Valproic Acid Increased Autophagic Flux in human Multiple Myeloma Cells in Vitro

Discovering Potential in Non-Cancer Medications: A Promising Breakthrough for Multiple Myeloma Patients

MM is a common type of cancer that unfortunately leads to a significant number of deaths each year. The majority of the reported MM cases are detected in the advanced stages, posing significant challenges for treatment. Additionally, all MM patients eventually develop resistance or experience relapse; therefore, advances in treatment are needed. However, developing new anti-cancer drugs, especially for MM, requires significant financial investment and a lengthy development process. The study of drug repurposing involves exploring the potential of existing drugs for new therapeutic uses. This can significantly reduce both time and costs, which are typically a major concern for MM patients. The utilization of pre-existing non-cancer drugs for various myeloma treatments presents a highly efficient and cost-effective strategy, considering their prior preclinical and clinical development. The drugs have shown promising potential in targeting key pathways associated with MM progression and resistance. Thalidomide exemplifies the success that can be achieved through this strategy. This review delves into the current trends, the challenges faced by conventional therapies for MM, and the importance of repurposing drugs for MM. This review highlights a noncomprehensive list of conventional therapies that have potentially significant anti-myeloma properties and anti-neoplastic effects. Additionally, we offer valuable insights into the resources that can help streamline and accelerate drug repurposing efforts in the field of MM.

Toosendanin Induces Hepatocyte Damage by Inhibiting Autophagic Flux via TFEB-Mediated Lysosomal Dysfunction

Toosendanin (TSN) is a triterpenoid from the fruit or bark of Melia toosendan Sieb et Zucc, which has clear antitumor and insecticidal activities, but it possesses limiting hepatotoxicity in clinical application. Autophagy is a degradation and recycling mechanism to maintain cellular homeostasis, and it also plays an essential role in TSN-induced hepatotoxicity. Nevertheless, the specific mechanism of TSN on autophagy-related hepatotoxicity is still unknown. The hepatotoxicity of TSN in vivo and in vitro was explored in this study. It was found that TSN induced the upregulation of the autophagy-marker microtubule-associated proteins 1A/1B light chain 3B (LC3B) and P62, the accumulation of autolysosomes, and the inhibition of autophagic flux. The middle and late stages of autophagy were mainly studied. The data showed that TSN did not affect the fusion of autophagosomes and lysosomes but significantly inhibited the acidity, the degradation capacity of lysosomes, and the expression of hydrolase cathepsin B (CTSB). The activation of autophagy could alleviate TSN-induced hepatocyte damage. TSN inhibited the expression of transcription factor EB (TFEB), which is a key transcription factor for many genes of autophagy and lysosomes, such as CTSB, and overexpression of TFEB alleviated the autophagic flux blockade caused by TSN. In summary, TSN caused hepatotoxicity by inhibiting TFEB-lysosome-mediated autophagic flux and activating autophagy by rapamycin (Rapa), which could effectively alleviate TSN-induced hepatotoxicity, indicating that targeting autophagy is a new strategy to intervene in the hepatotoxicity of TSN.

Pharmacological Properties of 4', 5, 7-Trihydroxyflavone (Apigenin) and Its Impact on Cell Signaling Pathways

Plant bioactive compounds, particularly apigenin, have therapeutic potential and functional activities that aid in the prevention of infectious diseases in many mammalian bodies and promote tumor growth inhibition. Apigenin is a flavonoid with low toxicities and numerous bioactive properties due to which it has been considered as a traditional medicine for decades. Apigenin shows synergistic effects in combined treatment with sorafenib in the HepG2 human cell line (HCC) in less time and statistically reduces the viability of tumor cells, migration, gene expression and apoptosis. The combination of anti-cancerous drugs with apigenin has shown health promoting potential against various cancers. It can prevent cell mobility, maintain the cell cycle and stimulate the immune system. Apigenin also suppresses mTOR activity and raises the UVB-induced phagocytosis and reduces the cancerous cell proliferation and growth. It also has a high safety threshold, and active (anti-cancer) doses can be gained by consuming a vegetable and apigenin rich diet. Apigenin also boosted autophagosome formation, decreased cell proliferation and activated autophagy by preventing the activity of the PI3K pathway, specifically in HepG2 cells. This paper provides an updated overview of apigenin's beneficial anti-inflammatory, antibacterial, antiviral, and anticancer effects, making it a step in the right direction for therapeutics. This study also critically analyzed the effect of apigenin on cancer cell signaling pathways including the PI3K/AKT/MTOR, JAK/STAT, NF-κB and ERK/MAPK pathways.

All-Trans-Retinoic Acid Combined With Valproic Acid Can Promote Differentiation in Myeloid Leukemia Cells by an Autophagy Dependent Mechanism

Acute myeloid leukemia (AML) is an aggressive blood cancer with an overall survival of 30%. One form of AML, acute promyelocytic leukemia (APL) has become more than 90% curable with differentiation therapy, consisting of all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO). Application of differentiation therapy to other AML subtypes would be a major treatment advance. Recent studies have indicated that autophagy plays a key role in the differentiation of ATRA-responsive APL cells. In this study, we have investigated whether differentiation could be enhanced in ATRA resistant cells by promoting autophagy induction with valproic acid (VPA). ATRA sensitive (NB4) and resistant leukemia cells (NB4R and THP-1) were co-treated with ATRA and valproic acid, followed by assessment of autophagy and differentiation. The combination of VPA and ATRA induced autophagic flux and promoted differentiation in ATRA-sensitive and -resistant cell lines. shRNA knockdown of ATG7 and TFEB autophagy regulators impaired both autophagy and differentiation, demonstrating the importance of autophagy in the combination treatment. These data suggest that ATRA combined with valproic acid can promote differentiation in myeloid leukemia cells by mechanism involving autophagy.

Interleukin-10 regulates starvation-induced autophagy through the STAT3-mTOR-p70s6k axis in hepatic stellate cells

The degree of activation of hepatic stellate cells (HSCs) is closely related to the level of autophagy in HSCs. We previously showed that interleukin-10 (IL-10) strongly inhibits HSC activation in rat fibrotic liver. However, little is known about the effect of IL-10 on HSC autophagy. For investigation of the effect of IL-10 on starvation-induced autophagy in immortal rat hepatic stellate cells (HSC-T6) and the molecular mechanism, HSC-T6 cells were incubated with serum-free DMEM for different periods and treated with IL-10 at different concentrations. Transmission electron microscopy (TEM), analysis of autophagic flux and Western blotting (WB) assays were used to observe changes in autophagosome morphology and number and autophagy-related protein expression in HSC-T6 cells and to evaluate the regulatory effect of IL-10 on starvation-induced autophagy. Cryptotanshinone (CPT) and rapamycin (Rapa) were used to block activation of the signal transducer and activator of transcription 3 (STAT3) and mTOR signaling pathways, respectively. STAT3-mTOR-p70s6k signaling pathway proteins were analyzed by WB to assess the signaling pathway by which IL-10 regulates autophagy. WB showed an increased LC3II/I ratio, increased Beclin1 expression, and decreased p62 expression in HSC-T6 cells starved for 3 h (p < 0.05). IL-10 inhibited the increases in the LC3II/I ratio and Beclin1 expression and upregulated p62 expression (p < 0.05), and the optimal IL-10 concentration was 20 ng/mL. TEM and double-labeled immunofluorescence analysis showed that IL-10 inhibited autophagosome formation and autophagic flux, as indicated by the decreased numbers of double-membrane autophagosomes and yellow autophagic puncta. Further examination of signaling pathway molecules showed that phosphorylation of the mTOR, STAT3, and p70s6k proteins was significantly decreased during starvation-induced autophagy, but IL-10 could increase mTOR, STAT3, and p70s6k protein phosphorylation (p < 0.05). Blocking either the mTOR or STAT3 pathway reversed the inhibitory effect of IL-10 on starvation-induced autophagy in HSC-T6 cells (p < 0.05). IL-10 suppresses starvation-induced autophagosome formation through activation of the STAT3-mTOR-p70s6k axis in HSC-T6 cells.

Acute Valproate Exposure Induces Mitochondrial Biogenesis and Autophagy with FOXO3a Modulation in SH-SY5Y Cells

Valproic acid (VPA) is an antiepileptic drug found to induce mitochondrial dysfunction and autophagy in cancer cell lines. We treated the SH-SY5Y cell line with various concentrations of VPA (1, 5, and 10 mM). The treatment decreased cell viability, ATP production, and mitochondrial membrane potential and increased reactive oxygen species production. In addition, the mitochondrial DNA copy number increased after VPA treatment in a dose-dependent manner. Western blotting showed that the levels of mitochondrial biogenesis-related proteins (PGC-1α, TFAM, and COX4) increased, though estrogen-related receptor expression decreased after VPA treatment. Further, VPA treatment increased the total and acetylated FOXO3a protein levels. Although SIRT1 expression was decreased, SIRT3 expression was increased, which regulated FOXO3 acetylation in the mitochondria. Furthermore, VPA treatment induced autophagy via increased LC3-II levels and decreased p62 expression and mTOR phosphorylation. We suggest that VPA treatment induces mitochondrial biogenesis and autophagy via changes in FOXO3a expression and posttranslational modification in the SH-SY5Y cell line.

Apigenin induced autophagy and stimulated autophagic lipid degradation

Apigenin, as a natural flavonoid, has been proved to have many biological effects. Our previous research has found the antiadipogenic effects of apigenin on HepG2 cells. Autophagy is intimately associated with the metabolism of lipid droplets (LDs) and is considered to be one of the lipid breakdown pathways. However, there is no study to elucidate the lipid-lowering mechanism of apigenin from the perspective of autophagy. Here, we investigated the possible role of apigenin in autophagy and lipid accumulation in palmitic acid (PA)-induced HepG2 cells. Our results showed that apigenin increased autophagosome formation and the LC3-II/I ratio, but decreased the p-mTOR/mTOR ratio and P62 protein expression. The effects of apigenin were blocked by chloroquine (CQ). Likewise, apigenin significantly stimulated autophagic flux in the cytoplasm. This effect also could be blocked by CQ. Moreover, apigenin decreased the lipid content and co-localization of LDs with LC3, and CQ could block these effects. Thus, we proposed that apigenin induced autophagy and stimulated autophagic lipid degradation in PA-treated HepG2 cells.