The Impact of NAD Bioavailability on DNA Double-Strand Break Repair Capacity in Human Dermal Fibroblasts after Ionizing Radiation.

Nicotinamide adenine dinucleotide (NAD) serves as a substrate for protein deacetylases sirtuins and poly(ADP-ribose) polymerases, which are involved in the regulation of DNA double-strand break (DSB) repair molecular machinery by various mechanisms. However, the impact of NAD bioavailability on DSB repair remains poorly characterized. Herein, using immunocytochemical analysis of γH2AX, a marker for DSB, we investigated the effect of the pharmacological modulation of NAD levels on DSB repair capacity in human dermal fibroblasts exposed to moderate doses of ionizing radiation (IR).

Purine nucleoside phosphorylase controls nicotinamide riboside metabolism in mammalian cells.

Nicotinamide riboside (NR) is an effective precursor of nicotinamide adenine dinucleotide (NAD) in human and animal cells. NR supplementation can increase the level of NAD in various tissues and thereby improve physiological functions that are weakened or lost in experimental models of aging or various human pathologies. However, there are also reports questioning the efficacy of NR supplementation.

Equilibrative Nucleoside Transporters Mediate the Import of Nicotinamide Riboside and Nicotinic Acid Riboside into Human Cells.

Nicotinamide riboside (NR), a new form of vitamin B3, is an effective precursor of nicotinamide adenine dinucleotide (NAD) in human and animal cells. The introduction of NR into the body effectively increases the level of intracellular NAD and thereby restores physiological functions that are weakened or lost in experimental models of aging and various pathologies. Despite the active use of NR in applied biomedicine, the mechanism of its transport into mammalian cells is currently not understood.

Degradation of Extracellular NAD Intermediates in Cultures of Human HEK293 Cells.

Nicotinamide adenine dinucleotide (NAD) is an essential redox carrier, whereas its degradation is a key element of important signaling pathways. Human cells replenish their NAD contents through NAD biosynthesis from extracellular precursors. These precursors encompass bases nicotinamide (Nam) and nicotinic acid and their corresponding nucleosides nicotinamide riboside (NR) and nicotinic acid riboside (NAR), now collectively referred to as vitamin B3.

Relative Human Telomere Length Quantification by Real-Time PCR.

Telomere measurement by quantitative PCR amplification is a well-known simple method to detect telomere length that involves large numbers of samples. The method has been developed by Cawthon in 2002 (Cawthon, Nucleic Acids Res 30:47e-47, 2002) and remains the most frequently used technique either in original or modified version. Telomere length is estimated by comparing the amount of telomere repeat amplification product (T) to a single copy gene (S) product.