A novel conjugate of low-molecular-weight heparin and Cu,Zn-superoxide dismutase: study on its mechanism in preventing brain reperfusion injury after ischemia in gerbils.

Low-molecular-weight heparin (LMWH) and Cu,Zn-superoxide dismutase (SOD) were extensively investigated on preventing brain reperfusion injury after ischemia (BRII) in the past few years and both exhibited some advantages as well as limits in practice. To explore whether chemical modification for LMWH and SOD can lead to improved bioactivity,in our present study, we examined the efficacy of LMWH conjugated SOD (LMWH−SOD) in the model of BRII gerbils. Ischemia/reperfusion was performed for 5 min by clamping the bilateral common carotid arteries of gerbils. LMWH−SOD, SOD and the mixture of LMWH and SOD (LMWH+SOD) were administered intravenously to corresponding animals just before ischemia. 24 h after reperfusion, serum malondialdehyde (MDA) content and SOD activity were measured, the expression of intercellular adhesion molecule-1 (ICAM-1) was examined by immunohistochemistry, and the brain sections were processed for Nissl staining and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labeling.The results showed that LMWH−SOD significantly lowered MDA content (P<0.001, versus SOD and LMWH+SOD) and elevated SOD activity (P<0.05, versus SOD and LMWH+SOD) in the serum of BRII gerbils. Immunohistochemical results indicated ICAM-1 positive staining was lighter, pyramidal cells of hippocampal CA1 region were more regular and the changes in cell edema were minor, and apoptosis of hippocampal cells was milder in LMWH−SOD treated animals than in SOD or LMWH+SOD treated animals, untreated BRII animals and sham-operated animals. The results suggest that the novel LMWH−SOD conjugate can inhibit upregulation of ICAM-1 and prevent neuronal cell apoptosis in BRII gerbils, and the LMWH−SOD conjugate has better anti-inflammatory and neuroprotective effects in BRII than native SOD and the mixture of LMWH and SOD.

Downregulation of AMP-activated protein kinase by Cidea-mediated ubiquitination and degradation in brown adipose tissue.

We previously showed that Cidea(-/-) mice are resistant to diet-induced obesity through the upregulation of energy expenditure. The AMP-activated protein kinase (AMPK), consisting of catalytic alpha subunit and regulatory subunits beta and gamma, has a pivotal function in energy homoeostasis. We show here that AMPK protein levels and enzymatic activity were significantly increased in the brown adipose tissue of Cidea(-/-) mice. We also found that Cidea is colocalized with AMPK in the endoplasmic reticulum and forms a complex with AMPK in vivo through specific interaction with the beta subunit of AMPK, but not with the alpha or gamma subunit. When co-expressed with Cidea, the stability of AMPK-beta subunit was dramatically reduced due to increased ubiquitination-mediated degradation, which depends on a physical interaction between Cidea and AMPK. Furthermore, AMPK stability and enzymatic activity were increased in Cidea(-/-) adipocytes differentiated from mouse embryonic fibroblasts or preadipocytes. Our data strongly suggest that AMPK can be regulated by Cidea-mediated ubiquitin-dependent proteosome degradation, and provide a molecular explanation for the increased energy expenditure and lean phenotype in Cidea-null mice.