Self-regulation of BAX-induced cell death

TRAIL-induced apoptosis and proteasomal activity - Mechanisms, signalling and interplay

Programmed cell death, in particular apoptosis, is essential during development and tissue homeostasis, and also is the primary strategy to induce cancer cell death by cytotoxic therapies. Precision therapeutics targeting TRAIL death receptors are being evaluated as novel anti-cancer agents, while in parallel highly specific proteasome inhibitors have gained approval as drugs. TRAIL-dependent signalling and proteasomal control of cellular proteostasis are intricate processes, and their interplay can be exploited to enhance therapeutic killing of cancer cells in combination therapies. This review provides detailed insights into the complex signalling of TRAIL-induced pathways and the activities of the proteasome. It explores their core mechanisms of action, pharmaceutical druggability, and describes how their interplay can be strategically leveraged to enhance cell death responses in cancer cells. Offering this comprehensive and timely overview will allow to navigate the complexity of the processes governing cell death mechanisms in TRAIL- and proteasome inhibitor-based treatment conditions.

Chemical modulation of cytosolic BAX homodimer potentiates BAX activation and apoptosis

The BCL-2 family protein BAX is a major regulator of physiological and pathological cell death. BAX predominantly resides in the cytosol in a quiescent state and upon stress, it undergoes conformational activation and mitochondrial translocation leading to mitochondrial outer membrane permeabilization, a critical event in apoptosis execution. Previous studies reported two inactive conformations of cytosolic BAX, a monomer and a dimer, however, it remains unclear how they regulate BAX. Here we show that, surprisingly, cancer cell lines express cytosolic inactive BAX dimers and/or monomers. Expression of inactive dimers, results in reduced BAX activation, translocation and apoptosis upon pro-apoptotic drug treatments. Using the inactive BAX dimer structure and a pharmacophore-based drug screen, we identify a small-molecule modulator, BDM19 that binds and activates cytosolic BAX dimers and prompts cells to apoptosis either alone or in combination with BCL-2/BCL-XL inhibitor Navitoclax. Our findings underscore the role of the cytosolic inactive BAX dimer in resistance to apoptosis and demonstrate a strategy to potentiate BAX-mediated apoptosis.

Biological effect of PM10 on airway epithelium-focus on obstructive lung diseases

Recently, a continuous increase in environmental pollution has been observed. Despite wide-scale efforts to reduce air pollutant emissions, the problem is still relevant. Exposure to elevated levels of airborne particles increased the incidence of respiratory diseases. PM₁₀ constitute the largest fraction of air pollutants, containing particles with a diameter of less than 10 μm, metals, pollens, mineral dust and remnant material from anthropogenic activity. The natural airway defensive mechanisms against inhaled material, such as mucus layer, ciliary clearance and macrophage phagocytic activity, may be insufficient for proper respiratory function. The epithelium layer can be disrupted by ongoing oxidative stress and inflammatory processes induced by exposure to large amounts of inhaled particles as well as promote the development and exacerbation of obstructive lung diseases. This review draws attention to the current state of knowledge about the physical features of PM₁₀ and its impact on airway epithelial cells, and obstructive pulmonary diseases.

Cognitive impairment in myocardial infarction and heart failure

Myocardial infarction (MI) occurs when coronary blood flow is decreased due to an obstruction/occlusion of the vessels, leading to myocardial death and progression to heart failure (HF). Cognitive impairment, anxiety, depression and memory loss are the most frequent mental health problems among patients with HF. The most common cause of cognitive decline is cardiac systolic dysfunction, which leads to reduced cerebral perfusion. Several in vivo and clinical studies provide information regarding the underlying mechanisms of HF in brain pathology. Neurohormonal activation, oxidative stress, inflammation, glial activation, dendritic spine loss and brain programmed cell death are all proposed as contributors of cognitive impairment in HF. Furthermore, several investigations into the effects of various medications on brain pathology utilizing MI models have been reported. In this review, potential mechanisms involving HF-associated cognitive impairment, as well as neuroprotective interventions in HF models, are discussed and summarized. In addition, gaps in the surrounding knowledge, including the types of brain cell death and the effects of cell death inhibitors in HF, are presented and discussed. This review provides valuable information that will suggest the potential therapeutic strategies for cognitive impairment in patients with HF.

Pharmacodynamic modeling of synergistic birinapant/paclitaxel interactions in pancreatic cancer cells

Background

For most patients, pancreatic adenocarcinoma responds poorly to treatment, and novel therapeutic approaches are needed. Standard-of-care paclitaxel (PTX), combined with birinapant (BRP), a bivalent mimetic of the apoptosis antagonist SMAC (second mitochondria-derived activator of caspases), exerts synergistic killing of PANC-1 human pancreatic adenocarcinoma cells.

Methods

To investigate potential mechanisms underlying this synergistic pharmacodynamic interaction, data capturing PANC-1 cell growth, apoptosis kinetics, and cell cycle distribution were integrated with high-quality IonStar-generated proteomic data capturing changes in the relative abundance of more than 3300 proteins as the cells responded to the two drugs, alone and combined.

Results

PTX alone (15 nM) elicited dose-dependent G2/M-phase arrest and cellular polyploidy. Combined BRP/PTX (150/15 nM) reduced G2/M by 35% and polyploid cells by 45%, and increased apoptosis by 20%. Whereas BRP or PTX alone produced no change in the pro-apoptotic protein pJNK, and a slight increase in the anti-apoptotic protein Bcl2, the drug combination increased pJNK and decreased Bcl2 significantly compared to the vehicle control. A multi-scale, mechanism-based mathematical model was developed to investigate integrated birinapant/paclitaxel effects on temporal profiles of key proteins involved in kinetics of cell growth, death, and cell cycle distribution.

Conclusions

The model, consistent with the observed reduction in the Bcl2/BAX ratio, suggests that BRP-induced apoptosis of mitotically-arrested cells is a major contributor to the synergy between BRP and PTX. Coupling proteomic and cellular response profiles with multi-scale pharmacodynamic modeling provides a quantitative mechanistic framework for evaluating pharmacodynamically-based drug-drug interactions in combination chemotherapy, and could potentially guide the development of promising drug regimens.

[Anti-tumor and immune-modulating effect of Jiawei Sijunzi decoction in mice bearing hepatoma H22 tumor]

OBJECTIVE

To investigate the antitumor activity of Jiawei Sijunzi decoction and study its liver and kidney toxicity and its effect on the immune system in a tumor-bearing mouse model.

METHODS

Hepatoma H22 tumor-bearing mouse models were randomized into model group, cyclophosphamide (CTX) group, and low-, moderate-, and high-dose Jiawei Sijunzi decoction groups (JW-L, JW-M, and JW-H groups, respectively). The antitumor activity of Jiawei Sijunzi decoction was assessed by calculating the tumor inhibition rate and pathological observation of the tumor tissues. Immunohistochemistry was used to detect the expressions of Bax, Bcl-2, Bax/Bcl-2 and caspase-3 in the tumors. The liver and kidney toxicity of Jiawei Sijunzi decoction was analyzed by evaluating the biochemical indicators of liver and kidney functions. The immune function of the tumor-bearing mice were assessed by calculating the immune organ index, testing peripheral blood routines, and detection of serum IL-2 and TNF-α levels using enzyme-linked immunosorbent assay.

RESULTS

Compared with that in the model group, the tumor mass in CTX, JW-M and JW-H groups were all significantly reduced (P < 0.05) with cell rupture and necrosis in the tumors. Immunohistochemistry revealed obviously up-regulated expressions of Bax and caspase-3 and down- regulated expression of Bcl-2 protein with an increased Bax/Bcl-2 ratio in CTX, JW-M and JW-H groups. Treatment with Jiawei Sijunzi decoction significantly reduced Cr, BUN, AST and ALT levels, improved the immune organ index, increased peripheral blood leukocytes, erythrocytes and hemoglobin levels, and up-regulated the levels of TNF-α and IL-2 in the tumor-bearing mice. These changes were especially significant in JW-H group when compared with the parameters in the model group (P < 0.01).

CONCLUSIONS

Jiawei Sijunzi decoction has a strong anti-tumor activity and can improve the liver and kidney functions of tumor-bearing mice. Its anti-tumor effect may be attributed to the up-regulation of Bax, caspase-3, TNF-α and IL-2 levels and the down-regulation of Bcl-2 expression as well as the enhancement of the non-specific immune function.

The mechanism of ATF3 repression of epithelial-mesenchymal transition and suppression of cell viability in cholangiocarcinoma via p53 signal pathway

The aim of this research was to determine the underlying mechanism of activating transcription factor 3 (ATF3) on cell proliferation, invasion, migration and epithelial‐mesenchymal transition (EMT). The differentially expressed mRNAs in cholangiocarcinoma (CC) and its adjacent tissues were screened by microarray analysis, and the expression of ATF3 was detected through Quantitative real time polymerase chain reaction (qRT‐PCR) and Western blot. The expression of EMT markers and p53‐related proteins was analysed by Western blot. Analyses using the Cell Counting Kit‐8 and TUNEL were performed to assess the rate of apoptosis and cell proliferation. Scratch wound and transwell assays were performed to study cell migration and invasion. Activating transcription factor 3 was restrained in CC cell lines and tissues and inhibited EMT while activating the p53 signalling pathway. Knockdown of ATF3 promoted cell proliferation but reduced the rate of apoptosis by inhibiting p53 signalling. Cell migration and invasion can be strengthened by ATF3 through activating the p53 signalling pathway.

Lipopolysaccharide induces human olfactory ensheathing glial apoptosis by promoting mitochondrial dysfunction and activating the JNK-Bnip3-Bax pathway

Olfactory ensheathing glia (OEG) play an important role in regulating the regeneration of an injured nervous system. However, chronic inflammation damage reduces the viability of OEG via poorly understood mechanisms. We aimed to investigate the pathological responses of OEG in response to LPS-mediated inflammation stress in vitro. The results indicated that lipopolysaccharide (LPS) treatment significantly reduced the viability of OEG in a dose-dependent fashion. Mechanistically, LPS stimuli induced mitochondrial oxidative damage, mitochondrial fragmentation, mitochondrial metabolism disruption, and mitochondrial apoptosis activation. Furthermore, we verified that LPS modulated mitochondrial apoptosis by promoting Bax upregulation, and this process was regulated by the JNK-Bnip3 pathway. Inhibition of the JNK-Bnip3 pathway prevented LPS-mediated Bax activation, thus attenuating OEG apoptosis. Altogether, our data illustrated that LPS-mediated inflammation injury evoked mitochondrial abnormalities in OEG damage via the JNK-Bnip3-Bax pathway. This finding provides a potential target to protect OEG against chronic inflammation stress.

Differential Impacts of Alternative Splicing Networks on Apoptosis

Apoptosis functions as a common mechanism to eliminate unnecessary or damaged cells during cell renewal and tissue development in multicellular organisms. More than 200 proteins constitute complex networks involved in apoptotic regulation. Imbalanced expressions of apoptosis-related factors frequently lead to malignant diseases. The biological functions of several apoptotic factors are manipulated through alternative splicing mechanisms which expand gene diversity by generating discrete variants from one messenger RNA precursor. It is widely observed that alternatively-spliced variants encoded from apoptosis-related genes exhibit differential effects on apoptotic regulation. Alternative splicing events are meticulously regulated by the interplay between trans-splicing factors and cis-responsive elements surrounding the regulated exons. The major focus of this review is to highlight recent studies that illustrate the influences of alternative splicing networks on apoptotic regulation which participates in diverse cellular processes and diseases.