Aldehyde dehydrogenase-2 activation decreases acetaminophen hepatotoxicity by prevention of mitochondrial depolarization.

Oxidative stress contributes to acetaminophen (APAP) hepatotoxicity. Since lipid peroxidation produces reactive aldehydes, we investigated whether activation of mitochondrial aldehyde dehydrogenase-2 (ALDH2) with Alda-1 decreases liver injury after APAP. Male C57BL/6 mice fasted overnight received Alda-1 (20 mg/kg, i.p.) or vehicle 30 min before APAP (300 mg/kg, i.p.). Blood and livers were collected 2 or 24 h after APAP. Intravital multiphoton microscopy of rhodamine 123 (Rh123) and propidium iodide (PI) fluorescence was conducted 6 h after APAP administration to detect mitochondrial polarization status and cell death. 4-Hydroxynonenal protein adducts were present in 0.1% of tissue area without APAP treatment but increased to 7% 2 h after APAP treatment, which Alda-1 blunted to 1%. Serum alanine and aspartate aminotransferases increased to 7594 and 9768 U/L at 24 h respectively, which decreased ≥72% by Alda-1. Alda-1 also decreased centrilobular necrosis at 24 h after APAP from 47% of lobular areas to 21%. N-acetyl-p-benzoquinone imine protein adduct formation and c-Jun-N-terminal kinase phosphorylation increased after APAP as expected, but Alda-1 did not alter these changes. Without APAP, no mitochondrial depolarization was detected by intravital microscopy. At 6 h after APAP, 62% of tissue area showed depolarization, which decreased to 33.5% with Alda-1. Cell death as detected by PI labeling increased from 0 to 6.8 cells per 30× field 6 h after APAP, which decreased to 0.6 cells by Alda-1. In conclusion, aldehydes are important mediators of APAP hepatotoxicity. Accelerated aldehyde degradation by ALDH2 activation with Alda-1 decreases APAP hepatotoxicity by protection against mitochondrial dysfunction.

Aldehyde dehydrogenase-2 activation by Alda-1 decreases necrosis and fibrosis after bile duct ligation in mice.

BACKGROUND AND AIM: Liver fibrosis is a leading cause of mortality worldwide. Oxidative stress is a key component in the pathogenesis of liver fibrosis. We investigated the role of aldehyde formation resulting from lipid peroxidation in cholestatic liver injury and fibrosis. METHODS: C57Bl/6J mice underwent bile duct ligation (BDL) or sham operation. One hour after surgery and daily thereafter, animals were given Alda-1 (20 mg/kg, s.c.), an aldehyde dehydrogenase-2 activator, or equivalent volume of vehicle. Blood and livers were collected after 3 and 14 days. RESULTS: Serum alanine aminotransferase (ALT) increased from 39.8 U/L after sham operation to 537 U/L 3 days after BDL, which Alda-1 decreased to 281 U/L. Biliary infarcts with a periportal distribution developed with an area of 7.8% at 14 days after BDL versus 0% area after sham operation. Alda-1 treatment with BDL decreased biliary infarcts to 1.9%. Fibrosis detected by picrosirius red staining increased from 1.6% area in sham to 7.3% after BDL, which decreased to 3.8% with Alda-1. Alda-1 suppression of fibrosis was additionally confirmed by second harmonic generation microscopy. After BDL, collagen-I mRNA increased 12-fold compared to sham, which decreased to 6-fold after Alda-1 treatment. Smooth muscle α-actin expression in the liver, a marker of activated stellate cells, increased from 1% area in sham to 18.7% after BDL, which decreased to 5.3% with Alda-1. CD68-positive macrophages increased from 33.4 cells/field in sham to 134.5 cells/field after BDL, which decreased to 64.9 cells/field with Alda-1. Lastly, 4-hydroxynonenal adduct (4-HNE) immunofluorescence increased from 2.5% area in sham to 14.1% after BDL. Alda-1 treatment decreased 4-HNE to 2.2%. CONCLUSION: Accelerated aldehyde degradation by Alda-1 decreases BDL-induced liver necrosis, inflammation, and fibrosis, implying that aldehydes play an important role in the pathogenesis of cholestatic liver injury and fibrosis.

The neuroblast and angioblast chemotaxic factor SDF-1 (CXCL12) expression is briefly up regulated by reactive astrocytes in brain following neonatal hypoxic-ischemic injury.

BACKGROUND: Stromal cell-derived factor 1 (SDF-1 or CXCL12) is chemotaxic for CXCR4 expressing bone marrow-derived cells. It functions in brain embryonic development and in response to ischemic injury in helping guide neuroblast migration and vasculogenesis. In experimental adult stroke models SDF-1 is expressed perivascularly in the injured region up to 30 days after the injury, suggesting it could be a therapeutic target for tissue repair strategies. We hypothesized that SDF-1 would be expressed in similar temporal and spatial patterns following hypoxic-ischemic (HI) injury in neonatal brain. RESULTS: Twenty-five 7-day-old C57BL/J mice underwent HI injury. SDF-1 expression was up regulated up to 7 days after the injury but not at the later time points. The chief sites of SDF-1 up regulation were astrocytes, their foot processes along blood vessels and endothelial cells. CONCLUSION: The localization of SDF-1 along blood vessels in the HI injury zone suggests that these perivascular areas are where chemotaxic signaling for cellular recruitment originates and that reactive astrocytes are major mediators of this process. The associated endothelium is likely to be the site for vascular attachment and diapedesis of CXCR4 receptor expressing cells to enter the injured tissue. Here we show that, relative to adults, neonates have a significantly smaller window of opportunity for SDF-1 based vascular chemotaxic recruitment of bone marrow-derived cells. Therefore, without modification, following neonatal HI injury there is only a narrow period of time for endogenous SDF-1 mediated chemotaxis and recruitment of reparative cells, including exogenously administered stem/progenitor cells.