Stressed platelets ASK1 for a MAPK

Abrogating PDK4 activates autophagy-dependent ferroptosis in breast cancer via ASK1/JNK pathway

BACKGROUND

Targeting ferroptosis mediated by autophagy presents a novel therapeutic approach to breast cancer, a mortal neoplasm on the global scale. Pyruvate dehydrogenase kinase isozyme 4 (PDK4) has been denoted as a determinant of breast cancer metabolism. The target of this study was to untangle the functional mechanism of PDK4 in ferroptosis dependent on autophagy in breast cancer.

METHODS

RT-qPCR and western blotting examined PDK4 mRNA and protein levels in breast cancer cells. Immunofluorescence staining appraised light chain 3 (LC3) expression. Fe (2 +) assay estimated total iron level. Relevant assay kits and C11-BODIPY (591/581) staining evaluated lipid peroxidation level. DCFH-DA staining assayed intracellular reactive oxygen species (ROS) content. Western blotting analyzed the protein levels of autophagy, ferroptosis and apoptosis-signal-regulating kinase 1 (ASK1)/c-Jun N-terminal kinase (JNK) pathway-associated proteins.

RESULTS

PDK4 was highly expressed in breast cancer cells. Knockdown of PDK4 induced the autophagy of breast cancer cells and 3-methyladenine (3-MA), an autophagy inhibitor, countervailed the promoting role of PDK4 interference in ferroptosis in breast cancer cells. Furthermore, PDK4 knockdown activated ASK1/JNK pathway and ASK1 inhibitor (GS-4997) partially abrogated the impacts of PDK4 absence on the autophagy and ferroptosis in breast cancer cells.

CONCLUSION

To sum up, deficiency of PDK4 activated ASK1/JNK pathway to stimulate autophagy-dependent ferroptosis in breast cancer.

Oxidative Stress-Induced Platelet Apoptosis/Activation: Alleviation by Purified Curcumin via ASK1-JNK/p-38 Pathway

Platelets are known for their indispensable role in hemostasis and thrombosis. However, alteration in platelet function due to oxidative stress is known to mediate various health complications, including cardiovascular diseases and other health complications. To date, several synthetic molecules have displayed antiplatelet activity; however, their uses are associated with bleeding and other adverse effects. The commercially available curcumin is generally a mixture of three curcuminoids: curcumin, demethoxycurcumin, and bisdemethoxycurcumin. Although crude curcumin is known to inhibit platelet aggregation, the effect of purified curcumin on platelet apoptosis, activation, and aggregation remains unclear. Therefore, in this study, curcumin was purified from a crude curcumin mixture and the effects of this preparation on the oxidative stress-induced platelet apoptosis and activation was evaluated. 2,2'-Azobis(2-methylpropionamidine) dihydrochloride (AAPH) compound was used as an inducer of oxidative stress. Purified curcumin restored AAPH-induced platelet apoptotic markers like reactive oxygen species, intracellular calcium level, mitochondrial membrane potential, cardiolipin peroxidation, cytochrome c release from mitochondria to the cytosol, and phosphatidyl serine externalization. Further, it inhibited the agonist-induced platelet activation and aggregation, demonstrating its antiplatelet activity. Western blot analysis confirms protective effect of the purified curcumin against oxidative stress-induced platelet apoptosis and activation via downregulation of MAPKs protein activation, including ASK1, JNK, and p-38. Together, these results suggest that the purified curcumin could be a potential therapeutic bioactive molecule to treat the oxidative stress-induced platelet activation, apoptosis, and associated complications.

Effect of stimulated platelets in COVID-19 thrombosis: Role of alpha7 nicotinic acetylcholine receptor

Since early 2020, SARS-CoV-2-induced infection resulted in global pandemics with high morbidity, especially in the adult population. COVID-19 is a highly prothrombotic condition associated with subsequent multiorgan failure and lethal outcomes. The exact mechanism of the prothrombotic state is not well understood and might be multifactorial. Nevertheless, platelets are attributed to play a crucial role in COVID-19-associated thrombosis. To date, platelets' role was defined primarily in thrombosis and homeostasis. Currently, more focus has been set on their part in inflammation and immunity. Moreover, their ability to release various soluble factors under activation as well as internalize and degrade specific pathogens has been highly addressed in viral research. This review article will discuss platelet role in COVID-19-associated thrombosis and their role in the cholinergic anti-inflammatory pathway. Multiple studies confirmed that platelets display a hyperactivated phenotype in COVID-19 patients. Critically ill patients demonstrate increased platelet activation markers such as P-selectin, PF4, or serotonin. In addition, platelets contain acetylcholine and express α7 nicotinic acetylcholine receptors (α7nAchR). Thus, acetylcholine can be released under activation, and α7nAchR can be stimulated in an autocrine manner and support platelet function. α7 receptor is one of the most important mediators of the anti-inflammatory properties as it is associated with humoral and intrinsic immunity and was demonstrated to contribute to better outcomes in COVID-19 patients when under stimulation. Hematopoietic α7nAchR deficiency increases platelet activation and, in experimental studies, α7nAchR stimulation can diminish the pro-inflammatory state and modulate platelet reactiveness via increased levels of NO. NO has been described to inhibit platelet adhesion, activation, and aggregation. In addition, acetylcholine has been demonstrated to decrease platelet aggregation possibly by blocking the e p-38 pathway. SARS-CoV-2 proteins have been found to be similar to neurotoxins which can bind to nAChR and prevent the action of acetylcholine. Concluding, the platelet role in COVID-19 thrombotic events could be explained by their active function in the cholinergic anti-inflammatory pathway.

Tannins as Hemostasis Modulators

The hemostasis system is often affected by complications associated with cardiovascular diseases, which results in thromboembolic events. Compounds of plant origin and plant extracts are considered as a promising source of substances that could modulate the functioning of the hemostasis system and thus reduce the risk of thromboembolism. Among them, tannins, which are plant-origin compounds with potential effects in hemostasis, deserve a special mention. This paper describes the hemostasis-modifying ability of three groups of tannins, namely ellagitannins, gallotannins, and procyanidins. The review highlights the desirable as well as undesirable influence of tannins on specific components of hemostasis, namely platelets, coagulation system, fibrinolysis system, and endothelium, and the multidirectional effect of these compounds on the thrombotic process. Studies performed under normal and pathological conditions such as diabetes or hypercoagulation are described, and the pathophysiology-dependent action of tannins is also highlighted. Most of the studies presented in the paper were performed in vitro, and due to the low bioavailability of tannins more studies should be conducted in the future to understand their actual activity in vivo.

Astaxanthin alleviates inflammatory pain by regulating the p38 mitogen-activated protein kinase and nuclear factor-erythroid factor 2-related factor/heme oxygenase-1 pathways in mice

Inflammatory pain is a complex process that has a substantial negative impact on post-injury quality of life. Astaxanthin (AST), which is a lipid-soluble red-orange carotenoid that is found in lobsters, inhibits the development and maintenance of inflammation in mice via its antioxidant and anti-inflammatory activities. However, the specific mechanisms underlying these effects remain unclear. In this study, we aimed to elucidate the mechanism by which astaxanthin alleviated inflammation using a mouse model with Complete Freund's adjuvant (CFA)-induced inflammatory pain. Mechanical allodynia and thermal hyperalgesia were observed on days 1-14 post CFA injection. Expression of p38 mitogen-activated protein kinase (MAPK) in the left paw and L4-6 dorsal root ganglia (DRG) were upregulated in the CFA-induced mice. Expression of the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathways were also increased. Astaxanthin relieved mechanical allodynia and thermal hyperalgesia induced by CFA and inhibited the inflammatory response (e.g., infiltration of inflammatory cells and production of inflammatory factors) in the ipsilateral paw and DRG. Additionally, AST  inhibited p38 MAPK and enhanced Nrf2/HO-1 contents in the left paw and DRG, and reversed the pain induced by p38 MAPK agonist and Nrf2 inhibitors. These findings suggest that AST exerts anti-inflammatory effects and regulates p38 MAPK and Nrf2/HO-1 to alleviate inflammatory pain. AST may be a potential therapeutic agent for relieving inflammation.

ASK1/p38‑mediated NLRP3 inflammasome signaling pathway contributes to aberrant retinal angiogenesis in diabetic retinopathy

Diabetic retinopathy (DR) is the leading cause of blindness among the working-age population in several countries. Despite the available treatments, some patients are diagnosed at the late stages of the disease when treatment is more difficult. Hence, it is crucial that novel targets are identified in order to improve the clinical therapy of DR. In the present study, an animal model of DR and a cell model using primary human retinal microvascular endothelial cells exposed to high glucose were constructed to examine the association between apoptosis signal-regulating kinase 1 (ASK1)/p38 and NLR family pyrin domain containing 3 (NLRP3) in DR. The results revealed that DR induced inflammatory response and micro-vascular cell proliferation. NLRP3 contributed to DR-mediated inflammatory development and progression, which promoted the expression of inflammatory-related cytokines. In addition, NLRP3 promoted the tube formation of retinal microvascular endothelial cells and angiogenesis. Moreover, further research indicated that the NLRP3-mediated aberrant retinal angiogenesis in DR was regulated by ASK1 and p38. It was thus suggested that ASK1/p38 may be novel target for the treatment of DR.

The Cell Cycle Checkpoint System MAST(L)-ENSA/ARPP19-PP2A is Targeted by cAMP/PKA and cGMP/PKG in Anucleate Human Platelets

The cell cycle is controlled by microtubule-associated serine/threonine kinase-like (MASTL), which phosphorylates the cAMP-regulated phosphoproteins 19 (ARPP19) at S62 and 19e/α-endosulfine (ENSA) at S67and converts them into protein phosphatase 2A (PP2A) inhibitors. Based on initial proteomic data, we hypothesized that the MASTL-ENSA/ARPP19-PP2A pathway, unknown until now in platelets, is regulated and functional in these anucleate cells. We detected ENSA, ARPP19 and various PP2A subunits (including seven different PP2A B-subunits) in proteomic studies of human platelets. ENSA-S109/ARPP19–S104 were efficiently phosphorylated in platelets treated with cAMP- (iloprost) and cGMP-elevating (NO donors/riociguat) agents. ENSA-S67/ARPP19-S62 phosphorylations increased following PP2A inhibition by okadaic acid (OA) in intact and lysed platelets indicating the presence of MASTL or a related protein kinase in human platelets. These data were validated with recombinant ENSA/ARPP19 and phospho-mutants using recombinant MASTL, protein kinase A and G. Both ARPP19 phosphorylation sites S62/S104 were dephosphorylated by platelet PP2A, but only S62-phosphorylated ARPP19 acted as PP2A inhibitor. Low-dose OA treatment of platelets caused PP2A inhibition, diminished thrombin-stimulated platelet aggregation and increased phosphorylation of distinct sites of VASP, Akt, p38 and ERK1/2 MAP kinases. In summary, our data establish the entire MASTL(like)–ENSA/ARPP19–PP2A pathway in human platelets and important interactions with the PKA, MAPK and PI3K/Akt systems.

Reduced nicotinamide adenine dinucleotide phosphate inhibits rat platelet aggregation and p38 phosphorylation

Previous studies found that reduced nicotinamide adenine dinucleotide phosphate (NADPH) protected neurons against ischemia/reperfusion-induced injury. In addition to ROS reduction and ATP increment, preliminary data suggested that NADPH inhibited ADP and thrombin-induced platelet aggregation. As the effect of NADPH on platelet function was not reported by other investigators, the actions of NADPH on platelet function and mechanisms of actions were investigated in the present study. In vitro studies, the effects of different concentrations of NADPH on platelet aggregation induced by ADP (10 μM), thrombin (0.05 U/mL) or AA (50 μM) were determined. The results showed that NADPH could inhibit platelet aggregation induced by ADP, thrombin or AA in a concentration dependent manner. When the inhibitory effects of NAD⁺, NADH, NADP⁺ and NADPH on platelet aggregation were compared, NADPH demonstrated the relatively best effect on platelet aggregation. In vivo studies, the effects of NADPH on platelet aggregation, tail bleeding time, coagulation response and ferric chloride-induced thrombosis were determined in mice or rats. The maximum aggregation rate of platelets of rats injected with NADPH (5 mg/kg) was lower than platelets from control rats. NADPH transiently prolonged tail bleeding time in mice at 30 min after the injection of NADPH (7.5 mg/kg), while aspirin (15 mg/kg) significantly prolonged the tail bleeding time in mice at all time points examined. NADPH (5 mg/kg), as well as aspirin (10 mg/kg), had no effect on coagulation response in rats. Using a FeCl₃-induced abdominal aorta injury thrombosis model, administration of NADPH (5 mg/kg) significantly delayed the onset of vessel occlusion, while aspirin (10 mg/kg) almost completely prevented the vessel occlusion. With microscopic examination the thrombi in injured vessel sections of rats received NADPH were much smaller and less dense than that of rats received vehicle treatment. ADP induced an increase in phosphorylation of p38 and the effect was markedly inhibited by the p38 inhibitor SB203580. Similarly, NADPH also inhibited ADP-induced phosphorylation of p38. Similar to NADPH, SB203580 robustly inhibited ADP- and thrombin-induced platelet aggregation. In addition, NADPH also reduced ADP-induced increases in ROS in platelets. The current results demonstrated that NADPH inhibited platelet aggregation, oxidative stress and p38 phosphorylation, suggesting that NADPH might be a novel compound for management of high risk of cardiovascular disease.