Abnormal intracellular calcium homeostasis associated with vulnerability in the nerve cells from heroin-dependent rat

Blocking the CD38/cADPR pathway plays a double-edged role in LPS stimulated microglia

Whether the CD38/cyclic ADP-ribose (cADPR) pathway plays a protective or detrimental role in neuroinflammation remains controversial. This study aimed to determine the role of CD38 in neuroinflammation using lipopolysaccharide (LPS)-stimulated BV2 microglial cells and co-cultured Neuro-2a (N2a) cells. In monoculture experiments, BV2 cells were divided into control, CD38 interference (CD38Ri), negative control (NC), LPS, CD38Ri+LPS, NC+LPS and 8-Br-cADPR+LPS groups. In co-culture experiments, N2a cells were co-cultured with BV2 cells for 48h. Nicotinamide adenine dinucleotide (NAD⁺), cADPR and intracellular Ca²⁺ levels and CD38 expression increased significantly in LPS-stimulated BV2 cells. CD38 knockdown or 8-Br-cADPR treatment significantly reduced NAD⁺, cADPR and intracellular Ca²⁺ levels. CD38 knockdown increased iNOS and NO levels in BV2 cells without LPS treatment; however, CD38 knockdown or 8-Br-cADPR treatment reduced iNOS and NO levels in BV2 cells with LPS treatment. CD38 knockdown increased the ratio of TUNEL-positive cells and cleaved Caspase 3/Caspase 3 ratio, and decreased the Bcl-2/Bax ratio in BV2 cells without LPS treatment; however, CD38 knockdown reduced the TUNEL positivity in BV2 cells with LPS treatment. CD38 knockdown or 8-Br-cADPR inhibited TNF-α, IL-6 (interleukin-6) and IL-1β levels in LPS-stimulated BV2 cells. Co-culture with CD38 knockdown or 8-Br-cADPR-treated BV2 cells did not influence apoptosis or iNOS expression in N2a cells. In conclusion, our results indicate that blocking the CD38/cADPR pathway reduces intracellular Ca²⁺, NO and the secretion of proinflammatory cytokines. CD38 knockdown exerted a detrimental effect in apoptosis and NO production in normal microglia, but played a protective role in apoptosis and NO production in LPS-stimulated microglia.

Assessment of individual differences in the rat nucleus accumbens transcriptome following taste-heroin extended access

Heroin addiction is a disease of chronic relapse that harms the individual through devaluation of personal responsibilities in favor of finding and using drugs. Only some recreational heroin users devolve into addiction but the basis of these individual differences is not known. We have shown in rats that avoidance of a heroin-paired taste cue reliably identifies individual animals with greater addiction-like behavior for heroin. Here rats received 5min access to a 0.15% saccharin solution followed by the opportunity to self-administer either saline or heroin for 6h. Large Suppressors of the heroin-paired taste cue displayed increased drug escalation, motivation for drug, and drug loading behavior compared with Small Suppressors. Little is known about the molecular mechanisms of these individual differences in addiction-like behavior. We examined the individual differences in mRNA expression in the nucleus accumbens (NAc) of rats that were behaviorally stratified by addiction-like behavior using next-generation sequencing. We hypothesized that based on the avoidance of the drug-paired cue there will be a unique mRNA profile in the NAc. Analysis of strand-specific whole genome RNA-Seq data revealed a number of genes differentially regulated in NAc based on the suppression of the natural saccharine reward. Large Suppressors exhibited a unique mRNA prolife compared to Saline controls and Small Suppressors. Genes related to immunity, neuronal activity, and behavior were differentially expressed among the 3 groups. In total, individual differences in avoidance of a heroin-paired taste cue are associated with addiction-like behavior along with differential NAc gene expression.