Interface of Phospholipase Activity, Immune Cell Function, and Atherosclerosis

Role of Proinflammatory Cytokines and Genetic Factors Related to Metabolic Alterations in People Living with HIV/AIDS

Metabolic alterations are a common problem in people living with HIV (PLHIV), as a result of a stage of chronic inflammation that affects the homeostasis of the organism. Prolonged exposure to antiretroviral therapy has been associated with developing lipodystrophies that modify lipoprotein metabolism and inflammatory markers such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), which are mediators of the immune response. The study aimed to associate TNF-α and IL-6 levels with their polymorphisms and metabolic alterations in PLIHV. We hypothesized that TNF-α and IL-6 levels and their polymorphisms are associated with metabolic alterations. In total, 185 PLHIV and 51 HIV-negative people were included. Biochemical parameters were determined by colorimetric assay, cytokine levels by immunoassay, and allelic discrimination by quantitative polymerase chain reaction. A correlation was found between TNF-α levels and the variables cholesterol (r = -0.171, P = 0.020) and high-density lipoprotein (HDL) (r = -0.245, P = 0.001). There are associations between HDL levels (P = 0.011) and GG genotype of rs1800629. The results suggest a metabolic alteration related to the constant immune response, especially the production of proinflammatory cytokines such as TNF-α and IL-6. It was observed that genetic factors may influence metabolism alteration, mainly in lipids.

The role and regulation of phospholipase D in metabolic disorders

Phospholipase D (PLD) is an enzyme that catalyzes the hydrolysis of phosphatidylcholine into phosphatidic acid and free choline. In mammals, PLD exists in two well-characterized isoforms, PLD1 and PLD2, and it plays pivotal roles as signaling mediators in various cellular functions, such as cell survival, differentiation, and migration. These isoforms are predominantly expressed in diverse cell types, including many immune cells, such as monocytes and macrophages, as well as non-immune cells, such as epithelial and endothelial cells. Several previous studies have revealed that the stimulation of these cells leads to an increase in PLD expression and its enzymatic products, potentially influencing the pathological responses in a wide spectrum of diseases. Metabolic diseases, exemplified by conditions, such as diabetes, obesity, hypertension, and atherosclerosis, pose significant global health challenges. Abnormal activation or dysfunction of PLD emerges as a potential contributing factor to the pathogenesis and progression of these metabolic disorders. Therefore, it is crucial to thoroughly investigate and understand the intricate relationship between PLD and metabolic diseases. In this review, we provide an in-depth overview of the functional roles and molecular mechanisms of PLD involved in metabolic diseases. By delving into the intricate interplay between PLD and metabolic disorders, this review aims to offer insights into the potential therapeutic interventions.

Phospholipases and Reactive Oxygen Species Derived Lipid Biomarkers in Healthy and Diseased Humans and Animals - A Focus on Lysophosphatidylcholine

Phospholipids (PL) are converted into lipid biomarkers by the action of phospholipases and reactive oxygen species (ROS), which are activated or released under certain physiological and pathophysiological conditions. Therefore, the in vivo concentration of such lipid biomarkers [e.g., lysophospholipids (LPLs)] is altered in humans and animals under different conditions such as inflammation, stress, medication, and nutrition. LPLs are particularly interesting because they are known to possess pro- and anti-inflammatory properties and may be generated by two different pathways: either by the influence of phospholipase A₂ or by different reactive oxygen species that are generated in significant amounts under inflammatory conditions. Both lead to the cleavage of unsaturated acyl residues. This review provides a short summary of the mechanisms by which lipid biomarkers are generated under in vitro and in vivo conditions. The focus will be on lysophosphatidylcholine (LPC) because usually, this is the LPL species which occurs in the highest concentration and is, thus, easily detectable by chromatographic and spectroscopic methods. Finally, the effects of lipid biomarkers as signaling molecules and their roles in different human and animal pathologies such as infertility, cancer, atherosclerosis, and aging will be shortly discussed.