lungs of rats treated with cadmium and carvacrol

BACKGROUND

The potential protective properties of carvacrol (CRV), which possesses various biological and pharmacological properties, against lung toxicity caused by cadmium (Cd), a major environmental pollutant, were investigated in the present study.

METHODS AND RESULTS

In the study, rats were given 25 or 50 mg/kg CRV orally 30 min after administrating 25 mg/kg cadmium chloride for seven days. Subsequently, the levels of 8-OHdG, MMP-2, and MMP-9, as well as markers of oxidative stress, inflammation, and apoptosis, were analyzed in the lung tissue of the animals. The results revealed that CRV exhibited antioxidant characteristics and raised SOD, CAT, GPx, and CAT levels and decreased the MDA levels induced by Cd. It also suppressed proinflammatory cytokines by lowering the levels of CRV NF-κB and p38 MAPK, thus exerting an anti-inflammatory effect against Cd. It was found that the levels of Bax, Caspase-3, and cytochrome c increased by Cd were decreased by the application of CRV. CRV also showed an anti-apoptotic effect by increasing Bcl-2 levels. The levels of 8-OHdG, MMP2, and MMP9, which increased with Cd administration, were observed to reduce after treatment with CRV.

CONCLUSIONS

The results indicate that CRV has protective properties against Cd-induced lung toxicity.

Acrylamide Induced Oxidative Cellular Senescence in Embryonic Fibroblast Cell Line (NIH 3T3): A Protection by Carvacrol

Background: Stress-induced cellular senescence is a perpetual state of cell cycle arrest occurring in proliferating cells in response to stressful conditions. It is believed that oxidative stress plays a unique role in this process. As a reactive chemical compound that can induce oxidative stress, acrylamide is widely applied in several fields. Carvacrol is a liquid phenolic monoterpenoid found in essential oils of some plants and is known for its antioxidant and anticarcinogenic properties. Objectives: The current study aimed to evaluate the effects of carvacrol on oxidative stress and cellular senescence induced by acrylamide in the NIH 3T3 cell line. Methods: NIH 3T3 embryonic fibroblast cells were exposed to different concentrations of acrylamide, carvacrol, and H2O2 in a cell culture medium. The level of β-galactosidase (SA-β-gal) activity, as a marker of cellular senescence, was measured using staining and quantitative assays. Furthermore, to measure oxidative stress parameters, the content of glutathione and lipid peroxidation were determined. Results: Acrylamide could induce premature senescence evident by the elevated lipid peroxidation and SA-β-gal activity and declined cell viability and glutathione. Moreover, carvacrol showed beneficial effects on both acrylamide- and H2O2-induced cellular senescence by significantly reversing or subsiding the effect of oxidative stress and mediating its consequences. Conclusions: It can be concluded that carvacrol has protective effects against oxidative cellular senescence induced by acrylamide in the NIH 3T3 cell line.

Antioral Squamous Cell Carcinoma Effects of Carvacrol via Inhibiting Inflammation, Proliferation, and Migration Related to Nrf2/Keap1 Pathway

Objective

To observe the therapeutic effect of Carvacrol on oral squamous cell carcinoma (OSCC) and dissect underlying molecular mechanisms.

Methods

Keap1/Nrf2, NALP3, Vimentin, and E-cadherin expression was detected in OSCC and normal oral mucosa (NOM) tissues using immunofluorescence or western blot. When treated with Carvacrol or tert-butylhydroquinone (TBHQ) that activates Nrf2, the expression of Keap1/Nrf2/HO-1, epithelial-mesenchymal transition- (EMT-) related proteins, and NALP3 was examined in OSCC cells. Nrf2 was silenced by treatment with sh-Nrf2 or ML385. After silencing Nrf2 or Carvacrol treatment, cell proliferation and migration were assessed by clone formation and scratch and transwell tests in OSCC cells. Moreover, the expression of Keap1/Nrf2/HO-1, EMT-related proteins, and NALP3 was detected.

Results

Keap1/Nrf2, NALP3, Vimentin, and E-cadherin proteins were all significantly upregulated in OSCC than NOM tissues. Carvacrol significantly suppressed Keap1/Nrf2/HO-1 activation. Carvacrol or silencing Nrf2 markedly inhibited the expression of Keap1/Nrf2/HO-1, EMT-related proteins, and NALP3 inflammasome in OSCC cells. Furthermore, clone formation and migration capacities were suppressed following treatment with Carvacrol or Nrf2 depletion. The opposite results were found when there is overexpression of Nrf2. However, Carvacrol distinctly improved the cancer-promoting effect induced by Nrf2 overexpression.

Conclusion

Our findings suggested that Carvacrol ameliorated inflammation, proliferation, and migration for OSCC, which was related to inhibition of the Nrf2/Keap1 pathway.

Pinocembrin-7-Methylether Protects SH-SY5Y Cells Against 6-Hydroxydopamine-Induced Neurotoxicity via Modulating Nrf2 Induction Through AKT and ERK Pathways

The present study aimed to evaluate the neuroprotective effects and underlying mechanisms of pinocembrin-7-methylether (PME), a natural bioflavonoid, in 6-hydroxydopamine (6-OHDA)-induced models of Parkinson's disease in vivo and in vitro. First, we found that PME decreased apoptosis in 6-OHDA-intoxicated SH-SY5Y cells. PME also blocked several 6-OHDA-induced mitochondrial apoptotic cascades, including loss of mitochondrial membrane potential, caspase 3 and PARP activation, and a decrease in the Bcl-2/Bax ratio. Also, PME suppressed 6-OHDA-induced oxidative stress while increasing antioxidant enzymatic activity. Further investigations indicated that PME significantly enhanced nuclear accumulation of Nrf2, improved ARE promoter activity, and upregulated HO-1 and NQO1 expression levels. In addition, siRNA-mediated Nrf2 knockdown abolished PME-induced anti-oxidative and anti-apoptotic effects. Interestingly, we found that PME promoted phosphorylation of AKT and ERK, whereas pharmacological inhibition of AKT or ERK pathways diminished PME-induced Nrf2 activation and protective actions. Moreover, PME attenuated 6-OHDA-induced loss of dopaminergic neurons and ameliorated locomotor deficiency in zebrafish, supporting the neuroprotective actions of PME in vivo. In summary, we found that PME conferred neuroprotection against 6-OHDA-induced neurotoxicity in PD models in vivo and in vitro. Taken together, our findings suggest that activation of Nrf2/ARE/HO-1 signaling cascades contributes to PME-induced anti-oxidative and neuroprotective actions, which are at least partially mediated by AKT and ERK pathways.

Carvacrol as a Potential Neuroprotective Agent for Neurological Diseases: A Systematic Review Article

BACKGROUND & OBJECTIVE

Neurological diseases are becoming a significant problem worldwide, with the elderly at a higher risk of being affected. Several researchers have investigated the neuroprotective effects of Carvacrol (CAR) (5-isopropyl-2-methyl phenol). This review systematically surveys the existing literature on the impact of CAR when used as a neuroprotective agent in neurological diseases.

METHOD

The systematic review involved English articles published in the last ten years obtained from PubMed, Google Scholar, and Scopus databases. The following descriptors were used to search the literature: "Carvacrol" [Title] AND "neuroprotective (neuroprotection)" [Title] OR "stroke, traumatic brain injury, Alzheimer's disease, Parkinson's disease, seizure, epilepsy [Title].

RESULTS

A total of 208 articles were retrieved during the search process, but only 20 studies met the eligibility criteria and were included for review. A total of 20 articles were identified, in which the efficacy of CAR was described in experimental models of stroke, traumatic brain injury, Parkinson's disease, Alzheimer's disease, , epilepsy, and seizure, through motor deficits improvements in neurochemical activity, especially antioxidant systems, reducing inflammation, oxidative stress and apoptosis as well as inhibition of TRPC1 and TRPM7.

CONCLUSION

The data presented in this study support the beneficial impact of CAR on behavioural and neurochemical deficits. CAR benefits accrue because of its anti-apoptotic, antioxidant, and anti-inflammatory properties. Therefore, CAR has emerged as an alternative treatment for neurological disorders based on its properties.

The Neurotrophic-Like Effect of Carvacrol: Perspective for Axonal and Synaptic Regeneration

Carvacrol (CARV) is a phytochemical widely used as flavoring, preservative, and fragrance in food and cosmetic industries. CARV is able to cross the blood-brain barrier (BBB) and has demonstrated protective potential against neurodegenerative diseases by several mechanisms, including antioxidant, anti-inflammatory, anticholinesterase, and antiapoptotic effects. However, it is not known whether CARV is able to modulate axonal and synaptic plasticity, crucial events in cognition, memory, and learning. Abnormalities in axonal and synaptic plasticity, low levels of neurotrophins, and bioenergetic failure have been associated with the pathogenesis of neurodegenerative diseases, including Parkinson's (PD) and Alzheimer's diseases (ADs). Small lipophilic molecules with neurotrophic activity might be able to restore the axonal and synaptic networks that are lost in neurodegenerative processes. Therefore, this study investigated the neurotrophic potential of CARV in PC12 cell-based neuronal model. Carvacrol induced neurite outgrowth by activating the NGF high-affinity trkA receptor and the downstream PI3K-AKT and MAPK-ERK pathways, without depending on NGF. In addition, CARV increased the expression of proteins involved in neuronal plasticity (β-tubulin III, F-actin, 200-kDa neurofilament, GAP-43 and synapsin-I) and improved bioenergetics (AMPKα, p-AMPKα, and ATP). Our study showed, for the first time, a promising neurotrophic mechanism of CARV that could be beneficial in neurodegenerative and neurological diseases.

Essential Oils as a Potential Neuroprotective Remedy for Age-Related Neurodegenerative Diseases: A Review

Despite the improvements in life expectancy, neurodegenerative conditions have arguably become the most dreaded maladies of older people. The neuroprotective and anti-ageing potentials of essential oils (EOs) are widely evaluated around the globe. The objective of this review is to analyse the effectiveness of EOs as neuroprotective remedies among the four common age-related neurodegenerative diseases. The literature was extracted from three databases (PubMed, Web of Science and Google Scholar) between the years of 2010 to 2020 using the medical subject heading (MeSH) terms "essential oil", crossed with "Alzheimer's disease (AD)", "Huntington's disease (HD)", "Parkinson's disease (PD)" or "amyotrophic lateral sclerosis (ALS)". Eighty three percent (83%) of the studies were focused on AD, while another 12% focused on PD. No classifiable study was recorded on HD or ALS. EO from Salvia officinalis has been recorded as one of the most effective acetylcholinesterase and butyrylcholinesterase inhibitors. However, only Cinnamomum sp. has been assessed for its effectiveness in both AD and PD. Our review provided useful evidence on EOs as potential neuroprotective remedies for age-related neurodegenerative diseases.

Behavioral Tests in Neurotoxin-Induced Animal Models of Parkinson's Disease

Currently, neurodegenerative diseases are a major cause of disability around the world. Parkinson's disease (PD) is the second-leading cause of neurodegenerative disorder after Alzheimer's disease. In PD, continuous loss of dopaminergic neurons in the substantia nigra causes dopamine depletion in the striatum, promotes the primary motor symptoms of resting tremor, bradykinesia, muscle rigidity, and postural instability. The risk factors of PD comprise environmental toxins, drugs, pesticides, brain microtrauma, focal cerebrovascular injury, aging, and hereditary defects. The pathologic features of PD include impaired protein homeostasis, mitochondrial dysfunction, nitric oxide, and neuroinflammation, but the interaction of these factors contributing to PD is not fully understood. In neurotoxin-induced PD models, neurotoxins, for instance, 6-hydroxydopamine (6-OHDA), 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 1-Methyl-4-phenylpyridinium (MPP+), paraquat, rotenone, and permethrin mainly impair the mitochondrial respiratory chain, activate microglia, and generate reactive oxygen species to induce autooxidation and dopaminergic neuronal apoptosis. Since no current treatment can cure PD, using a suitable PD animal model to evaluate PD motor symptoms' treatment efficacy and identify therapeutic targets and drugs are still needed. Hence, the present review focuses on the latest scientific developments in different neurotoxin-induced PD animal models with their mechanisms of pathogenesis and evaluation methods of PD motor symptoms.

Carvacrol may alleviate vascular inflammation in diabetic db/db mice

Type 2 diabetes mellitus (T2DM) is associated with chronic low‑grade inflammation. Carvacrol has been confirmed to possess anti‑inflammatory properties, but its effect on diabetic vasculature remains unknown. The aim of the present study was to investigate the possible protective effects of carvacrol against vascular endothelial inflammation. The mice were divided into four groups (n=15 per group) as follows: Non‑diabetic control mice, db/db mice, db/db mice + carvacrol (low) and db/db mice + carvacrol (high) groups. The effects of carvacrol on the pathomorphism of the thoracoabdominal aorta in db/db mice were evaluated using hematoxylin and eosin and Masson's trichrome staining. The serum levels of insulin signaling molecules, such as phosphorylated insulin receptor, phosphorylated insulin receptor substrate‑1, insulin, triglyceride (TG) and inflammatory cytokines [tumor necrosis factor‑α, interleukin (IL)‑1β, IL‑6 and IL‑8] were measured by ELISA. Furthermore, the protein levels of the toll‑like receptor (TLR)4/nuclear factor (NF)‑κB inflammatory signaling pathway molecules were investigated in the thoracoabdominal aorta of db/db mice and in high glucose‑induced endothelial cells. Vascular endothelial cell apoptosis and viability were assessed by using flow cytometry and Cell Counting Kit‑8 assays, respectively. The results demonstrated that carvacrol alleviated vascular endothelial cell injury. Carvacrol reduced the expression levels of insulin signaling molecules, insulin, TG and inflammatory cytokines in the serum of db/db mice. Moreover, carvacrol reduced the activation of the TLR4/NF‑κB signaling pathway in vivo and in vitro. In vitro, carvacrol inhibited high glucose‑induced endothelial cell function by promoting vascular endothelial cell apoptosis and suppressing cell viability. These findings demonstrated that carvacrol could alleviate endothelial dysfunction and vascular inflammation in T2DM.

Effect of long-term treatment of Carvacrol on glucose metabolism in Streptozotocin-induced diabetic mice

BACKGROUND

Carvacrol is a food additive with various bioactivities, including reducing the blood glucose level as well as improvement of heart function, in diabetic mice. We explored the antihyperglycemic effect of carvacrol and its effect on the key hepatic enzymes accounting for glucose metabolism.

METHODS

A streptozotocin (STZ)-induced diabetes-mellitus model in mice was used. Mice were divided randomly into a control group, diabetic group, low dose carvacrol-treated diabetic group (10 mg/kg body weight [BW]), and high dose carvacrol-treated diabetic group (20 mg/kg BW). Carvacrol was injected intraperitoneally (i.p.) in each carvacrol-treated group daily for 4 weeks and 6 weeks, respectively. The level of random plasma glucose, fasting plasma glucose, and plasma insulin was determined at 4 weeks and 6 weeks after carvacrol administration. The plasma level of total cholesterol (TC), triglycerides (TG), aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and the activity of hepatic key enzymes related to glucose metabolism were determined.

RESULTS

Carvacrol treatment decreased the levels of random plasma glucose and fasting plasma glucose, significantly in a dose-dependent manner. A significant improvement in glucose tolerance and a significant decrease in the plasma level of TG were observed in carvacrol-treated diabetic mice at a dose of 20 mg/kg BW compared with that in vehicle-treated diabetic mice. There was no significant difference in the plasma level of TC and insulin between vehicle-treated diabetic mice and carvacrol-treated diabetic mice. Carvacrol treatment at a dose of 20 mg/kg BW significantly reduced the plasma level of LDH but not AST, ALT, or ALP, compared with that in the vehicle-treated diabetic group. The activity of hexokinase (HK), 6-phosphofructokinase (PFK), and citrate synthetase (CS) was increased by carvacrol treatment in diabetic mice.

CONCLUSIONS

Carvacrol exerted an anti-hyperglycemic effect in STZ-induced diabetic mice. This was achieved through regulating glucose metabolism by increasing the activity of the hepatic enzymes HK, PFK, and CS.