Poly (ADP-ribose) polymerase-1 initiated neuronal cell death pathway--do androgens matter?

Area of Science:

• Neuroscience
• Molecular Biology
• Endocrinology

Background:

• Poly (ADP-ribose) polymerases (PARP) activation contributes to ischemic brain damage via neuronal nicotinamide adenine dinucleotide (NAD(+)) depletion and caspase-independent cell death.
• PARP-mediated cell death exhibits sexual dimorphism, impacting male but not female brains during ischemic events.

Purpose of the Study:

• To investigate the hypothesis that androgen signaling is essential for the male-specific neuronal cell death pathway mediated by PARP.
• To elucidate the role of androgen-androgen receptor signaling in PARP-dependent ischemic brain injury in males.

Main Methods:

• Utilized male PARP-1 knockout mice and wild-type (WT) littermates subjected to focal cerebral ischemia (MCAO).
• Administered the PARP inhibitor PJ34, performed castration (CAST) to remove testicular androgens, and conducted androgen replacement therapy.
• Assessed brain damage and measured PARP-1 expression levels in response to experimental manipulations.

Main Results:

• Male PARP-1 knockout mice and WT mice treated with PJ34 showed reduced ischemic damage compared to controls.
• The protective effect of PJ34 was abolished by castration and restored by androgen replacement, indicating androgen dependence.
• Castrated PARP-1 knockout mice exhibited increased damage, which was reversed by androgen replacement in an androgen receptor-dependent manner.
• Ischemia-induced increase in PARP-1 expression was significantly diminished in the absence of testicular androgens.

Conclusions:

• PARP-mediated neuronal cell death in the male brain following ischemic stroke is dependent on intact androgen-androgen receptor signaling.
• Androgen signaling plays a critical role in regulating PARP-1 expression and its contribution to ischemic brain injury in males.
• These findings highlight a novel sex-specific mechanism in ischemic neurodegeneration, with implications for targeted therapies.