Peroxiredoxin 6 Modulates Insulin Secretion and Beta Cell Death via a Mitochondrial Dynamic Network

Francesca Pacifici; David Della-Morte; Barbara Capuani; Andrea Coppola; Maria Giovanna Scioli; Giulia Donadel; Aikaterini Andreadi; Fabiola Ciccosanti; Gian Maria Fimia; Alfonso Bellia; Augusto Orlandi; Davide Lauro

doi:10.3389/fendo.2022.842575

Peroxiredoxin 6 Modulates Insulin Secretion and Beta Cell Death via a Mitochondrial Dynamic Network

Front Endocrinol (Lausanne). 2022 Mar 18:13:842575. doi: 10.3389/fendo.2022.842575. eCollection 2022.

Authors

Affiliations

¹ Department of Systems Medicine, University of Rome "Tor Vergata", Rome, Italy.
² Department of Human Sciences and Quality of Life Promotion, San Raffaele University, Rome, Italy.
³ Department of Neurology and Evelyn F. McKnight Brain Institute, Miller School of Medicine, University of Miami, Miami, FL, United States.
⁴ Anatomic Pathology, Department of Biomedicine and Prevention, University of Rome "Tor Vergata", Rome, Italy.
⁵ Department of Clinical Sciences and Translational Medicine, University of Rome "Tor Vergata", Rome, Italy.
⁶ Department of Epidemiology, Preclinical Research and Advanced Diagnostics, National Institute for Infectious Diseases L. Spallanzani, Istituto Di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy.
⁷ Department of Molecular Medicine, Sapienza University of Rome, Rome, Italy.
⁸ Department of Medical Sciences, Fondazione Policlinico Tor Vergata, Rome, Italy.

Abstract

In pancreatic beta cells, mitochondrial metabolism controls glucose-stimulated insulin secretion (GSIS) by ATP production, redox signaling, and calcium (Ca²⁺) handling. Previously, we demonstrated that knockout mice for peroxiredoxin 6 (Prdx6^-/- ), an antioxidant enzyme with both peroxidase and phospholipase A2 activity, develop a mild form of diabetes mellitus with a reduction in GSIS and in peripheral insulin sensitivity. However, whether the defect of GSIS present in these mice is directly modulated by Prdx6 is unknown. Therefore, the main goal of the present study was to evaluate if depletion of Prdx6 affects directly GSIS and pancreatic beta β-cell function. Murine pancreatic β-cell line (βTC6) knockdown for Prdx6 (Prdx6^KD) was employed, and insulin secretion, ATP, and intracellular Ca²⁺ content were assessed in response to glucose stimulation. Mitochondrial morphology and function were also evaluated through electron microscopy, and by testing mitochondrial membrane potential, oxygen consumption, and mitochondrial mass. Prdx6^KD cells showed a significant reduction in GSIS as confirmed by decrease in both ATP release and Ca²⁺ influx. GSIS alteration was also demonstrated by a marked impairment of mitochondrial morphology and function. These latest are mainly linked to mitofusin downregulation, which are, in turn, strictly related to mitochondrial homeostasis (by regulating autophagy) and cell fate (by modulating apoptosis). Following a pro-inflammatory stimulus (typical of diabetic subjects), and in agreement with the deregulation of mitofusin steady-state levels, we also observed an enhancement in apoptotic death in Prdx6^KD compared to control cells. We analyzed molecular mechanisms leading to apoptosis, and we further demonstrated that Prdx6 suppression activates both intrinsic and extrinsic apoptotic pathways, ultimately leading to caspase 3 and PARP-1 activation. In conclusion, Prdx6 is the first antioxidant enzyme, in pancreatic β-cells, that by controlling mitochondrial homeostasis plays a pivotal role in GSIS modulation.

Keywords: apoptosis; diabetes mellitus; insulin secretion; mitochondrial function; mitochondrial morphology; oxidative stress.

MeSH terms

Animals
Apoptosis
Insulin / metabolism
Insulin Secretion
Insulin-Secreting Cells* / metabolism
Mice
Mitochondrial Dynamics
Peroxiredoxin VI* / genetics
Peroxiredoxin VI* / metabolism

Substances

Insulin
Peroxiredoxin VI
Prdx6 protein, mouse