Potentiation of the ligand-binding activity of integrin alpha3beta1 via association with tetraspanin CD151

CD151, one of the tetraspanins, forms a stable complex with integrin alpha3beta1, the major laminin receptor on the cell surface. We found that 8C3, an anti-CD151 mAb obtained by screening for reactivity with integrin alpha3beta1-CD151 complexes, was capable of dissociating CD151 from integrin alpha3beta1, thereby allowing us to deplete CD151 from purified integrin alpha3beta1-CD151 complexes. The CD151-free integrin alpha3beta1 thus obtained showed a significant reduction in its ability to bind to laminin-10/11, a high-affinity ligand for integrin alpha3beta1, with a concomitant reduction in its reactivity with mAb AG89, which recognizes activated beta1-containing integrins. These results raised the possibility that the association of integrin alpha3beta1 with CD151 potentiates the ligand-binding activity of the integrin through sustaining its activated conformation. In support of this possibility, the ligand-binding activity was restored when CD151-free integrin alpha3beta1 was reassociated with purified CD151. 8C3-induced dissociation of CD151 from integrin alpha3beta1 was also demonstrated on the surface of living cells by fluorescent resonance energy transfer imaging, accompanied by a concomitant reduction in the cell adhesion to laminin-10/11-coated substrates. CD151 knock-down by RNA interference also resulted in a reduction in the adhesive activity of the cells. Taken together, these results indicate that CD151 association modulates the ligand-binding activity of integrin alpha3beta1 through stabilizing its activated conformation not only with purified proteins but also in a physiological context.     

Inflammatory responses in cuff-induced atherosclerosis in rabbits

Cuff-treatment of the rabbit carotid artery produced a diffuse intimal thickening which resembled early lesions of atherosclerosis. A limited amount of focal endothelial damage occurred first (0.5 h), leukocytes infiltrated the subendothelium and extensive endothelial denudation occurred at 24 h. At 3 days, the regenerating endothelium covered the denuded area, and the media was edematous. At 7 days proliferation of intimal cells became visible. Maximum intimal thickening occurred at 3 weeks. Daily injection of dexamethasone (0.01-10 mg/kg i.m.) and ticlopidine (1-100 mg/kg i.m.) dose-dependently attenuated the intimal thickening. Indomethacin had little effect. Inflammatory exudate from zymosan-activated air pouch induced chemotaxis of rat smooth muscle cells (SMC) in vitro. Similar chemotactic activity was observed with leukotriene B4 (LTB4) but not with the other lipoxygenase products tested. The exudate contained reasonable amounts of LTB4, which would account for its chemotactic activity. Dexamethasone inhibited the chemotaxis by the exudate and proliferation of SMC. These results are discussed in relation to the mechanism of atherogenesis. It is concluded that leukocytes play a major role in cuff-induced intimal thickening, and that their products cause endothelial denudation and SMC chemotaxis. Involvement of platelet aggregation in atherogenesis is also suggested.     

Impairment of angiogenic activity in the serum from patients with coronary aneurysms due to Kawasaki disease.

BACKGROUND: The inflammatory mediators play an important role in the progression of coronary vasculitis in Kawasaki disease (KD), but effects of KD serum including inflammatory mediators on endothelial cells remain unknown. We hypothesized that serum activity to stimulate in vitro human umbilical vein endothelial cells (HUVEC) tube formation might be impaired in KD. METHODS AND RESULTS: Serum from patients with coronary aneurysms was less active in stimulating HUVEC tube formation than serum from patients without coronary aneurysms or febrile controls. In patients with coronary aneurysms, the reduction in the serum angiogenic activity was documented already before KD treatment (p=0.03 vs healthy controls, p=0.08 vs febrile controls) and enhanced after intravenous immune globulin plus aspirin (p<0.001 vs healthy controls, p=0.002 vs febrile controls); both drugs did not affect the assay studied. This reduction was greater in patients who later developed giant aneurysms >8 mm compared with those who developed small to moderate aneurysms (p=0.01). The reduced serum angiogenic activity was partly caused by the reduction in the serum activity of stimulating HUVEC proliferation. CONCLUSIONS: Serum activity to stimulate HUVEC tube formation was impaired in KD patients who later developed larger coronary aneurysms, which may be associated with the severity of vascular injury.     

Hemodialysis as a Risk Factor for Ceftriaxone‐Associated Pseudolithiasis in Adults

Ceftriaxone‐associated biliary pseudolithiasis is common among children; however, there are only a few reports of pseudolithiasis in adult patients on HD. This retrospective cohort study included 278 adult patients on ceftriaxone therapy from 1 February 2016 to 1 September 2018. Pseudolithiasis was defined as a new development of sludge or stones in the gallbladder within 60 days of ceftriaxone therapy. After excluding patients with preexisting gallstones and a history of cholecystectomy, 113 patients on maintenance HD, and another 98 patients were enrolled as the HD and control group, respectively. Thirteen patients developed pseudolithiasis. Its incidence was significantly higher in the HD group than that in the control group. Multivariate logistic regression analyses showed that development of pseudolithiasis was significantly associated with HD and ceftriaxone dose. Therefore, HD in patients receiving ceftriaxone therapy appears to be associated with a risk of pseudolithiasis. These findings highlight the need for careful follow‐up.