Cloning and characterization of ADAMTS11, an aggrecanase from the ADAMTS family.

Aggrecan is responsible for the mechanical properties of cartilage. One of the earliest changes observed in arthritis is the depletion of cartilage aggrecan due to increased proteolytic cleavage within the interglobular domain. Two major sites of cleavage have been identified in this region at Asn(341)-Phe(342) and Glu(373)-Ala(374). While several matrix metalloproteinases have been shown to cleave at Asn(341)-Phe(342), an as yet unidentified protein termed "aggrecanase" is responsible for cleavage at Glu(373)-Ala(374) and is hypothesized to play a pivotal role in cartilage damage. We have identified and cloned a novel disintegrin metalloproteinase with thrombospondin motifs that possesses aggrecanase activity, ADAMTS11 (aggrecanase-2), which has extensive homology to ADAMTS4 (aggrecanase-1) and the inflammation-associated gene ADAMTS1. ADAMTS11 possesses a number of conserved domains that have been shown to play a role in integrin binding, cell-cell interactions, and extracellular matrix binding. We have expressed recombinant human ADAMTS11 in insect cells and shown that it cleaves aggrecan at the Glu(373)-Ala(374) site, with the cleavage pattern and inhibitor profile being indistinguishable from that observed with native aggrecanase. A comparison of the structure and expression patterns of ADAMTS11, ADAMTS4, and ADAMTS1 is also described. Our findings will facilitate the study of the mechanisms of cartilage degradation and provide targets to search for effective inhibitors of cartilage depletion in arthritic disease.     

Quality of life following parotidectomy for malignant and benign disease

Parotidectomy is performed for benign or malignant tumors and for selected benign inflammatory and autoimmune conditions. Possible associated complications include facial nerve paralysis, pain, loss of sensation, gustatory sweating, and facial scarring. Global quality of life in patients undergoing parotidectomy has not been reported. The implications of facial surgery with the catastrophic potential of facial nerve paralysis may severely affect quality of life. A quality-of-life study was conducted in patients undergoing parotidectomy for benign and malignant diseases to define the significance of associated morbidity and its impact on quality of life. A quality-of-life instrument was specifically created, based on the principles of the University of Washington Quality of Life questionnaire, and mailed to the patients. Questions addressed recognized complications of parotidectomy. Patient group results were compared for age above and below 45 years, sex, benign versus malignant disease, presence or absence of Frey syndrome, and presence or absence of benign pleomorphic adenoma. Forty-six percent of 125 patients meeting the study criteria fully replied to the questionnaire. The global health score was 3.5, corresponding with "good" to "very good." Except for local sensation, which had a score of 50, all other domains scored above 76. Change in appearance, gustatory sweating, and pain were reported by 70 percent, 57 percent, and 30 percent, respectively. Importance attributed to all domains except facial function was low. Pain was encountered significantly less in patients younger than 45 years of age, and scores for appearance were also highly significant in this age group. Postoperative sequelae were noted in the majority of patients. The dominant sequelae were altered sensation, change in appearance, Frey syndrome, and pain. A degree of permanent postoperative facial nerve impairment was reported by 10 patients. Nevertheless, overall, parotidectomy does not seem to severely affect quality of life.     

Nitric oxide-dependent generation of reactive species in sickle cell disease. Actin tyrosine induces defective cytoskeletal polymerization

The intermittent vascular occlusion occurring in sickle cell disease (SCD) leads to ischemia-reperfusion injury and activation of inflammatory processes including enhanced production of reactive oxygen species and increased expression of inducible nitric-oxide synthase (NOS2). Appreciating that impaired nitric oxide-dependent vascular function and the concomitant formation of oxidizing and nitrating species occur in concert with increased rates of tissue reactive oxygen species production, liver and kidney NOS2 expression, tissue 3-nitrotyrosine (NO(2)Tyr) formation and apoptosis were evaluated in human SCD tissues and a murine model of SCD. Liver and kidney NOS2 expression and NO(2)Tyr immunoreactivity were significantly increased in SCD mice and humans, but not in nondiseased tissues. TdT-mediated nick end-label (TUNEL) staining showed apoptotic cells in regions expressing elevated levels of NOS2 and NO(2)Tyr in all SCD tissues. Gas chromatography mass spectrometry analysis revealed increased plasma protein NO(2)Tyr content and increased levels of hepatic and renal protein NO(2)Tyr derivatives in SCD (21.4 +/- 2.6 and 37.5 +/- 7.8 ng/mg) versus wild type mice (8.2 +/- 2.2 and 10 +/- 1.2 ng/mg), respectively. Western blot analysis and immunoprecipitation of SCD mouse liver and kidney proteins revealed one principal NO(2)Tyr-containing protein of 42 kDa, compared with controls. Enzymatic in-gel digestion and MALDI-TOF mass spectrometry identified this nitrated protein as actin. Electrospray ionization and fragment analysis by tandem mass spectrometry revealed that 3 of 15 actin tyrosine residues are nitrated (Tyr(91), Tyr(198), and Tyr(240)) at positions that significantly modify actin assembly. Confocal microscopy of SCD human and mouse tissues revealed that nitration led to morphologically distinct disorganization of filamentous actin. In aggregate, we have observed that the hemoglobin point mutation of sickle cell disease that mediates hemoglobin polymerization defects is translated, via inflammatory oxidant reactions, into defective cytoskeletal polymerization.     

Distinct dimer interaction and regulation in nitric-oxide synthase types I,II, and III

Homodimer formation activates all nitric-oxide synthases (NOSs). It involves the interaction between two oxygenase domains (NOSoxy) that each bind heme and (6R)-tetrahydrobiopterin (H4B) and catalyze NO synthesis from L-Arg. Here we compared three NOSoxy isozymes regarding dimer strength, interface composition, and the ability of L-Arg and H4B to stabilize the dimer, promote its formation, and protect it from proteolysis. Urea dissociation studies indicated that the relative dimer strengths were NOSIIIoxy > NOSIoxy > NOSIIoxy (endothelial NOSoxy (eNOSoxy) > neuronal NOSOXY (nNOSoxy) > inducible NOSoxy (iNOSoxy)). Dimer strengths of the full-length NOSs had the same rank order as judged by their urea-induced loss of NO synthesis activity. NOSoxy dimers containing L-Arg plus H4B exhibited the greatest resistance to urea-induced dissociation followed by those containing either molecule and then by those containing neither. Analysis of crystallographic structures of eNOSoxy and iNOSoxy dimers showed more intersubunit contacts and buried surface area in the dimer interface of eNOSoxy than iNOSoxy, thus revealing a potential basis for their different stabilities. L-Arg plus H4B promoted dimerization of urea-generated iNOSoxy and nNOSoxy monomers, which otherwise was minimal in their absence, and also protected both dimers against trypsin proteolysis. In these respects, L-Arg alone was more effective than H4B alone for nNOSoxy, whereas for iNOSoxy the converse was true. The eNOSoxy dimer was insensitive to proteolysis under all conditions. Our results indicate that the three NOS isozymes, despite their general structural similarity, differ markedly in their strengths, interfaces, and in how L-Arg and H4B influence their formation and stability. These distinguishing features may provide a basis for selective control and likely help to regulate each NOS in its particular biologic milieu.