Proceedings of The Physiological Society

University of Oxford (2011) Proc Physiol Soc 23, C99

Oral Communications

The role of Annexin A1 in the manifestation of sexual dimorphisms in murine cerebral and systemic inflammatory responses to endotoxin

E. L. Hughes1, P. O. Cover1, J. C. Buckingham2, F. N. Gavins1

1. Wolfson Neuroscience Laboratories, Imperial College London, London, United Kingdom. 2. Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, United Kingdom.

Sexually dimorphic inflammatory responses have been noticed in numerous diseases. As females of childbearing capability are generally less prone than males to morbidity and mortality resulting from inflammatory disease such as sepsis[1,2], it is thought that oestrogen is partly responsible for these differences[3]. Annexin A1 (AnxA1) is an endogenous anti-inflammatory protein that is partly upregulated by oestrogen[4]; therefore, we investigated the role of oestrogen in modulating the neuro- and systemic protection of AnxA1 in experimental murine sepsis. Male and female C57BL/6 (WT) and AnxA1-null (C57BL/6 background) mice were used. Endotoxaemia was induced by i.p. lipopolysaccharide injection (LPS; 10 μg/mouse) for 2 h, followed by quantification of leukocyte-endothelial cell interactions (L/ECI) in cerebral and mesenteric microcirculation by intravital microscopy under terminal anaesthesia (ketamine 150 mg/kg and xylazine 7.5 mg/kg, i.p.). Next the effects of oestrogen were assessed by ovariectomy (OVX) under isoflurane inhalation anaesthesia (4% for induction, 1.5-2.5% for maintenance in O2, sufficient to abolish a pedal reflex), followed by 8 d with or without oestrogen replacement prior to LPS treatment and intravital microscopy of the brain and mesentery as before. Data were considered statistically significant when P<0.05 by ANOVA with Bonferroni’s post test and are expressed as mean ± SEM. n=5-6 mice/group. LPS increased L/ECI in both vascular beds in all animals. OVX increased LPS-induced leukocyte adhesion in cerebral (1247.0 ± 125.4 cells) and mesenteric (10.2 ± 1.0 cells) vessels of WT mice, which was reversed by oestrogen replacement to 378.9 ± 71.4 and 6.6 ± 2.4 cells, respectively (P<0.05 in both cases). However, in the brains (but not mesenteries) of OVX AnxA1-null female mice, oestrogen replacement potentiated both LPS-induced leukocyte adhesion (to 2047.0 ± 378.8 cells, compared with 994.7 ± 109.4 cells in the non-oestrogen group; P<0.05) and plasma TNF-α levels (205.00 ± 53.11 pg/ml vs. below detectable levels in non-oestrogen group; P<0.05). Our data suggest that oestrogen potentiates the vascular response to LPS in cerebrovessels, but not systemically, and that AnxA1 has an important role in protecting the brain from oestrogen’s potentially harmful effects.

Where applicable, experiments conform with Society ethical requirements