Activation of CaMKKβ/AMPKα pathway by 2-AG in human platelets

Endocannabinoid hydrolases differentially distribute in platelets and red blood cells and are differentially released by thrombin

BACKGROUND

Plasma levels of the major endocannabinoids 2-arachidonoylgycerol (2AG) and anandamide (N-arachidonoylethanolamine, AEA) have been identified to vary independently with particular pathological conditions. The levels of these endocannabinoids are tightly regulated by two hydrolytic enzymes, monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), respectively.

OBJECTIVES

In this study, we have quantified these enzyme activities in the major blood fractions.

PATIENTS/METHODS

In blood fractions from human volunteers, radiometric assays were used to quantify monoacylglycerol lipase and fatty acid amide hydrolase. Tagging with fluorophosphonate-rhodamine allowed quantification of platelet serine hydrolase activities.

RESULTS

Fatty acid amide hydrolase activity was highest in platelets, while MAGL activity was most abundant in erythrocytes. Sampling the blood of donors on two further occasions 15 days apart showed no significant change in platelet FAAH or erythrocyte MAGL activities. Activities were not different when comparing female donors with males. Storage of these blood fractions at - 80 °C was associated with a rapid loss in enzyme activities, which could largely by avoided by storage in liquid nitrogen. Incubation of platelets and erythrocytes in the presence of thrombin lead to release of measurable FAAH, but not MAGL, activity. Tagging of serine hydrolase activities with fluorophosphonate-rhodamine allowed confirmation of MAGL activity in platelet preparations, as well as multiple other enzymes.

CONCLUSIONS

These investigations suggest a potential role for FAAH in regulation of coagulation, while the role of MAGL in blood requires further investigation.

Disorders of cancer metabolism: The therapeutic potential of cannabinoids

Abnormal energy metabolism, as one of the important hallmarks of cancer, was induced by multiple carcinogenic factors and tumor-specific microenvironments. It comprises aerobic glycolysis, de novo lipid biosynthesis, and glutamine-dependent anaplerosis. Considering that metabolic reprogramming provides various nutrients for tumor survival and development, it has been considered a potential target for cancer therapy. Cannabinoids have been shown to exhibit a variety of anticancer activities by unclear mechanisms. This paper first reviews the recent progress of related signaling pathways (reactive oxygen species (ROS), AMP-activated protein kinase (AMPK), mitogen-activated protein kinases (MAPK), phosphoinositide 3-kinase (PI3K), hypoxia-inducible factor-1alpha (HIF-1α), and p53) mediating the reprogramming of cancer metabolism (including glucose metabolism, lipid metabolism, and amino acid metabolism). Then we comprehensively explore the latest discoveries and possible mechanisms of the anticancer effects of cannabinoids through the regulation of the above-mentioned related signaling pathways, to provide new targets and insights for cancer prevention and treatment.

Endocannabinoids effect on oxidative status of human platelets

Reactive oxygen species (ROS) are known to regulate platelet activation. Since endocannabinoids behave as platelet agonists, we investigated the effect of two endocannabinoids, 2-arachidonoylglycerol (2AG) and anandamide (AEA) on the oxidative status of human platelets. We have demonstrated that 2AG and AEA stimulate ROS production, superoxide anion formation and lipid peroxidation. The effect is dose and time dependent and mainly occurs through the involvement of cannabinoid receptor 1 (CB1) since all tested parameters are greatly reduced by SR141716, the CB1 specific inhibitor. The specific inhibitor of cannabinoid receptor 2 (CB2) SR144528 produces a very small inhibition. The involvement of syk/PI3K/AKT/mTor pathway in oxidative stress induced by endocannabinoids is shown. Nicotinamide adenine dinucleotide phosphate oxidase seems to be poorly involved in the endocannabinoids effect. Concerning the aerobic metabolism, it has been demonstrated that endocannabinoids reduce the oxygen consumption and adenosine triphosphate synthesis, both in the presence of pyruvate + malate or succinate. In addition, endocannabinoids inhibit the activity of respiratory complexes II, III and IV and increase the activity of respiratory complex I. The endocannabinoids effect on aerobic metabolism seems to be also a CB1 mediated mechanism. Thus, in human platelets oxidative stress induced by endocannabinoids, mainly generated in the respiratory chain through the activation of complex I and the inhibition of complex II, III and IV, may lead to thrombotic events, contributing to cardiovascular diseases.

Mitochondrial ALDH2 protects against lipopolysaccharide-induced myocardial contractile dysfunction by suppression of ER stress and autophagy

Lipopolysaccharide (LPS), an essential component of outer membrane of the Gram-negative bacteria, plays a pivotal role in myocardial anomalies in sepsis. Recent evidence depicted an essential role for mitochondrial aldehyde dehydrogenase (ALDH2) in cardiac homeostasis. This study examined the effect of ALDH2 on endotoxemia-induced cardiac anomalies. Echocardiographic, cardiac contractile and intracellular Ca²⁺ properties were examined. Our results indicated that LPS impaired cardiac contractile function (reduced fractional shortening, LV end systolic diameter, peak shortening, maximal velocity of shortening/relengthening, prolonged relengthening duration, oxidation of SERCA, and intracellular Ca²⁺ mishandling), associated with ER stress, inflammation, O₂^- production, increased autophagy, CAMKKβ, phosphorylated AMPK and suppressed phosphorylation of mTOR, the effects of which were significantly attenuated or negated by ALDH2. LPS promoted early endosomal formation (as evidenced by RAB4 and RAB5a), apoptosis and necrosis (MTT and LDH) while decreasing late endosomal formation (RAB7 and RAB 9), the effects were reversed by ALDH2. In vitro study revealed that LPS-induced SERCA oxidation, autophagy and cardiac dysfunction were abrogated by ALDH2 activator Alda-1, the ER chaperone TUDCA, the autophagy inhibitor 3-MA, or the AMPK inhibitor Compound C. The beneficial effect of Alda-1 against LPS was nullified by AMPK activator AICAR or rapamycin. CAMKKβ inhibition failed to rescue LPS-induced ER stress. Tunicamycin-induced cardiomyocyte dysfunction was ameliorated by Alda-1 and autophagy inhibition, the effect of which was abolished by rapamycin. These data suggested that ALDH2 protected against LPS-induced cardiac anomalies via suppression of ER stress, autophagy in a CAMKKβ/AMPK/mTOR-dependent manner.

Propofol Regulates Neural Stem Cell Proliferation and Differentiation via Calmodulin-Dependent Protein Kinase II/AMPK/ATF5 Signaling Axis

BACKGROUND

Propofol can cause degeneration of developing brain cells and subsequent long-term learning or memory impairment. However, at the early stage of embryonic development, the molecular mechanism of propofol-induced inhibition in neural stem cells (NSCs) neurogenesis is still unclear. The aim of this study was to determine the role of propofol in NSCs neurogenesis and, more importantly, to explore the underlying mechanism.

METHODS

First, a single intraperitoneal injection of propofol was performed in pregnant mice, and 6 hours after administration of propofol, the hippocampus RNA and the protein of the embryos' brains was extracted to analyze the expression of neuron-specific markers. Second, the primary NSCs were isolated from the hippocampus of mouse embryonic brain and then treated with propofol for cell viability, immunostaining, and transwell assays; more importantly, we performed RNA sequencing (RNA-seq) and q-reverse transcription polymerase chain reaction assays to identify genes regulated by propofol; the Western blot, small interfering RNA (SiRNA), and luciferase reporter assays were used to study the effects of propofol on calmodulin-dependent protein kinase (CaMk) II/5' adenosine monophosphate-activated protein kinase (AMPK)/activating transcription factor 5 (ATF5) signaling pathway.

RESULTS

Our results indicated that propofol treatment could inhibit the proliferation, migration, and differentiation of NSCs. The results of RNA-seq assays showed that propofol treatment resulted in downregulation of a group of Ca-dependent genes. The following mechanism studies showed that propofol regulates the proliferation, differentiation, and migration of NSCs through the CaMkII/phosphorylation of serine at amino acid position 485 (pS485)/AMPK/ATF5 signaling pathway.

CONCLUSIONS

The results from study demonstrated that propofol inhibits the proliferation, differentiation, and migration of NSCs, and these effects are partially mediated by CaMkII/pS485/AMPK/ATF5 signaling pathway.

AMPK-ACC signaling modulates platelet phospholipids and potentiates thrombus formation

AMP-activated protein kinase (AMPK) α1 is activated in platelets on thrombin or collagen stimulation, and as a consequence, phosphorylates and inhibits acetyl-CoA carboxylase (ACC). Because ACC is crucial for the synthesis of fatty acids, which are essential for platelet activation, we hypothesized that this enzyme plays a central regulatory role in platelet function. To investigate this, we used a double knock-in (DKI) mouse model in which the AMPK phosphorylation sites Ser79 on ACC1 and Ser212 on ACC2 were mutated to prevent AMPK signaling to ACC. Suppression of ACC phosphorylation promoted injury-induced arterial thrombosis in vivo and enhanced thrombus growth ex vivo on collagen-coated surfaces under flow. After collagen stimulation, loss of AMPK-ACC signaling was associated with amplified thromboxane generation and dense granule secretion. ACC DKI platelets had increased arachidonic acid-containing phosphatidylethanolamine plasmalogen lipids. In conclusion, AMPK-ACC signaling is coupled to the control of thrombosis by specifically modulating thromboxane and granule release in response to collagen. It appears to achieve this by increasing platelet phospholipid content required for the generation of arachidonic acid, a key mediator of platelet activation.