Serum pantetheinase/vanin levels regulate erythrocyte homeostasis and severity of malaria

The vitamin B5/coenzyme A axis: A target for immunomodulation?

Coenzyme A (CoA) serves as a vital cofactor in numerous enzymatic reactions involved in energy production, lipid metabolism, and synthesis of essential molecules. Dysregulation of CoA-dependent metabolic pathways can contribute to chronic diseases, such as inflammatory diseases, obesity, diabetes, cancer, and cardiovascular disorders. Additionally, CoA influences immune cell activation by modulating the metabolism of these cells, thereby affecting their proliferation, differentiation, and effector functions. Targeting CoA metabolism presents a promising avenue for therapeutic intervention, as it can potentially restore metabolic balance, mitigate chronic inflammation, and enhance immune cell function. This might ultimately improve the management and outcomes for these diseases. This review will more specifically focus on the contribution of pathways regulating the availability of the CoA precursor Vitamin B5/pantothenate in vivo and modulating the development of Th17-mediated inflammation, CD8-dependent anti-tumor immunity but also tissue repair processes in chronic inflammatory or degenerative diseases.

The spectrum of clinical biomarkers in severe malaria and new avenues for exploration

Globally, malaria is a public health concern, with severe malaria (SM) contributing a major share of the disease burden in malaria endemic countries. In this context, identification and validation of SM biomarkers are essential in clinical practice. Some biomarkers (C-reactive protein, angiopoietin 2, angiopoietin-2/1 ratio, platelet count, histidine-rich protein 2) have yielded interesting results in the prognosis of Plasmodium falciparum severe malaria, but for severe P. vivax and P. knowlesi malaria, similar evidence is missing. The validation of these biomarkers is hindered by several factors such as low sample size, paucity of evidence-evaluating studies, suboptimal values of sensitivity/specificity, poor clinical practicality of measurement methods, mixed Plasmodium infections, and good clinical value of the biomarkers for concurrent infections (pneumonia and current COVID-19 pandemic). Most of these biomarkers are non-specific to pathogens as they are related to host response and hence should be regarded as prognostic/predictive biomarkers that complement but do not replace pathogen biomarkers for clinical evaluation of SM patients. This review highlights the importance of research on diagnostic/predictive/therapeutic biomarkers, neglected malaria species, and clinical practicality of measurement methods in future studies. Finally, the importance of omics technologies for faster identification/validation of SM biomarkers is also included.

Forward Genetics in Apicomplexa Biology: The Host Side of the Story

Forward genetic approaches have been widely used in parasitology and have proven their power to reveal the complexities of host-parasite interactions in an unbiased fashion. Many aspects of the parasite’s biology, including the identification of virulence factors, replication determinants, antibiotic resistance genes, and other factors required for parasitic life, have been discovered using such strategies. Forward genetic approaches have also been employed to understand host resistance mechanisms to parasitic infection. Here, we will introduce and review all forward genetic approaches that have been used to identify host factors involved with Apicomplexa infections, which include classical genetic screens and QTL mapping, GWAS, ENU mutagenesis, overexpression, RNAi and CRISPR-Cas9 library screens. Collectively, these screens have improved our understanding of host resistance mechanisms, immune regulation, vaccine and drug designs for Apicomplexa parasites. We will also discuss how recent advances in molecular genetics give present opportunities to further explore host-parasite relationships.

A NIR fluorescent probe for Vanin-1 and its applications in imaging, kidney injury diagnosis, and the development of inhibitor

Vanin-1 is an amidohydrolase that catalyses the conversion of pantetheine into the amino-thiol cysteamine and pantothenic acid (coenzyme A precursor), which plays a vital role in multiple physiological and pathological processes. In this study, an enzyme-activated near-infrared (NIR) fluorescent probe (DDAV) has been constructed for sensitively detecting Vanin-1 activity in complicated biosamples on the basis of its catalytic characteristics. DDAV exhibited a high selectivity and sensitivity toward Vanin-1 and was successfully applied to the early diagnosis of kidney injury in cisplatin-induced kidney injury model. In addition, DDAV could serve as a visual tool for in situ imaging endogenous Vanin-1 in vivo. More importantly, Enterococcus faecalis 20247 which possessed high expression of Vanin-1 was screened out from intestinal bacteria using DDAV, provided useful guidance for the rational use of NSAIDs in clinic. Finally, oleuropein as a potent natural inhibitor for Vanin-1 was discovered from herbal medicines library using a high-throughput screening method using DDAV, which held great promise for clinical therapy of inflammatory bowel disease.

What role for cysteamine in the defence against infection?

The aminothiol cysteamine has many potential therapeutic applications and is also an endogenous molecule, produced in the body via the activity of pantetheinase enzymes such as vanin-1. This simple small molecule is highly reactive in biological settings and much is yet unknown about its endogenous role in innate immunity to infection, including the impact of cysteamine on bacterial pathogens. We discuss the literature surrounding its biochemistry and challenges to its development as well as the multiple beneficial properties which have been uncovered that support research into its development as novel antimicrobial therapy.

Red emission ratio fluorescent probe for the activity of vanin-1 and imaging in vivo

Pantetheinase, also known as Vanin-1, catalyzes pantetheine to decompose into the precursor of CoA - pantothenic acid and aminothiol cysteamine. Studies have shown that Vanin-1 plays an important role in many important physiological pathologies. In this paper, a new red emission ratio fluorescent probe DCM-PA (I_{640 nm}/I_{564 nm}) has been implemented to detect the activity of Vanin-1 in cells and vivo. DCM-PA has short response time (30 min), high selectivity and low sensitivity (DL =0.69 ng/mL). Also, we have applied DCM-PA for imaging in cells and mice, and the results have indicated that the probe has a non-negligible potential for monitoring the activity of Vanin-1 in situ, benefiting further to study the role of Vanin-1 in physiology and pathology. In addition, the up-regulation of this enzyme by starvation confirmed the inevitable connection between diabetes and abnormal expression of Vanin-1.

The Pathophysiological Role of CoA

The importance of coenzyme A (CoA) as a carrier of acyl residues in cell metabolism is well understood. Coenzyme A participates in more than 100 different catabolic and anabolic reactions, including those involved in the metabolism of lipids, carbohydrates, proteins, ethanol, bile acids, and xenobiotics. However, much less is known about the importance of the concentration of this cofactor in various cell compartments and the role of altered CoA concentration in various pathologies. Despite continuous research on these issues, the molecular mechanisms in the regulation of the intracellular level of CoA under pathological conditions are still not well understood. This review summarizes the current knowledge of (a) CoA subcellular concentrations; (b) the roles of CoA synthesis and degradation processes; and (c) protein modification by reversible CoA binding to proteins (CoAlation). Particular attention is paid to (a) the roles of changes in the level of CoA under pathological conditions, such as in neurodegenerative diseases, cancer, myopathies, and infectious diseases; and (b) the beneficial effect of CoA and pantethine (which like CoA is finally converted to Pan and cysteamine), used at pharmacological doses for the treatment of hyperlipidemia.

Visible to Near-Infrared Emission Ratiometric Fluorescent Probe for the Detection of Vanin-1 In Vivo

Pantetheinase (Vanin-1) is an ectoenzyme, which involves the metabolic pathway of coenzyme A (CoA), and can decompose pantetheine into pantothenic acid (CoA precursor) and aminothiol cysteamine. Previous studies have revealed that Vanin-1 with essential biological functions is closely related to many diseases. However, the lack of simple and effective detection methods has severely hindered the further study of Vanin-1's physiological functions. In this work, we have developed a near-infrared (NIR) emission ratio fluorescent probe TMN-PA (I_645 nm/I_568 nm) that enables us to detect Vanin-1 rapidly (in 15 min) with a minimum detection limit of 0.37 ng/mL. What is more, this probe shows excellent potential in in situ real-time monitoring of the endogenous Vanin-1, contributing to further research on Vanin-1 and understanding its mechanisms in physiological pathology. To our knowledge, this probe is the first NIR emission ratio (I_645 nm/I_568 nm) fluorescent probe ever reported to monitor the activity of Vanin-1 in vivo.

Regulation of coenzyme A levels by degradation: the 'Ins and Outs'

Coenzyme A (CoA) is the predominant acyl carrier in mammalian cells and a cofactor that plays a key role in energy and lipid metabolism. CoA and its thioesters (acyl-CoAs) regulate a multitude of metabolic processes at different levels: as substrates, allosteric modulators, and via post-translational modification of histones and other non-histone proteins. Evidence is emerging that synthesis and degradation of CoA are regulated in a manner that enables metabolic flexibility in different subcellular compartments. Degradation of CoA occurs through distinct intra- and extracellular pathways that rely on the activity of specific hydrolases. The pantetheinase enzymes specifically hydrolyze pantetheine to cysteamine and pantothenate, the last step in the extracellular degradation pathway for CoA. This reaction releases pantothenate in the bloodstream, making this CoA precursor available for cellular uptake and de novo CoA synthesis. Intracellular degradation of CoA depends on specific mitochondrial and peroxisomal Nudix hydrolases. These enzymes are also active against a subset of acyl-CoAs and play a key role in the regulation of subcellular (acyl-)CoA pools and CoA-dependent metabolic reactions. The evidence currently available indicates that the extracellular and intracellular (acyl-)CoA degradation pathways are regulated in a coordinated and opposite manner by the nutritional state and maximize the changes in the total intracellular CoA levels that support the metabolic switch between fed and fasted states in organs like the liver. The objective of this review is to update the contribution of these pathways to the regulation of metabolism, physiology and pathology and to highlight the many questions that remain open.

Host genetics in malaria: lessons from mouse studies

Malaria remains a deadly parasitic disease caused by Plasmodium, claiming almost half a million lives every year. While parasite genetics and biology are often the major targets in many studies, it is becoming more evident that host genetics plays a crucial role in the outcome of the infection. Similarly, Plasmodium infections in mice also rely heavily on the genetic background of the mice, and often correlate with observations in human studies, due to their high genetic homology with humans. As such, murine models of malaria are a useful tool for understanding host responses during Plasmodium infections, as well as dissecting host-parasite interactions through various genetic manipulation techniques. Reverse genetic approach such as quantitative trait loci studies and random mutagenesis screens have been employed to discover novel host genes that affect malaria susceptibility in mouse models, while other targeted studies utilize mouse models to validate observation from human studies. Herein, we review the findings from the past and present studies on murine models of hepatic and erythrocytic stages of malaria and speculate on how the current mouse models benefit from the recent development in CRISPR/Cas9 gene editing technology.

Proteomic Analysis of Non-depleted Serum Proteins from Bottlenose Dolphins Uncovers a High Vanin-1 Phenotype

Targeted approaches have been widely used to help explain physiological adaptations, but few studies have used non-targeted omics approaches to explore differences between diving marine mammals and terrestrial mammals. A rank comparison of undepleted serum proteins from common bottlenose dolphins (Tursiops truncatus) and pooled normal human serum led to the discovery of 11 proteins that appeared exclusive to dolphin serum. Compared to the comprehensive human plasma proteome, 5 of 11 serum proteins had a differential rank greater than 200. One of these proteins, Vanin-1, was quantified using parallel reaction monitoring in dolphins under human care and free-ranging dolphins. Dolphin serum Vanin-1 ranged between 31–106 μg/ml, which is 20–1000 times higher than concentrations reported for healthy humans. Serum Vanin-1 was also higher in dolphins under human care compared to free-ranging dolphins (64 ± 16 vs. 47 ± 12 μg/ml P < 0.05). Vanin-1 levels positively correlated with liver enzymes AST and ALT, and negatively correlated with white blood cell counts and fibrinogen in free-ranging dolphins. Major differences exist in the circulating blood proteome of the bottlenose dolphin compared to terrestrial mammals and exploration of these differences in bottlenose dolphins and other marine mammals may identify veiled protective strategies to counter physiological stress.

Metabolic adaptation of tissues to stress releases metabolites influencing innate immunity

Recent developments have demonstrated that metabolic rewiring imposed by adaptation of tissues to stress leads to the release of various metabolites which directly or indirectly impact innate immune responses and inflammation. Some metabolites can behave as second messengers and leave local cues in tissues. Immune cells which infiltrate stressed tissues reorient their metabolism to cope with these microenvironmental cues while preserving their effector functions in tissues.