Carnosic acid protects starvation-induced SH-SY5Y cell death through Erk1/2 and Akt pathways, autophagy, and FoxO3a

Neuroprotective Effects of Carnosic Acid: Insight into Its Mechanisms of Action

Carnosic acid is a diterpenoid abundantly present in plants belonging to the genus Rosmarinus and Salvia of the family Lamiaceae, accounting for their application in traditional medicine. The diverse biological properties of carnosic acid that include antioxidant, anti-inflammatory, and anticarcinogenic activities have instigated studies on its mechanistic role, providing further insights into its potential as a therapeutic agent. Accumulating evidence has established the relevance of carnosic acid as a neuroprotective agent exhibiting therapeutic efficacy in combatting neuronal-injury-induced disorders. The physiological importance of carnosic acid in the mitigation of neurodegenerative disorders is just beginning to be understood. This review summarizes the current data on the mode of action through which carnosic acid exerts its neuroprotective role that may serve to strategize novel therapeutic approaches for these debilitating neurodegenerative disorders.

Multi-Target Effects of ß-Caryophyllene and Carnosic Acid at the Crossroads of Mitochondrial Dysfunction and Neurodegeneration: From Oxidative Stress to Microglia-Mediated Neuroinflammation

Inflammation and oxidative stress are interlinked and interdependent processes involved in many chronic diseases, including neurodegeneration, diabetes, cardiovascular diseases, and cancer. Therefore, targeting inflammatory pathways may represent a potential therapeutic strategy. Emerging evidence indicates that many phytochemicals extracted from edible plants have the potential to ameliorate the disease phenotypes. In this scenario, ß-caryophyllene (BCP), a bicyclic sesquiterpene, and carnosic acid (CA), an ortho-diphenolic diterpene, were demonstrated to exhibit anti-inflammatory, and antioxidant activities, as well as neuroprotective and mitoprotective effects in different in vitro and in vivo models. BCP essentially promotes its effects by acting as a selective agonist and allosteric modulator of cannabinoid type-2 receptor (CB2R). CA is a pro-electrophilic compound that, in response to oxidation, is converted to its electrophilic form. This can interact and activate the Keap1/Nrf2/ARE transcription pathway, triggering the synthesis of endogenous antioxidant “phase 2” enzymes. However, given the nature of its chemical structure, CA also exhibits direct antioxidant effects. BCP and CA can readily cross the BBB and accumulate in brain regions, giving rise to neuroprotective effects by preventing mitochondrial dysfunction and inhibiting activated microglia, substantially through the activation of pro-survival signalling pathways, including regulation of apoptosis and autophagy, and molecular mechanisms related to mitochondrial quality control. Findings from different in vitro/in vivo experimental models of Parkinson’s disease and Alzheimer’s disease reported the beneficial effects of both compounds, suggesting that their use in treatments may be a promising strategy in the management of neurodegenerative diseases aimed at maintaining mitochondrial homeostasis and ameliorating glia-mediated neuroinflammation.

Targeting autophagy in ethnomedicine against human diseases

ETHNOPHARMACOLOGICAL RELEVANCE

In the past five years, ethnopharmacy-based drugs have been increasingly used in clinical practice. It has been reported that hundreds of ethnopharmacy-based drugs can modulate autophagy to regulate physiological and pathological processes, and ethnomedicines also have certain therapeutic effects on illnesses, revealing the important roles of these medicines in regulating autophagy and treating diseases.

AIM OF THE STUDY

This study reviews the regulatory effects of natural products on autophagy in recent years, and discusses their pharmacological effects and clinical applications in the process of diseases. It provides a preliminary literature basis and reference for the research of plant drugs in the regulation of autophagy.

MATERIALS AND METHODS

A comprehensive systematic review in the fields of relationship between autophagy and ethnomedicine in treating diseases from PubMed electronic database was performed. Information was obtained from documentary sources.

RESULTS

We recorded some illnesses associated with autophagy, then classified them into different categories reasonably. Based on the uses of these substances in different researches of diseases, a total of 80 active ingredients or compound preparations of natural drugs were searched. The autophagy mechanisms of these substances in the treatments of divers diseases have been summarized for the first time, we also looked forward to the clinical application of some of them.

CONCLUSIONS

Autophagy plays a key function in lots of illnesses, the regulation of autophagy has become one of the important means to prevent and treat these diseases. About 80 compounds and preparations involved in this review have been proved to have therapeutic effects on related diseases through the mechanism of autophagy. Experiments in vivo and in vitro showed that these compounds and preparations could treat these diseases by regulating autophagy. The typical natural products curcumin and tripterine have powerful roles in regulating autophagy and show good and diversified curative effects.

Carnosic acid depends on glutathione to promote mitochondrial protection in methylglyoxal-exposed SH-SY5Y cells

Methylglyoxal (MG) is an endogenously produced toxicant that induces mitochondrial dysfunction leading to impaired redox biology homeostasis, bioenergetics collapse, and cell death in mammalian cells. However, MG toxicity is particularly relevant to neurons and glia given their chemical and metabolic characteristics. Here, we have investigated whether a pretreatment with carnosic acid (CA) would be able to promote mitochondrial protection in human neuroblastoma SH-SY5Y cells exposed to MG. We found that a pretreatment with CA at 1 μM for 12 h prevented the MG-induced lipid peroxidation and protein carbonylation and nitration in the membranes of mitochondria obtained from the SH-SY5Y cells. CA also prevented the MG-elicited Complexes I and V dysfunction, adenosine triphosphate (ATP) levels decline, and loss of mitochondrial membrane potential (MMP). Moreover, CA also reduced the mitochondrial production of the radical anion superoxide (O₂^-•) in the MG-challenged cells. We found that CA upregulated the synthesis of glutathione (GSH) by increasing the activity of the γ-glutamylcysteine ligase (γ-GCL). Inhibition of the GSH synthesis by buthionine sulfoximine (BSO) abolished the CA-induced mitochondrial protection. Besides, inhibition of the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway, as well as silencing of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), suppressed the CA-stimulated protection and the synthesis of GSH. Thus, CA promoted mitochondrial protection by a PI3K/Akt/Nrf2/γ-GCL/GSH axis in MG-treated SH-SY5Y cells.

Carnosic acid alleviates depression-like behaviors on chronic mild stressed mice via PPAR-γ-dependent regulation of ADPN/FGF9 pathway

RATIONALE

The pathway of adiponectin (ADPN)/fibroblast growth factor 9 (FGF9) was recently thought as a key role in the development of depression. ADPN is crucially regulated by peroxisome proliferator-activated receptor-gamma (PPAR-γ). Natural material carnosic acid (CA) has been applied for therapeutics of mental disorders.

OBJECTIVES

To evaluate the antidepressive effect of CA in stress-treated mice and define whether its effects is involved in the regulation of ADPN/FGF9 pathway.

METHODS

In vivo study, the levels of ADPN and FGF9 in both serum and hippocampus tissues, the expressions of ADPN receptor 2 (AdipoR2) in hippocampus and PPAR-γ in abdominal adipose, as well as the pathological changes of hippocampus were determined in 28-day period of chronic unpredictable mild stress (CUMS)-induced depression model of male ICR (Institute of Cancer Research) mice or adipo^-/- mice. In vitro study, the level of ADPN and the mRNA expressions of both ADPN and PPAR-γ were determined in mouse 3T3-L1 preadipocytes.

RESULTS

In vivo study, treatment with CA (50 or 100 mg/kg per day) for 21 days markedly suppressed depressive-like behaviors, the elevating levels of FGF9 and decreasing levels of ADPN in both serum and hippocampus tissues, the downregulating protein and mRNA expressions of AdipoR2 in hippocampus and PPAR-γ in abdominal adipose, as well as the pathological injury of hippocampus induced by CUMS in male ICR mice. The antidepressive effects of CA were markedly attenuated in male CUMS-treated adipo^-/- mice. In vitro study, incubation with CA (3-30 μmol/L) for 24 h could concentration-dependently upregulate the mRNA expressions of both PPAR-γ and ADPN as well as increase the level of ADPN. The experiments using PPAR-γ-specific inhibitor GW9662 and transient transfection with mutated PPAR-γ-binding site promotor constructs showed that the activation of PPAR-γ mediated CA-induced ADPN expression in adipocytes.

CONCLUSIONS

CA could significantly improve stress-induced depressive disorder, which may be related to regulating the dysfunction of ADPN-FGF9 pathway via activating PPAR-γ in adipocytes.

Rosemary extract increases neuronal cell glucose uptake and activates AMPK

Glucose is the primary metabolic substrate of neurons and is responsible for supporting many vital functions including neuronal signalling. Decreases in glucose uptake and utilization are common characteristics of dementia, particularly Alzheimer's disease, and thus agents that can restore neuronal glucose availability may be especially valuable to the field. Diets rich in antioxidants and polyphenols have been associated with reductions in the risk of chronic disease that are associated with aging. In previous studies, rosemary extract (RE) has been reported to have antioxidant, anti-inflammatory, anticancer, and antidiabetic properties. The purpose of the present study was to explore the effects of RE on neuronal glucose uptake. Human SH-SY5Y neuroblastoma cells exposed to varied concentrations of RE showed a dose-dependent increase in glucose uptake, with a significant increase observed following treatment with 5 µg/mL RE for 2 h (159% ± 20.81% of control) that was comparable to maximum insulin stimulation (135.6% ± 3.2% of control). This increase in glucose uptake was paralleled by increases in AMP-activated protein kinase (AMPK), but not Akt, phosphorylation/activation. The present study is the first to report that treatment with rosemary extract can stimulate glucose uptake in a neuronal cell line. These results demonstrate the potential of RE to be used as an agent to regulate neuronal glucose homeostasis. Novelty: RE increases neuronal glucose uptake. RE activates AMPK in neurons. RE increases neuronal glucose uptake independently of insulin signalling.

Anti-stress effects of rosemary (Rosmarinus officinalis L.) leaf extract on intestinal goblet cells and immobility of forced-swimming test in BALB/c mice

We investigated the anti-stress effect of rosemary (Rosmarinus officinalis L.) leaf extract (RLE) on restraint-stressed mice and found that RLE alleviated decreases in the number of intestinal goblet cells and amount of hepatic triglycerides. It also decreased the immobility time in the forced-swimming test and activation of microglia in the brain, suggesting that RLE has beneficial effects on stress-induced dysfunctions.

Preventive and Protective Roles of Dietary Nrf2 Activators Against Central Nervous System Diseases

Central nervous system diseases are major health issues and are often associated with disability or death. Most central nervous system disorders are characterized by high levels of oxidative stress. Nuclear factor erythroid 2 related factor (Nrf2) is known for its ability to regulate the expression of a series of enzymes with antioxidative, prosurvival, and detoxification effects. Under basal conditions, Nrf2 forms a complex with Kelch-like ECH associated protein 1, leading to Nrf2 inactivation via ubiquitination and degradation. However, following exposure of Keap1 to oxidative stress, Nrf2 is released from Keap1, activated, and translocated into the nucleus. Upon nuclear entry, Nrf2 binds to antioxidant response elements (ARE), thereby inducing the expression of genes such as glutathione s-transferase, heme oxygenase 1, and NADPH quinine oxidoreductase 1. Many dietary phytochemicals have been reported to activate the protective Nrf2/ARE pathway. Here, we review the preventive and protective effects of dietary Nrf2 activators against CNS diseases, including stroke, traumatic brain injury, Alzheimer's disease, and Parkinson's disease.

An Integrated Proteomics and Bioinformatics Approach Reveals the Anti-inflammatory Mechanism of Carnosic Acid

Drastic macrophages activation triggered by exogenous infection or endogenous stresses is thought to be implicated in the pathogenesis of various inflammatory diseases. Carnosic acid (CA), a natural phenolic diterpene extracted from Salvia officinalis plant, has been reported to possess anti-inflammatory activity. However, its role in macrophages activation as well as potential molecular mechanism is largely unexplored. In the current study, we sought to elucidate the anti-inflammatory property of CA using an integrated approach based on unbiased proteomics and bioinformatics analysis. CA significantly inhibited the robust increase of nitric oxide and TNF-α, downregulated COX2 protein expression, and lowered the transcriptional level of inflammatory genes including Nos2, Tnfα, Cox2, and Mcp1 in LPS-stimulated RAW264.7 cells, a murine model of peritoneal macrophage cell line. The LC-MS/MS-based shotgun proteomics analysis showed CA negatively regulated 217 LPS-elicited proteins which were involved in multiple inflammatory processes including MAPK, nuclear factor (NF)-κB, and FoxO signaling pathways. A further molecular biology analysis revealed that CA effectually inactivated IKKβ/IκB-α/NF-κB, ERK/JNK/p38 MAPKs, and FoxO1/3 signaling pathways. Collectively, our findings demonstrated the role of CA in regulating inflammation response and provide some insights into the proteomics-guided pharmacological mechanism study of natural products.

Knockdown of SIRT1 Suppresses Bladder Cancer Cell Proliferation and Migration and Induces Cell Cycle Arrest and Antioxidant Response through FOXO3a-Mediated Pathways

Bladder cancer (BCa) is one of the most common tumors, but its underlying mechanism has not been fully clarified. Our transcriptome analysis suggested a close link of Sirtuins, Peroxisome Proliferator-Activated Receptor (PPAR), cell cycle regulation, reactive oxygen species (ROS) metabolism, and Forkhead Box Class O (FOXO) signaling pathway in BCa. SIRT1 is a key member of Sirtuins, playing important roles in aging and energy metabolism, which has been reported to be involved in various metabolic diseases and tumors. We observed that SIRT1 was upregulated in BCa tissues at both mRNA and protein levels. By establishing a SIRT1-knockdown BCa cell model, our results suggested that proliferation and viability were suppressed. Moreover, migration rate was inhibited as well, possibly via reduction of epithelial-mesenchymal transition (EMT). In addition, cell cycle arrest was significantly induced, consisting with strongly decreased proteins involved (CDK2/4/6). Furthermore, ROS production was slightly reduced, accompanied by increasing of antioxidant enzymes and total/acetylated FOXO3a. Consistently with our Path-net analysis, we observed no significant alteration of apoptosis in the SIRT1-knockdown BCa cells. Taken together, our results suggested that SIRT1 deficiency in BCa cells could suppress cell viability by activating antioxidant response and inducing cell cycle arrest possibly via FOXO3a-related pathways.

Capsaicin Suppresses Cell Proliferation, Induces Cell Cycle Arrest and ROS Production in Bladder Cancer Cells through FOXO3a-Mediated Pathways

Capsaicin (CAP), a highly selective agonist for transient receptor potential vanilloid type 1 (TRPV1), has been widely reported to exhibit anti-oxidant, anti-inflammation and anticancer activities. Currently, several therapeutic approaches for bladder cancer (BCa) are available, but accompanied by unfavorable outcomes. Previous studies reported a potential clinical effect of CAP to prevent BCa tumorigenesis. However, its underlying molecular mechanism still remains unknown. Our transcriptome analysis suggested a close link among calcium signaling pathway, cell cycle regulation, ROS metabolism and FOXO signaling pathway in BCa. In this study, several experiments were performed to investigate the effects of CAP on BCa cells (5637 and T24) and NOD/SCID mice. Our results showed that CAP could suppress BCa tumorigenesis by inhibiting its proliferation both in vitro and in vivo. Moreover, CAP induced cell cycle arrest at G0/G1 phase and ROS production. Importantly, our studies revealed a strong increase of FOXO3a after treatment with CAP. Furthermore, we observed no significant alteration of apoptosis by CAP, whereas Catalase and SOD2 were considerably upregulated, which could clear ROS and protect against cell death. Thus, our results suggested that CAP could inhibit viability and tumorigenesis of BCa possibly via FOXO3a-mediated pathways.