Oestradiol and the selective oestrogen receptor modulator (
SERM)
raloxifene have been shown to ameliorate
collagen-induced arthritis (CIA) in rats and in mice. One aim was to investigate if
raloxifene exerts its anti-arthritic and anti-osteoporotic effects during the induction or effector phase of
arthritis. A second aim was to analyse if
raloxifene activates the oestrogen response element (ERE) to produce its immune-modulator effects. CIA or
collagen-antibody-induced
arthritis (CAIA) was induced in ovariectomized DBA/1-mice. CIA was used for evaluation of treatment during the induction, and CAIA for the effector phase of
arthritis and
osteoporosis development.
Raloxifene,
oestradiol or vehicle was administered 5 days/week. The clinical disease was evaluated continuously. Bone marrow density (BMD) was analysed with peripheral quantitative computer tomography, paws were collected for histological examination, and sera were analysed for markers of bone and cartilage turnover and proinflammatory
cytokines. Transgenic
luciferase (Luc)-ERE mice were immunized with
collagen (CII), and after 10 days injected once with
raloxifene,
oestradiol or vehicle before termination. Spleens were analysed for
luciferase activity to measure ERE activation. Treatment with
oestradiol or
raloxifene during the induction phase of CIA failed to affect
arthritis.
Raloxifene did not hamper disease activity in CAIA, whereas
oestradiol delayed the onset and ameliorated the severity. Both
raloxifene and
oestradiol preserved BMD in CAIA. CII-immunization increased the
oestradiol-induced ERE activation in spleen, and
raloxifene activated the ERE at about 25% the intensity of
oestradiol. Further experiments are needed to elucidate the exact mechanisms behind this finding.