Inhibition of aminoacylase 3 protects rat brain cortex neuronal cells from the toxicity of 4-hydroxy-2-nonenal mercapturate and 4-hydroxy-2-nonenal

Abstract

4-Hydroxy-2-nonenal (HNE) and acrolein are highly reactive neurotoxic products of lipid peroxidation that accumulate in Alzheimer’s and Parkinson’s disease brain and are implicated in the pathogenesis and progression of these neurological diseases. Conjugation with glutathione (GSH) initiates the HNE and acrolein detoxification pathway, which generates the mercapturates of HNE and acrolein that can be excreted. Prior work has shown that the efficiency of the GSH-dependent renal detoxification of haloalkene derived mercapturates is significantly decreased upon their deacetylation. Moreover the deacetylated products are rapidly transformed via β-lyases into toxic compounds responsible for the nephrotoxicity of the mercapturates. Because the enzymes of the GSH-conjugation pathway and β-lyases are expressed in brain, we hypothesized that a similar toxicity mechanism may be initiated in brain by the deacetylation of HNE and acrolein mercapturates. The present study was performed to identify an enzyme(s) involved in HNE and acrolein mercapturate deacetylation, characterize the brain expression of this enzyme and determine whether its inhibition decreases HNE and HNE mercapturate toxicity in neurons. We demonstrated that of two candidate enzymes known to deacetylate mercapturic acids, aminoacylases 1 (AA1) and 3 (AA3), only AA3 efficiently deacetylates both HNE and acrolein mercapturates. AA3 was further localized to neurons and blood vessels. Using a small molecule screen we further generated high-affinity AA3 inhibitors. Two of them completely protected rat brain cortex neurons expressing AA3 from the toxicity of HNE mercapturate. The results suggest that AA3 mediated deacetylation of HNE mercapturate may be involved in the neurotoxicity of HNE.

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“…The TRPA1 agonist acrolein has not yet been found to act through other TRP receptors; it is an endogenous product of lipid peroxidation, associated with neurodegenerative diseases, reperfusion injury, and chronic inflammation (Tsirulnikov et al, 2012). In addition, acrolein is a major constituent of smoke, in particular of the gas phase of cigarette smoke, and there it accompanies a variety of further volatile TRPA1 agonists, such as formaldehyde, acetaldehyde, and crotonaldehyde (Roemer et al, 2012).…”

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“…The University of California Los Angeles is investigating aminoacylase 3 inhibitors for the potential treatment of AD, PD, and other neurodegenerative diseases. Inhibition of aminoacylase 3 protected cortex neuronal cells from the toxicity of 4-hydroxy-2nonenal [371].…”

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“…Mouse AA3, with high structural and sequencing homology (with human AA3 [11,12,16], was used in this study. Mouse AA3 was expressed in Escherichia coli as an N-terminally Strep(II)tagged protein using the pRSET vector (Invitrogen, Carlsbad, CA, USA).…”

“…The AA3 mediated deacetylation of N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine, the excretable product of the GSH-dependent detoxification of trichloroethylene, in renal proximal tubules [15] is responsible for acute renal failure induced by trichloroethylene [12,13]. The AA3 mediated deacetylation of a mercapturic acid generated during the GSH-dependent detoxification of a toxic aldehyde 4-hydroxynonenal is neurotoxic [16]. Inhibition of AA3 completely protects neuronal cells from 4-hydroxynonenal toxicity [16].…”

“…The AA3 mediated deacetylation of a mercapturic acid generated during the GSH-dependent detoxification of a toxic aldehyde 4-hydroxynonenal is neurotoxic [16]. Inhibition of AA3 completely protects neuronal cells from 4-hydroxynonenal toxicity [16]. …”