Differential responses of pancreatic β-cells to ROS and RNS

Area of Science:

• Cell Biology
• Biochemistry
• Signaling Pathways

Background:

• Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are critical mediators of cellular signaling.
• These species play significant roles in determining cell fate, including apoptosis and survival.
• Pancreatic beta-cells are particularly vulnerable to oxidative and nitrosative stress.

Purpose of the Study:

• To investigate the distinct signaling pathways activated by ROS and RNS in pancreatic beta-cells.
• To elucidate the mechanisms by which these reactive species control beta-cell viability.
• To understand how different forms of stress lead to selective cell fate decisions.

Main Methods:

• Utilized nitric oxide and hydrogen peroxide (H₂O₂) as model ROS/RNS.
• Assessed DNA damage, cell viability, and AMPK activation.
• Examined activation of unfolded protein response, heat shock response, MAPK signaling, p53 stabilization, and poly(ADP-ribose) polymerase (PARP) activation.
• Investigated the role of GAPDH nuclear localization.

Main Results:

• Both nitric oxide and H₂O₂ induced DNA damage, reduced cell viability, and activated AMPK.
• Nitric oxide activated unfolded protein response, heat shock response, and MAPK signaling.
• H₂O₂ stimulated p53 stabilization and PARP activation but not UPR, heat shock, or MAPK signaling.
• H₂O₂-induced cell death was PARP-dependent, while nitric oxide-induced death was PARP-independent and linked to GAPDH nuclear localization.

Conclusions:

• ROS and RNS activate common pathways (AMPK, DNA damage) but diverge in downstream signaling controlling pancreatic beta-cell fate.
• Cell death mechanisms are selective for the type of reactive species, with H₂O₂ acting via PARP and nitric oxide via a PARP-independent pathway involving GAPDH.
• These findings reveal stress-selective mechanisms governing beta-cell responses to oxidative and nitrosative stress.