Background/Purpose: NAD⁺ is a key cofactor and second messenger for multiple cellular processes that exhibits antioxidant, anti-apoptotic, and anti-inflammatory properties. Numerous publications and clinical trials have shown the beneficial effects of NAD⁺ boosters in different diseases. However, to date no studies have evaluated the NAD⁺ metabolism and the therapeutic effects of NAD⁺ boosters in RA patients.
Aims: 1- To study the NAD⁺ metabolism in RA patients and its association with key clinical features; 2-To evaluate the effect of anti-TNF therapy in the NAD⁺ metabolism; 3- To analyze the beneficial effects of NAD⁺ boosters in leukocytes from active RA patients.

Methods: Plasma and PBMCs were purified from 100 RA patients and 50 healthy donors (HDs). NAD⁺ levels were determined by using the NAD/NADH-Glo Assay. Gene expression analysis of markers related to the synthesis (NAMPT, NMNAT2, NRK1), transport (Cx43) and consumption of NAD⁺ (PARP-1, Sirtuin-1, CD157, CD38 y CD73) were performed in PBMCs by RT-PCR.

Moreover, in a second cohort of 50 RA patients treated with anti-TNF therapy, changes in the levels of NAD⁺ were analyzed before and after 6 months of treatment.

In parallel, PBMCs from a third cohort of 10 active RA patients were treated ex vivo with 1 mM of NAD⁺ boosters including nicotinamide (NAM), nicotinamide riboside (NR), and nicotinamide mononucleotide (NMN). After 24 hours, intracellular reactive oxygen species (ROS) levels and the % of apoptotic PBMCs were assessed by flow cytometry. Finally, a panel of key pro-inflammatory genes was evaluated by RT-PCR.

Results: NAD⁺ levels were significantly reduced in plasma of RA patients compared with HDs, and directly related to disease activity. Accordingly, the expression levels of genes involved in the consumption of NAD⁺ such as SIRT-1, CD38 and PARP-1 were found up-regulated in PBMCs from RA patients. The levels of NAMPT and Cx43 were found increased suggesting a compensatory response of the organism against the depletion of NAD⁺ levels. The altered metabolism of NAD⁺ was associated with the increased expression of several cytokines such as TNF, IL6, IL1, IL8 and CCL2 highlighting the role of inflammation in the altered NAD⁺ metabolism.

Anti-TNF therapy restored the altered NAD⁺ levels towards those showed by HDs. Furthermore, the clinical response promoted by anti-TNF therapy correlated with changes in NAD⁺ levels.

In vitro treatments of PBMCs isolated from active RA patients with NAD⁺ boosters significantly increased the NAD⁺ levels and promoted a deep reduction of intracellular ROS levels, the percentage of apoptotic cells and the expression levels of key inflammatory mediators, such as IL-6, IL-8, IL-1b, TNF-α, CCL2, IL-23, and STAT-3.

Conclusion: 1. NAD⁺ metabolism is altered and associated with the disease activity and the pro-inflammatory status of RA patients. 2. Anti-TNF therapy restored NAD⁺ levels, which was directly linked to the clinical effectiveness. 3. NAD⁺ boosters reduced the oxidative, apoptotic, and inflammatory profile of RA leukocytes through the parallel increase of intracellular NAD⁺ levels. Thus, NAD⁺ boosters might be considered novel therapeutic tools for RA patients.

Supported by: FIS18/0837,RTI2018-100695-B-I00,P18-RT-4264,CVI276

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-nad-metabolism-is-altered-in-rheumatoid-arthritis-and-its-modulation-with-nad-boosters-exhibits-key-anti-inflammatory-and-anti-oxidant-effects/