Reinvestigation of the effect of carbenoxolone on the induction of heat shock proteins

Systematic review of neurological diseases and carbenoxolone: A double-edged sword?

In this systematic review, we aim to clarify common findings on carbenoxolone's effects on neurological conditions, including stroke, across studies and identify areas where knowledge remains incomplete. We searched several electronic databases, including PubMed, Web of Science, and the Cochrane Library, from their inception and finally included 60 studies in our review. This review reveals carbenoxolone's neuroprotective properties, such as gap junction inhibition, inhibiting the enzyme 11β-hydroxysteroid dehydrogenase (HSD) type I, inducing heat shock proteins, and inhibiting amyloid β42 aggregation. Conversely, it highlights carbenoxolone's neurotoxic potential, including inhibiting the enzyme 11β-HSD type II, mitochondrial dysfunction, and impaired astrocytic uptake of excitotoxic substances. Gap junctions also act as a pathway for neurotrophic factors and drugs that provide neuroprotection, and their inhibition by carbenoxolone may be detrimental to neuronal survival. In the systematic review, the comparison of carbenoxolone concentrations used in in vitro experiments that reported inhibition of 11β-HSD and gap junctions showed significant differences, with higher concentrations noted for gap junction inhibition. Induction of heat shock proteins and inhibition of amyloid-β were limited to long-term administration. Studies related to stroke demonstrated that all instances of hemorrhagic stroke exhibited neurotoxic effects. Additionally, studies administering carbenoxolone after cerebral ischemia reported poor outcomes in experiments with higher dosages and in chronic phases. In conclusion, carbenoxolone presents both neuroprotective and neurotoxic potential, necessitating cautious application in clinical settings. Future research should prioritize comprehensive, high-throughput studies to elucidate carbenoxolone's diverse mechanisms and long-term impacts, optimizing its therapeutic potential for neurological diseases.

The therapeutic potential of glycyrrhizic acid and its metabolites in neurodegenerative diseases: Evidence from animal models

Neurodegenerative diseases, mostly occurring in the elderly population, are the significant cause of disability and death worldwide. The pathogenesis of neurodegenerative diseases is still largely unknown yet, although they have been continuously explored. Thus, there is still a lack of safe, effective, and low side effect drugs in clinical practice for the treatment of neurodegenerative diseases. Pieces of accumulating evidence have demonstrated that licorice played neuroprotective roles in various neurodegenerative diseases. In the past two decades, increasing studies have indicated that glycyrrhizic acid (GL), the main active ingredient from traditional Chinese medicine licorice (widely used in the food industry) and a triterpenoid saponin with multiple pharmacological effects (such as anti-oxidant, anti-inflammatory, and immune regulation), and its metabolites (glycyrrhetinic acid and carbenoxolone) play a neuroprotective role in a range of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease and epilepsy. This review will elaborate on the multiple neuroprotective mechanisms of GL and its metabolites in this series of diseases, aiming to provide a basis for further research on these protective drugs for neurodegenerative diseases and their clinical application. In summary, GL may be a promising candidate drug for the therapy of neurodegenerative diseases.

Modulating Stress Proteins in Response to Therapeutic Interventions for Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative illness characterized by the degeneration of dopaminergic neurons in the substantia nigra, resulting in motor symptoms and without debilitating motors. A hallmark of this condition is the accumulation of misfolded proteins, a phenomenon that drives disease progression. In this regard, heat shock proteins (HSPs) play a central role in the cellular response to stress, shielding cells from damage induced by protein aggregates and oxidative stress. As a result, researchers have become increasingly interested in modulating these proteins through pharmacological and non-pharmacological therapeutic interventions. This review aims to provide an overview of the preclinical experiments performed over the last decade in this research field. Specifically, it focuses on preclinical studies that center on the modulation of stress proteins for the treatment potential of PD. The findings display promise in targeting HSPs to ameliorate PD outcomes. Despite the complexity of HSPs and their co-chaperones, proteins such as HSP70, HSP27, HSP90, and glucose-regulated protein-78 (GRP78) may be efficacious in slowing or preventing disease progression. Nevertheless, clinical validation is essential to confirm the safety and effectiveness of these preclinical approaches.

Enhancing regulatory T-cell function via inhibition of high mobility group box 1 protein signaling in immune thrombocytopenia

Primary immune thrombocytopenia (ITP) is the most common acquired autoimmune bleeding disorder. Abnormally increased levels of High Mobility Group Box 1 (HMGB1) protein associate with thrombocytopenia and therapeutic outcome in ITP. Previous studies proposed that a natural inhibitor of HMGB1, 18β-glycyrrhetinic acid (18β-GA), could be used for its anti-inflammatory and immune-modulatory effects, although its ability to correct immune balance in ITP is unclear. In this study, we showed that plasma HMGB1 correlated negatively with platelet counts in ITP patients, and confirmed that 18β-GA stimulated the production of regulatory T cells (Treg), restored the balance of CD4+ T-cell subsets and enhanced the suppressive function of Treg through blocking the effect on HMGB1 in patients with ITP. HMGB1 short hairpin RNA interference masked the effect of 18β-GA in Treg of ITP patients. Furthermore, we found that 18β-GA alleviated thrombocytopenia in mice with ITP. Briefly, anti-CD61 immune-sensitized splenocytes were transferred into severe combined immunodeficient mice to induce a murine model of severe ITP. The proportion of circulating Treg increased significantly, while the level of plasma HMGB1 and serum antiplatelet antibodies decreased significantly in ITP mice along 18β-GA treatment. In addition, 18β-GA reduced phagocytic activity of macrophages towards platelets both in ITP patients and ITP mice. These results indicate that 18β-GA has the potential to restore immune balance in ITP via inhibition of HMGB1 signaling. In short, this study reveals the role of HMGB1 in ITP, which may serve as a potential target for thrombocytopenia therapy.

The Induction of Heat Shock Protein 70 after Oral Administration of Concentrated Brewed Rice Vinegar Kurozu in Mice

Heat shock protein 70 (HSP70) is induced by various stresses. Since HSP70 has a protein refolding activity and an anti-inflammatory activity, the HSP70 induction will help cells from harmful acute stresses. Feeding a diet containing concentrated brewed rice vinegar Kurozu (CK) diet for 5 wk resulted in an increase of HSP70 in the brains of mice. In the present study, we evaluated whether oral feeding of 25 μL CK induces HSP70 mRNA in brain and other tissues. HSP70 mRNA was significantly increased in the esophagus, small intestine, liver, and brown adipose tissue within 1 h after the oral administration of CK. A weaker induction of HSP70 mRNA was demonstrated in the stomach, large intestine, and brain. HSP70 mRNA induction returned to basal levels within 3 h after feeding. We doubted that the induction of HSP70 mRNA was caused by manual restraint of the mice during CK administration. Manual restraint of the mice did not influence HSP70 mRNA expression in intestine 1 h after these treatments. Our results suggest that transient HSP70 mRNA induction by oral feeding of CK was not caused by retention stress. There are some compounds in CK that increase HSP70 mRNA in various tissues.

Changes in Expressions of HSP27, HSP70, and Soluble Glycoprotein in Heart Failure Rats Complicated with Pulmonary Edema and Correlations with Cardiopulmonary Functions

The study is aimed at investigating the changes in expressions of heat shock protein 27 (HSP27), HSP70, and soluble glycoprotein (SGP) in heart failure (HF) rats complicated with pulmonary edema and exploring their potential correlations with cardiopulmonary functions. The rat model of HF was established, and the rats were divided into HF model group (model group, n = 15) and normal group (n = 15). After successful modeling, MRI and ECG were applied to detect the cardiac function indexes of the rats. The myocardial function indexes were determined, the injury of myocardial tissues was observed via hematoxylin and eosin (HE) staining, and the content of myeloperoxidase (MPO), matrix metalloproteinase-9 (MMP-9), and tumor necrosis factor-alpha (TNF-α) in the blood was measured. The partial pressure of oxygen (PaO2) and oxygenation index (OI) were observed, and the airway resistance and lung compliance were examined. Moreover, quantitative polymerase chain reaction (qPCR) and Western blotting assay were performed to detect the gene and protein expression levels of HSP27, HSP70, and SGP130. The levels of serum creatine kinase (CK), creatine (Cr), and blood urea nitrogen (BUN) were increased markedly in model group (p < 0.05). Model group had notably decreased fractional shortening (FS) and ejection fraction (EF) compared with normal group (p < 0.05), while the opposite results of left ventricular end-diastolic diameter (LVEDD) and left ventricular end-systolic diameter (LVESD) were detected. In model group, the content of serum MPO, MMP-9, and TNF-α was raised remarkably (p < 0.05), OI and PaO2 were reduced notably (p < 0.05), the airway resistance was increased (p < 0.05), and the lung compliance was decreased (p < 0.05). Obviously elevated gene and protein expression levels of HSP27, HSP70, and SGP130 were detected in model group (p < 0.05). The expressions of HSP27, HSP70, and SGP130 are increased in HF rats complicated with pulmonary edema, seriously affecting the cardiopulmonary functions of the rats.

Autoantibodies to heat shock proteins 60, 70, and 90 in patients with rheumatoid arthritis

Heat shock proteins (HSP) have been reported to impact immune responses and to be associated with rheumatoid arthritis (RA). Recently, we provided evidence for a role of autoantibodies to Hsp40 in patients with RA. In this study, we aimed at investigating the humoral autoimmune response to Hsp60, Hsp70, and Hsp90 in RA patients (n = 39). In comparison with healthy controls (n = 40), circulating IgG, IgM, and IgA autoantibodies against Hsp60, Hsp70, and Hsp90 were significantly increased in RA patients. Non-parametric statistical analysis, however, revealed no significant association between anti-HSP and disease activity or disease progression. On the other hand, positive correlations between serum levels of anti-Hsp60 IgG and IL-4 (Th2-like cytokine) or between serum levels of anti-Hsp90 IgG and IFN-ɣ (Th1-like cytokine) were found to be statistically significant in RA. In addition, a significant inverse correlation was found for serum levels of anti-Hsp70 IgM and TNF-α (Th1-like cytokine) in RA. Our results suggest a pronounced anti-Hsp60, anti-Hsp70, and anti-Hsp90 humoral autoimmune response in RA patients that seems not to be directly linked to RA pathophysiology, however, may have a potential modulatory impact on inflammatory status in this disease. Further investigations are needed to clarify the role of anti-HSP autoantibodies in RA.

Heat shock proteins and DNA repair mechanisms: an updated overview

Heat shock proteins (HSPs), also known as molecular chaperones, participate in important cellular processes, such as protein aggregation, disaggregation, folding, and unfolding. HSPs have cytoprotective functions that are commonly explained by their antiapoptotic role. Their involvement in anticancer drug resistance has been the focus of intense research efforts, and the relationship between HSP induction and DNA repair mechanisms has been in the spotlight during the past decades. Because DNA is permanently subject to damage, many DNA repair pathways are involved in the recognition and removal of a diverse array of DNA lesions. Hence, DNA repair mechanisms are key to maintain genome stability. In addition, the interactome network of HSPs with DNA repair proteins has become an exciting research field and so their use as emerging targets for cancer therapy. This article provides a historical overview of the participation of HSPs in DNA repair mechanisms as part of their molecular chaperone capabilities.

HSP27 modulates survival signaling in endosulfan-exposed human peripheral blood mononuclear cells treated with curcumin

Endosulfan, a well-known organochlorine pesticide, induces apoptosis and depletion of reduced glutathione (GSH) in human peripheral blood mononuclear cells (PBMC). Thus, for the amelioration of its effect, antioxidant and antiapoptotic potential of curcumin was evaluated. For ascertaining the attenuating effect of curcumin, various biochemical indices of cell damage such as cytotoxicity, oxidative stress, apoptosis (phosphatidylserine externalization, DNA fragmentation, and cytochrome c) in human PBMC was evaluated following endosulfan exposure (0-100 µM). To assess the role of HSP27 on endosulfan-induced apoptosis, the expression of HSP27 was examined. Curcumin (25 µM) increased cell viability significantly. As evident from the restoration of GSH, antiapoptotic potential was directly proportional to their antioxidant nature of curcumin. The present study indicates that the beneficial effect of curcumin on endosulfan-induced cytotoxicity is related to the induced synthesis of HSP27, emphasizing its antioxidant and therapeutic potential as well as underscoring the mechanism of pesticide-induced toxicity at cellular level. Taken together, these findings suggest that curcumin protects against endosulfan-induced immunotoxicity in human PBMC by attenuating apoptosis.

Inhibition of neuroinflammation and mitochondrial dysfunctions by carbenoxolone in the rotenone model of Parkinson's disease

α-Synuclein aggregation contributes to the Parkinson's disease (PD) pathology in multiple ways-the two most important being the activation of neuroinflammation and mitochondrial dysfunction. Our recent studies have shown the beneficial effects of a heat shock protein (HSP) inducer, carbenoxolone (Cbx), in reducing the aggregation of α-synuclein in a rotenone-based rat model of PD. The present study was designed to explore its ability to attenuate the α-synuclein-mediated alterations in neuroinflammation and mitochondrial functions. The PD model was generated by the rotenone administration (2 mg/kg b.wt.) to the male SD rats for a period of 5 weeks. Cbx (20 mg/kg b.wt.) co-administration was seen to reduce the activation of astrocytes incited by rotenone. Subsequently, the release of pro-inflammatory cytokines TNF-α, IL-6, and IL-1β was inhibited. Further, the expression level of various inflammatory mediators such as COX-2, iNOS, and NF-κB was also reduced following Cbx co-treatment. Cbx was also shown to reduce the rotenone-induced decline in activity of mitochondrial complexes-I, -II, and -IV. Protection of mitochondrial functions and reduction in neuroinflammation lead to the lesser production of ROS and subsequently reduced oxidative stress. This was reflected by the increase in both the cytosolic and mitochondrial GSH levels as well as SOD activity during Cbx co-treatment. Thus, Cbx reduces the inflammatory response and improves the mitochondrial dysfunctions by reducing α-synuclein aggregation. In addition, it also reduces the associated oxidative stress. Due to its ability to target the multiple pathways implicated in the PD, Cbx can serve as a highly beneficial prophylactic agent.

Chemical induction of Hsp70 reduces α-synuclein aggregation in neuroglioma cells

Misfolding and aggregation of α-synuclein (α-syn) is associated with the development of a number of neurodegenerative diseases including Parkinson's disease (PD). Analyses of post mortem tissues revealed the presence of molecular chaperones within α-syn aggregates, suggesting that chaperones play a role in α-syn misfolding and aggregation. In fact, inhibition of chaperone activity aggravates α-syn toxicity, and the overexpression of chaperones, particularly 70-kDa heat shock protein (Hsp70), protects against α-syn-induced toxicity. In this study, we investigated the effect of carbenoxolone (CBX), a glycyrrhizic acid derivative previously reported to upregulate Hsp70, in human neuroglioma cells overexpressing α-syn. We report that CBX treatment lowers α-syn aggregation and prevents α-syn-induced cytotoxicity. We demonstrate further that Hsp70 induction by CBX arises from activation of heat shock factor 1 (HSF1). The Hsp70 inhibitor MAL3-101 and the Hsp70 enhancer 115-7c led to an increase or decrease in α-syn aggregation, respectively, in agreement with these findings. In summary, this study provides a proof-of-principle demonstration that chemical modulation of the Hsp70 machine is a promising strategy to prevent α-syn aggregation.

Carbenoxolone induces apoptosis and inhibits survivin and survivin-ΔEx3 genes expression in human leukemia K562 cells

BACKGROUND AND THE PURPOSE OF THE STUDY

Leukemia is a malignant disorder of the blood progenitor/stem cells which is characterized by abnormal proliferation of white blood cells. Although anti-cancer drugs induce apoptosis in cancerous cells, drug resistance is the significant problem mainly due to over-expression of inhibitors of apoptosis proteins (IAPs) such as survivin. In this content, it has been reported that an anti-inflammatory drug, Carbenoxolone (CBX), could induce apoptosis and growth inhibition in several types of cancerous cells. In the present study, effects of CBX on apoptosis and level of the expression of survivin gene and its ΔEx3 splicing variant have were evaluated in K562 cells.

METHODS

K562 cells were cultured and treated with different concentrations of CBX (50-300 µM) at different time intervals (12-48 hrs). Trypan blue exclusion test was used to evaluate cell viability. Fluorescent microscopy (Acridine Orange/Ethidium Bromide double staining) and DNA fragmentation assay were used to study apoptosis. The expression level of survivin and its ΔEx3 splice variant were studied by RT-PCR.

RESULTS AND MAJOR CONCLUSION

It was found that both growth inhibition and apoptosis occurred in K562 cells. In addition, down-regulation of survivin and survin-ΔEx3 were observed, after 2-4 hrs treatment with 150 µM of CBX. However, the expression level of survivin and its ΔEx3 splice variant increased in subsequent time (6-12 hrs) nearly to the level of control cells. From the results of this study, it may be concluded that CBX can be considered as a candidate for further studies in CML treatment, especially in the case of drug-resistant leukemia cells.

Gap junctions: the claymore for cancerous cells

INTRODUCTION

Gap junctions play an important role in the cell proliferation in mammalian cells as well as carcinogenesis. However, there are controversial issues about their role in cancer pathogenesis. This study was designed to evaluate genotoxicity and cytotoxicity of Carbenoxolone (CBX) as a prototype of inter-cellular gap junction blocker in MCF7 and BT20 human breast cancer cells.

METHODS

The MCF7and BT20 human breast cancer cell lines were cultivated, and treated at designated confluency with different doses of CBX. Cellular cytotoxicity was examined using standard colorimetric assay associated with cell viability tests. Gene expression evaluation was carried out using real time polymerase chain reaction (PCR).

RESULTS

MCF7 and BT20 cells were significantly affected by CBX in a dose dependent manner in cell viability assays. Despite varying expression of genes, down regulation of pro- and anti-apoptotic genes was observed in these cells.

CONCLUSION

Based upon this investigation, it can be concluded that CBX could affect both low and high proliferative types of breast cancer cell lines and disproportionate down regulation of both pre- and anti-apoptotic genes may be related to interacting biomolecules, perhaps via gap junctions.