Derivatives of 6-cinnamamido-quinoline-4-carboxamide impair lysosome function and induce apoptosis

4-Aminoquinoline as a privileged scaffold for the design of leishmanicidal agents: structure-property relationships and key biological targets

Leishmaniasis is one of the most important neglected tropical diseases, with more than two million new cases annually. It is endemic in several regions worldwide, representing a public health problem for more than 88 countries, in particular in the tropical and subtropical regions of developing countries. At the moment, there are neither approved vaccines nor effective drugs for the treatment of human leishmaniasis for any of its three typical clinical manifestations, and, importantly, the drugs of clinical use have several side effects, require complex administration regimens, present high cost, and are ineffective in many populations due to pathogen resistance. Moreover, beyond the pharmacological exigencies, there are other challenges concerning its parasitic nature, such as its great genetic plasticity and adaptability, enabling it to activate a battery of genes to develop resistance quickly. All these aspects demand the identification and development of new, safe, and effective chemical systems, which must not only be focused on medicinal chemistry and pharmacological aspects but also consider key aspects relative to parasite survival. In this sense, the quinolines and, in particular, 4-aminoquinoline, represent a privileged scaffold for the design of potential leishmanicidal candidates due not only to their versatility to generate highly active and selective compounds but also to their correlation with well-defined biological targets. These facts make it possible to generate safe leishmanicidal agents targeted at key aspects of parasite survival. The current review summarizes the most current examples of leishmanicidal agents based on 4-aminoquinolines focusing the analysis on two essential aspects: (i) structure-property relationship to identify the key pharmacophores and (ii) mode of action focused on key targets in parasite survival (e.g., depolarization of potential mitochondrial, accumulation into macrophage lysosome, and immunostimulation of host cells). With that information, we seek to give useful guidelines for interested researchers to face the drug discovery and development process for selective and potent leishmanicidal agents based on 4-aminoquinolines.

Optimizing autophagy modulation for enhanced TRAIL-mediated therapy: Unveiling the superiority of late-stage inhibition over early-stage inhibition to overcome therapy resistance in cancer

Autophagy is a vital mechanism that eliminates large cytoplasmic components via lysosomal degradation to maintain cellular homeostasis. The role of autophagy in cancer treatment has been studied extensively. Autophagy primarily prevents tumour initiation by maintaining genomic stability and preventing cellular inflammation. However, autophagy also supports cancer cell survival and growth by providing essential nutrients for therapeutic resistance. Thus, autophagy has emerged as a promising strategy for overcoming resistance and enhancing anti-cancer therapy. Inhibiting autophagy significantly improves the sensitivity of lung, colorectal, breast, liver and prostate cancer cells to tumour necrosis factor-related apoptosis-inducing ligand (TRAIL). This review investigates the intricate interplay between autophagy modulation and TRAIL-based therapy, specifically focussing on comparing the efficacy of late-stage autophagy inhibition versus early-stage inhibition in overcoming cancer resistance. We expose the distinctive advantages of late-stage autophagy inhibition by exploring the mechanisms underlying autophagy's impact on TRAIL sensitivity. Current preclinical and clinical investigations are inspected, showing the potential of targeting late-stage autophagy for sensitizing resistant cancer cells to TRAIL-induced apoptosis. This review emphasizes the significance of optimizing autophagy modulation to enhance TRAIL-mediated therapy and overcome the challenge of treatment resistance in cancer. We offer insights and recommendations for guiding the development of potential therapeutic strategies aimed at overcoming the challenges posed by treatment-resistant cancers.

Chlamydia psittaci inclusion membrane protein CPSIT_0842 induces macrophage apoptosis through MAPK/ERK-mediated autophagy

Chlamydia psittaci is a multi-host zoonotic pathogen, which mainly infects poultry and inflicts an appreciable economic burden on the livestock farming industry. C. psittaci inclusion membrane proteins are uniquely positioned at the host-pathogen interface and are important virulence proteins. We have previously confirmed that Incs regulate host cell survival to help Chlamydia sp. evade host-cell-mediated defense mechanisms. However, the role of the Inc, CPSIT_0842, in the regulation of cell death following the establishment of persistent C. psittaci infection remains unknown. This study explored the effect of CPSIT_0842 on the crosstalk between the autophagic and apoptotic pathways in macrophages. Results showed that CPSIT_0842 initiated autophagy and blocked autophagic flux in human macrophages, as indicated by autophagy-related protein LC3-II, Beclin-1, and p62 upregulation, autophagosome accumulation, and lysosomal protein LAMP1 diminution. We also showed that the disruption of autophagic flux had a regulatory effect on CPSIT_0842-induced apoptosis. Moreover, the suppression of autophagy initiation by 3-methyladenine attenuated CPSIT_0842-induced apoptosis. By contrast, the induction of autophagic flux by rapamycin did not significantly affect CPSIT_0842-induced apoptosis. Taken together, these findings demonstrate that CPSIT_0842 induced macrophage apoptosis by initiating incomplete autophagy through the MAPK/ERK/mTOR signaling pathway, which may be instrumental to the ability of C. psittaci to evade the host innate immune response and establish persistent infection. The improved understanding of the autophagic and cell death pathways triggered upon bacterial inclusion will likely help in the development of novel treatment strategies for chlamydia infection.

ERK: A Double-Edged Sword in Cancer. ERK-Dependent Apoptosis as a Potential Therapeutic Strategy for Cancer

The RAF/MEK/ERK signaling pathway regulates diverse cellular processes as exemplified by cell proliferation, differentiation, motility, and survival. Activation of ERK1/2 generally promotes cell proliferation, and its deregulated activity is a hallmark of many cancers. Therefore, components and regulators of the ERK pathway are considered potential therapeutic targets for cancer, and inhibitors of this pathway, including some MEK and BRAF inhibitors, are already being used in the clinic. Notably, ERK1/2 kinases also have pro-apoptotic functions under certain conditions and enhanced ERK1/2 signaling can cause tumor cell death. Although the repertoire of the compounds which mediate ERK activation and apoptosis is expanding, and various anti-cancer compounds induce ERK activation while exerting their anti-proliferative effects, the mechanisms underlying ERK1/2-mediated cell death are still vague. Recent studies highlight the importance of dual-specificity phosphatases (DUSPs) in determining the pro- versus anti-apoptotic function of ERK in cancer. In this review, we will summarize the recent major findings in understanding the role of ERK in apoptosis, focusing on the major compounds mediating ERK-dependent apoptosis. Studies that further define the molecular targets of these compounds relevant to cell death will be essential to harnessing these compounds for developing effective cancer treatments.

Demethylzeylasteral (T-96) initiates extrinsic apoptosis against prostate cancer cells by inducing ROS-mediated ER stress and suppressing autophagic flux

Background

Demethylzeylasteral (T-96) is a pharmacologically active triterpenoid monomer extracted from Tripterygium wilfordii Hook F (TWHF) that has been reported to exhibit anti-neoplastic effects against several types of cancer cells. However, the potential anti-tumour effects of T-96 against human Prostate cancer (CaP) cells and the possible underlying mechanisms have not been well studied.

Results

In the current study, T-96 exerted significant cytotoxicity to CaP cells in vitro and induced cell cycle arrest at S-phase in a dose-dependent manner. Mechanistically, T-96 promoted the initiation of autophagy but inhibited autophagic flux by inducing ROS-mediated endoplasmic reticulum (ER) stress which subsequently activated the extrinsic apoptosis pathway in CaP cells. These findings implied that T-96-induced ER stress activated the caspase-dependent apoptosis pathway to inhibit proliferation of CaP cells. Moreover, we observed that T-96 enhances the sensitivity of CaP cells to the chemotherapeutic drug, cisplatin.

Conclusions

Taken together, our data demonstrated that T-96 is a novel modulator of ER stress and autophagy, and has potential therapeutic applications against CaP in the clinic.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40659-021-00350-6.

Targeting Tristetraprolin Expression or Functional Activity Regulates Inflammatory Response Induced by MSU Crystals

The RNA-binding protein tristetraprolin (TTP) is an anti-inflammatory factor that prompts the mRNA decay of target mRNAs and is involved in inflammatory diseases such as rheumatoid arthritis (RA). TTP is regulated by phosphorylation, and protein phosphatase 2A (PP2A) can dephosphorylate TTP to activate its mRNA-degrading function. Some small molecules can enhance PP2A activation. Short interfering RNA (siRNA) targeting TTP expression or PP2A agonist (Arctigenin) was administered to monosodium urate (MSU) crystal-induced J774A.1 cells, and the expression of inflammatory related genes was detected by RT-PCR and Western blot assays. The effects of Arctigenin in mouse models of acute inflammation induced by MSU crystals, including peritonitis and arthritis, were evaluated. The data indicated that TTP expression levels and endogenous PP2A activity were increased in MSU-crystal treated J774A.1 cells. TTP knockdown exacerbated inflammation-related genes expression and NLRP3 inflammasome activation. However, PP2A agonist treatment (Arctigenin) suppressed MSU crystal-induced inflammation in J774A.1 cells. Arctigenin also relieved mitochondrial reactive oxygen species (mtROS) production and improved lysosomal membrane permeability in MSU crystal-treated J774A.1 cells. Moreover, TTP knockdown reversed the anti-inflammatory and antioxidant effects of Arctigenin. Oral administration of Arctigenin significantly alleviated foot pad swelling, the number of inflammatory cells in peritoneal lavage fluids and the production of IL-1β in the mouse model of inflammation induced by MSU crystals. Collectively, these data imply that targeting TTP expression or functional activity may provide a potential therapeutic strategy for inflammation caused by MSU crystals.

Qizhen capsule inhibits colorectal cancer by inducing NAG-1/GDF15 expression that mediated via MAPK/ERK activation

ETHNOPHARMACOLOGICAL RELEVANCE

Qizhen capsule (QZC) is a traditional Chinese medicine (TCM) preparation that has been widely used in clinical practice and exerts promising therapeutic effects against breast, lung, and gastric cancers. However, studies have not reported whether QZC inhibits colorectal cancer (CRC) development and progression. Meanwhile, the underlying molecular mechanisms of its anticancer activity have not been studied.

AIM OF THE STUDY

To investigate the anticancer effects of QZC on CRC and the possible underlying molecular mechanisms of QZC in vitro and in vivo.

MATERIALS AND METHODS

The MTT assay and flow cytometry were used to determine the viability and apoptosis of HCT116 and HT-29 cancer cells. A xenograft nude mouse model was used to study the antitumor effects of QZC in vivo. Western blotting was performed to determine the expression of key proteins responsible for the molecular mechanisms elicited by QZC. Immunofluorescence staining was performed to detect the expression of nonsteroidal anti-inflammatory drug (NSAID)-activated gene-1 or growth differentiation factor-15 (NAG-1/GDF15). Small interfering RNAs (siRNAs) were used to silence NAG-1/GDF15 in cells.

RESULTS

In this study, QZC significantly reduced the viability of HCT116 and HT-29 cells and induced apoptosis in dose- and time-dependent manners, but displayed much less toxicity toward normal cells. QZC-induced apoptosis in HCT116 cells was accompanied by the deregulation of the expression of the Bcl-2, Bax, PARP, caspase-3, and caspase-9 proteins. Furthermore, QZC induced NAG-1/GDF15 expression in HCT116 cells, while silencing of NAG-1/GDF15 attenuated QZC-induced apoptosis and cell death. Next, QZC increased the phosphorylation of mTOR, AMPK, p38, and MAPK/ERK in HCT116 cells. We then demonstrated that QZC-induced apoptosis and NAG-1/GDF15 upregulation were mediated by MAPK/ERK activation. Moreover, QZC significantly inhibited HCT116 xenograft tumor growth in nude mice, which was accompanied by NAG/GDF15 upregulation and MAPK/ERK activation. QZC also prevented 5-FU-induced weight loss or cachexia in tumor-bearing mice. The expression of Ki67 and PCNA was suppressed, while cleaved caspase-3 level and TUNEL staining were increased in the tumor sections from QZC-treated mice compared to the control.

CONCLUSION

QZC is a novel anticancer agent for CRC that targets NAG-1/GDF15 via the MAPK/ERK signaling pathway.

Role of lysosomes in physiological activities, diseases, and therapy

Long known as digestive organelles, lysosomes have now emerged as multifaceted centers responsible for degradation, nutrient sensing, and immunity. Growing evidence also implicates role of lysosome-related mechanisms in pathologic process. In this review, we discuss physiological function of lysosomes and, more importantly, how the homeostasis of lysosomes is disrupted in several diseases, including atherosclerosis, neurodegenerative diseases, autoimmune disorders, pancreatitis, lysosomal storage disorders, and malignant tumors. In atherosclerosis and Gaucher disease, dysfunction of lysosomes changes cytokine secretion from macrophages, partially through inflammasome activation. In neurodegenerative diseases, defect autophagy facilitates accumulation of toxic protein and dysfunctional organelles leading to neuron death. Lysosomal dysfunction has been demonstrated in pathology of pancreatitis. Abnormal autophagy activation or inhibition has been revealed in autoimmune disorders. In tumor microenvironment, malignant phenotypes, including tumorigenesis, growth regulation, invasion, drug resistance, and radiotherapy resistance, of tumor cells and behaviors of tumor-associated macrophages, fibroblasts, dendritic cells, and T cells are also mediated by lysosomes. Based on these findings, a series of therapeutic methods targeting lysosomal proteins and processes have been developed from bench to bedside. In a word, present researches corroborate lysosomes to be pivotal organelles for understanding pathology of atherosclerosis, neurodegenerative diseases, autoimmune disorders, pancreatitis, and lysosomal storage disorders, and malignant tumors and developing novel therapeutic strategies.

Tubeimoside I Inhibits Cell Proliferation and Induces a Partly Disrupted and Cytoprotective Autophagy Through Rapidly Hyperactivation of MEK1/2-ERK1/2 Cascade via Promoting PTP1B in Melanoma

Tubeimoside I (TBMS1), also referred to as tubeimoside A, is a natural compound extracted from the plant Tu Bei Mu (Bolbostemma paniculatum), which is a traditional Chinese herb used to treat multiple diseases for more than 1,000 years. Studies in recent years reported its anti-tumor activity in several cancers. However, whether it is effective in melanoma remains unknown. In the current study, we discovered that TBMS1 treatment inhibited melanoma cell proliferation in vitro and tumorigenecity in vivo. Besides, we also observed that TBMS1 treatment induced a partly disrupted autophagy, which still remained a protective role, disruption of which by chloroquine (CQ) or 3-methyladenine (3-MA) enhanced TBMS1-induced cell proliferation inhibition. CQ combined with TBMS1 even induced cellular apoptosis. BRAF(V600E) mutation and its continuously activated downstream MEK1/2-ERK1/2 cascade are found in 50% of melanomas and are important for malanomagenesis. However, hyperactivating MEK1/2-ERK1/2 cascade can also inhibit tumor growth. Intriguingly, we observed that TBMS1 rapidly hyperactivated MEK1/2-ERK1/2, inhibition of which by its inhibitor SL-327 rescued the anti-cancerous effects of TBMS1. Besides, the targets of TBMS1 were predicted by the ZINC Database based on its structure. It is revealed that protein-tyrosine phosphatase 1B (PTP1B) might be one of the targets of TBMS1. Inhibition of PTP1B by its selective inhibitor TCS401 or shRNA rescued the anti-cancerous effects of TBMS1 in melanoma cells. These results indicated that TBMS1 might activate PTP1B, which further hyperactivates MEK1/2-ERK1/2 cascade, thereby inhibiting cell proliferation in melanoma. Our results provided the potentiality of TBMS1 as a drug candidate for melanoma therapy and confirmed that rapidly hyperactivating an oncogenic signaling pathway may also be a promising strategy for cancer treatment.

Role of autophagy in regulation of cancer cell death/apoptosis during anti-cancer therapy: focus on autophagy flux blockade

Autophagy is a self-degradation process in which the cytoplasmic cargoes are delivered to the lysosomes for degradation. As the cargoes are degraded/recycled, the autophagy process maintains the cellular homeostasis. Anti-cancer therapies induce apoptosis and autophagy concomitantly, and the induced autophagy normally prevents stress responses that are being induced. In such cases, the inhibition of autophagy can be a reasonable strategy to enhance the efficacy of anti-cancer therapies. However, recent studies have shown that autophagy induced by anti-cancer drugs causes cell death/apoptosis induction, indicating a controversial role of autophagy in cancer cell survival or death/apoptosis. Therefore, in the present review, we aimed to assess the signaling mechanisms involved in autophagy and cell death/apoptosis induction during anti-cancer therapies. This review summarizes the process of autophagy, autophagy flux and its blockade, and measurement and interpretation of autophagy flux. Further, it describes the signaling pathways involved in the blockade of autophagy flux and the role of signaling molecules accumulated by autophagy blockade in cell death/apoptosis in various cancer cells during anti-cancer therapies. Altogether, it implies that factors such as types of cancer, drug therapies, and characteristics of autophagy should be evaluated before targeting autophagy for cancer treatment.

Disulfiram suppresses NLRP3 inflammasome activation to treat peritoneal and gouty inflammation

The NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome plays a vital role in mediating the innate immune system. Its aberrant activation contributes to the progression of several devastating diseases such as acute peritonitis, acute liver injury, sepsis, gout, and others. However, the medications targeting NLRP3 inflammasome are not available in the clinic. Reusing marketed drugs, which have been already proved to possess good pharmacokinetic profiles and safety, is a strategy to develop new NLRP3 inflammasome inhibitors for clinical trials. In this study, we identified disulfiram (DSF), an old marketed drug as a treatment for alcoholism, could effectively inhibit NLRP3 inflammasome activation and suppress pyroptotic cell death. DSF prevented lysosomal cathepsin B releasing into the cytoplasm, which in turn inactivated the NLRP3 inflammasome. DSF also reduced mitochondrial-independent ROS production. More importantly, treatment with DSF showed remarkable therapeutic effects on the LPS-induced peritoneal inflammation and MSU-induced gouty inflammation. This study provides a potential pharmacological approach to treating NLRP3-driven diseases and a tool to study NLRP3 biology.

Effect of Ganoderma applanatum polysaccharides on MAPK/ERK pathway affecting autophagy in breast cancer MCF-7 cells

Fungal polysaccharides have become hotspots in the field of health foods due to their antitumor activity in recent years. In this experiment, antitumor effect of the medicinal fungus Ganoderma applanatum polysaccharide (GAP) was investigated in human breast cancer MCF-7 cells, as well as the molecular mechanism of its effect on autophagy. Results showed that GAP contains three polysaccharides with molecular weights of 6.36 × 10⁵ Da, 4.25 × 10⁵ Da, and 2.53 × 10⁵ Da and which composed of rhamnose, glucose, arabinose, fucose in the molar ratio of 1:22:16.1:3.2. GAP inhibited the proliferation and migration of MCF-7 cells in a time-dose-dependent manner, the maximum inhibition rate reached 50.2% at 500 μg/mL in 48 h. Flow cytometry analysis showed that GAP could induce apoptosis, treatment of cells with GAP could result in up-regulation of gene and protein levels of autophagy-associated markers LC3 and Beclin-1; addition of autocrine late inhibitor CQ significantly raised the protein expression level of LC3II. The mitogen-activated protein kinases (MAPK) signaling pathway was not only related to the apoptotic pathway but also to the autophagy pathway; Western blot analysis showed that MAPK signaling pathway is involved in GAP-induced autophagy in MCF-7 cells. Detection of the relevant signaling pathway protein showed that the expression of p-ERK1/2 protein was down-regulated, however the expression of p-p38 and p-JNK protein was up-regulated. These results indicate that GAP could induce early autophagy in MCF-7 cells via the MAPK/ERK pathway. In conclusion, GAP showed strong antitumor activity by inducing apoptosis and autophagy through MAPK signaling pathway in MCF-7 cells, suggesting the molecular mechanism of fungal polysaccharide on its antitumor activity.

Autophagic flux disruption contributes to Ganoderma lucidum polysaccharide-induced apoptosis in human colorectal cancer cells via MAPK/ERK activation

Targeting autophagy may serve as a promising strategy for cancer therapy. Ganoderma lucidum polysaccharide (GLP) has been shown to exert promising anti-cancer effects. However, the underlying mechanisms remain elusive. Whether GLP regulates autophagy in cancer has never been reported. In this study, GLP induced the initiation of autophagy in colorectal cancer (CRC) HT-29 and HCT116 cells, as evidenced by enhanced level of LC3-II protein, GFP-LC3 puncta, and increased formation of double membrane vacuoles. However, GLP treatment caused marked increase of p62 expression. Addition of late stage autophagy inhibitor, chloroquine (CQ), further enhanced LC3-II and p62 level, as well as increased autophagosome accumulation, suggesting a blockage of autophagic flux by GLP in CRC cells. We then found GLP blocked autophagosome and lysosome fusion as determined by mRFP-GFP-LC3 colocalization analysis. Mechanistic study revealed that GLP-induced disruption of autophagosome-lysosome fusion is due to reduced lysosome acidification and lysosomal cathepsin activities. Cell viability and flow cytometry assays revealed that GLP-induced autophagosome accumulation is responsible for GLP-induced apoptosis in CRC cells. In line with this, inhibition of autophagy initiation by 3-methyladenine (3-MA), an early stage autophagy inhibitor, attenuated GLP-induced apoptosis. In contrast, suppression of autophagy at late stage by CQ enhanced the anti-cancer effect of GLP. Furthermore, we demonstrated that GLP-induced autophagosome accumulation and apoptosis is mediated via MAPK/ERK activation. Finally, GLP inhibited tumor growth and also inhibited autophagic flux in vivo. These results unveil new molecular mechanism underlying anti-cancer effects of GLP, suggesting that GLP is a potent autophagy inhibitor and might be useful in anticancer therapy.

Triple-edged therapy targeting intracellular alkalosis and extracellular acidosis in cancer

Extracellular acidity and intracellular alkalinity are two of the characteristics hallmarks of malignant cells and their environment. This involves an inversion of the extracellular/intracellular pH gradient when compared with normal cells and it gives malignant cells proliferative and invasive advantages. Thus, the reversal of the pH gradient is a legitimate objective in the treatment of cancer and may be accomplished with drugs already used for other purposes and/or with specific new drugs that are currently being studied. The aim of this review is to describe a triple approach for reversing this gradient inversion using the concerted utilization of proton extrusion inhibitors, mitochondrial poisons and lysosomal poisons that should act synergistically through different mechanisms. The scheme presented here is compatible with almost all the chemotherapeutic protocols currently being used.