Submitted on May 13, 2009
Revised on September 28, 2009
Accepted on October 5, 2009
Estrogen replacement therapy in diabetic ovariectomized female rats potentiates postischemic leukocyte adhesion in cerebral venules via a RAGE-related process
Hao-Liang Xu1, Francesco Vetri2, Hae-Kyung Lee2, Shuhua Ye, Chanannait Paisansathan, Lizhen Mao1, Fulong Tan2, and Dale A. Pelligrino2*
1 Univ. of Illinois at Chicago
2 University of Illinois at Chicago
* To whom correspondence should be addressed. E-mail: dpell{at}uic.edu.
We tested the hypothesis that the documented transformation of 17
-estradiol (E2) from a counter-inflammatory agent, in non-diabetic (ND) rats, to a pro-inflammatory agent, in rats with diabetes mellitus (DM), is due to enhanced contributions from the receptor for advanced glycation end-products (RAGE). Rhodamine 6G-labeled leukocytes were observed through a closed cranial window. In vivo pial venular leukocyte adherence and infiltration was measured over 10h reperfusion, after transient forebrain ischemia, in DM (streptozotocin) vs ND intact, ovariectomized (OVX) and E2-replaced (for 7 -10 days) OVX (OVE) females. The role of RAGE was examined in two ways: (1) RAGE knockdown via topical application of RAGE antisense (AS) vs missense (MS) oligodeoxynucleotide (ODN); or (2) intracerebroventricular (icv) injection of the RAGE decoy inhibitor, soluble RAGE (sRAGE). Among diabetic rats, the lowest levels of cortical RAGE mRNA and immunoreactivity of the RAGE ligand, AGE, were seen in OVX females, with significantly higher levels exhibited in intact and OVE females. However, results from analysis of cortical RAGE protein only partially tracked those findings. When comparing ND to DM rats, cortical AGE immunoreactivity was significantly lower in OVE and intact females, but similar in OVX rats. In DM rats, the level of post-ischemic leukocyte adhesion and infiltration (highest to lowest) was OVE > intact >> untreated OVX. In NDs, adhesion was highest in the untreated OVX group. Leukocyte extravasation was observed at >6 hours post-ischemia, but only in diabetic OVE and intact females and in ND OVX (untreated) rats. Pretreatment with RAGE AS-ODN or sRAGE attenuated post-ischemic leukocyte adhesion, and prevented infiltration, but only in the diabetic OVE and intact groups. These results indicate that the exacerbation of post-ischemic leukocyte adhesion by chronic E2 replacement therapy (ERT) in diabetic OVX females involves a RAGE-related mechanism. Targeting RAGE may restore the neuroprotective effect of ERT in diabetic females.
