Structural basis for selective inhibition of cyclooxygenase-2 by anti-inflammatory agents

Prostaglandins and glucocorticoids are potent mediators of inflammation. Non-steroidal anti-inflammatory drugs (NSAIDs) exert their effects by inhibition of prostaglandin production. The pharmacological target of NSAIDs is cyclooxygenase (COX, also known as PGH synthase), which catalyses the first committed step in arachidonic-acid metabolism. Two isoforms of the membrane protein COX are known: COX-1, which is constitutively expressed in most tissues, is responsible for the physiological production of prostaglandins; and COX-2, which is induced by cytokines, mitogens and endotoxins in inflammatory cells, is responsible for the elevated production of prostaglandins during inflammation. The structure of ovine COX-1 complexed with several NSAIDs has been determined. Here we report the structures of unliganded murine COX-2 and complexes with flurbiprofen, indomethacin and SC-558, a selective COX-2 inhibitor, determined at 3.0 to 2.5 A resolution. These structures explain the structural basis for the selective inhibition of COX-2, and demonstrate some of the conformational changes associated with time-dependent inhibition.     

The ordered assembly of the phiX174-type primosome. I. Isolation and identification of intermediate protein-DNA complexes

The phiX-type primosome was discovered during the resolution and reconstitution in vitro of the complementary strand DNA replication step of the phiX174 viral life cycle. This multienzyme bidirectional helicase-primase complex can provide the DNA unwinding and Okazaki fragment-priming functions at the replication fork and has been implicated in cellular DNA replication, repair, and recombination. We have used gel mobility shift assays and enhanced chemiluminescence Western analysis to isolate and identify the pathway of primosome assembly at a primosome assembly site (PAS) on a 300-nucleotide-long single-stranded DNA fragment. The first three steps do not require ATP and are as follows: (i) PriA recognition and binding to the PAS, (ii) stabilization of the PriA-PAS complex by the addition of PriB, and (iii) formation of a PriA-PriB-DnaT-PAS complex. Subsequent formation of the preprimosome involves the ATP-dependent transfer of DnaB from a DnaB-DnaC complex to the PriA-PriB-DnaT-PAS complex. The final preprimosomal complex contains PriA, PriB, DnaT, and DnaB but not DnaC. A transient interaction between the preprimosome and DnaG generates the five-protein primosome. As described in an accompanying article (Ng, J. Y., and Marians, K. J. (1996) J. Biol. Chem. 271, 15649-15655), when assembled on intact phiX174 phage DNA, the primosome also contains PriC.     

Myocardial perfusion damage after mediastinal irradiation for Hodgkin''s disease: a thallium-201 single photon emission tomography study

Conflicting data have been reported on the incidence of myocardial abnormalities after mediastinal irradiation for Hodgkin's disease. We studied myocardial perfusion in 31 clinically asymptomatic patients (13 male, 18 female, mean age 35 years) 7 years (range 3-11 years) after mantle field radiotherapy. Thallium-201 tomoscintigraphic data were obtained after exercise, 4 h later and at rest (8-15 days later). Images were analysed visually and quantitatively (sectorial quantification of 201Tl uptake on the bull's eye images of the short-axis slices) compared with those of 35 subjects with a low likelihood of coronary artery disease. Twenty-five tomographic data sets were available. Images were visually abnormal in 21 patients (84%) showing an heterogeneous 201Tl uptake. In 68%, the sectorial 201Tl uptake was lower than the mean 201Tl uptake value minus 2 standard deviations measured in subjects with a low likelihood of coronary artery disease. Significant redistribution (quantitatively assessed > or = 10%) was present in 10 patients (40%). In most of the patients, the location and the shape of the defect(s) could not be anatomically related to an epicardial coronary vessel disease. These results indicate that after mediastinal irradiation the 201Tl myocardial uptake is frequently abnormal. The observed patterns suggest a disease of the small coronary vessels and/or the existence of a myocardial fibrosis rather than epicardial coronary artery disease.     

Determinants of Economic Cost Related to Low Back Pain among Nurses at a University Hospital

Little is known of the genetic factors that may contribute to the development of chronic idiopathic thrombocytopenic purpura (cITP). We have previously shown that a developmentally regulated Vh gene (Humhv3005) is absent in 10/41 (24%) of patients with systemic lupus erythematosus while it is absent in only 7/88 (8%) of normal controls. This finding suggests that a homozygous deletion of an Ig variable (V) gene may alter the immune system and thus predispose the host to an autoimmune disorder. We have analyzed the same gene in 44 patients with cITP and found that Humhv3005 and like genes were absent in a higher percentage of patients (14 of 44, 31.8%) than they were absent in either normals (7/88, 8%, p = 0.002) or thrombocytopenic patients without cITP (6/53, 11.3%, p = 0.042); the hv3005 deletion frequency in the latter group did not differ from that in normals (P = 0.74). These data suggest that deletions of Humhv3005 and/or highly homologous Vh genes may predispose individuals to the development of cITP, and may contribute toward production of pathogenic antiplatelet antibodies.     

Surveillance for Ross River virus infection using blood donors

The number of clinical Ross River virus (RRV) infections (epidemic polyarthritis) each year in Australia continues to grow despite extensive vector control programs. There is a need, therefore, for a surveillance program that can give sufficient warning of outbreaks of the disease so that highly focused preventative measures may be undertaken. The ability of a surveillance program, based on voluntary Red Cross blood donations, to predict outbreaks of epidemic polyarthritis was evaluated. Anti-RRV IgM antibody was detected in significant numbers of blood donors from throughout the state of Queensland 6-9 weeks prior to an increase in the number of notified cases of epidemic polyarthritis. At a local level, significant numbers of anti-RRV IgM blood donors were detected in Brisbane in 1996 four weeks prior to an increase in the number of notified cases of epidemic polyarthritis. This system of surveillance is technically simple, rapid (results are obtained in 2-3 days), it samples the human population from throughout the state, and it gives timely warning of outbreaks of epidemic polyarthritis.     

Elevated Fos expression in the nucleus tractus solitarii is associated with reduced baroreflex response in spontaneously hypertensive rats

We delineated the functional role of Fos protein at the nucleus tractus solitarii in the manifestation of reduced baroreceptor reflex control of heart rate during hypertension, using spontaneously hypertensive rats (SHR), stroke-prone SHR, Wistar-Kyoto rats, or Sprague-Dawley rats. Microinjection into the bilateral nucleus tractus solitarii of an antisense oligonucleotide that targets against the initiation codon of c-fos mRNA significantly potentiated the baroreceptor reflex in response to 30 minutes of sustained increase in blood pressure. Of particular note was the restoration of both the impaired sensitivity and capacity of baroreceptor reflex in SHR and stroke-prone SHR to levels comparable to those in normotensive rats. Likewise, the number of Fos-immunoreactive nuclei evoked by the sustained increase in blood pressure in the caudal nucleus tractus solitarii of SHR and stroke-prone SHR was reduced, after this antisense c-fos treatment, to the basal level exhibited by the normotensive animals. Control treatment with the corresponding sense oligonucleotide, an antisense oligonucleotide that targets against a different portion of the coding sequence of the c-fos mRNA or artificial cerebrospinal fluid, on the other hand, elicited no discernible effect on either the baroreceptor reflex response or the induced expression of Fos protein in the nucleus tractus solitarii by baroreceptor activation. We also found that the basal level of Fos expression in the caudal nucleus tractus solitarii was significantly elevated in the SHR and stroke-prone SHR. Together, these novel findings suggest that an elevated expression of basal Fos protein in the NTS during hypertension may be associated with the dysfunction in baroreceptor reflex control of heart rate.     

Effect of seleno-organic compounds on leukotriene B4 biosynthesis

Leukotrienes (LTs) are a group of metabolites of arachidonic acid through the 5-lipoxygenase pathway. Among these metabolites, LTB4 is an important mediator of inflammatory disease. Recently, it has been shown that seleno-organic compounds are very biologically active. One of them, Ebselen [2-phenyl-1,2-benzoisoselenazol-3 (2H) one] is a new seleno-organic compound with very low toxicity while exhibits anti-inflammatory activity. Attempt to search for seleno-organic compounds as anti-inflammatory drugs and establish structure-activity relationships, ten ebselen derivatives with modifications in the 2-phenyl moiety were studied with respect to their effects on LTB4 biosynthesis. p-substituted compounds were shown to have stronger inhibitory activity on LTB4 biosynthesis than o-substituted compounds and ebselen itself. Among the p-substituted compounds, polar-inducing group-substituted compounds showed stronger activity than compounds substituted with polar-conjugated groups. Among the compounds substituted with polar-inducing groups, strongpolar groups exhibited stronger activity than weakpolar groups.     

Percutaneous transluminal coronary angioplasty in a child with Kawasaki disease

A successful attempt at percutaneous transluminanl coronary angioplasty (PTCA) to relieve stenosis of the mid-portion of the left anterior descending artery was achieved in a 6-year 9-month old boy who had multiple coronary aneurysms and stenosis due to Kawasaki disease. Despite the progression of coronary stenosis he had been well except for the perfusion defect of the anterior wall of myocardium on 99mTc-MIBI SPECT with dipyridamole infusion until PTCA was carried out after 4-year 4-months of the onset of illness. The area of stenosis was 70% before PTCA and 20% after PTCA. No restenosis at the site of PTCA was observed on follow-up angiography at 26 months after PTCA. This successful attempt may indicate that this procedure should be considered early in subclinical stenosis to prevent ischemic cardiac damage.     

Diurnal melatonin and cortisol secretion profiles in medicated schizophrenic patients

Although melatonin and/or cortisol secretions have been suggested as markers for both circadian and noradrenaline dysfunctions in psychiatric illnesses, especially in affective disorders, studies of melatonin and cortisol in schizophrenic patients are rare. We evaluated the circadian profiles of melatonin and cortisol secretion in schizophrenic patients and control subjects. A total of 21 medicated Taiwanese male paranoid schizophrenic inpatients (mean age, 27.3 +/- 7.2 yr) and 21 age- and sex-matched controls underwent 24-hour neuroendocrine screening. Melatonin and cortisol concentrations were measured at 2-hour intervals from 0800 h to 2200 h, and at 1-hour intervals from 2300 h to 0700 h. The standard dexamethasone suppression test was performed the next day to provide an index of hypothalamic-pituitary-adrenal axis (HPA) function. The results showed that the circadian rhythm of plasma melatonin secretion was disrupted in schizophrenics compared with controls, whereas the 24-hour profile of plasma cortisol was preserved. The melatonin to cortisol ratio was significantly higher in control subjects than in schizophrenic patients. Results of the dexamethasone suppression tests indicated that there were no functional changes in the HPA axis in schizophrenic patients. Five drug-naive schizophrenic patients studied simultaneously, but whose data were not included in the above analyses, had results consistent with those of the maintenance-medicated patients. Our findings suggest the presence of abnormal melatonin metabolism in Taiwanese schizophrenics, which may possibly be related to the pathophysiologic process itself. However, broader pathogenetic aspects of these neuroendocrine interrelations remain to be clarified.