Alcohol induced NLRP3 inflammasome activation in the brain of rats is attenuated by ATRA supplementation

Abstract

Alcohol abuse affects several neurological pathways and causes significant alterations in the brain. Abstention from alcohol is an effective intervention against alcohol related diseases. But the recovery of the damaged cells to normal presents a major problem in those who have stopped alcohol consumption. Hence therapeutic interventions are needed. Our previous studies have shown that all trans retinoic acid (ATRA) is effective in reducing alcohol induced neuro toxicity. Chronic alcohol administration up-regulates and activates the NLRP3 inflammasome leading to caspase-1 activation and IL-1β production causing neuroinflammation. Hence, we investigated whether ATRA has any impact on NLRP3 inflammasomes activation. Rats were divided into two groups and were maintained for 90 days as control and ethanol group (4 ​g/kg body weight). After 90 days, ethanol administration was stopped and animals in the control group were divided into control and control ​+ ​ATRA (100 ​μg/kg body weight per day) groups; those in the ethanol group as ethanol abstention and ATRA (100 ​μg/kg body weight per day) and maintained for 30 days. Administration of ATRA reduced reactive oxygen species and endotoxins which were elevated in alcoholic rats. There was also reduction in the expression of NLRP3 inflammasome and caspase 1. Our results suggested ATRA down regulated NLRP3 activation with concomitant decrease in the release of caspase -1 and production of IL1β. However, all these parameters were higher in abstention in comparison with ATRA supplemented group. In short therapeutic intervention with ATRA regressed alcohol induced inflammasome activation better than abstention.

Keywords: ATRA; Caspase-1; Endotoxins; IL-1β; NLRP3.

Fig. 1

Schematic representation of experimental design

Fig. 2

Values are expressed as mean ​± ​SEM of six rats in each group. Values not sharing a common superscript differ significantly at p ​< ​0.05* The μM p-nitroaniline lib/min/mg protein. [E ​= ​Ethanol, A ​= ​Abstention].

Fig. 3

Values are expressed as mean ​± ​SEM of six rats in each group. Values not sharing a common superscript differ significantly at p ​< ​0.05.

Fig. 4

*One EU is approximately equivalent to 100 ​pg of E. Coli LPS- the amount present in around 105 bacteria. Values are expressed as mean ​± ​SEM of six rats in each group. Values not sharing a common superscript differ significantly at p ​< ​0.05.

Fig. 5

NLRP3, Caspase-1 and IL-1b mRNAs quantified by qPCR and the products standardized against their respective β-actin controls. Fold change (Y-axis) represents the expression of the target gene mRNAs relative to that of the control group. Values are expressed as mean ​± ​SEM of six rats in each group. Values not sharing a common superscript differ significantly at p ​< ​0.05.