Pretreatment with the ALDH2 agonist Alda-1 reduces intestinal injury induced by ischaemia and reperfusion in mice. Clin Sci (Lond). 2017;131:1123-1136. [PMID: 28325855 PMCID: PMC5434792 DOI: 10.1042/cs20170074]

Suppression of aldehyde dehydrogenase 2 in kidney proximal tubules contributes to kidney fibrosis through Transforming Growth Factor-β signaling

Chronic kidney disease (CKD) is an increasingly prevalent disorder that poses a significant global health and socioeconomic burden. East Asian countries such as China, Taiwan, Japan, and South Korea have a higher incidence and prevalence of kidney failure when compared to Western nations, and the reasons for this discrepancy remain unclear. Aldehyde dehydrogenase 2 (ALDH2) is an essential detoxifying enzyme for exogenous and endogenous aldehyde metabolism in mitochondria. Inactivating mutations at E504K and E487K are found in 35-45% of East Asian populations and has been linked to a higher risk of various disorders, including cardiovascular diseases and cancer. However, little is known about the role of ALDH2 in CKD. Here, we characterized the expression pattern of ALDH2 in normal and CKD human and mouse kidneys and demonstrated that ALDH2 expression was significantly reduced, and that the protein level was inversely correlated with the degree of CKD and fibrosis. Further, we treated ALDH2∗2 knock-in mice, a loss of ALDH2 function model, with aristolochic acid and found that these mice showed enhanced fibrosis. Moreover, ALDH2 deficiency was associated with kidney fibrosis involving epithelial cell differentiation process in vivo and in vitro. However, ALDH2 overexpression protected proximal tubule epithelial cells from transforming growth factor-β-induced dedifferentiation or partial epithelial-mesenchymal transdifferentiation in vitro. Thus, our findings yield important clinical information regarding the development and progression of CKD involving ALDH2, especially among East Asian populations.

Alda-1 attenuation of binge alcohol-caused atrial arrhythmias through a novel mechanism of suppressed c-Jun N-terminal Kinase-2 activity

Holiday Heart Syndrome (HHS) is caused by excessive binge alcohol consumption, and atrial fibrillation (AF) is the most common arrhythmia among HHS patients. AF is associated with substantial morbidity and mortality, making its prevention and treatment of high clinical interest. This study defines the anti-AF action of Alda-1 (an established cardioprotective agent) and the underlying mechanisms of the action in our well-characterized HHS and cellular models. We found that Alda-1 effectively eliminated binge alcohol-evoked Ca2+ triggered activities (Ca2+ waves, prolonged Ca2+ transient diastolic decay) and arrhythmia inducibility in intact mouse atria. We then demonstrated that alcohol impaired human RyR2 channels (isolated from organ donors' hearts). The functional role of alcohol-caused RyR2 channel dysfunction in Ca2+ triggered arrhythmic activities was evidenced in a unique transgenic mouse model with a loss-of-function mutation (RyR2E4872Q+/-). Alda-1 is known to activate aldehyde dehydrogenase 2 (ALDH2), a key enzyme in alcohol detoxification. However, we found an increased level of ALDH2 and a preserved normal balance of pro- vs anti-apoptotic signaling in binge alcohol exposed hearts and H9c2 differentiated myocytes, which suggests that the link of alcohol-ALDH2-apoptosis is unlikely to be a key factor leading to binge alcohol-evoked arrhythmogenicity. We have previously reported that binge alcohol-activated stress response kinase JNK2 causatively drives Ca2+-triggered atrial arrhythmogenicity. Here, we found that JNK2-specific inhibition in either isolated human RyR2 channels or intact mouse atria abolished alcohol-evoked RyR2 channel dysfunction and Ca2+ triggered arrhythmic activities, suggesting a strong alcohol-JNK2-RyR2 interaction in atrial arrhythmogenicity. Furthermore, we revealed, for the first time, that Alda-1 suppresses JNK2 (but not JNK1) enzyme activity independently of ALDH2, which in turn alleviates binge alcohol-evoked Ca2+ triggered atrial arrhythmogenesis. Our findings provide novel mechanistic insights into the anti-arrhythmic action of Alda-1 and suggest that Alda-1 represents a potential preventative agent for AF management for HHS patients.

Aldehyde dehydrogenase-2 deficiency aggravates neuroinflammation, nociception, and motor impairment in a mouse model of multiple sclerosis

Aldehyde dehydrogenase-2 deficiency (ALDH2∗2) found in 36 % of Han Chinese, affects approximately 8 % of the world population. ALDH2 is a mitochondrial key enzyme in detoxifying reactive aldehydes to less reactive forms. Studies demonstrate a potential link between ALDH2∗2 mutation and neurodegenerative diseases. Multiple sclerosis (MS) is an incurable and disabling neurodegenerative autoimmune disease that induces motor, and cognitive impairment, and hypersensitivity, including chronic pain. Accumulating evidence suggests that reactive aldehydes, such as 4-hydroxynonenal (4-HNE), contribute to MS pathogenesis. Here, using knock-in mice carrying the inactivating point mutation in ALDH2, identical to the mutation found in Han Chinese, we showed that the impairment in ALDH2 activity heightens motor disabilities, and hypernociception induced by experimental autoimmune encephalomyelitis (EAE). The deleterious clinical signs are followed by glial cell activation in the spinal cord and increased 4-HNE levels in the spinal cord and serum. Importantly, the pharmacological ALDH2 activation by Alda-1 ameliorates EAE-induced hypernociception and motor impairment in both wild-type and ALDH2∗2KI mice. Reduced hypernociception was associated with less early growth response protein 1 (EGR1), neuronal and glial activation, and reactive aldehyde accumulation in the spinal cord and serum. Taken together, our data suggest that the mitochondrial enzyme ALDH2 plays a role in regulating clinical, cellular, and molecular responses associated with EAE. This indicates that ALDH2 could serve as a molecular target for MS control, with ALDH2 activators, like Alda-1 as potential neuroprotective candidates. Furthermore, ALDH2∗2 carriers may be at increased risk of developing more accentuated MS symptoms.

Targeting cell death pathways in intestinal ischemia-reperfusion injury: a comprehensive review

Intestinal ischemia-reperfusion (I/R) is a multifaceted pathological process, and there is a lack of clear treatment for intestinal I/R injury. During intestinal I/R, oxidative stress and inflammation triggered by cells can trigger a variety of cell death mechanisms, including apoptosis, autophagy, pyroptosis, ferroptosis, and necrosis. These cell death processes can send a danger signal for the body to be damaged and prevent intestinal I/R injury. Therefore, identifying key regulatory molecules or markers of these cell death mechanisms when intestinal I/R injury occurs may provide valuable information for the treatment of intestinal I/R injury. This paper reviews the regulatory molecules and potential markers that may be involved in regulating cell death during intestinal I/R and elaborates on the cell death mechanism of intestinal I/R injury at the molecular level to provide a theoretical basis for discovering new molecules or markers regulating cell death during intestinal I/R injury and provides ideas for drug development for the treatment of intestinal I/R injury.

Host ALDH2 deficiency aggravates nonalcoholic steatohepatitis through gut-liver axis

Nonalcoholic steatohepatitis (NASH) is the major cause of liver dysfunction. Animal and population studies have shown that mitochondrial aldehyde dehydrogenase (ALDH2) is implicated in fatty liver disease. However, the role of ALDH2 in NASH and the underlying mechanisms remains unclear. To address this issue, ALDH2 knockout (ALDH2-/-) mice and wild-type littermate mice were fed a methionine-and choline-deficient (MCD) diet to induce a NASH model. Fecal, serum, and liver samples were collected and analyzed to investigate the impact of the gut microbiota and bile acids on this process. We found that MCD-fed ALDH2-/- mice exhibited increased serum pro-inflammation cytokines, hepatic inflammation and fat accumulation than their wild-type littermates. MCD-fed ALDH2-/- mice exhibited worsened MCD-induced intestinal inflammation and barrier damage, and gut microbiota disorder. Furthermore, mice receiving microbiota from MCD-fed ALDH2-/- mice had increased severity of NASH compared to those receiving microbiota from MCD-fed wild-type mice. Notably, the intestinal Lactobacillus was significantly reduced in MCD-fed ALDH2-/- mice, and gavage with Lactobacillus cocktail significantly improved MCD-induced NASH. Finally, we found that ALDH2-/- mice had reduced levels of bile salt hydrolase and specific bile acids, especially lithocholic acid (LCA), accompanied by downregulated expression of the intestinal FXR-FGF15 pathway. Supplementation of LCA in ALDH2-/- mice upregulated intestinal FXR-FGF15 pathway and alleviated NASH. In summary, ALDH2 plays a critical role in the development of NASH through modulation of gut microbiota and bile acid. The findings suggest that supplementing with Lactobacillus or LCA could be a promising therapeutic approach for treating NASH exacerbated by ALDH2 deficiency.

Naringin protects against inflammation and apoptosis induced by intestinal ischemia-reperfusion injury through deactivation of cGAS-STING signaling pathway

Effective amelioration of ischemia/reperfusion (I/R)-induced intestinal injury and revealing its mechanisms remain the challenges in both preclinic and clinic. Potential mechanisms of naringin in ameliorating I/R-induced intestinal injury remain unknown. Based on pre-experiments, I/R-injured rat intestine in vivo and hypoxia-reoxygenation (H/R)-injured IEC-6 cells in vitro were used to verify that naringin-alleviated I/R-induced intestinal injury was mediated via deactivating cGAS-STING signaling pathway. Naringin improved intestinal damage using hematoxylin and eosin staining and decreased alanine aminotransferase and aspartate aminotransferase contents in plasma. Naringin decreased inflammation characterized by reducing IL-6, IL-1β, TNF-α, and IFN-β contents in both plasma and IEC-6 cells. Naringin mitigated oxidative stress via recovering superoxide dismutase, glutathione, and malondialdehyde levels in the I/R-injured intestine. Naringin reduced the expression of apoptotic proteins, including Bax, caspase-3, and Bcl-2, and reduced terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling-positive cells both in vivo and in vitro, and decreased Hoechst 33342 signals in vitro. cGAS, STING, p-TBK1, p-IRF3, and NF-κB expressions were up-regulated both in vivo and in vitro respectively and the up-regulated indexes were reversed by naringin. Transfection of cGAS-siRNA and cGAS-cDNA significantly down-regulated and up-regulated cGAS-STING signaling-related protein expressions, respectively, and partially weakened naringin-induced amelioration on these indexes, suggesting that deactivation of cGAS-STING signaling is the crucial target for naringin-induced amelioration on I/R-injured intestine.

Activation of aldehyde dehydrogenase-2 improves ischemic random skin flap survival in rats

Objective

Random skin flaps have many applications in plastic and reconstructive surgeries. However, distal flap necrosis restricts wider clinical utility. Mitophagy, a vital form of autophagy for damaged mitochondria, is excessively activated in flap ischemia/reperfusion (I/R) injury, thus inducing cell death. Aldehyde dehydrogenase-2 (ALDH2), an allosteric tetrameric enzyme, plays an important role in regulating mitophagy. We explored whether ALDH2 activated by N-(1,3-benzodioxol-5-ylmethyl)-2,6-dichlorobenzamide (Alda-1) could reduce the risk of ischemic random skin flap necrosis, and the possible mechanism of action.

Methods

Modified McFarlane flap models were established in 36 male Sprague-Dawley rats assigned randomly to three groups: a low-dose Alda-1 group (10 mg/kg/day), a high-dose Alda-1 group (20 mg/kg/day) and a control group. The percentage surviving skin flap area, neutrophil density and microvessel density (MVD) were evaluated on day 7. Oxidative stress was quantitated by measuring the superoxide dismutase (SOD) and malondialdehyde (MDA) levels. Blood perfusion and skin flap angiogenesis were assessed via laser Doppler flow imaging and lead oxide-gelatin angiography, respectively. The expression levels of inflammatory cytokines (IL-1β, IL-6, and TNF-α), vascular endothelial growth factor (VEGF), ALDH2, PTEN-induced kinase 1 (PINK1), and E3 ubiquitin ligase (Parkin) were immunohistochemically detected. Indicators of mitophagy such as Beclin-1, p62, and microtubule-associated protein light chain 3 (LC3) were evaluated by immunofluorescence.

Results

Alda-1 significantly enhanced the survival area of random skin flaps. The SOD activity increased and the MDA level decreased, suggesting that Alda-1 reduced oxidative stress. ALDH2 was upregulated, and mitophagy-related proteins (PINK1, Parkin, Beclin-1, p62, and LC3) were downregulated, indicating that ALDH2 inhibited mitophagy through the PINK1/Parkin signaling pathway. Treatment with Alda-1 reduced neutrophil infiltration and expressions of inflammatory cytokines. Alda-1 significantly upregulated VEGF expression, increased the MVD, promoted angiogenesis, and enhanced blood perfusion.

Conclusion

ALDH2 activation can effectively enhance random skin flap viability via inhibiting PINK1/Parkin-dependent mitophagy. Moreover, enhancement of ALDH2 activity also exerts anti-inflammatory and angiogenic properties.

Alda-1 ameliorates air embolism-induced acute lung injury

OBJECTIVE

Evidence suggests that aldehyde dehydrogenase 2 (ALDH2) offers protection against damage caused by oxidative stress in diverse rodent models. Nonetheless, the effect of Alda-1, a compound that activates ALDH2, on acute lung injury (ALI) induced by air embolism (AE) remains unclear. The objective of this study was to explore the protective effects of Alda-1 in ALI induced by AE.

METHODS

A rat model of in situ isolated perfused lung was established to investigate AE-induced ALI. Air was infused into the pulmonary artery at 0.25 mL/min for 1 minute. Before inducing AE, different doses (10, 20, or 30 mg/kg) of Alda-1 were given through intraperitoneal injection. Pathological changes in lung tissue were assessed using hematoxylin-eosin staining. We performed Western blot analysis to assess the protein levels of ALDH2,4-hydroxy-trans-2-nonenal (4-HNE), Bcl-2, caspase-3, phosphatidylinositol 3-kinase (PI3K), Akt, IκB-α, and nuclear NF-κB.

RESULTS

Notably, AE results were demonstrated as harmful to the lungs, which is evidenced by intensified lung edema and disruption of lung tissue structure. Furthermore, AE caused a decrease in ALDH2 expression, increased accumulation of 4-HNE and MDA, infiltration of neutrophils, increased production of inflammatory cytokines, apoptosis, and upregulation of the PI3K/Akt and NF-κB signaling pathways within the lungs. Administration of a 20 mg/kg dose of Alda-1 alleviated the detrimental effects induced by AE.

CONCLUSION

Alda-1 shows promise in mitigating AE-induced ALI, possibly through the upregulation of ALDH2 expression and suppression of the PI3K/Akt and NF-κB signaling pathways. Further research is warranted to validate these findings and to explore their translational potential in human subjects.

ALDH2 deficiency increases susceptibility to binge alcohol-induced gut leakiness, endotoxemia, and acute liver injury in mice through the gut-liver axis

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is the major enzyme responsible for metabolizing toxic acetaldehyde to acetate and acts as a protective or defensive protein against various disease states associated with alcohol use disorder (AUD), including alcohol-related liver disease (ARLD). We hypothesized that Aldh2-knockout (KO) mice are more susceptible to binge alcohol-mediated liver injury than wild-type (WT) mice through increased oxidative stress, gut leakiness and endotoxemia. Therefore, this study aimed to investigate the protective role of ALDH2 in binge alcohol-induced gut permeability, endotoxemia, and acute inflammatory liver injury by exposing Aldh2-KO or WT mice to a single oral dose of binge alcohol 3.5, 4.0, or 5.0 g/kg. Our findings showed for the first time that ALDH2 deficiency in Aldh2-KO mice increases their sensitivity to binge alcohol-induced oxidative and nitrative stress, enterocyte apoptosis, and nitration of gut tight junction (TJ) and adherent junction (AJ) proteins, leading to their degradation. These resulted in gut leakiness and endotoxemia in Aldh2-KO mice after exposure to a single dose of ethanol even at 3.5 g/kg, while no changes were observed in the corresponding WT mice. The elevated serum endotoxin (lipopolysaccharide, LPS) and bacterial translocation contributed to systemic inflammation, hepatocyte apoptosis, and subsequently acute liver injury through the gut-liver axis. Treatment with Daidzin, an ALDH2 inhibitor, exacerbated ethanol-induced cell permeability and reduced TJ/AJ proteins in T84 human colon cells. These changes were reversed by Alda-1, an ALDH2 activator. Furthermore, CRISPR/Cas9-mediated knockout of ALDH2 in T84 cells increased alcohol-mediated cell damage and paracellular permeability. All these findings demonstrate the critical role of ALDH2 in alcohol-induced epithelial barrier dysfunction and suggest that ALDH2 deficiency or gene mutation in humans is a risk factor for alcohol-mediated gut and liver injury, and that ALDH2 could be an important therapeutic target against alcohol-associated tissue or organ damage.

The Effects of Alda-1 Treatment on Renal and Intestinal Injuries After Cardiopulmonary Resuscitation in Pigs

Aim

After successful cardiopulmonary resuscitation (CPR), most survivors will develop acute kidney injury and intestinal barrier dysfunction, both of which contribute to the poor outcomes of cardiac arrest (CA) victims. Recently, the aldehyde dehydrogenase 2 (ALDH2) agonist, Alda-1 was shown to effectively alleviate regional ischemia/reperfusion injury of various organs. In the present study, we investigated the effects of Alda-1 treatment on renal and intestinal injuries after CA and resuscitation in pigs.

Methods

Twenty-four male domestic pigs were randomly divided into one of the three groups: sham (n = 6), CPR (n = 10), or CPR+Alda-1 (n = 8). CA was induced and untreated for 8 min, and then CPR was performed for 8 min in the CPR and CPR+Alda-1 groups. At 5 min after resuscitation, a dose of 0.88 mg/kg of Alda-1 was intravenously administered in the CPR+Alda-1 group. The biomarkers of renal and intestinal injuries after resuscitation were regularly measured for a total of 24 h. Subsequently, the animals were euthanized, and then renal and intestinal tissues were obtained for the measurements of ALDH2 activity and expression, and cell apoptosis and ferroptosis.

Results

Five of the 10 animals in the CPR group and six of the eight animals in the CPR+Alda-1 group were successfully resuscitated. After resuscitation, the levels of biomarkers of renal and intestinal injuries were significantly increased in all animals experiencing CA and resuscitation compared with the sham group; however, Alda-1 treatment significantly alleviated renal and intestinal injuries compared to the CPR group. Post-resuscitation ALDH2 activity was significantly decreased and its expression was markedly reduced in the kidney and intestine in those resuscitated animals compared with the sham group; nevertheless, both of them were significantly greater in those animals receiving Alda-1 treatment compared to the CPR group. In addition, renal, intestinal apoptosis and ferroptosis after resuscitation were observed in the CPR and CPR+Alda-1 groups, in which both of them were significantly milder in the CPR+Alda1 group than in the CPR group.

Conclusions

The activation of ALDH2 by Alda-1 treatment significantly alleviated post-resuscitation renal and intestinal injuries through the inhibition of cell apoptosis and ferroptosis in a pig model of CA and resuscitation.

Mitochondrial DNA Release Contributes to Intestinal Ischemia/Reperfusion Injury

Mitochondria release many damage-associated molecular patterns (DAMPs) when cells are damaged or stressed, with mitochondrial DNA (mtDNA) being. MtDNA activates innate immune responses and induces inflammation through the TLR-9, NLRP3 inflammasome, and cGAS-STING signaling pathways. Released inflammatory factors cause damage to intestinal barrier function. Many bacteria and endotoxins migrate to the circulatory system and lymphatic system, leading to systemic inflammatory response syndrome (SIRS) and even damaging the function of multiple organs throughout the body. This process may ultimately lead to multiple organ dysfunction syndrome (MODS). Recent studies have shown that various factors, such as the release of mtDNA and the massive infiltration of inflammatory factors, can cause intestinal ischemia/reperfusion (I/R) injury. This destroys intestinal barrier function, induces an inflammatory storm, leads to SIRS, increases the vulnerability of organs, and develops into MODS. Mitophagy eliminates dysfunctional mitochondria to maintain cellular homeostasis. This review discusses mtDNA release during the pathogenesis of intestinal I/R and summarizes methods for the prevention or treatment of intestinal I/R. We also discuss the effects of inflammation and increased intestinal barrier permeability on drugs.

Aldehyde Dehydrogenase 2 as a Therapeutic Target in Oxidative Stress-Related Diseases: Post-Translational Modifications Deserve More Attention

Aldehyde dehydrogenase 2 (ALDH2) has both dehydrogenase and esterase activity; its dehydrogenase activity is closely related to the metabolism of aldehydes produced under oxidative stress (OS). In this review, we recapitulate the enzyme activity of ALDH2 in combination with its protein structure, summarize and show the main mechanisms of ALDH2 participating in metabolism of aldehydes in vivo as comprehensively as possible; we also integrate the key regulatory mechanisms of ALDH2 participating in a variety of physiological and pathological processes related to OS, including tissue and organ fibrosis, apoptosis, aging, and nerve injury-related diseases. On this basis, the regulatory effects and application prospects of activators, inhibitors, and protein post-translational modifications (PTMs, such as phosphorylation, acetylation, S-nitrosylation, nitration, ubiquitination, and glycosylation) on ALDH2 are discussed and prospected. Herein, we aimed to lay a foundation for further research into the mechanism of ALDH2 in oxidative stress-related disease and provide a basis for better use of the ALDH2 function in research and the clinic.

Shaping of Hepatic Ischemia/Reperfusion Events: The Crucial Role of Mitochondria

Hepatic ischemia reperfusion injury (HIRI) is a major hurdle in many clinical scenarios, including liver resection and transplantation. Various studies and countless surgical events have led to the observation of a strong correlation between HIRI induced by liver transplantation and early allograft-dysfunction development. The detrimental impact of HIRI has driven the pursuit of new ways to alleviate its adverse effects. At the core of HIRI lies mitochondrial dysfunction. Various studies, from both animal models and in clinical settings, have clearly shown that mitochondrial function is severely hampered by HIRI and that its preservation or restoration is a key indicator of successful organ recovery. Several strategies have been thus implemented throughout the years, targeting mitochondrial function. This work briefly discusses some the most utilized approaches, ranging from surgical practices to pharmacological interventions and highlights how novel strategies can be investigated and implemented by intricately discussing the way mitochondrial function is affected by HIRI.

Critical role of mitochondrial aldehyde dehydrogenase 2 in acrolein sequestering in rat spinal cord injury

Lipid peroxidation-derived aldehydes, such as acrolein, the most reactive aldehyde, have emerged as key culprits in sustaining post-spinal cord injury (SCI) secondary pathologies leading to functional loss. Strong evidence suggests that mitochondrial aldehyde dehydrogenase-2 (ALDH2), a key oxidoreductase and powerful endogenous anti-aldehyde machinery, is likely important for protecting neurons from aldehydes-mediated degeneration. Using a rat model of spinal cord contusion injury and recently discovered ALDH2 activator (Alda-1), we planned to validate the aldehyde-clearing and neuroprotective role of ALDH2. Over an acute 2 day period post injury, we found that ALDH2 expression was significantly lowered post-SCI, but not so in rats given Alda-1. This lower enzymatic expression may be linked to heightened acrolein-ALDH2 adduction, which was revealed in co-immunoprecipitation experiments. We have also found that administration of Alda-1 to SCI rats significantly lowered acrolein in the spinal cord, and reduced cyst pathology. In addition, Alda-1 treatment also resulted in significant improvement of motor function and attenuated post-SCI mechanical hypersensitivity up to 28 days post-SCI. Finally, ALDH2 was found to play a critical role in in vitro protection of PC12 cells from acrolein exposure. It is expected that the outcome of this study will broaden and enhance anti-aldehyde strategies in combating post-SCI neurodegeneration and potentially bring treatment to millions of SCI victims. All animal work was approved by Purdue Animal Care and Use Committee (approval No. 1111000095) on January 1, 2021.

Pharmacological Activation Of Aldehyde Dehydrogenase 2 Protects Against Heatstroke-Induced Acute Lung Injury by Modulating Oxidative Stress and Endothelial Dysfunction

Heatstroke (HS) can cause acute lung injury (ALI). Heat stress induces inflammation and apoptosis via reactive oxygen species (ROS) and endogenous reactive aldehydes. Endothelial dysfunction also plays a crucial role in HS-induced ALI. Aldehyde dehydrogenase 2 (ALDH2) is a mitochondrial enzyme that detoxifies aldehydes such as 4-hydroxy-2-nonenal (4-HNE) protein adducts. A single point mutation in ALDH2 at E487K (ALDH2*2) intrinsically lowers the activity of ALDH2. Alda-1, an ALDH2 activator, attenuates the formation of 4-HNE protein adducts and ROS in several disease models. We hypothesized that ALDH2 can protect against heat stress-induced vascular inflammation and the accumulation of ROS and toxic aldehydes. Homozygous ALDH2*2 knock-in (KI) mice on a C57BL/6J background and C57BL/6J mice were used for the animal experiments. Human umbilical vein endothelial cells (HUVECs) were used for the in vitro experiment. The mice were directly subjected to whole-body heating (WBH, 42°C) for 1 h at 80% relative humidity. Alda-1 (16 mg/kg) was administered intraperitoneally prior to WBH. The severity of ALI was assessed by analyzing the protein levels and cell counts in the bronchoalveolar lavage fluid, the wet/dry ratio and histology. ALDH2*2 KI mice were susceptible to HS-induced ALI in vivo. Silencing ALDH2 induced 4-HNE and ROS accumulation in HUVECs subjected to heat stress. Alda-1 attenuated the heat stress-induced activation of inflammatory pathways, senescence and apoptosis in HUVECs. The lung homogenates of mice pretreated with Alda-1 exhibited significantly elevated ALDH2 activity and decreased ROS accumulation after WBH. Alda-1 significantly decreased the WBH-induced accumulation of 4-HNE and p65 and p38 activation. Here, we demonstrated the crucial roles of ALDH2 in protecting against heat stress-induced ROS production and vascular inflammation and preserving the viability of ECs. The activation of ALDH2 by Alda-1 attenuates WBH-induced ALI in vivo.

Mycobacterium avium subsp. paratuberculosis Proteome Changes Profoundly in Milk

Mycobacterium avium subspecies paratuberculosis (MAP) are detectable viable in milk and other dairy products. The molecular mechanisms allowing the adaptation of MAP in these products are still poorly understood. To obtain information about respective adaptation of MAP in milk, we differentially analyzed the proteomes of MAP cultivated for 48 h in either milk at 37 °C or 4 °C or Middlebrook 7H9 broth as a control. From a total of 2197 MAP proteins identified, 242 proteins were at least fivefold higher in abundance in milk. MAP responded to the nutritional shortage in milk with upregulation of 32% of proteins with function in metabolism and 17% in fatty acid metabolism/synthesis. Additionally, MAP upregulated clusters of 19% proteins with roles in stress responses and immune evasion, 19% in transcription/translation, and 13% in bacterial cell wall synthesis. Dut, MmpL4_1, and RecA were only detected in MAP incubated in milk, pointing to very important roles of these proteins for MAP coping with a stressful environment. Dut is essential and plays an exclusive role for growth, MmpL4_1 for virulence through secretion of specific lipids, and RecA for SOS response of mycobacteria. Further, 35 candidates with stable expression in all conditions were detected, which could serve as targets for detection. Data are available via ProteomeXchange with identifier PXD027444.

MicroRNA-146a overexpression alleviates intestinal ischemia/reperfusion-induced acute lung injury in mice

Previous studies have shown that microRNAs (miRs), such as miR-146a play an important role in the pathogenesis of intestinal ischemia/reperfusion (I/R)-induced injury; however, the role of miR-146a in intestinal I/R-induced acute lung injury has not been elucidated. An intestinal I/R-induced injury mouse model was established in the present study by clamping the superior mesenteric artery and expression levels of miR-146a in intestinal and lung tissue samples were evaluated using reverse transcription-quantitative PCR (RT-qPCR). Intestinal and lung histopathological characteristics in mice with intestinal I/R-induced injury were assessed by hematoxylin and eosin staining, and mRNA and protein expression levels in intestinal and lung tissue samples were evaluated using RT-qPCR and western blotting, respectively. miR-146a expression was significantly downregulated in the intestinal and lung tissue samples of mice with intestinal I/R-induced injury. Intestinal I/R injury-induced histopathological changes in the lung and intestines, and pulmonary edema in mice transduced with an adenoviral miR-146a-overexpression vector (the miR-146a overexpression group) were alleviated. mRNA expression levels of TNF-α, IL-1β, IFN-γ and TGF-β1, and protein expression levels of TNF receptor-associated factor 6, phosphorylated-p65 NF-κB, cleaved caspase-3 and cleaved caspase-9 in lung and intestinal tissue samples were downregulated in I/R-miR-146a-overexpressing mice, compared with those from the I/R-negative control group. Thus, the present study identified that pre-treatment with the miR-146a overexpression vector alleviated intestinal I/R-induced acute lung injury in mice.

Detoxification of Reactive Aldehydes by Alda-1 Treatment Ameliorates Experimental Autoimmune Encephalomyelitis in Mice

Reactive aldehydes are generated as a toxic end-product of lipid peroxidation under inflammatory oxidative stress condition which is a well-established phenomenon in the pathogenesis of multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Alda-1, a selective agonist of mitochondrial aldehyde dehydrogenase 2 (ALDH2), is known to detoxify the reactive aldehydes. In this study, we investigated the effect of Alda-1 on CNS myelin pathology associated with reactive aldehydes and mitochondrial/peroxisomal dysfunctions in a mouse model of EAE. Daily treatment of EAE mice with Alda-1, starting at the peak of disease, ameliorated the clinical manifestation of disease along with the improvement of motor functions. Accordingly, Alda-1 treatment improved demyelination and neuroaxonal degeneration in EAE mice. EAE mice had increased levels of reactive aldehyde species, such as 4-hydroxynonenal (4-HNE), malondialdehyde (MDA), and acrolein (ACL) in the spinal cords and these levels were significantly reduced in Alda-1-treated EAE mice. Furthermore, Alda-1 treatment improved the loss of mitochondrial (OXPHOS) and peroxisomal (PMP70 and catalase) proteins as well as mitochondrial/peroxisomal proliferation factors (PGC-1α and PPARs) in the spinal cords of EAE mice. Taken together, this study demonstrates the therapeutic efficacy of ALDH2-agonist Alda-1 in the abatement of EAE disease through the detoxification of reactive aldehydes, thus suggesting Alda-1 as a potential therapeutic intervention for MS.

Alda-1 Attenuates Hyperoxia-Induced Acute Lung Injury in Mice

Acute lung injury (ALI), a milder form of acute respiratory distress syndrome (ARDS), is a leading cause of mortality in older adults with an increasing prevalence. Oxygen therapy, is a common treatment for ALI, involving exposure to a high concentration of oxygen. Unfortunately, hyperoxia induces the formation of reactive oxygen species which can cause an increase in 4-HNE (4-hydroxy 2 nonenal), a toxic byproduct of lipid peroxidation. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) serves as an endogenous shield against oxidative stress-mediated damage by clearing 4-HNE. Alda-1 [(N-(1, 3 benzodioxol-5-ylmethyl)-2, 6- dichloro-benzamide)], a small molecular activator of ALDH2, protects against reactive oxygen species-mediated oxidative stress by promoting ALDH2 activity. As a result, Alda-1 shields against ischemic reperfusion injury, heart failure, stroke, and myocardial infarction. However, the mechanisms of Alda-1 in hyperoxia-induced ALI remains unclear. C57BL/6 mice implanted with Alzet pumps received Alda-1 in a sustained fashion while being exposed to hyperoxia for 48 h. The mice displayed suppressed immune cell infiltration, decreased protein leakage and alveolar permeability compared to controls. Mechanistic analysis shows that mice pretreated with Alda-1 also experience decreased oxidative stress and enhanced levels of p-Akt and mTOR pathway associated proteins. These results show that continuous delivery of Alda-1 protects against hyperoxia-induced lung injury in mice.

Alda-1 attenuates hyperoxia-induced mitochondrial dysfunction in lung vascular endothelial cells

Acute lung injury (ALI) is a major cause of morbidity and mortality worldwide, especially in aged populations. Mitochondrial damage is one of the key features of ALI. Hyperoxia-induced lung injury model in mice has been widely used for ALI study because it features many ALI phenotypes including, but not limited to, mitochondrial and vascular endothelial cell damage. Recently, accumulating evidence has shown that mitochondrial aldehyde dehydrogenase 2 (ALDH2) has a protective effect against oxidative stress mediated cell damage in epithelial cells. However, it is not known whether ALDH2 protects against oxidative stress in vascular endothelial cells. In this current study, we attempted to find the capacity of Alda-1 [(N-(1,3benzodioxol-5-ylmethyl)-2,6- dichloro-benzamide), an ALDH2 activator] to protect against oxidative stress in human microvascular endothelial cells (HMVEC). HMVEC pretreated with Alda-1 prior to hyperoxic exposure vs non-treated controls showed i) lower 4-hydroxynonenal (4-HNE) levels, ii) significantly decreased expressions of Bax and Cytochrome C, iii) partially restored activity and expression of ALDH2 and iv) significantly improved mitochondrial membrane potential. These results suggest that ALDH2 protein in lung vascular endothelial cells is a promising therapeutic target for the treatment of ALI and that Alda-1 is a potential treatment option.

Pretreatment with the ALDH2 activator Alda‑1 protects rat livers from ischemia/reperfusion injury by inducing autophagy

Hepatic ischemia/reperfusion injury (HIRI) is a complex pathophysiological process that often leads to poor clinical prognosis. Clinically, the effective means to alleviate HIRI are limited. The aim of the present study was to investigate whether Alda-1, an activator of mitochondrial aldehyde dehydrogenase 2 (ALDH2), had a protective effect on HIRI and to investigate the mechanisms underlying this protective effect. Sprague-Dawley rats were treated with Alda-1 or Daidzin, an ALDH2 inhibitor, 30 min before partial (70%) warm liver ischemia to induce HIRI. The 48 rats were randomly divided into four groups: Sham, ischemia injury (IR), IR-Alda-1, and IR-Daidzin. After 6 and 24 h of reperfusion, serum and liver tissue samples were collected and stored for further experiments. Alanine aminotransferase, aspartate aminotransferase and hematoxylin & eosin staining was used to evaluate the liver damage. Western blotting and reverse transcription-quantitative PCR were used to detect the expression of related proteins and mRNA. TUNEL staining was used to observe the apoptosis of liver cells. Transmission electron microscopy was used to detect the mitochondrial injuries. Alda-1 pretreatment ameliorated the HIRI-induced damage to the liver function and reduced histological lesions. Alda-1 also increased ALDH2 activity after HIRI. Moreover, the pretreatment with Alda-1 reduced the accumulation of toxic aldehyde 4-hydroxy-2-nonenal, decreased the production of reactive oxygen species and malondialdehyde, reversed the damage to the liver mitochondria, attenuated hepatocyte apoptosis and inhibited the HIRI-induced inflammatory response, including high-mobility group box 1/toll-like receptor 4 signaling. Alda-1 also induced autophagy by upregulating autophagy-related 7 and Rab7 increasing the microtubule associated protein 1 light chain 3 αII/I ratio and inhibiting p62 expression. ALDH2-induced autophagy was dependent on the activation of the AKT/mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) signaling pathways. In conclusion, the findings of the present study suggested that Alda-1 may protect the liver against HIRI-induced damage, including hepatic enzyme injury, acetaldehyde accumulation, oxidative stress, hepatocyte apoptosis and inflammation. Alda-1 may confer this protection by inducing autophagy through the AKT/mTOR and AMPK signaling pathways. Therefore, ALDH2 could represent a potential pharmacological target in the clinical treatment of HIRI.

Aldehyde dehydrogenase 2 protects against abdominal aortic aneurysm formation by reducing reactive oxygen species, vascular inflammation, and apoptosis of vascular smooth muscle cells

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is an enzyme that detoxifies aldehydes by converting them to carboxylic acids. ALDH2 deficiency is known to increase oxidative stress. Increased oxidative stress plays a pivotal role in abdominal aortic aneurysm (AAA) pathogenesis. Reactive oxygen species (ROS) promote degradation of the extracellular matrix (ECM) and vascular smooth muscle cell (VSMC) apoptosis. Reducing oxidative stress by an ALDH2 activator could have therapeutic potential for limiting AAA development. We hypothesized that ALDH2 deficiency could increase the risk for AAA by decreasing ROS elimination and that an ALDH2 activator could provide an alternative option for AAA treatment. The National Center for Biotechnology (NCBI) Gene Expression Omnibus (GEO) database was used. Human aortic smooth muscle cells (HASMCs) were used for the in vitro experiments. Gene-targeted ALDH2*2 KI knock-in mice on a C57BL/6J background and apolipoprotein E knockout (ApoE KO) mice were obtained. An animal model of AAA was constructed using osmotic minipumps to deliver 1000 ng/kg/min angiotensin II (AngII) for 28 days. Patients with AAA had significantly lower ALDH2 expression levels than normal subjects. ALDH2*2 KI mice were susceptible to AngII administration, exhibiting significantly increased AAA incidence rates and increased aortic diameters. Alda-1, an ALDH2 activator, reduced AngII-induced ROS production, NF-kB activation, and apoptosis in HASMCs. Alda-1 attenuated AngII-induced aneurysm formation and decreased aortic expansion in ApoE KO mice. We concluded that ALDH2 deficiency is associated with the development of AAAs in humans and a murine disease model. ALDH2 deficiency increases susceptibility to AngII-induced AAA formation by attenuating anti-ROS effects and increasing VSMC apoptosis and vascular inflammation. Alda-1 was shown to attenuate the progression of experimental AAA in a murine model.

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.

Targeting liver aldehyde dehydrogenase-2 prevents heavy but not moderate alcohol drinking

Aldehyde dehydrogenase 2 (ALDH2), a key enzyme for detoxification the ethanol metabolite acetaldehyde, is recognized as a promising therapeutic target to treat alcohol use disorders (AUDs). Disulfiram, a potent ALDH2 inhibitor, is an approved drug for the treatment of AUD but has clinical limitations due to its side effects. This study aims to elucidate the relative contribution of different organs in acetaldehyde clearance through ALDH2 by using global- (Aldh2 ^-/-) and tissue-specific Aldh2-deficient mice, and to examine whether liver-specific ALDH2 inhibition can prevent alcohol-seeking behavior. Aldh2 ^-/- mice showed markedly higher acetaldehyde concentrations than wild-type (WT) mice after acute ethanol gavage. Acetaldehyde levels in hepatocyte-specific Aldh2 knockout (Aldh2 ^Hep-/-) mice were significantly higher than those in WT mice post gavage, but did not reach the levels observed in Aldh2 ^-/- mice. Energy expenditure and motility were dramatically dampened in Aldh2 ^-/- mice, but moderately decreased in Aldh2 ^Hep-/- mice compared to controls. In the 2-bottle paradigm and the drinking-in-the-dark model, Aldh2 ^-/- mice drank negligible volumes from ethanol-containing bottles, whereas Aldh2 ^Hep-/- mice showed reduced alcohol preference at high but not low alcohol concentrations. Glial cell- or neuron-specific Aldh2 deficiency did not affect voluntary alcohol consumption. Finally, specific liver Aldh2 knockdown via injection of shAldh2 markedly decreased alcohol preference. In conclusion, although the liver is the major organ responsible for acetaldehyde metabolism, a cumulative effect of ALDH2 from other organs likely also contributes to systemic acetaldehyde clearance. Liver-targeted ALDH2 inhibition can decrease heavy drinking without affecting moderate drinking, providing molecular basis for hepatic ALDH2 targeting/editing for the treatment of AUD.

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.

SIRT3-mediated deacetylation of PRDX3 alleviates mitochondrial oxidative damage and apoptosis induced by intestinal ischemia/reperfusion injury

Background

Hydrogen peroxide (H₂O₂)-induced mitochondrial oxidative damage is critical to intestinal ischemia/reperfusion (I/R) injury, and PRDX3 is an efficient H₂O₂ scavenger that protects cells from mitochondrial oxidative damage and apoptosis. However, the function of PRDX3 in intestinal I/R injury is unclear. The aim of this study was to investigate the precise mechanism underlying the involvement of PRDX3 in intestinal I/R injury.

Methods

An intestinal I/R model was established in mice with superior mesenteric artery occlusion, and Caco-2 cells were subjected to hypoxia/reoxygenation (H/R) for the in vivo simulation of I/R.

Results

PRDX3 expression was decreased during intestinal I/R injury, and PRDX3 overexpression significantly attenuated H/R-induced mitochondrial oxidative damage and apoptosis in Caco-2 cells. The level of acetylated PRDX3 was clearly increased both in vivo and in vitro. The inhibition of SIRTs by nicotinamide (NAM) increased the level of acetylated PRDX3 and impaired the antioxidative activity of PRDX3. Furthermore, NAM did not increase the acetylation of PRDX3 in sirtuin-3 (SIRT3)-knockdown Caco-2 cells. Importantly, PRDX3 acetylation was increased in mice lacking SIRT3, and this effect was accompanied by serious mitochondrial oxidative damage, apoptosis and remote organ damage after intestinal I/R injury. We screened potential sites of PRDX3 acetylation in the previously reported acetylproteome through immunoprecipitation (IP) experiments and found that SIRT3 deacetylates K253 on PRDX3 in Caco-2 cells. Furthermore, PRDX3 with the lysine residue K253 mutated to arginine (K253R) increased its dimerization in Caco-2 cells after subjected to 12 h hypoxia and followed 4 h reoxygenation. Caco-2 cells transfected with the K253R plasmid exhibited notably less mitochondrial damage and apoptosis, and transfection of the K253Q plasmid abolished the protective effect of PRDX3 overexpression. Analysis of ischemic intestines from clinical patients further verified the correlation between SIRT3 and PRDX3.

Conclusions

PRDX3 is a key protective factor for intestinal I/R injury, and SIRT3-mediated PRDX3 deacetylation can alleviate intestinal I/R-induced mitochondrial oxidative damage and apoptosis.

Phytoconstituents in the Management of Pesticide Induced Parkinson’s Disease- A Review

Recent studies have suggested that environmental factors have a crucial role in triggering and/ or propagating the pathological changes in Parkinson’s disease (PD). Although many studies have been and being performed by utilizing MPTP like chemicals to study the effectiveness of new extracts and compounds in PD, a little focus was made on the role of pesticides. Since agricultural fields account for 37.7% of land area worldwide and the use of pesticides is an important risk factor in neurodegeneration, there is a crucial need to focus on the association between pesticides and PD. Benomyl, a benzimidazole fungicide is being widely used in India in cultivation of tropical crops. Studies prove the chronic exposure of benomyl leads to aldehyde dehydrogenase inhibition caused DOPAL toxicity, subsequently leading to dopamine degradation and Parkinson’s disease. Till date, there is no remedy for pesticide induced Parkinson’s disease. This review provides an insight of the pathophysiological aspects of pesticide induced Parkinson’s disease and also enlightens the importance of aldehyde dehydrogenase enzyme in neuroprotection.

Targeting ALDH2 in Atherosclerosis: Molecular Mechanisms and Therapeutic Opportunities

Aldehyde dehydrogenase 2 (ALDH2) is an important member of the functional aldehyde dehydrogenases (ALDHs) family in human beings, playing a fundamental role in the detoxification of acetaldehyde and other aldehydes. In recent years, a number of researches have given attention to the association between ALDH2 and atherosclerosis, which provided insights on targeting ALDH2 for therapeutic intervention of atherosclerosis. In this review, these inspiring studies will be discussed, and the clinical implications and concerns will be expounded.

Alda-1 Ameliorates Liver Ischemia-Reperfusion Injury by Activating Aldehyde Dehydrogenase 2 and Enhancing Autophagy in Mice

Aldehyde dehydrogenase 2 (ALDH2) is a key enzyme for metabolism of reactive aldehydes, but its role during liver ischemia-reperfusion injury (IRI) remains unclear. In the present study, we investigated the effects of the ALDH2 activator, Alda-1, in liver IRI and elucidated the underlying mechanisms. Mice were pretreated with Alda-1 and subjected to a 90 min hepatic 70% ischemia model, and liver tissues or serum samples were collected at indicated time points after reperfusion. We demonstrated that Alda-1 pretreatment had a hepatoprotective role in liver IRI as evidenced by decreased liver necrotic areas, serum ALT/AST levels, and liver inflammatory responses. Mechanistically, Alda-1 treatment enhanced ALDH2 activity and subsequently reduced the accumulation of reactive aldehydes and toxic protein adducts, which result in decreased hepatocyte apoptosis and mitochondrial dysfunction. We further demonstrated that Alda-1 treatment could activate AMPK and autophagy and that AMPK activation was required for Alda-1-mediated autophagy enhancement. These findings collectively indicate that Alda-1-mediated ALDH2 activation could be a promising strategy to improve liver IRI by clearance of reactive aldehydes and enhancement of autophagy.

Alda-1, an aldehyde dehydrogenase-2 agonist, causes deterioration in renal functions following ischemia-reperfusion injury due to crystalline nephropathy

Renal ischemia-reperfusion injury (IRI) induces the production of aldehydes which are detoxified by aldehyde dehydrogenases (ALDHs). Alda-1 is a selective ALDH2 agonist and its protective effect was demonstrated in several conditions. The effect of Alda-1 on the kidney or on renal IRI was not investigated. We investigated the effect of Alda-1 on the renal dysfunction following IRI. Wistar rats underwent left IRI for 40 min. Group-Alda (n = 11) received Alda-1 starting 24 h before IRI and continued for 7 days thereafter when renal functions were measured. Group-Vx (n = 11) underwent similar protocol but received the dissolvent. Alda-1 did not affect renal blood flow or glomerular filtration rate in the left ischemic kidney in Group-Alda compared to Group-Vx (3.05 ± 0.50 vs. 3.53 ± 0.70, and 0.40 ± 0.06 vs. 0.51 ± 0.08, respectively, p > .05 for both). However, left renal fractional sodium excretion was higher in Group-Alda (2.80 ± 0.43 vs. 1.37 ± 0.36, p = .02). Alda-1 also adversely affected the gene expressions of kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin (217 ± 38 vs. 99 ± 13 and 49 ± 13 vs. 20 ± 5, respectively, p < .05 for both) and the alterations in tumor necrosis factor-α, transforming growth factor-β1, plasminogen activator inhibitor-1, fibronectin 1 and p53 (4.4 ± 0.9 vs. 2.1 ± 0.3, 1.5 ± 0.1 vs. 1.1 ± 0.1, 30.0 ± 2.7 vs. 11.7 ± 2.3, 3.6 ± 0.4 vs. 2.1 ± 0.2 and 1.3 ± 0.1 vs. 0.9 ± 0.07, respectively, p ≤ .05 for all). This was associated with intratubular crystal deposition suggestive of crystalline nephropathy. Alda-1 exacerbated the IRI-induced renal tubular dysfunction and alterations in markers of acute kidney injury, biomarkers of inflammation, fibrosis and apoptosis and this was associated with intratubular crystal deposition suggestive of crystalline nephropathy.

Aldehyde Dehydrogenase 2 (ALDH2) in Rat Fatty Liver Cold Ischemia Injury

Institut George Lopez-1 (IGL-1) and Histidine-tryptophan-ketoglutarate (HTK) solutions are proposed as alternatives to UW (gold standard) in liver preservation. Their composition differs in terms of the presence/absence of oncotic agents such as HES or PEG, and is decisive for graft conservation before transplantation. This is especially so when fatty (steatotic) livers are used since these grafts are more vulnerable to ischemia insult during conservation. Their composition determines the extent of the subsequent reperfusion injury after transplantation. Aldehyde dehydrogenase-2 (ALDH2), a mitochondrial enzyme, has been reported to play a protective role in warm ischemia-reperfusion injury (IRI), but its potential in fatty liver cold ischemic injury has not yet been investigated. We evaluated the relevance of ALDH2 activity in cold ischemia injury when fatty liver grafts from Zucker Obese rats were preserved in UW, HTK, and IGL-1 solutions, in order to study the mechanisms involved. ALDH2 upregulation was highest in livers preserved in IGL-1. It was accompanied by a decrease in transaminases, apoptosis (Caspase 3 and TUNEL assay), and lipoperoxidation, which was concomitant with the effective clearance of toxic aldehydes such as 4-hydroxy-nonenal. Variations in ATP levels were also determined. The results were consistent with levels of NF-E2 p45-related factor 2 (Nrf2), an antioxidant factor. Here we report for the first time the relevance of mitochondrial ALDH2 in fatty liver cold preservation and suggest that ALDH2 could be considered a potential therapeutic target or regulator in clinical transplantation.

Role of aldehyde dehydrogenase 2 in ischemia reperfusion injury: An update

Aldehyde dehydrogenase 2 (ALDH2) is best known for its critical detoxifying role in liver alcohol metabolism. However, ALDH2 dysfunction is also involved in a wide range of human pathophysiological situations and is associated with complications such as cardiovascular diseases, diabetes mellitus, neurodegenerative diseases and aging. A growing body of research has shown that ALDH2 provides important protection against oxidative stress and the subsequent loading of toxic aldehydes such as 4-hydroxy-2-nonenal and adducts that occur in human diseases, including ischemia reperfusion injury (IRI). There is increasing evidence of its role in IRI pathophysiology in organs such as heart, brain, small intestine and kidney; however, surprisingly few studies have been carried out in the liver, where ALDH2 is found in abundance. This study reviews the role of ALDH2 in modulating the pathways involved in the pathophysiology of IRI associated with oxidative stress, autophagy and apoptosis. Special emphasis is placed on the role of ALDH2 in different organs, on therapeutic "preconditioning" strategies, and on the use of ALDH2 agonists such as Alda-1, which may become a useful therapeutic tool for preventing the deleterious effects of IRI in organ transplantation.

The mitochondrially targeted antioxidant MitoQ protects the intestinal barrier by ameliorating mitochondrial DNA damage via the Nrf2/ARE signaling pathway

Disruption of the mucosal barrier following intestinal ischemia reperfusion (I/R) is life threatening in clinical practice. Mitochondrial dysfunction and oxidative stress significantly contribute to the early phase of I/R injury and amplify the inflammatory response. MitoQ is a mitochondrially targeted antioxidant that exerts protective effects following I/R injury. In the present study, we aimed to determine whether and how MitoQ protects intestinal epithelial cells (IECs) from I/R injury. In both in vivo and in vitro studies, we found that MitoQ pretreatment downregulated I/R-induced oxidative stress and stabilized the intestinal barrier, as evidenced by MitoQ-treated I/R mice exhibiting attenuated intestinal hyperpermeability, inflammatory response, epithelial apoptosis, and tight junction damage compared to controls. Mechanistically, I/R elevated mitochondrial 8-hydroxyguanine content, reduced mitochondrial DNA (mtDNA) copy number and mRNA transcription levels, and induced mitochondrial disruption in IECs. However, MitoQ pretreatment dramatically inhibited these deleterious effects. mtDNA depletion alone was sufficient to induce apoptosis and mitochondrial dysfunction of IECs. Mitochondrial transcription factor A (TFAM), a key activator of mitochondrial transcription, was significantly reduced during I/R injury, a phenomenon that was prevented by MitoQ treatment. Furthermore, we observed that thee protective properties of MitoQ were affected by upregulation of cellular antioxidant genes, including HO-1, NQO-1, and γ-GCLC. Transfection with Nrf2 siRNA in IECs exposed to hypoxia/reperfusion conditions partially blocked the effects of MitoQ on mtDNA damage and mitochondrial oxidative stress. In conclusion, our data suggest that MitoQ exerts protective effect on I/R-induced intestinal barrier dysfunction.

The potential of aldehyde dehydrogenase 2 as a therapeutic target in cardiovascular disease

INTRODUCTION

Mitochondrial aldehyde dehydrogenase (ALDH-2) plays a major role in the ethanol detoxification pathway by removing acetaldehyde. Therefore, ALDH-2 inhibitors such as disulfiram represent the first therapeutic targeting of ALDH-2 for alcoholism therapy. Areas covered: Recently, ALDH-2 was identified as an essential bioactivating enzyme of the anti-ischemic organic nitrate nitroglycerin, bringing ALDH-2 again into the focus of clinical interest. Mechanistic studies on the nitroglycerin bioactivation process revealed that during bioconversion of nitroglycerin and in the presence of reactive oxygen and nitrogen species the active site thiols of ALDH-2 are oxidized and the enzyme activity is lost. Thus, ALDH-2 activity represents a useful marker for cardiovascular oxidative stress, a concept, which has been meanwhile supported by a number of animal disease models. Mechanistic studies on the protective role of ALDH-2 in different disease processes identified the detoxification of 4-hydroxynonenal by ALDH-2 as a fundamental process of cardiovascular, cerebral and antioxidant protection. Expert opinion: The most recent therapeutic exploitation of ALDH-2 includes activators of the enzyme such as Alda-1 but also cell-based therapies (ALDH-bright cells) that deserve further clinical characterization in the future.

Baicalin protects H9c2 cardiomyocytes against hypoxia/reoxygenation-induced apoptosis and oxidative stress through activation of mitochondrial aldehyde dehydrogenase 2

Baicalin, a flavonoid glycoside separated from Scutellaria baicalensis, has cardioprotection against ischaemia/reperfusion (I/R) injury. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is considered as an endogenous protective mechanism against I/R injury depending on its anti-oxidant and anti-apoptotic characteristics. The present study demonstrates whether ALDH2 contributes to the cardioprotection of baicalin against hypoxia/reoxygenation (H/R)-inudced H9c2 cardiomyocytes injury. Our results observed that H/R treatment resulted in a significant decrease in cells viability and obvious increases in caspase-3 activity and apoptosis rate in H9c2 cells, while these alterations were evidently reversed by baicalin pretreatment. Simultaneously, baicalin mitigated H/R-induced the decreases in the levels of ALDH2 mRNA and protein as well as the activity of ALDH2 in H9c2 cells. However, we found that daidzin, an ALDH2 antagonist, remarkably attenuated baicalin-elicited inhibitory action on H/R-induced the downregulation of cells viability and Bcl-2 protein expression, and the upregulations of caspase-3 activity, apoptosis rate, cytochrome c and Bax proteins expressions in H9c2 cells. In addition, baicalin reversed H/R-induced oxidative stress as evidenced by the downregulation of malondialdehyde (MAD) and 4-hydroxy aldehydes (4-HNE) levels, the inhibition of endogenous reactive oxygen species (ROS) generation, and the downregulation of superoxide dismutase (SOD) activity induced by H/R treatment, while these effects were also blocked by daidzin. Furthermore, we found that Alda-1, an ALDH2 agonist, also abolished H/R-induced cytotoxicity, apoptosis, and oxidative stress, indicating that ALDH2 mediated H/R-induced H9c2 cell injury. Overall, these results suggested that baicalin prevents H/R-induced apoptosis and oxidative stress through enhancing ALDH activity and expression in H9c2 cardiomyocytes.

Pharmacological enrollment of aldehyde dehydrogenase modulators to assist treating ischemia reperfusion-induced intestinal injury: is there a gap to be bridged?

This commentary highlights the research presented by Zhu et al. [1]. In this issue of the Clinical Science, the authors evaluated the protective effect of Alda-1 (a novel class of small molecule aldehyde dehydrogenase (ALDH2) activators) in the intestinal ischemia reperfusion (IR) injury. Remarkably, enhancing the ADLH2 activity by the use of Alda-1 can ameliorate several deleterious effects related to aldehydes, and may provide a better protection against an injury preestablished by IR. Together, an innovative metabolic strategy for treating patients with IR injury could be the use of ALDH modulators in a near future.

p-JAK2 plays a key role in catalpol-induced protection against rat intestinal ischemia/reperfusion injury

Catalpol attenuated rat intestinal I/R injury by decreasing mitochondria-mediated apoptosis through blocking the JAK2/STAT3 signaling pathwayviaselective inhibition of p-JAK2.