PX-12

The enduring nature of drug-associated memories is an essential factor contributing to the relapse. Drug-related cues can activate drug memories, making them enter reconsolidation, during which interventions can effectively disrupt these memories. Interventions targeting memory reconsolidation present a promising therapeutic strategy for addressing substance use disorders (SUDs). Oxidative stress can disrupt neural function and impair memory. Thioredoxin-1 (Trx-1) effectively alleviates oxidative stress and reduces inflammation levels. However, few studies have connected Trx-1 to drug memory or explored its specific role in reconsolidation. This research employed the conditioned place preference (CPP) model to investigate the effects of Trx-1 inhibitors on the reconsolidation of morphine- and cocaine-related memories. Results show that immediate administration of PX-12, a Trx-1 inhibitor, after retrieval significantly attenuated the reinstatement of cocaine and morphine CPP induced by both cues and the drug itself, with the effect lasting for at least 14 days. In contrast, the inhibition of Trx-1, either 6 hours following retrieval or in the absence of retrieval, does not influence drug-seeking behaviors associated with cocaine or morphine. Furthermore, Trx-1 inhibitor itself did not produce any preferences. In summary, our results indicate that Trx-1 activity is crucial for cocaine- and morphine-related memories, and that the Trx-1 inhibitor may serve as a potential treatment for drug abuse.

Transglutaminase 2 (TG2)-mediated enzymatic modification of gliadin peptides plays a major role in the pathogenesis of celiac disease (CD). Different inhibitory mechanisms have been reported to reduce TG2 activity but comparative data on the cellular level are lacking. Furthermore, recent evidence suggested that endogenous redox proteins such as endoplasmic reticulum resident protein 57 (ERp57, inhibits TG2) and thioredoxin-1 (TRX, activates TG2) may regulate TG2 activity. In this study, we aimed to compare the effects and applicability of different inhibitors on the activity of recombinant and cellular TG2. Furthermore, we investigated the role of ERp57 and TRX in the context of CD by using siRNA-mediated knockdown in Caco-2 cells.

The effect of TG2 inhibitors on recombinant and extracellular TG2 activity was investigated by using photometric and fluorometric quantitation of the cross-linking of biotinylated gliadin peptide P56-88 or 5-(biotinamido)-pentylamine. After siRNA knockdown, the protein levels of ERp57, TRX, and TG2 as well as TG2 activity were investigated by using Western blotting and fluorometry in Caco-2 cells.

The active-site-directed inhibitors ERW1041, KCC009, and cysteamine as well as the allosteric inhibitor LDN27219 revealed the most prominent reduction in recombinant and cellular (35%–50%) TG2 activity. In contrast, PX12, S-Nitroso-N-acetyl-DL-penicillamine, zinc chloride, and ascorbic acid either did not affect TG2 activity or had only moderate effects at high doses close to cytotoxic concentrations. SiRNA knockdown of TG2 resulted in a prominent reduction (63%) in TG2 activity, whereas knockdown of ERp57 did not; knockdown of TRX only slightly (27%) reduced TG2 activity.

Active-site-directed inhibitors, LDN27219 and knockdown of TG2 expression significantly reduced extracellular TG2 activity and represent potential alternative treatment targets in the context of CD.