Naja atra Cardiotoxin 1 Induces the FasL/Fas Death Pathway in Human Leukemia Cells

The p38 MAPK/snail signaling axis participates in cadmium-induced lung cancer cell migration and invasiveness

To determine that p38 MAPK activation contributes to the migration and invasion of lung cancer cells caused by cadmium (Cd). A549 lung cancer cell migration and invasion were assessed using a transwell plate system, and the role of p38 was determined by knocking down p38 activity with two different inhibitors of p38. The activity of p38 was measured by western blot analysis using phospho-specific p38 antibodies and normalized to blots using antibodies directed to total p38 proteins. Snail transcripts were measured using qRT-PCR. The inhibition of p38 blocked Cd-induced migration and invasion, which correlated with an increased activation of p38 as a function of dose and time. Furthermore, Cd-induced activation of p38 MAPK controlled the increase of snail mRNA expression. The p38 MAPK/snail signaling axis was involved in Cd-induced lung cancer cell migration and invasion.

High-throughput virtual screening, pharmacophore modelling and antagonist effects of small molecule inhibitors against cytotoxin-induced cytotoxicity

Cobra venom cytotoxins (CTX) cause dermonecrosis in envenomed patients who suffered from limb amputations due to the limitation of serotherapy-based antivenoms. This study aimed to identify small molecule inhibitors against CTX. A structure-based high-throughput virtual screening (HTVS) was conducted based on a conserved CTX, using the Natural Product Activity and Species Source (NPASS) screening library. The hits were valerenic acid, 1-oxo-2H-isoquinoline-4-carboxylic acid, acenaphthene, and 5-bromopyrrole-2-carboxamide, which interacted with contemporary antivenom binding site A and functional loops I-III of CTX, respectively, in molecular docking studies. Furthermore, molecular dynamic simulations were performed along with analysis of ligand fitness through their pharmacophore and pharmacokinetics properties. The antagonist effects of these hits on CTX-induced cytotoxicity were examined in human keratinocytes (HaCaT). Despite having a low binding affinity (KD = 14.45 × 10-4 M), acenaphthene demonstrated a significant increase of cell viability at 6 h and 24 h in experimental envenomed HaCaT. It also demonstrated the highest neutralization potency against CTX with a median effective concentration (EC50) of 0.05 mL/mg. Acenaphthene interacted with the functional loop II, which is the crucial cytotoxic site of CTX. It has an aromatic ring as its primary pharmacophoric feature, commonly used for rational drug design. In conclusion, acenaphthene could be a promising lead compound as a small molecule inhibitor.Communicated by Ramaswamy H. Sarma.

Effects of SIDT2 on the miR-25/NOX4/HuR axis and SIRT3 mRNA stability lead to ROS-mediated TNF-α expression in hydroquinone-treated leukemia cells

Our previous studies indicated that the benzene metabolite hydroquinone (HQ) evokes the ROS/p38 MAPK/protein phosphatase 2A/tristetraprolin axis, leading to increased TNF-α expression in human acute myeloid leukemia cell lines U937 and HL-60. In this study, we aimed to identify the upstream pathway involved in ROS-mediated TNF-α expression. HQ treatment increased SIDT2 expression, which subsequently decreased miR-25 and SIRT3 expression in U937 cells. Notably, miR-25 downregulation promoted SIDT2 expression in HQ-treated U937 cells. SIDT2 induced lysosomal degradation of SIRT3 mRNA, but inhibited miR-25 expression through a lysosome-independent pathway. MiR-25 inhibition reduced NOX4 mRNA turnover, resulting in increased NOX4 protein levels. NOX4 induces mitochondrial ROS production and HuR downregulation. Restoration of HuR expression increased SIRT3 expression, suggesting that NOX4-mediated HuR downregulation promotes SIDT2-mediated degradation of SIRT3 mRNA. Inhibition of NOX4 or SIRT3 overexpression abolished HQ-induced ROS production, thereby abolishing TNF-α upregulation. Overall, these results indicate that SIDT2 regulates the miR-25/NOX4/HuR axis and SIRT3 mRNA destabilization, leading to ROS-mediated TNF-α upregulation in HQ-treated U937 cells. HQ-induced increase in TNF-α expression in HL-60 cells was also mediated through a similar pathway.

The secretory phenotypes of envenomed cells: Insights into venom cytotoxicity

Snake envenomation is listed as Category A Neglected Tropical Diseases (NTD) by World Health Organization, indicates a severe public health problem. The global figures for envenomation cases are estimated to be more than 1.8 million annually. Even if the affected victims survive the envenomation, they might suffer from permanent morbidity due to local envenomation. One of the most prominent local envenomation is dermonecrosis. Dermonecrosis is a pathophysiological outcome of envenomation that often causes disability in the victims due to surgical amputations, deformities, contracture, and chronic ulceration. The key venom toxins associated with this local symptom are mainly attributed to substantial levels of enzymatic and non-enzymatic toxins as well as their possible synergistic actions. Despite so, the severity of the local tissue damage is based on macroscopic observation of the bite areas. Furthermore, limited knowledge is known about the key biomarkers involved in the pathogenesis of dermonecrosis. The current immunotherapy with antivenom is also ineffective against dermonecrosis. These local effects eventually end up as sequelae. There is also a global shortage of toxins-targeted therapeutics attributed to inadequate knowledge of the actual molecular mechanisms of cytotoxicity. This chapter discusses the characterization of secretory phenotypes of dermonecrosis as an advanced tool to indicate its severity and pathogenesis in envenomation. Altogether, the secretory phenotypes of envenomed cells and tissues represent the precise characteristics of dermonecrosis caused by venom toxins.

D-Mannose prevents bone loss under weightlessness

BACKGROUND

Astronauts undergo significant microgravity-induced bone loss during space missions, which has become one of the three major medical problems hindering human's long-term space flight. A risk-free and antiresorptive drug is urgently needed to prevent bone loss during space missions. D-mannose is a natural C-2 epimer of D-glucose and is abundant in cranberries. This study aimed to investigate the protective effects and potential mechanisms of D-mannose against bone loss under weightlessness.

METHODS

The hind legs of tail-suspended (TS) rats were used to mimic weightlessness on Earth. Rats were administered D-mannose intragastrically. The osteoclastogenic and osteogenic capacity of D-mannose in vitro and in vivo was analyzed by micro-computed tomography, biomechanical assessment, bone histology, serum markers of bone metabolism, cell proliferation assay, quantitative polymerase chain reaction, and western blotting. RNA-seq transcriptomic analysis was performed to detect the underlying mechanisms of D-mannose in bone protection.

RESULTS

The TS rats showed lower bone mineral density (BMD) and poorer bone morphological indices. D-mannose could improve BMD in TS rats. D-mannose inhibited osteoclast proliferation and fusion in vitro, without apparent effects on osteoblasts. RNA-seq transcriptomic analysis showed that D-mannose administration significantly inhibited the cell fusion molecule dendritic cell-specific transmembrane protein (DC-STAMP) and two indispensable transcription factors for osteoclast fusion (c-Fos and nuclear factor of activated T cells 1 [NFATc1]). Finally, TS rats tended to experience dysuria-related urinary tract infections (UTIs), which were suppressed by treatment with D-mannose.

CONCLUSION

D-mannose protected against bone loss and UTIs in rats under weightlessness. The bone protective effects of D-mannose were mediated by inhibiting osteoclast cell fusion. Our findings provide a potential strategy to protect against bone loss and UTIs during space missions.

Current Insights in the Mechanisms of Cobra Venom Cytotoxins and Their Complexes in Inducing Toxicity: Implications in Antivenom Therapy

Cytotoxins (CTXs), an essential class of the non-enzymatic three-finger toxin family, are ubiquitously present in cobra venoms. These low-molecular-mass toxins, contributing to about 40 to 60% of the cobra venom proteome, play a significant role in cobra venom-induced toxicity, more prominently in dermonecrosis. Structurally, CTXs contain the conserved three-finger hydrophobic loops; however, they also exhibit a certain degree of structural diversity that dictates their biological activities. In their mechanism, CTXs mediate toxicity by affecting cell membrane structures and membrane-bound proteins and activating apoptotic and necrotic cell death pathways. Notably, some CTXs are also responsible for depolarizing neurons and heart muscle membranes, thereby contributing to the cardiac failure frequently observed in cobra-envenomed victims. Consequently, they are also known as cardiotoxins (CdTx). Studies have shown that cobra venom CTXs form cognate complexes with other components that potentiate the toxic effects of the venom's individual component. This review focuses on the pharmacological mechanism of cobra venom CTXs and their complexes, highlighting their significance in cobra venom-induced pathophysiology and toxicity. Furthermore, the potency of commercial antivenoms in reversing the adverse effects of cobra venom CTXs and their complexes in envenomed victims has also been discussed.

The myth of cobra venom cytotoxin: More than just direct cytolytic actions

Cobra venom cytotoxin (CTX) is a non-enzymatic three-finger toxin that constitutes 40-60% of cobra venom. Thus, it plays an important role in the pathophysiology of cobra envenomation, especially in local dermonecrosis. The three-finger hydrophobic loops of CTX determine the cytotoxicity. Nevertheless, the actual mechanisms of cytotoxicity are not fully elucidated as they involve not only cytolytic actions but also intracellular signalling-mediated cell death pathways. Furthermore, the possible transition cell death pattern remains to be explored. The actual molecular mechanisms require further studies to unveil the relationship between different CTXs from different cobra species and cell types which may result in differential cell death patterns. Here, we discuss the biophysical interaction of CTX with the cell membrane involving four binding modes: electrostatic interaction, hydrophobic partitioning, isotropic phase, and oligomerisation. Oligomerisation of CTX causes pore formation in the membrane lipid bilayer. Additionally, the CTX-induced apoptotic pathway can be executed via death receptor-mediated extrinsic pathways and mitochondrial-mediated intrinsic pathways. We also discuss lysosomal-mediated necrosis and the occurrence of necroptosis following CTX action. Collectively, we provided an insight into concentration-dependent transition of cell death pattern which involves different mechanistic actions. This contributes a new direction for further investigation of cytotoxic pathways activated by the CTXs for future development of biotherapeutics targeting pathological effects caused by CTX.