Quantification of SARM1 NADase Activity in Human Peripheral Blood Mononuclear Cells

Area of Science:

• Biochemistry
• Cell Biology
• Neuroscience

Background:

• Sterile α and TIR motif-containing protein-1 (SARM1) is a key enzyme in axon degeneration and a therapeutic target for neurodegenerative diseases.
• Emerging evidence suggests SARM1's role in metabolic diseases and bone fragility, but methods to quantify its activity in humans are lacking.
• Peripheral blood mononuclear cells (PBMCs) are an accessible cell type for clinical screening, but functional SARM1 NADase activity in PBMCs is not well understood.

Purpose of the Study:

• To develop and validate a method for quantifying SARM1 activation potential in human PBMCs.
• To investigate basal SARM1 activity and its response to activators and inhibitors in PBMCs.
• To establish PBMCs as a potential clinical readout for SARM1 activity.

Main Methods:

• Human PBMCs were treated with SARM1 agonist pyrinuron (Vacor) and SARM1 inhibitor DSRM-3716.
• Downstream changes in cellular metabolites, including cyclic ADP-ribose (cADPR), ADP-ribose (ADPR), NAD+, NMN, and ATP, were analyzed.
• A working model of PBMC SARM1 activation was generated based on metabolite profiling.

Main Results:

• Pyrinuron treatment induced a dose-dependent increase in cADPR and the cADPR:ADPR ratio in PBMCs.
• This activation was significantly reduced by the SARM1 inhibitor DSRM-3716.
• Characterization of multiple metabolites (NAD+, NMN, NaMN, ATP, AMP, IMP, inosine, succinyl adenosine) provided insights into the SARM1 activation pathway in PBMCs.

Conclusions:

• Human PBMCs exhibit detectable SARM1 activation potential.
• The developed method allows for quantification of SARM1 activity and activation potential in PBMCs.
• PBMCs can serve as a valuable clinical tool for assessing SARM1 activity in various disease contexts.