Neuroprotective effects of Alda-1 mitigate spinal cord injury in mice: involvement of Alda-1-induced ALDH2 activation-mediated suppression of reactive aldehyde mechanisms

Spinal cord injury (SCI) is associated with high production and excessive accumulation of pathological 4-hydroxy-trans-2-nonenal (4-HNE), a reactive aldehyde, formed by SCI-induced metabolic dysregulation of membrane lipids. Reactive aldehyde load causes redox alteration, neuroinflammation, neurodegeneration, pain-like behaviors, and locomotion deficits. Pharmacological scavenging of reactive aldehydes results in limited improved motor and sensory functions. In this study, we targeted the activity of mitochondrial enzyme aldehyde dehydrogenase 2 (ALDH2) to detoxify 4-HNE for accelerated functional recovery and improved pain-like behavior in a male mouse model of contusion SCI. N-(1,3-benzodioxol-5-ylmethyl)-2,6-dichlorobenzamide (Alda-1), a selective activator of ALDH2, was used as a therapeutic tool to suppress the 4-HNE load. SCI was induced by an impactor at the T9–10 vertebral level. Injured animals were initially treated with Alda-1 at 2 hours after injury, followed by once-daily treatment with Alda-1 for 30 consecutive days. Locomotor function was evaluated by the Basso Mouse Scale, and pain-like behaviors were assessed by mechanical allodynia and thermal algesia. ALDH2 activity was measured by enzymatic assay. 4-HNE protein adducts and enzyme/protein expression levels were determined by western blot analysis and histology/immunohistochemistry. SCI resulted in a sustained and prolonged overload of 4-HNE, which parallels with the decreased activity of ALDH2 and low functional recovery. Alda-1 treatment of SCI decreased 4-HNE load and enhanced the activity of ALDH2 in both the acute and the chronic phases of SCI. Furthermore, the treatment with Alda-1 reduced neuroinflammation, oxidative stress, and neuronal loss and increased adenosine 5′-triphosphate levels stimulated the neurorepair process and improved locomotor and sensory functions. Conclusively, the results provide evidence that enhancing the ALDH2 activity by Alda-1 treatment of SCI mice suppresses the 4-HNE load that attenuates neuroinflammation and neurodegeneration, promotes the neurorepair process, and improves functional outcomes. Consequently, we suggest that Alda-1 may have therapeutic potential for the treatment of human SCI. Animal procedures were approved by the Institutional Animal Care and Use Committee (IACUC) of MUSC (IACUC-2019-00864) on December 21, 2019.

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.

In Vitro Bioavailability of the Hydrocarbon Fractions of Dimethyl Sulfoxide Extracts of Petroleum Substances

Determining the in vitro bioavailable concentration is a critical, yet unmet need to refine in vitro-to-in vivo extrapolation for unknown or variable composition, complex reaction product or biological material (UVCB) substances. UVCBs such as petroleum substances are commonly subjected to dimethyl sulfoxide (DMSO) extraction in order to retrieve the bioactive polycyclic aromatic compound (PAC) portion for in vitro testing. In addition to DMSO extraction, protein binding in cell culture media and dilution can all influence in vitro bioavailable concentrations of aliphatic and aromatic compounds in petroleum substances. However, these in vitro factors have not been fully characterized. In this study, we aimed to fill in these data gaps by characterizing the effects of these processes using both a defined mixture of analytical standards containing aliphatic and aromatic hydrocarbons, as well as 4 refined petroleum products as prototypical examples of UVCBs. Each substance was extracted with DMSO, and the protein binding in cell culture media was measured by using solid-phase microextraction. Semiquantitative analysis for aliphatic and aromatic compounds was achieved via gas chromatography-mass spectrometry. Our results showed that DMSO selectively extracted PACs from test substances, and that chemical profiles of PACs across molecular classes remained consistent after extraction. With respect to protein binding, chemical profiles were retained at a lower dilution (higher concentration), but a greater dilution factor (ie, lower concentration) resulted in higher protein binding in cell medium, which in turn altered the ultimate chemical profile of bioavailable PACs. Overall, this case study demonstrates that extraction procedures, protein binding in cell culture media, and dilution factors prior to in vitro testing can all contribute to determining the final bioavailable concentrations of bioactive constituents of UVCBs in vitro. Thus, in vitro-to-in vivo extrapolation for UVCBs may require greater attention to the concentration-dependent and compound-specific differences in recovery and bioavailability.

Activation of mitochondrial aldehyde dehydrogenase (ALDH2) by ALDA-1 reduces both the acquisition and maintenance of ethanol intake in rats: A dual mechanism?

A number of pre-clinical studies have shown that brain-generated acetaldehyde, the first metabolite of ethanol, exerts reinforcing effects that promote the acquisition of ethanol intake, while chronic intake maintenance appears to be mediated by alcohol-induced brain neuroinflammation/oxidative stress. Recently, it was described that N-(1,3-benzodioxol-5-ylmethyl)-2,6-dichlorobenzamide (ALDA-1) activates aldehyde dehydrogenase-2 (ALDH2), enzyme that catalyzes the oxidation of ethanol-derived acetaldehyde to acetate. The aim of this study was to determine the effects of ALDA-1 on both the acquisition and the maintenance of alcohol intake in alcohol-preferring UChB rats. For ethanol acquisition studies, naïve UChB rats were treated with five daily doses of ALDA-1 (12.5, 25 or 50 mg/kg, i.p.) from one day before the start of ethanol exposure. For chronic intake studies, UChB rats exposed for 98 days to a free access to 10% ethanol and water were treated daily with ALDA-1 (12.5, 25 or 50 mg/kg, i.p.) for five days. The administration of ALDA-1 reduced by 72-90% (p < 0.001) the acquisition of ethanol consumption in naïve rats. At chronic ethanol consumption, ALDA-1 reduced ethanol intake by 61-82% (p < 0.001). ALDA-1 administration increased by 3- and 2.3-fold the activity of ALDH2 in brain and liver, respectively. ALDA-1 did not affect saccharin consumption, nor it modified the rate of ethanol elimination. The study shows that the activation of ALDH2 by ALDA-1 is effective for inhibiting both the acquisition and the maintenance of chronic ethanol intake by alcohol-preferring rats. Thus, the activation of brain ALDH2 may constitute a novel approach in the treatment of alcohol use disorders.

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.

Synthesis and Evaluation of Chirally Defined Side Chain Variants of 7-Chloro-4-Aminoquinoline To Overcome Drug Resistance in Malaria Chemotherapy

A novel 4-aminoquinoline derivative [(S)-7-chloro-N-(4-methyl-1-(4-methylpiperazin-1-yl)pentan-2-yl)-quinolin-4-amine triphosphate] exhibiting curative activity against chloroquine-resistant malaria parasites has been identified for preclinical development as a blood schizonticidal agent. The lead molecule selected after detailed structure-activity relationship (SAR) studies has good solid-state properties and promising activity against in vitro and in vivo experimental malaria models. The in vitro absorption, distribution, metabolism, and excretion (ADME) parameters indicate a favorable drug-like profile.