Modulation of the expression of mRNAs for annexin 1 and formyl peptide receptors following inflammatory stress

Nicholas Buss1, Christopher John1, Pat Cover1, Stephanie Gresham2, Andrea Terron3, Julia Buckingham1
1Imperial College, London, United Kingdom, 2GlaxoSmithKline, Welwyn, United Kingdom, 3GlaxoSmithKline, Verona, Italy

Annexin 1 (ANXA1) is an important mediator of glucocorticoid regulatory effects within the neuroendocrine and host defence systems and evidence suggests its effects are mediated by formyl peptide receptors (FPRs; John et al., 2007). Little is known concerning the activation of the hypothalamo-pituitary-adrenocortical (HPA axis) by stressful stimuli e.g. lipopolysaccharide (LPS), and the influence on ANXA1 and FPR expression within the brain-neuroendocrine system. Here we examined the influence of LPS treatment on mRNA expression of ANXA1 and FPRs in murine brain, pituitary and adrenal gland.

LPS (250μg/ml/kg) or vehicle (saline; 1ml/kg) was administered intra-peritoneally to male C57BL/6 mice (approximately 11 weeks old, 25 to 30g). Mice were terminally anaesthetised with sodium pentobarbitone 0 (untreated) 2, 4, 8 or 24h post injection and perfused transcardially with saline. The following tissues were then removed, placed in RNAlater and then frozen for TaqMan® Real-Time RT-PCR of mRNAs for ANXA1, Fpr1, Fpr-rs1 and Fpr-rs2: hippocampus, hypothalamus, pituitary, adrenal and spleen. For normalisation, GAPDH, beta-actin and beta-microglobulin were also analysed.

Increases in plasma concentrations of ACTH [from 400±29.9 (saline) to 1342±124pg/ml, n=6, P<0.01) and corticosterone (from 61.5±14.3 (saline) to 951±86.7pg/mL, n=6, P<0.001] 2h post injection, were found. mRNAs for ANXA1, Fpr1, Fpr-rs1 and Fpr-rs2 were detected in all tissues studied from untreated controls. Rank order of expression levels were: ANXA1 mRNA: adrenal > spleen > hypothalamus > pituitary > hippocampus; Fpr1: spleen > hypothalamus > hippocampus > pituitary > adrenal; Fpr-rs1: spleen > pituitary > hypothalamus > adrenal > hippocampus; Fpr-rs2: spleen > hypothalamus > adrenal > pituitary > hippocampus. LPS treatment had no effect on mRNA expression for ANXA1, Fpr1, Fpr-rs1 and Fpr-rs2 in the hippocampus, hypothalamus or pituitary gland. By contrast, LPS had a profound effect on expression of mRNA for ANXA1 and FPRs at the adrenal level. For ANXA1, a 2-fold increase (p<0.01) compared to saline control was observed within 2h which then declined from 4h onwards to levels comparable with saline treated controls. Highly significant increases in the expression of FPRs within 2h; maximal at 4h when 28-fold (P<0.01); 58-fold (P<0.01) and 81-fold (P<0.01) increases in Fpr1, Fpr-rs1 and Fpr-rs2 mRNAs were observed respectively. The expression of these mRNAs then declined but did not reach those levels seen in untreated or saline animals by 24h.

These data support the growing evidence that FPRs contribute to HPA axis regulation in conditions of stress. They also raise the possibility that FPRs within the adrenal level are be particularly important in mediating the body’s protective adrenocortical responses to bacterial insults and, thus, support our recent data in ANXA1-null mice (Davies et al.,).

These studies were generously supported by GSK.

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