Molecular Cloning and Oxidative Modification of Human Lens ALDH1A1: Implication in Impaired Detoxification of Lipid Aldehydes

Abstract

Earlier studies showed that human lens ALDH1A1 plays a critical role in protection against oxidative stress-induced cytotoxicity in human lens epithelial cells (HLEC), and opacification of rat and mouse lens. The complete coding sequence of ALDH1A1 was cloned from human lens cDNA library by using PCR methods and expressed it in Escherichia coli. The cloned human lens ALDH1A1 cDNA encodes a 501-amino-acid protein (molecular mass = 54.8 kD) that is 100% identical to human liver ALDH1A1 and shares significant identity with the same isozyme from other tissues and species. The purified recombinant human lens ALDH1A1 exhibited optimal catalytic activity at pH 8 and preferred NAD+ as cofactor and specifically catalyzed the oxidation of toxic lipid aldehydes such as 4-hydroxynonenal (HNE; Km = 4.8 µM) and malonaldehyde (Km MDA = 3.5 µM). Citral, disulfiram, and cyanamide were found to inhibit human lens ALDH1A1 at IC50 values of 55, 101, and 22610 µM, respectively, whereas diethylstilbestrol (DES) was found to be an activator (EC50, 1.3 µM). Further, modification of recombinant human lens ALDH1A1 with nitric oxide donors such as S-nitroso-N-acetylpenicillamine (SNAP) and S-nitrosoglutathione (GSNO) significantly inhibited the enzyme activity. It therefore appears that activation of ALDH1A1, which efficiently catalyzes the detoxification of lipid-derived toxic aldehydes, and/or prevention of its oxidative modification may be novel therapeutic interventions against oxidative stress-induced lens pathologies.

Topically applied metal chelator reduces thermal injury progression in a rat model of brass comb burn

“…Among the various signaling targets of HNE, are cell cycle regulators such as,c-Jun NH2-terminal kinase (JNK), p38 mitogen-activated protein kinases (p38MAPK), , protein kinase C-β and -δ (PKC-β and PKC-δ) [49]. Oxidative stress/HNE can inactivate and down regulate ALDH and induce toxicity; conversely activation and upregulation of ALDH prevents oxidation-/HNE-associated damage in cells and tissues [18–19,21–23,25,26,52–55] Our current study, for the first time, demonstrates that thermal injury induced a long lasting decrease in the expression of two of ALDH1A1 and ALDH2 in the untreated unburned interspaces. The decreased expression of these enzymes may be a result of direct effect of heat energy itself or other inflammatory factors released after thermal injury.…”

“…We then carried out immunohistochemistry (IHC) labeling of known reactive aldehydes (HNE, MDA, ACR) in order to determine the effect of topical application of the metal chelator on lipid aldehyde production. Aldehyde dehydrogenases (ALDH1A1 and ALDH2 ) efficiently detoxify these aldehydes [21–24] and therefore play an important role, to combat toxicity ,especially under oxidative stress [20, 21, 25, 26]. Expression of ALDH1 and ALDH2 was evaluated in order to demonstrate the effect of LF lotion on the production of reactive aldehydes through maintaining cellular defense abilities against LA production after burn injury.…”

Aldehyde Dehydrogenase Inhibitors: a Comprehensive Review of the Pharmacology, Mechanism of Action, Substrate Specificity, and Clinical Application

“…Most isozymes share the same catalytic mechanism for both dehydrogenase and esterase activity, except for ALDH6A1, which uses CoA as a cofactor rather than NAD(P ϩ ) (Kazmi et al, 1992;Xiao et al, 2009). This feature of the ALDH superfamily probably relates to the following catalytic residues being highly conserved: Cys302, Lys192, and Glu268.…”

Activator Protein-1 Regulation of Murine Aldehyde Dehydrogenase 1a1

“…It regulates normal growth, differentiation, and development of adult epithelia by synthesizing RA, a ligand for the nuclear RA receptor and retinoid X receptor. The Aldh1a1 gene is expressed at high levels in mouse hematopoietic stem cells and is critical for hematopoietic stem cell differentiation and function (Gasparetto et al, 2012) Because the substrate specificity and kinetics of murine and human ALDH1A1 are similar based on our studies and those of others (Xiao et al, 2009;Makia et al, 2011), we characterized the molecular regulation of murine Aldh1a1. Such information may assist interpretation of future research using transgenic models to study aldehyde toxicity in atherosclerosis and cardiovascular medicine.…”

“…The induction of Aldh1a1 gene expression in the mouse liver probably represents a mechanism of the liver to protect itself 612 against electrophile and oxidant-induced damage generated from endogenous and exogenous compounds or during inflammatory disease conditions. Because the mouse and human enzyme display very similar substrate specificity and enzyme kinetics (Xiao et al, 2009;Makia et al, 2011) and the 5Ј-flanking regions are significantly conserved between the species, normal and transgenic mice may allow the testing of the protective effects of ALDH1A1 against lipid aldehyde toxicity associated with atherosclerosis and cardiotoxity of endogenous and exogenous aldehydes.…”