Detection of nicotinamide adenine dinucleotide (NAD) in cells and blood plasma
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Priv,-Doz. Dr. med. Felix Krenzien and Dr. Jennifer Kirwan (Technologieplattform Metabolomik, Max-Delbrück-Centrum für Molekulare Medizin, Berlin) successfully applied for a grant within the Else Kröner Fresenius Stiftung funding line: Translational Research.

Recently, the molecule nicotinamide adenine dinucleotide (NAD) has attracted attention as it is involved in various important regulatory mechanisms, immune signaling, aging and regenerative processes. In this regard, it occupies key positions in many redox reactions of the body due to its role as a redox couple (NAD as an oxidized species and NADH as a reduced species). Consequently, NAD homeostasis (the maintenance of NAD in cells) is considered essential. The scientific consensus for many years was that the oxidized species resides exclusively in the intracellular milieu (iNAD). However, recent findings indicate that NAD also exists extracellularly (eNAD) and it is present in virtually all body fluids (from lymph to saliva to blood plasma). Based on these findings, precursors of NAD have recently been approved by the FDA and are commercially available. Measurement of eNAD in blood plasma is problematic due to its low concentration in the nanomolar range. However, quantifying eNAD plasma levels but also eNAD concentrations in cells is necessary to monitor the intake of NAD or its precursors and to adjust their dosage precisely.
The primary objective of this project is to validate, bioanalyze,and to document the assay for eNAD according to the ICH-M10 guidance document endorsed by the U. S. Food and Drug Administration (FDA). Adherence to the principles presented in this guideline should improve the quality and consistency of bioanalytical data, thereby supporting assay development and market approval. In addition, the assay will also be established for the measurement of intracellular NAD (iNAD), and validation of iNAD quantification will also be performed according to the guideline.

In the second part of the project, a clinical study will be conducted to determine whether the intake of nicotinamide riboside (precursor of NAD) leads to a change in eNAD and iNAD. Thus, the basis for an indication-dependent bioanalysis of the measurement of NAD will be developed to monitor the intake of NAD and its precursor or to adjust the dosage specifically on the basis of the quantification.
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Our manuscript "Depletion of donor dendritic cells ameliorates immunogenicity of both skin and hind limb transplants" has been accepted for publication in Frontiers in Immunology, section Alloimmunity and Transplantation. Authors are Muhammad Imtiaz Ashraf, Joerg Mengwasser, Anja Reutzel-Selke, Dietrich Polenz, Kirsten Führer, Steffen Lippert, Peter Tang, Edward Michaelis, Rusan Catar, Johann Pratschke, Christian Witzel, Igor M. Sauer, Stefan G. Tullius, and Barbara Kern.

Acute cellular rejection remains a significant obstacle affecting successful outcomes of organ transplantation including vascularized composite tissue allografts (VCA). Donor antigen presenting cells (APC), particularly dendritic cells (DC), orchestrate early alloimmune responses by activating recipient effector T cells. Employing a targeted approach, we investigated the impact of donor-derived conventional DC (cDC) and APC on the immunogenicity of skin and skin-containing VCA grafts, using mouse models of skin and hind limb transplantation.
By post-transplantation day 6, skin grafts demonstrated severe rejections, characterized by predominance of recipient CD4 T cells. In contrast, hind limb grafts showed moderate rejection, primarily infiltrated by CD8 T cells. While donor depletion of cDC and APC reduced frequencies, maturation, and activation of DC in all analysed tissues of skin transplant recipients, reduction in DC activities was only observed in the spleen of hind limb recipients. Donor cDC and APC depletion did not impact all lymphocyte compartments but significantly affected CD8 T cells and activated CD4 T in lymph nodes of skin recipients. Moreover, both donor APC and cDC depletion attenuated the Th17 immune response, evident by significantly reduced Th17 (CD4+IL-17+) cells in the spleen of skin recipients and reduced levels of IL-17E and lymphotoxin-α in the serum samples of both skin and hind limb recipients. In conclusion, our findings underscore the highly immunogenic nature of skin component in VCA. The depletion of donor APC and cDC mitigates the immunogenicity of skin grafts while exerting minimal impact on VCA.




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