NAD+ exhaustion by CD38 upregulation contributes to blood pressure elevation and vascular damage in hypertension

NAD+ deficiency plays essential roles in the hyperuricemia of stroke-prone spontaneously hypertensive rat via xanthine dehydrogenase to xanthine oxidase conversion

Inhibition of xanthine oxidoreductase (XOR) was shown to ameliorate the stroke susceptibility in the stroke-prone spontaneously hypertensive rat (SHRSP), suggesting hyperuricemia had a pathological role in this rat model. In this study, we thus aimed to explore mechanisms inducing hyperuricemia in SHRSP. XOR is known to have two forms, xanthine dehydrogenase (XDH) as the prototype and xanthine oxidase (XO) as the converted form through cleavage of a peptide bond or through formation of disulfide bonds in the enzyme. XO was shown to have a greater activity to produce UA and oxidative stress. We thus hypothesized that the excess conversion to XO caused the higher UA level in SHRSP. Male SHRSP at 10 weeks of age showed a higher serum level of UA and a higher activity of XO than those in Wistar-Kyoto rat. As the protein level of the total XOR did not differ between the two strains, the conversion to XO seemed responsible for the high UA level in SHRSP. Meanwhile, NAD+ level in SHRSP was lower than that in WKY, suggesting that low NAD+ promoted the conversion to XO in this strain. ß-nicotinamide mononucleotide (NMN) supplementation for 2 weeks increased NAD+ level and reduced the serum UA level as well as the XO activity in SHRSP. These observations supported that a low NAD+ accelerated the conversion of XDH to XO in SHRSP, which resulted in high UA. The current study suggested the potential significance of NMN supplementation in the treatment of hyperuricemia in humans.

The interplay of NAD and hypoxic stress and its relevance for ageing

Nicotinamide adenine dinucleotide (NAD) is an essential regulator of cellular metabolism and redox processes. NAD levels and the dynamics of NAD metabolism change with increasing age but can be modulated via the diet or medication. Because NAD metabolism is complex and its regulation still insufficiently understood, achieving specific outcomes without perturbing delicate balances through targeted pharmacological interventions remains challenging. NAD metabolism is also highly sensitive to environmental conditions and can be influenced behaviorally, e.g., by exercise. Changes in oxygen availability directly and indirectly affect NAD levels and may result from exposure to ambient hypoxia, increased oxygen demand during exercise, ageing or disease. Cellular responses to hypoxic stress involve rapid alterations in NAD metabolism and depend on many factors, including age, glucose status, the dose of the hypoxic stress and occurrence of reoxygenation phases, and exhibit complex time-courses. Here we summarize the known determinants of NAD-regulation by hypoxia and evaluate the role of NAD in hypoxic stress. We define the specific NAD responses to hypoxia and identify a great potential of the modulation of NAD metabolism regarding hypoxic injuries. In conclusion, NAD metabolism and cellular hypoxia responses are strongly intertwined and together mediate protective processes against hypoxic insults. Their interactions likely contribute to age-related changes and vulnerabilities. Targeting NAD homeostasis presents a promising avenue to prevent/treat hypoxic insults and - conversely - controlled hypoxia is a potential tool to regulate NAD homeostasis.

A luminescent-based protocol for NAD+/NADH detection in C. elegans, mice, and human whole blood

Here, we present a NAD+/NADH detection assay for evaluating NAD+, NADH, and NAD+/NADH ratio across diverse biological models, including Caenorhabditis elegans, mouse muscle tissue, mouse whole blood, and human whole blood. We describe steps for sample collection and preparation from different models as well as detection and calculation of NAD+ and NADH levels. This protocol is applicable for quantifying cellular/tissue NAD+ and NADH levels across different biological models.

The Role of NAD+ Metabolism in Cardiovascular Diseases: Mechanisms and Prospects

Nicotinamide adenine dinucleotide (NAD+) is a promising anti-aging molecule that plays a role in cellular energy metabolism and maintains redox homeostasis. Additionally, NAD+ is involved in regulating deacetylases, DNA repair enzymes, inflammation, and epigenetics, making it indispensable in maintaining the basic functions of cells. Research on NAD+ has become a hotspot, particularly regarding its potential in cardiovascular disease (CVD). Many studies have demonstrated that NAD+ plays a crucial role in the occurrence and development of CVD. This review summarizes the biosynthesis and consumption of NAD+, along with its precursors and their effects on raising NAD+ levels. We also discuss new mechanisms of NAD+ regulation in cardiovascular risk factors and its effects of NAD+ on atherosclerosis, aortic aneurysm, heart failure, hypertension, myocardial ischemia-reperfusion injury, diabetic cardiomyopathy, and dilated cardiomyopathy, elucidating different mechanisms and potential treatments. NAD+-centered therapy holds promising advantages and prospects in the field of CVD.

Platelet Membrane-Encapsulated Poly(lactic-co-glycolic acid) Nanoparticles Loaded with Sildenafil for Targeted Therapy of Vein Graft Intimal Hyperplasia

Autologous vein grafts have attracted widespread attention for their high transplantation success rate and low risk of immune rejection. However, this technique is limited by the postoperative neointimal hyperplasia, recurrent stenosis and vein graft occlusion. Hence, we propose the platelet membrane-coated Poly(lactic-co-glycolic acid) (PLGA) containing sildenafil (PPS). Platelet membrane (PM) is characterised by actively targeting damaged blood vessels. The PPS can effectively target the vein grafts and then slowly release sildenafil to treat intimal hyperplasia in the vein grafts, thereby preventing the progression of vein graft restenosis. PPS effectively inhibits the proliferation and migration of vascular smooth muscle cell (VSMCs) and promotes the migration and vascularisation of human umbilical vein endothelial cells (HUVECs). In a New Zealand rabbit model of intimal hyperplasia in vein grafts, the PPS significantly suppressed vascular stenosis and intimal hyperplasia at 14 and 28 days after surgery. Thus, PPS represents a nanomedicine with therapeutic potential for treating intimal hyperplasia of vein grafts.

Targeted NAD+ repletion via biomimetic nanoparticle enables simultaneous management of intimal hyperplasia and accelerated re-endothelialization: A proof-of-concept study toward next-generation of endothelium-protective, anti-restenotic therapy

Endovascular interventions often fail due to restenosis, primarily caused by smooth muscle cell (SMC) proliferation, leading to intimal hyperplasia (IH). Current strategies to prevent restenosis are far from perfect and impose significant collateral damage on the fragile endothelial cell (EC), causing profound thrombotic risks. Nicotinamide adenine dinucleotide (NAD+) is a co-enzyme and signaling substrate implicated in redox and metabolic homeostasis, with a pleiotropic role in protecting against cardiovascular diseases. However, a functional link between NAD+ repletion and the delicate duo of IH and EC regeneration has yet to be established. NAD+ repletion has been historically challenging due to its poor cellular uptake and low bioavailability. We have recently invented the first nanocarrier that enables direct intracellular delivery of NAD+ in vivo. Combining the merits of this prototypic NAD+-loaded calcium phosphate (CaP) nanoparticle (NP) and biomimetic surface functionalization, we created a biomimetic P-NAD+-NP with platelet membrane coating, which enabled an injectable modality that targets IH with excellent biocompatibility. Using human cell primary culture, we demonstrated the benefits of NP-assisted NAD+ repletion in selectively inhibiting the excessive proliferation of aortic SMC, while differentially protecting aortic EC from apoptosis. Moreover, in a rat balloon angioplasty model, a single-dose treatment with intravenously injected P-NAD+-NP immediately post angioplasty not only mitigated IH, but also accelerated the regeneration of EC (re-endothelialization) in vivo in comparison to control groups (i.e., saline, free NAD+ solution, empty CaP-NP). Collectively, our current study provides proof-of-concept evidence supporting the role of targeted NAD+ repletion nanotherapy in managing restenosis and improving reendothelialization.

Parishin Alleviates Pulmonary Fibrosis by Reducing CD38 Levels in Naturally Aging Mice

Parishin, a natural compound, has demonstrated significant potential in mitigating age-related phenotypes and improving outcomes in age-associated diseases. Given that aging is a major risk factor for numerous chronic conditions, including pulmonary fibrosis, we investigated parishin's effects on cellular senescence and lung health. In our study, we treated mouse lung epithelial cells with parishin and observed a reduction in cellular senescence markers alongside an upregulation of sirtuin 1 (SIRT1). Building on these in vitro findings, we administered parishin to naturally aged mice. The treatment resulted in decreased pulmonary fibrosis and reduced DNA damage in lung tissue. Notably, we found that parishin treatment led to a reduction in Cluster of differentiation 38 (CD38) levels, concomitant with an increase in SIRT1 expression. These findings indicate that parishin may enhance lung function in aged mice, suggesting its potential as a therapeutic agent for treating age-related pulmonary disorders.

LPS-LBP complex induced endothelial cell pyroptosis in aortic dissection is associated with gut dysbiosis

Acute aortic dissection (AAD) is the most severe traumatic disease affecting the aorta. Pyroptosis-mediated vascular wall inflammation is a crucial trigger for AAD, and the exact mechanism requires further investigation. In this study, our proteomic analysis showed that Lipopolysaccharide (LPS)-binding protein (LBP) was significantly upregulated in the plasma and aortic tissue of patients with AAD. Further, 16S rRNA sequencing of stool samples suggested that patients with AAD exhibit gut dysbiosis, which may lead to an impaired intestinal barrier and LPS leakage. By comparing with control mice, we found that LBP, including Pyrin Domain Containing Protein3 (NLRP3), the CARD-containing adapter apoptosis-associated speck-like protein (ASC), and Cleaved caspase-1, were upregulated in the AAD aorta, whereas gut intestinal barrier-related proteins were downregulated. Moreover, treated with LBPK95A (an LBP inhibitor) attenuated the incidence of AAD, the expression levels of pyroptosis-related factors, and the extent of vascular pathological changes compared to those in AAD mice. In addition, LPS and LBP treatment of human umbilical vein endothelial cells (HUVECs) activated TLR4 signaling and intracellular reactive oxygen species (ROS) production, which stimulated NLRP3 inflammasome formation and mediated pyroptosis in endothelial cells. Our findings showed that gut dysbiosis mediates pyroptosis by the LPS-LBP complex, thus providing new insights into developing AAD.

Elevated Salt or Angiotensin II Levels Induce CD38+ Innate Immune Cells in the Presence of Granulocyte-Macrophage Colony Stimulating Factor

Hypertension (HTN) impacts almost half of adults, predisposing them to cardiovascular disease and renal damage. Salt-sensitive HTN (SSHTN) and angiotensin II (A2)-induced HTN (A2HTN) both involve immune system activation and renal innate immune cell infiltration. Subpopulations of activated [Cluster of differentiation 38 (CD38)] innate immune cells, such as macrophages and dendritic cells (DCs), play distinct roles in modulating renal function and blood pressure. It is unknown how these cells become CD38+ or which subtypes are pro-hypertensive. When bone marrow-derived monocytes (BMDMs) were grown in granulocyte-macrophage colony stimulating factor (GM-CSF) and treated with salt or A2, CD38+ macrophages and CD38+ DCs increased. The adoptive transfer of GM-CSF-primed BMDMs into mice with either SSHTN or A2HTN increased renal CD38+ macrophages and CD38+ DCs. Flow cytometry revealed increased renal M1 macrophages and type-2 conventional DCs (cDC2s), along with their CD38+ counterparts, in mice with either SSHTN or A2HTN. These results were replicable in vitro. Either salt or A2 treatment of GM-CSF-primed BMDMs significantly increased bone marrow-derived (BMD)-M1 macrophages, CD38+ BMD-M1 macrophages, BMD-cDC2s, and CD38+ BMD-cDC2s. Overall, these data suggest that GM-CSF is necessary for the salt or A2 induction of CD38+ innate immune cells, and that CD38 distinguishes pro-hypertensive immune cells. Further investigation of CD38+ M1 macrophages and CD38+ cDC2s could provide new therapeutic targets for both SSHTN and A2HTN.

Immunological insights into hypertension: unraveling triggers and potential therapeutic avenues

Hypertension remains the leading cause of morbidity and mortality worldwide. Despite its prevalence, the development of novel antihypertensive therapies has only recently accelerated, with novel agents not yet commercialized, leaving a substantial proportion of individuals resistant to existing treatments. The intricate pathophysiology of hypertension is now understood to involve chronic low-grade inflammation, which places the immune system in the spotlight as a potential target for new therapeutics. This review explores the factors that initiate and sustain an immune response in hypertension, offering insights into potential targets for new treatments. Several factors contribute to immune activation in hypertension, including diet and damage-associated molecular pattern (DAMP) generation. Diets rich in fat or sodium can promote inflammation by inducing intestinal barrier dysfunction and triggering salt-sensitive receptors in T cells and dendritic cells. DAMPs, such as extracellular adenosine triphosphate and heat-shock protein 70, are released during episodes of increased blood pressure, contributing to immune cell activation and inflammation. Unconventional innate-like γδ T cells contribute to initiating and maintaining an immune response through their potential involvement in antigen presentation and regulating cytokine-mediated responses. Immunologic memory, sustained through the formation of effector memory T cells after exposure to hypertensive insults, likely contributes to maintaining an immune response in hypertension. When exposed to hypertensive insults, these memory cells are rapidly activated and contribute to elevated blood pressure and end-organ damage. Evidence from human hypertension, although limited, supports the relevance of distinct immune pathways in hypertension, and highlights the potential of targeted immune interventions in human hypertension. Diet and acute bouts of high blood pressure result in the release of dietary triggers, neoantigens, and damage-associated molecular patterns (DAMPs), which promote immune system activation. Elements such as lipopolysaccharides (LPS), sodium, heat-shock protein (HSP)70, extracellular adenosine triphosphate (eATP), and growth arrest-specific 6 (GAS6) promote activation of innate immune cells such as dendritic cells (DCs) and monocytes (Mo) through their respective receptors (toll-like receptor [TLR]4, amiloride-sensitive epithelial sodium channel [ENaC], TLR2/4, P2X7 receptor [P2RX7], and Axl) leading to costimulatory molecule expression and interleukin (IL)-1β and IL-23 production. The neoantigens HSP70 and isolevuglandins (IsoLGs) are presented to T cells by DCs and possibly γδ T cells, triggering T cell activation, IL-17 and interferon (IFN)-γ production, and the formation of T effector memory (TEM) cells in the kidney, perivascular adipose tissue, bone marrow, and spleen. Exposure of TEM cells to their cognate antigen or previous activating stimuli causes these cells rapid expansion and activation. Cumulatively, this inflammatory state contributes to hypertension and end-organ damage. The figure was created using images from smart.servier.com and is licensed under a Creative Commons Attribution 4.0 license (CC BY 4.0).

Nicotinamide Mononucleotide Supplementation: Understanding Metabolic Variability and Clinical Implications

Recent years have seen a surge in research focused on NAD+ decline and potential interventions, and despite significant progress, new discoveries continue to highlight the complexity of NAD+ biology. Nicotinamide mononucleotide (NMN), a well-established NAD+ precursor, has garnered considerable interest due to its capacity to elevate NAD+ levels and induce promising health benefits in preclinical models. Clinical trials investigating NMN supplementation have yielded variable outcomes while shedding light on the intricacies of NMN metabolism and revealing the critical roles played by gut microbiota and specific cellular uptake pathways. Individual variability in factors such as lifestyle, health conditions, genetics, and gut microbiome composition likely contributes to the observed discrepancies in clinical trial results. Preliminary evidence suggests that NMN's effects may be context-dependent, varying based on a person's physiological state. Understanding these nuances is critical for definitively assessing the impact of manipulating NAD+ levels through NMN supplementation. Here, we review NMN metabolism, focusing on current knowledge, pinpointing key areas where further research is needed, and outlining future directions to advance our understanding of its potential clinical significance.

Nicotinamide N-methyltransferase (NNMT): a novel therapeutic target for metabolic syndrome

Metabolic syndrome (MetS) represents a constellation of metabolic abnormalities, typified by obesity, hypertension, hyperglycemia, and hyperlipidemia. It stems from intricate dysregulations in metabolic pathways governing energy and substrate metabolism. While comprehending the precise etiological mechanisms of MetS remains challenging, evidence underscores the pivotal roles of aberrations in lipid metabolism and insulin resistance (IR) in its pathogenesis. Notably, nicotinamide N-methyltransferase (NNMT) has recently surfaced as a promising therapeutic target for addressing MetS. Single nucleotide variants in the NNMT gene are significantly correlated with disturbances in energy metabolism, obesity, type 2 diabetes (T2D), hyperlipidemia, and hypertension. Elevated NNMT gene expression is notably observed in the liver and white adipose tissue (WAT) of individuals with diabetic mice, obesity, and rats afflicted with MetS. Knockdown of NNMT elicits heightened energy expenditure in adipose and hepatic tissues, mitigates lipid accumulation, and enhances insulin sensitivity. NNMT catalyzes the methylation of nicotinamide (NAM) using S-adenosyl-methionine (SAM) as the donor methyl group, resulting in the formation of S-adenosyl-l-homocysteine (SAH) and methylnicotinamide (MNAM). This enzymatic process results in the depletion of NAM, a precursor of nicotinamide adenine dinucleotide (NAD+), and the generation of SAH, a precursor of homocysteine (Hcy). Consequently, this cascade leads to reduced NAD+ levels and elevated Hcy levels, implicating NNMT in the pathogenesis of MetS. Moreover, experimental studies employing RNA interference (RNAi) strategies and small molecule inhibitors targeting NNMT have underscored its potential as a therapeutic target for preventing or treating MetS-related diseases. Nonetheless, the precise mechanistic underpinnings remain elusive, and as of yet, clinical trials focusing on NNMT have not been documented. Therefore, further investigations are warranted to elucidate the intricate roles of NNMT in MetS and to develop targeted therapeutic interventions.

CD38 deficient mice are not protected from atherosclerosis

CD38 is a multifunctional enzyme implicated in chemotaxis of myeloid cells and lymphocyte activation, but also expressed by resident cells such as endothelial and smooth muscle cells. CD38 is important for host defense against microbes. However, CD38's role in the pathogenesis of atherosclerosis is controversial with seemingly conflicting results reported so far. To clarify the discrepancy of current literature on the effect of CD38 ablation on atherosclerosis development, we implanted a shear stress modifier around the right carotid artery in CD38-/- and WT mice. Hypercholesterolemia was induced by human gain-of-function PCSK9 (D374Y), introduced using AAV vector (serotype 9), combined with an atherogenic diet for a total of 9 weeks. Atherosclerosis was assessed at the aortic root, aortic arch and the right carotid artery. The findings can be summarized as follows: i) CD38-/- and WT mice had a similar atherosclerotic burden in all three locations, ii) No significant differences in monocyte infiltration or macrophage content could be seen in the plaques, and iii) The amount of collagen deposition in the plaques were also similar between CD38-/- and WT mice. In conclusion, our data suggest that CD38-/- mice are neither protected against nor prone to atherosclerosis compared to WT mice.