Methylglyoxal-Induced Dysfunction in Brain Endothelial Cells via the Suppression of Akt/HIF-1α Pathway and Activation of Mitophagy Associated with Increased Reactive Oxygen Species

Abstract

Methylglyoxal (MG) is a dicarbonyl compound, the level of which is increased in the blood of diabetes patients. MG is reported to be involved in the development of cerebrovascular complications in diabetes, but the exact mechanisms need to be elucidated. Here, we investigated the possible roles of oxidative stress and mitophagy in MG-induced functional damage in brain endothelial cells (ECs). Treatment of MG significantly altered metabolic stress as observed by the oxygen-consumption rate and barrier-integrity as found in impaired trans-endothelial electrical resistance in brain ECs. The accumulation of MG adducts and the disturbance of the glyoxalase system, which are major detoxification enzymes of MG, occurred concurrently. Reactive oxygen species (ROS)-triggered oxidative damage was observed with increased mitochondrial ROS production and the suppressed Akt/hypoxia-inducible factor 1 alpha (HIF-1α) pathway. Along with the disturbance of mitochondrial bioenergetic function, parkin-1-mediated mitophagy was increased by MG. Treatment of N-acetyl cysteine significantly reversed mitochondrial damage and mitophagy. Notably, MG induced dysregulation of tight junction proteins including occludin, claudin-5, and zonula occluden-1 in brain ECs. Here, we propose that diabetic metabolite MG-associated oxidative stress may contribute to mitochondrial damage and autophagy in brain ECs, resulting in the dysregulation of tight junction proteins and the impairment of permeability.

A Commonly Used Biocide 2-N-octyl-4-isothiazolin-3-oneInduces Blood–Brain Barrier Dysfunction via Cellular Thiol Modification and Mitochondrial Damage

“…The BBB, formed by brain endothelial cell (EC) lining, is a barrier that plays a protective role in brain homeostasis by regulating the flux of endogenous circulating substances or xenobiotics between the blood and brain [ 20 , 55 , 56 , 57 , 58 ]. Growing evidence indicates that the functional integrity of the BBB could be affected by blood-circulating substances [ 21 , 58 , 59 , 60 ]. Impairment of BBB function can lead to neurological damage, such as neuronal death and synaptic dysfunction, and is associated with various neurodegenerative and neurovascular diseases [ 61 , 62 , 63 ].…”

“…However, impairment of autophagic flux has been observed under pathologic conditions, including neurodegenerative diseases [ 81 , 82 ]. In our previous studies [ 20 , 21 ], we demonstrated that autophagy activated by hypoxia or methylglyoxal contributes to endothelial dysfunction by degrading tight junction proteins or mitochondria. Interestingly, dysregulated autophagy, either excessive or compromised, is known to be one of the major mechanisms of xenobiotic toxicity (He et al, 2020).…”

“…An in vitro permeability assay was performed as previously described [ 21 ]. A 0.4 µm pore polycarbonate membrane insert (Corning, New York, NY, USA) was used for the assay, and cells were seeded at a density of 0.2 × 10 5 cells per well and maintained for 6 d. Trans-endothelial electrical resistance (TEER) and FITC-dextran (m.w.…”

“…The blood–brain barrier (BBB) is a vascular endothelial cell (EC) system in the brain, tightly limiting the transportation of molecules from the blood to the central nervous system [ 19 , 20 , 21 ]. The BBB constitutes the neurovascular unit, which emphasizes the structural and functional relationship between neuronal, glial, and vascular cells, and plays a major role in regulating the brain microvascular environment [ 19 ].…”

“…The removal and biogenesis of mitochondria are tightly regulated, because excessive removal of mitochondria can reduce the number of healthy mitochondria involved in energy production and cell signaling that is required to maintain normal physiology [ 30 ]. We have recently shown that excessive activation of mitophagy is related to pathological conditions in ECs [ 21 ].…”