Inflammatory chemokine release of astrocytes in vitro is reduced by all‐trans retinoic acid

Abstract

The production of chemokines by astrocytes constitutes an important component of neuroinflammatory processes in the brain. As the transcriptional activator retinoic acid (RA), used for chemotherapy and dermatological applications, exerts anti-inflammatory effects on monocytes and lymphocytes, we have tested whether the physiologically occurring isomer, alltrans RA, affects chemokine expression by astrocytes. Under control conditions, primary cultures of murine cortical astrocytes expressed no or very low levels of CCL and CXCL chemokines. After treatment with bacterial lipopolysaccharides to simulate inflammation in vitro, we detected a strong increase in the release of CCL2 (to > 4 ng/mL in cell culture supernatant), CCL3 (> 20 ng/mL), CCL5 (> 25 ng/mL), CXCL1 (> 30 ng/mL) and CXCL2 (> 20 ng/mL). Although simultaneous exposure to RA did not significantly affect this response, 12 h pre-treatment with 0.1 lM all-trans RA strongly suppressed mRNA expression and protein release of all chemokines. The anti-inflammatory activity of RA engaged RA and retinoid X receptors and correlated with a decreased expression of the lipopolysaccharides co-receptor CD14. A minor reduction of nuclear NF-jB was observed but not significant, activation of Jun amino-terminal kinase, p38 and signal transducer and activator of transcription 3 were not altered by RA. The results suggest that retinoids should be further investigated as candidates for the treatment of neuroinflammation.

Retinoic acid receptor agonist Am80 inhibits CXCL2 production from microglial BV-2 cells via attenuation of NF-κB signaling

“…Consistent with these findings, we demonstrated here that 12-h pretreatment, but not simultaneous treatment, of Am80 strongly suppressed LPS-induced expression of CXCL2. The effect of Am80 was abolished by an RAR antagonist LE540, which was also consistent with the results reported for astrocyte cultures where LE540 cancelled the effect of all-trans retinoic acid [22].…”

“…In astrocyte cultures, all-trans retinoic acid inhibits LPS-induced expression of chemokines including CXCL2, only when applied from 12 h prior to LPS treatment [22]. Consistent with these findings, we demonstrated here that 12-h pretreatment, but not simultaneous treatment, of Am80 strongly suppressed LPS-induced expression of CXCL2.…”

“…A previous study by other investigators has reported that 12-h pretreatment with all-trans retinoic acid, an endogenous RAR agonist, inhibited LPS-induced CXCL2 expression in primary astrocyte cultures [22]. Similar to these observations, we found that 12-h pretreatment of BV-2 cells with Am80 (0.3-3 μM) significantly suppressed LPS-induced expression of CXCL2 mRNA ( Fig.…”

“…We particularly focused on expression of CXCL2, a chemokine known to mediate neutrophil chemotaxis in CNS [8,9], because our previous study has demonstrated that the therapeutic effect of an RAR agonist Am80 on intracerebral hemorrhage in mice may be attributable to inhibition of CXCL2 expression [13]. Although mechanistic studies of the effect of retinoids on chemokine expression have been performed in primary astrocyte cultures [22], whether microglia behave in a similar manner to astrocytes with regard to retinoid actions has not been addressed so far. Results of the present study indicate that the effects of retinoid on chemokine expression in microglia may have some similar, but also some different, properties as compared to those in astrocytes.…”

“…Because all-trans retinoic acid has been reported to diminish LPS-induced CD14 up-regulation in astrocytes [22], we examined CD14 expression in BV-2 cells. Application of LPS to BV-2 cells increased expression level of CD14 mRNA in a time-dependent manner (Fig.…”