Activation of phospholipase A2 by Hsp70 in vitro

Ambient NO2 exposure induced cardiotoxicity associated with gut microbiome dysregulation and glycerophospholipid metabolism disruption

An average daily increase of 10 μg/m³ in NO₂ concentrations could lead to an increased mortality in cardiovascular, cerebrovascular of 1.89%, 2.07%, but the mechanism by which NO₂ contributes to cardiotoxicity is rarely reported. In order to assess the cardiotoxicity of NO₂ inhalation (5 ppm), we firstly investigate the change of gut microbiota, serum metabonomics and cardiac proteome. Non-targeted LC-MS/MS metabonomics showed that NO₂ stress could perturb the glycerophospholipid metabolism in the serum, which might destabilize the bilayer configuration of cardiac lipid membranes. Furthermore, we observed that NO₂ inhalation caused augmented intercellular gap and inflammatory infiltration in the heart. Although 16 S rRNA gene amplification sequencing demonstrated that NO₂ exposure did not influence the intestinal microbial abundance and diversity, but glycerophospholipid metabolism disruption might be finally reflected in gut microbiom dysregulation, such as Sphingomonas, Koribacter, Actinomarina and Bradyrhizobium Turicibacter, Rothia, Globicatella and Aerococcus. Proteome mining revealed that differentially expressed genes (DEGs) in the heart after NO₂ stress were involved in necroptosis, mitophagy and ferroptosis. We further revealed that NO₂ increased the number of cardiac mitochondria with depletion of cristae by regulating the expression of Mfn2 and Hsp70. This study indicating Mfn2-meidcated imbalanced mitochondrial dynamics as a potential mechanism after NO₂-induced heart injury and suggesting microbiome dysregulation/glycerophospholipid metabolism exerts critical roles in cardiotoxicity caused by NO₂.

Short Linear Motifs Characterizing Snake Venom and Mammalian Phospholipases A2

Snake venom phospholipases A2 (PLA2s) have sequences and structures very similar to those of mammalian group I and II secretory PLA2s, but they possess many toxic properties, ranging from the inhibition of coagulation to the blockage of nerve transmission, and the induction of muscle necrosis. The biological properties of these proteins are not only due to their enzymatic activity, but also to protein–protein interactions which are still unidentified. Here, we compare sequence alignments of snake venom and mammalian PLA2s, grouped according to their structure and biological activity, looking for differences that can justify their different behavior. This bioinformatics analysis has evidenced three distinct regions, two central and one C-terminal, having amino acid compositions that distinguish the different categories of PLA2s. In these regions, we identified short linear motifs (SLiMs), peptide modules involved in protein–protein interactions, conserved in mammalian and not in snake venom PLA2s, or vice versa. The different content in the SLiMs of snake venom with respect to mammalian PLA2s may result in the formation of protein membrane complexes having a toxic activity, or in the formation of complexes whose activity cannot be blocked due to the lack of switches in the toxic PLA2s, as the motif recognized by the prolyl isomerase Pin1.

Activation of phospholipase A2 by prostaglandin in vitro

Prostaglandins are a diverse family of biological active molecules that are synthesized after liberation of arachnidonic or linolenic acid from the plasma membrane by phospholipase A2 (PLA2). Specific prostaglandins may be pro-inflammatory or anti-inflammatory due to a poorly understood biochemical equilibrium. Some of the anti-inflammatory prostaglandins namely, prostaglandin A1 (PGA1) and prostaglandin E1 (PGE1) have a cyclopentenone moiety that can react and modify a protein's activity. These two prostaglandins are electrophilic reactive lipid species and are formed as a result of the reaction cascade initiated by PLA2. It was of interest to study the interaction with these prostaglandins as they could either amplify or block this enzyme's activity. We found that the former is true initially as there is a shorter time to activate the protein on the lipid membrane and an overall increase in hydrolysis was observed when PGA1 and PGE1 prostaglandin was added with PLA2 and liposomes. The interfacial activation model was further explored in which there is a modification of the enzyme rather than a modifcation of the substrate. However, after a time the protein was shown to form amyloid like fibrils thereby blocking further hydrolysis. The fibrillization kinetics in the presence of the one of the prostaglandins was monitored using thioflavin T (ThT) and the resulting fibrils were characterized using transmission electron microscopy (TEM) and atomic force microscopy (AFM). Modification of PLA2 by these prostaglandins leading to amyloid like fibrils gives an additional perspective of control of the interfacial activation mechanism of this enzyme.

The dynamics and role of sphingolipids in eukaryotic organisms upon thermal adaptation

All living beings have an optimal temperature for growth and survival. With the advancement of global warming, the search for understanding adaptive processes to climate changes has gained prominence. In this context, all living beings monitor the external temperature and develop adaptive responses to thermal variations. These responses ultimately change the functioning of the cell and affect the most diverse structures and processes. One of the first structures to detect thermal variations is the plasma membrane, whose constitution allows triggering of intracellular signals that assist in the response to temperature stress. Although studies on this topic have been conducted, the underlying mechanisms of recognizing thermal changes and modifying cellular functioning to adapt to this condition are not fully understood. Recently, many reports have indicated the participation of sphingolipids (SLs), major components of the plasma membrane, in the regulation of the thermal stress response. SLs can structurally reinforce the membrane or/and send signals intracellularly to control numerous cellular processes, such as apoptosis, cytoskeleton polarization, cell cycle arresting and fungal virulence. In this review, we discuss how SLs synthesis changes during both heat and cold stresses, focusing on fungi, plants, animals and human cells. The role of lysophospholipids is also discussed.

Investigation of the therapeutic mechanism of subthreshold micropulse laser irradiation in retina

PURPOSE

Subthreshold micropulse laser irradiation has been used for the treatment of retinal edema; however, there are few reports about the mechanism of its therapeutic effect. In this study, we compared threshold short pulse and subthreshold micropulse laser irradiation in mice and investigated their mechanism.

METHODS

Nine to 12-week-old male C57BL/6J mice were used in this study. After general anesthesia, threshold short pulse or subthreshold micropulse laser irradiation was performed on the right eye using IQ577. Enucleation was performed 24 h after the laser irradiation, and histological and gene expression analyses were carried out.

RESULTS

Coagulation spots and atrophy of the retinal pigment epithelium were observed after threshold short pulse laser irradiation but not after subthreshold micropulse laser irradiation. Twenty-four hours after laser, aquaporin (AQP) 1, 2, 7, and 11 levels were significantly elevated by 1.7- to 3-fold in the threshold short pulse laser group compared with non-treated control group. AQP 3 was increased significantly and prominently by 100-fold. VEGF-A and VEGFR2 were upregulated 1.5- and 2.3-fold, respectively. In the subthreshold micropulse laser group, AQP 3 was increased by 6-fold compared with the non-treated control group. Angiopoietin-1 and the adrenomedullin (AM) receptor CLR were decreased by 0.6-fold and 0.5-fold, respectively.

CONCLUSION

Threshold short pulse laser irradiation caused retinal damage and prominent changes in the expression of various genes. Contrarily, subthreshold micropulse laser irradiation did not induce retinal damage; it upregulated AQP 3, which might have improved retinal edema by drainage of subretinal fluid.

Transcriptomic analysis reveals Apis mellifera adaptations to high temperature and high humidity

Temperature and humidity are the most important factors affecting the growth, reproduction, and survival of bees. Apis mellifera are important pollinating bees that are widely used in agricultural systems. However, the higher temperatures and humidity in greenhouses are not conducive to the survival of bees. Although previous research has revealed the behavioral responses and physiological mechanisms of honeybees to adapt to high temperature and humidity, there are few data on the exact molecular mechanisms involved. In our study, we investigated gene expression in A. mellifera under different temperature and humidity treatments, using transcriptomic analysis to identify differentially expressed genes (DEGs) and relevant biological processes. Based on the transcriptomic results, we selected several genes with significant differences in expression, and detected the expression patterns of these genes at different temperatures or humidity or different treatment times by q-RT PCR. In the high temperature treatments, 434 DEGs were identified; in the high humidity treatments, 86 DEGs were identified; in the combined high temperature and humidity treatments, 266 DEGs were identified. Analysis results showed that DEGs were enriched in pathways related to amino acid and fatty acid biosynthesis and metabolism under each treatment. In addition, heat shock proteins, zinc finger proteins, serine/threonine-protein kinases, and antioxidase were differentially expressed between the different treatments. The results of the q-RT PCR showed that the expression levels of these genes increased with increasing temperature and over treatment time. Our findings provide a general expression profile of the adaptive expression of heat-resistance genes responding to high temperature and high humidity in A. mellifera, including the expression patterns of several DEGs. Our data provide a basis for future research on the mechanisms underlying the adaptation of insects to high temperature and humidity.

Heptamer Peptide Disassembles Native Amyloid in Human Plasma Through Heat Shock Protein 70

Proteostasis, which includes the repair and disposal of misfolded proteins, depends, in part, on the activity of heat shock proteins (HSPs), a well-known class of chaperone molecules. When this process fails, abnormally folded proteins may accumulate in cells, tissues, and blood. These species are a hallmark of protein aggregation diseases, but also amass during aging, often in the absence of an identified clinical disorder. We report that a neuroprotective cyclic heptapeptide, CHEC-7, which has been applied systemically as a therapeutic in animal neurodegeneration models, disrupts such aggregates and inhibits amyloidogenesis when added in nanomolar concentrations to human plasma. This effect includes aggregates of amyloid beta (Aβ1-40, 1-42), prominent features of Alzheimer's disease pathology. The activity of endogenous HSP70, a recently discovered target of the peptide, is required as demonstrated by both antibody blocking and application of pifithrin-μ, an HSP70 inhibitor. CHEC-7 is the first high-affinity compound to stimulate HSP70's disaggregase activity and therefore enable this endogenous mechanism in a human systemic environment, increasing the likelihood of a convenient therapy for protein aggregate disease, including age-related failures of protein repair.

Understanding Early Post-Mortem Biochemical Processes Underlying Meat Color and pH Decline in the Longissimus thoracis Muscle of Young Blond d'Aquitaine Bulls Using Protein Biomarkers

Many studies on color biochemistry and protein biomarkers were undertaken in post-mortem beef muscles after ≥24 hours. The present study was conducted on Longissimus thoracis muscles of 21 Blond d'Aquitaine young bulls to evaluate the relationships between protein biomarkers present during the early post-mortem and known to be related to tenderness and pH decline and color development. pH values at 45 min, 3 h, and 30 h post-mortem were correlated with three, seven, and six biomarkers, respectively. L*a*b* color coordinates 24 h post-mortem were correlated with nine, five, and eight protein biomarkers, respectively. Regression models included Hsp proteins and explained between 47 and 59% of the variability between individuals in pH and between 47 and 65% of the variability in L*a*b* color coordinates. Proteins correlated with pH and/or color coordinates were involved in apoptosis or had antioxidative or chaperone activities. The main results include the negative correlations between pH45 min, pH3 h, and pHu and Prdx6, which may be explained by the antioxidative and phospholipase activities of this biomarker. Similarly, inducible Hsp70-1A/B and μ-calpain were correlated with L*a*b* coordinates, due to the protective action of Hsp70-1A/B on the proteolytic activities of μ-calpain on structural proteins. Correlations existed further between MDH1, ENO3, and LDH-B and pH decline and color stability probably due to the involvement of these enzymes in the glycolytic pathway and, thus, the energy status of the cell. The present results show that research using protein indicators may increase the understanding of early post-mortem biological mechanisms involved in pH and beef color development.

Protein-oxidized phospholipid interactions in cellular signaling for cell death: from biophysics to clinical correlations

Oxidative stress is associated with several major ailments. However, it is only recently that the developments in our molecular level understanding of the consequences of oxidative stress in modifying the chemical structures of biomolecules, lipids in particular, are beginning to open new emerging insights into the significance of oxidative stress in providing mechanistic insights into the etiologies of these diseases. In this brief review we will first discuss the role of lipid oxidation in controlling the membrane binding of cytochrome c, a key protein in the control of apoptosis. We then present an overview of the impact of oxidized phospholipids on the biophysical properties of lipid bilayers and continue to discuss, how these altered properties can account for the observed enhancement of formation of intermediate state oligomers by cytotoxic amyloid forming peptides associated with pathological conditions as well as host defense peptides of innate immunity. In the third part, we will discuss how the targeting of oxidized phospholipids by i) pathology associated peptides and ii) host defense peptides can readily explain the observed clinical correlations associating Alzheimer's and Parkinson's diseases with increased risk for type 2 diabetes and age-related macular degeneration, and the apparent protective effect of Alzheimer's and Parkinson's diseases from some cancers, as well as the inverse, apparent protection by cancer from Alzheimer's and Parkinson's diseases. This article is part of a Special Issue entitled: Oxidized phospholipids-Their properties and interactions with proteins.