Proline modulates the intracellular redox environment and protects mammalian cells against oxidative stress

Abstract

The potential of proline to suppress reactive oxygen species (ROS) and apoptosis in mammalian cells was tested by manipulating intracellular proline levels exogenously and endogenously by overexpression of proline metabolic enzymes. Proline was observed to protect cells against H 2 O 2 , tert-butyl hydroperoxide and a carcinogenic oxidative stress inducer but was not effective against superoxide generators such as menadione. Oxidative stress protection by proline requires the secondary amine of the pyrrolidine ring and involves preservation of the glutathione redox environment. Overexpression of proline dehydrogenase (PRODH), a mitochondrial flavoenzyme that oxidizes proline, resulted in 6-fold lower intracellular proline content and decreased cell survival relative to control cells. Cells overexpressing PRODH were rescued by pipecolate, an analog that mimics the antioxidant properties of proline, and by tetrahydro-2-furoic acid, a specific inhibitor of PRODH. In contrast, overexpression of the proline biosynthetic enzymes Δ 1 -pyrroline-5-carboxylate (P5C) synthetase (P5CS) and P5C reductase (P5CR) resulted in 2-fold higher proline content, significantly lower ROS levels and increased cell survival relative to control cells. In different mammalian cell lines exposed to physiological H 2 O 2 levels, increased endogenous P5CS and P5CR expression was observed indicating upregulation of proline biosynthesis is an oxidative stress response.

The metabolites of glutamine prevent hydroxyl radical-induced apoptosis through inhibiting mitochondria and calcium ion involved pathways in fish erythrocytes

“…These results demonstrated that Ala, Cit and Pro could protect erythrocytes against apoptosis through quenching • OH, inhibiting the generation of ROS or release of cytochrome c or chelating Ca 2 þ with subsequent preventing influx of Ca 2 þ and activation of calpain, caspase-8, caspase-9 and caspase-3. This is consistent with the report that Pro suppresses apoptosis in yeast cells and human embryonic kidney cells by decreasing ROS levels [15,113]. No pervious study has addressed the inhibition of Ala, Cit and Pro on the release of cytochrome c, influx of Ca 2 þ and activation of calpain, caspase-8, caspase-9 and caspase-3 in apoptotic cells.…”

“…Ala exerts cytoprotection against oxidative stress in human endothelial cells [13] and rat hepatocytes [14]. Pro protects against oxidative stress and apoptosis in mammalian cells [15]. Therefore, the metabolites may be the real inhibitors of oxidative stress and apoptosis in Gln-supplementation mammalian.…”

“…Thus, it is important to protect erythrocytes against oxidative stress and apoptosis. Because ROS and oxidative stress is an important factor leading to apoptosis in mammal erythrocytes, it is possible that Ala, Cit and Pro could protect mammal erythrocytes from apoptosis due to their antioxidant effects [13,15,28]. However, very little information is available to date on the inhibited effects of Ala, Cit or Pro on oxidative stress in mammal erythrocytes.…”

Glutathione deficit impairs myelin maturation: relevance for white matter integrity in schizophrenia patients

“…The genetic vulnerability factors involve either redox regulation genes directly affecting GSH metabolism, [19][20][21][22] or genes that indirectly lead to oxidative stress, including DISC1, PROD, G72, NRG and DTNBP1. [23][24][25][26][27] Environmental factors known to favor major psychiatric disorders also generate reactive oxygen species (ROS), which, if the redox regulation is impaired, will perturb the developing nervous system. As a consequence, two key systems essential for cognitive and affective functioning will be particularly affected: local microcircuits and long-range connections.…”

Perineuronal nets protect fast-spiking interneurons against oxidative stress

“…Oxidative stress and decreased levels of the endogenous antioxidant and redox regulator glutathione (GSH) are observed in the prefrontal cortex of patients (18)(19)(20). Therefore, redox dysregulation via impaired GSH synthesis (21,22) or abnormal function of proteins encoded by other susceptibility genes [i.e., proline dehydrogenase (oxidase) 1 (PRODH), disrupted in schizophrenia 1 (DISC1), D-amino acid oxidase activator (DAOA or G72), dystrobrevin binding protein 1 (DTNBP1)] (23)(24)(25)(26)(27) could, together with oxidative stress generated by environmental insults, contribute to the pathophysiology of these disorders (28,29).…”