Preparation, physicochemical and pharmacological study of curcumin solid dispersion with an arabinogalactan complexation agent

Enhancing the Solubility, Stability, and Bioavailability of Retinol Acetate through Mechanochemistry

This study utilizes mechanochemistry to prepare retinol acetate (RA) solid dispersion (RA-sodium starch octenyl succinate (SSOS)), resulting in improved solubility, stability, and bioavailability compared with raw RA and commercial RA microcapsules. RA, poloxamer 188, SSOS, and milling beads (8 mm) were mixed in a ratio of 2:1:8:220 (w/w) and ball-milled at 100 rpm for 3 h. RA-SSOS exhibited a solubility of 1020.35 μL/mL and a 98.09% retention rate after aging at 30 °C. Rats fed with RA-SSOS showed an ∼30% increase in organ RA content. Characterization analysis attributed the solubility and stabilization of RA-SSOS to hydrogen bonding between RA and SSOS, along with an amorphous state. RA-SSOS offers significant advantages for the pharmaceutical and food industries, leveraging mechanochemistry to enhance solid dispersions for hydrophobic compounds and optimize drug delivery.

Mechanochemical synthesis of cysteine-gum acacia intermolecular complex for multiple metal(loid) sequestration from herbal extracts

The ubiquitous heavy metal(loid)s (HMs) contamination has triggered great concern about food safety, while sequestration and separation of trace HMs from herbal extracts still calls for appropriate sorbent materials. In this work, gum acacia was modified by cysteine to form a cysteine-acacia intermolecular complex (Cys-GA complex) via facile mechanochemical synthesis, aiming at capturing multiple HMs simultaneously. Preliminary screening confirms the superiority of Cys-CA complex for both cationic and anionic HMs, and determines an optimum Cys/GA mass ratio of 9:1 to achieve high removal capacities for Pb(II) (938 mg g-1), Cd(II) (834 mg g-1), As(V) (496 mg g-1), and Cr(VI) (647 mg g-1) in simulated aqueous solution. The analysis on HMs-exhausted Cys-GA complex indicates that Pb(II), As(V), and Cr(VI) tend to be removed through chelation, electrostatic attraction, and reduction, while Cd(II) can only be chelated or adsorbed by electrostatic interaction. The batch experiments on commercial herbal (e.g. Panax ginseng, Glycine max, Sophora flavescens, Gardenia jasminoides, Cyclocarya paliurus, and Bamboo leaf) extracts indicate that Cys-GA complex can reduce HMs concentration to attain acceptable level that comply with International Organization for Standardization, with negligible negative effect on its active ingredients. This work provides a practical and convenient strategy to purify HMs-contaminated foods without introducing secondary pollution.

Crystallization inhibitory effects of konjac glucomannan, sodium alginate and xanthan gum on curcumin in supersaturated solution

Supersaturating drug delivery system (SDDS) is a promising approach to enhance the solubility of hydrophobic functional components. However, SDDS is thermodynamically unstable and crystallization tends to occur. In this work, curcumin was used as a model compound, and the crystallization inhibitory effect of konjac glucomannan (KGM), sodium alginate (SA) and xanthan gum (XTG) on curcumin in supersaturated solution was investigated. Amorphous solubility of curcumin was determined using ultraviolet extinction, fluorescence spectroscopy and dynamic light scattering methods. Nucleation induction time (NIT) and crystal growth rate of curcumin were evaluated using ultraviolet probe in the absence and presence of various natural polysaccharides (NPs). Results showed that amorphous solubility of curcumin was approximately 30 μg/mL in pH 6.8 phosphate buffer. NPs used in this work restrained nucleation or crystal growth of curcumin effectively. The NITs of curcumin in the absence of NPs and in the presence of XTG, KGM and SA (1 μg/mL) were 3.7, 60.7, 20.0 and 8.0 min, respectively. The crystal growth rate of curcumin in the absence of NPs and in the presence of XTG, SA and KGM (1 μg/mL) were 0.0103, 0.00752, 0.00286 and 0.000306 min^-1, respectively. The nucleation inhibitory effect of NPs on curcumin was ranked as XTG > KGM > SA. The order of crystal growth inhibition capacity of NPs was KGM > SA > XTG. In conclusion, NPs could be incorporated into SDDS to maintain supersaturation of hydrophobic components for enhanced bioavailability.

Mechanochemical Transformations of Polysaccharides: A Systematic Review

Taking into consideration the items of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), this study reviews application of mechanochemical approaches to the modification of polysaccharides. The ability to avoid toxic solvents, initiators, or catalysts during processes is an important characteristic of the considered approach and is in line with current trends in the world. The mechanisms of chemical transformations in solid reactive systems during mechanical activation, the structure and physicochemical properties of the obtained products, their ability to dissolve and swell in different media, to form films and fibers, to self-organize in solution and stabilize nanodispersed inorganic particles and biologically active substances are considered using a number of polysaccharides and their derivatives as examples.

Nano-delivery systems for food bioactive compounds in cancer: prevention, therapy, and clinical applications

Bioactive compounds represent a broad class of dietary metabolites derived from fruits and vegetables, such as polyphenols, carotenoids and glucosinolates with potential for cancer prevention. Curcumin, resveratrol, quercetin, and β-carotene have been the most widely applied bioactive compounds in chemoprevention. Lately, many approaches to encapsulating bioactive components in nano-delivery systems have improved biomolecules' stability and targeted delivery. In this review, we critically analyze nano-delivery systems for bioactive compounds, including polymeric nanoparticles (NPs), solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC), liposomes, niosomes, and nanoemulsions (NEs) for potential use in cancer therapy. Efficacy studies of the nanoformulations using cancer cell lines and in vivo models and updated human clinical trials are also discussed. Nano-delivery systems were found to improve the therapeutic efficacy of bioactive molecules against various types of cancer (e.g., breast, prostate, colorectal and lung cancer) mainly due to the antiproliferation and pro-apoptotic effects of tumor cells. Furthermore, some bioactive compounds have promised combination therapy with standard chemotherapeutic agents, with increased tumor efficiency and fewer side effects. These opportunities were identified and developed to ensure more excellent safety and efficacy of novel herbal medicines enabling novel insights for designing nano-delivery systems for bioactive compounds applied in clinical cancer therapy.

Trends in advanced oral drug delivery system for curcumin: A systematic review

Although curcumin is globally recognized for its health benefits, its clinical application has been restricted by its poor aqueous solubility and stability. To overcome these limitations, nanocarrier-based drug delivery systems (NDS) are one of the most effective approaches being extensively explored over the last few decades to improve curcumin's physicochemical and pharmacological effects. Various NDS could provide productive platforms for addressing the formulation challenge of curcumin, but evidence of such systems has not been summarized. This study aimed to systematically review current evidence of lipid and polymer-based NDS for an oral delivery of curcumin focusing on in vivo models and clinical studies. Among the 48 included studies, 3 studies were randomized controlled clinical trials, while 45 studies were animal models. To date, only five curcumin NDS have been studied in healthy volunteers: γ-cyclodextrin, phytosome, liposome, microemulsion and solid dispersion, while most curcumin NDS have been studied in animal models. Most included studies found that NDS could increase oral bioavailability of curcumin as compared to free curcumin. In conclusion, this systematic review showed evidence of the positive effect of NDS for enhancement of oral bioavailability of curcumin. EXECUTIVE SUMMARY: Curcumin is globally recognized for its health benefits, but its clinical application has been limited by its poor aqueous solubility and stability, which causes poor absorption in the gastrointestinal tract (GI tract) via oral administration. Nanocarrier-based drug delivery systems (NDS) are considered as a productive platform to solve the formulation challenge of curcumin, but evidence of such systems has not been summarized. This study aimed to systematically review current evidence of lipid and polymer-based NDS for an oral delivery of curcumin focusing on in vivo models and clinical studies. Overall, most studies found that all studied NDS could increase the absorption of curcumin as compared to free curcumin. Curcumin was rapidly absorbed and exhibited a long residence time after oral administration of curcumin NDS. In summary, this systematic review showed positive impacts of NDS for enhancement of oral absorption of curcumin.

Preparation of DNC Solid Dispersion by a Mechanochemical Method with Glycyrrhizic Acid and Polyvinylpyrrolidone to Enhance Bioavailability and Activity

To exploit aqueous-soluble formulation and improve the anticoccidial activity of 4,4'-dinitrocarbanilide (DNC, active component of nicarbazin), this paper prepared DNC/GA/PVP K30 solid dispersion (SD) with glycyrrhizic acid (GA) and polyvinylpyrrolidone (PVP) K30 by a mechanical ball milling method without using any organic solvent. Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy were used for the solid state characterization. High performance liquid chromatography, critical micelle concentration, particle characterization, and transmission electron microscopy were used to evaluate the behavior in aqueous solution. In addition, the oral bioavailability, tissue distribution, and anticoccidial activity of DNC/GA/PVP K30 SD were investigated as well. Compared with free drug, the novel formulation not only improved the solubility and dissolution rate of DNC, but also inhibited the fecal output of oocysts and enhanced the therapeutic effect of coccidiosis. According to the experiment results, the DNC/GA/PVP K30 SD increased 4.64-fold in oral bioavailability and dramatically enhanced the concentration in liver which provided a basis for further research in schistosomiasis. In summary, our findings suggested that DNC/GA/PVP K30 SD may have promising applications in the treatment of coccidiosis.

Formulation Design and Cell Cytotoxicity of Curcumin-Loaded Liposomal Solid Gels for Anti-Hepatitis C Virus

Backgrounds. Curcumin (CUR) is a low-molecular-weight polyphenolic substance obtained from the tuber part of Curcuma species. Anti-inflammatory and anti-hepatitis C virus (HCV) activities have been associated with CUR. However, its poor aqueous solubility and low systemic bioavailability have been the challenges in improving the therapeutic efficacy of curcumin. Aim. The study aimed to produce CUR-loaded liposomal solid gels as anti-HCV delivery systems. Parameters including the physical characteristics and the cell cytotoxicity properties were evaluated. Methods. The freeze-drying technique was applied to manufacture the CUR-loaded liposomal solid gels. Scanning electron microscopy (SEM), X-ray diffractometry (XRD), and differential thermal analysis (DTA) were involved to reveal the characteristics of the solid gels. Such characteristics were as follows: the morphology and the microscopic structure of the solid gels, the crystallinity structure of the curcumin, and the thermal properties of the mixtures. Furthermore, their cell cytotoxicity was investigated using a Huh7it cell line. Results. The SEM images confirmed that curcumin liposomes were intact and trapped in the solid gel matrix. The XRD data showed flat patterns diffractograms of the formulations, confirming the transformation of CUR from crystalline to amorphous form. The DTA thermograms showed a single melting endothermic peak at a higher temperature around 200°C, indicating a single-phase transition of the mixtures. The XRD and DTA data revealed the molecular dispersion of CUR in the developed formulations. The cytotoxicity data provided as cell cytotoxicity 50 (CC50) for all formulations were ≥25 mg. These data confirmed that the developed liposomal solid gels were not cytotoxic to Huh7it cell line, indicating that the anti-HCV activity would be through a specific pathway and not by its toxicity. Conclusion. The CUR-loaded liposomal solid gels exhibited the potential and offered an alternative dosage form to improve the therapeutic efficacy of curcumin as an anti-HCV.

Curcumin and n-acetylcysteine cocrystal produced with supercritical solvent: characterization, solubility, and preclinical evaluation of antinociceptive and anti-inflammatory activities

Curcumin presents a promising anti-inflammatory potential, but its low water-solubility and bioavailability hinder its application. In this sense, cocrystallization represents a tool for improving physicochemical properties, solubility, permeability, and bioavailability of new drug candidates. Thus, the aim of this work was to produce curcumin cocrystals (with n-acetylcysteine as coformer, which possesses anti-inflammatory and antioxidant activities), by the anti-solvent gas technique using supercritical carbon dioxide, and to test its antinociceptive and anti-inflammatory potential. The cocrystal was characterized by differential scanning calorimetry, powder X-ray diffraction and scanning electron microscopy. The cocrystal solubility and antichemotaxic activity were also assessed in vitro. Antinociceptive and anti-inflammatory activities were carried out in vivo using the acetic acid-induced abdominal writhing and carrageenan-induced paw oedema assays in mice. The results demonstrated the formation of a new crystalline structure, thereby confirming the successful formation of the cocrystal. The higher solubility of the cocrystal compared to pure curcumin was verified in acidic and neutral pH, and the cocrystal inhibited the chemotaxis of neutrophils in vitro. In vivo assays showed that cocrystal presents increased antinociceptive and anti-inflammatory potency when compared to pure curcumin, which could be related to an improvement in its bioavailability.

Preparation and Characterization of a Glycyrrhizic Acid-Based Drug Delivery System for Allergen-Specific Immunotherapy

The most effective method of treating allergic diseases, aimed not at relieving symptoms, but at eliminating the cause of the disease, is allergen-specific immunotherapy (AIT). To reduce the risk of side effects and improve the delivery of allergens to the mucosa, various delivery systems, such as liposomes, dendrimers, nanoparticles, etc., can be used. To date, there are data on the creation of delivery systems based on glycyrrhizic acid (GA) and its derivatives, but such a delivery system has not been used for allergen-specific therapy until now. It is also known that GA has an anti-inflammatory effect, shifts the balance towards Th1, and increases the number of Treg cells, meaning that it could potentially enhance the anti-allergic effect of AIT and reduce the risk of unwanted side effects. Thus, the study of the immunomodulatory effect of the supramolecular complexes (micelles) of GA with extracts of allergens holds promise for the development of new drugs for AIT.

Drug Delivery Strategies for Curcumin and Other Natural Nrf2 Modulators of Oxidative Stress-Related Diseases

Oxidative stress is associated with a wide range of diseases characterised by oxidant-mediated disturbances of various signalling pathways and cellular damage. The only effective strategy for the prevention of cellular damage is to limit the production of oxidants and support their efficient removal. The implication of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway in the cellular redox status has spurred new interest in the use of its natural modulators (e.g., curcumin, resveratrol). Unfortunately, most natural Nrf2 modulators are poorly soluble and show extensive pre-systemic metabolism, low oral bioavailability, and rapid elimination, which necessitates formulation strategies to circumvent these limitations. This paper provides a brief introduction on the cellular and molecular mechanisms involved in Nrf2 modulation and an overview of commonly studied formulations for the improvement of oral bioavailability and in vivo pharmacokinetics of Nrf2 modulators. Some formulations that have also been studied in vivo are discussed, including solid dispersions, self-microemulsifying drug delivery systems, and nanotechnology approaches, such as polymeric and solid lipid nanoparticles, nanocrystals, and micelles. Lastly, brief considerations of nano drug delivery systems for the delivery of Nrf2 modulators to the brain, are provided. The literature reviewed shows that the formulations discussed can provide various improvements to the bioavailability and pharmacokinetics of natural Nrf2 modulators. This has been demonstrated in animal models and clinical studies, thereby increasing the potential for the translation of natural Nrf2 modulators into clinical practice.

Inositol hexanicotinate self-micelle solid dispersion is an efficient drug delivery system in the mouse model of non-alcoholic fatty liver disease

Inositol hexanicotinate (IHN) self-micelle solid dispersion (SD) with glycyrrhizic acid (GA) and arabic gum (AG) was prepared by mechanical ball milling process to improve the solubility, stability of amorphous state, and bioavailability of IHN, which enhanced the treatment of IHN on hyperlipidemia and nonalcoholic fatty liver disease (NAFLD). The physicochemical properties of IHN/GA/AG SDs in solid state were characterized by differential scanning calorimetry, X-ray diffraction studies, and scanning electron microscopy. The characteristics of the sample solutions were analyzed by reverse-phase HPLC, particle characterization, critical micelle concentration, and transmission electron microscopy. Further pharmacokinetic study of this SD formulation in rats showed a significant 3.3-fold increase in bioavailability compared to pure IHN. Moreover, biomarkers in serum and liver of NAFLD mice were significantly ameliorated after oral administration of IHN/GA/AG SDs for 15 days. Altogether, these results establish the mechanochemically prepared IHN/GA/AG SDs as an efficacious formulation for the treatment of hyperlipidemia and NAFLD.

Research on Preparation of 5-ASA Colon-Specific Hydrogel Delivery System without Crosslinking Agent by Mechanochemical Method

PURPOSE

This study aims to overcome the challenges of the current oral targeted drug delivery system, such as the complex preparation process, poor biocompatibility, and delayed drug release.

METHODS

Here, a non-covalent polymer hydrogel was prepared using the mechanochemical method, and the solid phase loading of 5-amino salicylic acid (5-ASA) was realized.

RESULTS

The results obtained from the thermodynamics study, particle size analysis, and electron microscopy show that chitosan (CS) and sodium alginate (SA) form a pH-sensitive hydrogel under the mechanochemical force and also maintain good stability in aqueous solution. Fluorescent tracers study showed that the pH-sensitive hydrogel could achieve the targeted drug release in the colon and the retention time was over 12 h. Next, in vivo efficacy studies, change in mice body weight, DAI (disease activity index) score, thymus, and spleen index, and the diseased state of the mice colon revealed that the pH-sensitive hydrogel is an improved drug delivery system over 5-ASA API commercial preparations as observed in the efficacy and toxicological studies.

CONCLUSION

This method uses an innovative preparation technology that without the need of cross-linking agent to produce an efficient colon-targeted drug delivery system for the treatment of ulcerative colitis.

Solubility, Permeability, Anti-Inflammatory Action and In Vivo Pharmacokinetic Properties of Several Mechanochemically Obtained Pharmaceutical Solid Dispersions of Nimesulide

Nimesulide (NIM, N-(4-nitro-2-phenoxyphenyl)methanesulfonamide) is a relatively new nonsteroidal anti-inflammatory analgesic drug. It is practically insoluble in water (<0.02 mg/mL). This very poor aqueous solubility of the drug may lead to low bioavailability. The objective of the present study was to investigate the possibility of improving the solubility and the bioavailability of NIM via complexation with polysaccharide arabinogalactan (AG), disodium salt of glycyrrhizic acid (Na₂GA), hydroxypropyl-β-cyclodextrin (HP-β-CD) and MgCO₃. Solid dispersions (SD) have been prepared using a mechanochemical technique. The physical properties of nimesulide SD in solid state were characterized by differential scanning calorimetry and X-ray diffraction studies. The characteristics of the water solutions which form from the obtained solid dispersions were analyzed by reverse phase and gel permeation HPLC. It was shown that solubility increases for all complexes under investigation. These phenomena are obliged by complexation with auxiliary substances, which was shown by ¹H-NMR relaxation methods. The parallel artificial membrane permeability assay (PAMPA) was used for predicting passive intestinal absorption. Results showed that mechanochemically obtained complexes with polysaccharide AG, Na₂GA, and HP-β-CD enhanced permeation of NIM across an artificial membrane compared to that of the pure NIM. The complexes were examined for anti-inflammatory activity on a model of histamine edema. The substances were administered per os to CD-1 mice. As a result, it was found that all investigated complexes dose-dependently reduce the degree of inflammation. The best results were obtained for the complexes of NIM with Na₂GA and HP-β-CD. In noted case the inflammation can be diminished up to 2-fold at equal doses of NIM.

Mechanochemical and Size Reduction Machines for Biorefining

In recent years, we have witnessed an increasing interest in the application of mechanochemical methods for processing materials in biomass refining techniques. Grinding and mechanical pretreatment are very popular methods utilized to enhance the reactivity of polymers and plant raw materials; however, the choice of devices and their modes of action is often performed through trial and error. An inadequate choice of equipment often results in inefficient grinding, low reactivity of the product, excess energy expenditure, and significant wear of the equipment. In the present review, modern equipment employing various types of mechanical impacts, which show the highest promise for mechanochemical pretreatment of plant raw materials, is examined and compared—disc mills, attritors and bead mills, ball mills, planetary mills, vibration and vibrocentrifugal mills, roller and centrifugal roller mills, extruders, hammer mills, knife mills, pin mills, disintegrators, and jet mills. The properly chosen type of mechanochemical activation (and equipment) allows an energetically and economically sound enhancement of the reactivity of solid-phase polymers by increasing the effective surface area accessible to reagents, reducing the amount of crystalline regions and the diffusion coefficient, disordering the supramolecular structure of the material, and mechanochemically reacting with the target substances.

Amorphous systems for delivery of nutraceuticals: challenges opportunities

Amorphous solid products have recently gained a lot of attention as key solutions to improve the solubility and bioavailability of poorly soluble nutraceuticals. A pure amorphous drug is a high-energy form; physically/chemically unstable and so easily gets recrystallized into the less soluble crystalline form limiting solubility and bioavailability issues. Amorphous solid dispersion and co-amorphous are new formulation approach that stabilized unstable amorphous form through different mechanisms such as preventing mobility, high glass transition temperature and molecular interaction. Nutraceuticals have been received the utmost importance due to their health benefits. However, most of these compounds have been associated with poor oral bioavailability due to poor solubility, high lipophilicity, high melting point, poor permeability, degradability and rapid metabolism in the gastrointestinal tract (GIT) which limits its health benefits. This review provides us a systematic application of amorphous systems to the delivery of poorly soluble nutraceuticals, with the aim of overcoming their pharmacokinetic limitations and improved pharmacological potential. In particular, it describes the challenges associated with delivery of oral nutraceuticals, various methods involved in the preparation and characterization of amorphous systems and permeability enhancement of nutraceuticals are in detail.

Formulation of amorphous ternary solid dispersions of dapagliflozin using PEG 6000 and Poloxamer 188: solid-state characterization, ex vivo study, and molecular simulation assessment

The present study was designed to prepare dapagliflozin (DFG) loaded ternary solid dispersions (SDs) using the carrier blend polyethylene glycol 6000 (PEG 6000) and poloxamer 188 (PLX 188). The prepared DFG-SDs were evaluated for solubility study, physicochemical characterization and molecular simulation study. The prepared DFG-SDs showed significant higher solubility and dissolution vis-a-vis pure DFG and DFG physical mixture. The composition DFG:PEG:PLX (1:2.25:0.75 mM) showed the highest solubility (0.476 ± 0.016 mg/mL). The physicochemical characterization confirms the polymorphic transition of DFG from crystalline state to stable amorphous form. The prepared DFG-SDs showed a significantly higher dissolution (64.78 ± 2.34% to 78.41 ± 2.39%) than pure DFG (15.70 ± 3.54%). DFG-SD2 showed a significantly enhanced drug permeation (p<.05) (58.76 ± 4.65 µg/cm) as compared to pure DFG (14.97 ± 3.32 µg/cm). The molecular docking study result revealed a good hydrophobic interaction of DFG with the used carrier due to the lowest energy pose. The interaction occurs between the methylene bridges and the central hydrophobic chain of polyoxypropylene of the polymer. Therefore, DFG-SDs prepared by microwave irradiation method using hydrophilic carrier blend might be a promising strategy for improving the solubility and in vitro dissolution performance.

Developmental Strategies of Curcumin Solid Dispersions for Enhancing Bioavailability

BACKGROUND

Although curcumin has been demonstrated to be beneficial in treating various diseases, its low solubility, chemical stability and bioavailability limit its application, especially in cancer therapy.

METHODS

Solid dispersions have been utilized in the last few decades to improve the bioavailability and stability of curcumin.

RESULTS

However, there is a lack of summaries and classifications of the methods for preparing curcumin with this technology. The current review aims to overview the strategies used to develop solid dispersions containing curcumin for improving drug delivery. The classification of techniques for creating solid dispersions for curcumin was summarized, including systems for protecting curcumin degradation despite its chemical stability. The applications of advanced nanotechnologies in recent studies of solid dispersions were also discussed to explain the roles of nanoparticles in formulations.

CONCLUSION

This overview of recent developments in formulating solid dispersions for improving curcumin bioavailability will contribute to future studies of curcumin for clinical development.

Hyaluronic acid hydrophilic surface rehabilitating curcumin nanocrystals for targeted breast cancer treatment with prolonged biodistribution

Due to its high therapeutic efficiency and low systemic toxicity, natural bioactive curcumin has attracted more and more attention as a potential antineoplastic drug.

Curcumin protects against palmitic acid-induced apoptosis via the inhibition of endoplasmic reticulum stress in testicular Leydig cells

BACKGROUND

Palmitic acid (PA) is a common saturated fatty acid that induces apoptosis in various types of cells, including testicular Leydig cells. There is evidence suggesting that PA is increased in patients with obesity and that PA-induced cell apoptosis may play an important role in obesity-related male infertility. Curcumin, a natural polyphenol, has been reported to exert cytoprotective effects in various cell types. However, the cytoprotective effect of curcumin against PA-induced apoptosis in Leydig cells remains unknown. Therefore, the current study was performed to investigate the protective effects of curcumin in response to PA-induced toxicity and apoptosis in murine Leydig tumor cell line 1 (MLTC-1) cells and explore the mechanism underlying its anti-apoptotic action.

METHODS

MLTC-1 cells were cultured in Roswell Park Institute-1640 medium and divided into five groups. First four groups were treated with 50-400 μM PA, 400 μM PA + 5-40 μM curcumin, 400 μM PA + 500 nM 4-phenylbutyric acid (4-PBA, an endoplasmic reticulum (ER) stress inhibitor), and 500 nM thapsigargin (TG, an ER stress inducer) + 20 μM curcumin, respectively, followed by incubation for 24 h. Effects of PA and/or curcumin on viability, apoptosis, and ER stress in MLTC-1 cells were then determined by cell proliferation assay, flow cytometry, and western blot analysis. The fifth group of MLTC-1 cells was exposed to 400 μM of PA and 5 IU/mL of human chorionic gonadotropin (hCG) for 24 h in the absence and presence of curcumin, followed by measurement of testosterone levels in cell-culture supernatants by enzyme-linked immunosorbent assay (ELISA). Rats fed a high-fat diet (HFD) were treated with or without curcumin for 4 weeks, and the testosterone levels were detected by ELISA.

RESULTS

Exposure to 100-400 μM PA reduced cell viability, activated caspase 3, and enhanced the expression levels of the apoptosis-related protein BCL-2-associated X protein (BAX) and ER stress markers glucose-regulated protein 78 (GRP78) and CCAAT/enhancer binding protein homologous protein (CHOP) in MLTC-1 cells. Treating cells with 500 nM 4-PBA significantly attenuated PA-induced cytotoxicity through inhibition of ER stress. Curcumin (20 μM) significantly suppressed PA- or TG-induced decrease in cell viability, caspase 3 activity, and the expression levels of BAX, CHOP, and GRP78. In addition, treating MLTC-1 cells with 20 μM curcumin effectively restored testosterone levels, which were reduced in response to PA exposure. Similarly, curcumin treatment ameliorated the HFD-induced decrease in serum testosterone level in vivo.

CONCLUSIONS

The present study suggests that PA induces apoptosis via ER stress and curcumin ameliorates PA-induced apoptosis by inhibiting ER stress in MLTC-1 cells. This study suggests the application of curcumin as a potential therapeutic agent for the treatment of obesity-related male infertility.