Macrolide antibiotics inhibit prostaglandin E2 synthesis and mRNA expression of prostaglandin synthetic enzymes in human leukocytes

We investigated the action of macrolide antibiotics, which are considered to have anti-inflammatory activity, on lipopolysaccharide (LPS)-stimulated prostaglandin (PG) E2 synthesis and the expression of mRNAs for cytosolic phospholipase A2 (cPLA2), cyclooxygenase (COX)-1, and COX-2 in human leukocytes. The production of LPS-stimulated PGE2 was significantly increased in peripheral polymorphonuclear leukocytes (PMNLs) and in mononuclear leukocytes (MNLs). Amounts of mRNAs for COX-2 and cPLA2, but not for COX-1, were enhanced by LPS in PMNLs and MNLs. The LPS-enhanced PGE2 synthesis and the expression of cPLA2 and COX-2 mRNAs were inhibited by clarithromycin, azithromycin and dexamethasone in PMNLs and MNLs. The mRNA expression of COX-1 in PMNLs was decreased by clarithromycin and azithromycin. Macrolide antibiotics inhibited PGE2 synthesis in human leukocytes by suppressing cPLA2, COX-1, and COX-2 mRNA expression. These data indicate one mechanism of macrolide anti-inflammatory activity.     

Isolation, tissue distribution, and chromosomal localization of the human activation-induced cytidine deaminase (AID) gene

The gene encoding activation-induced cytidine deaminase (AID), a member of the cytidine deaminase family, was isolated from a murine B cell lymphoma line, CH12F3-2, induced by combined stimulation of TGF-beta, IL-4, and CD40L. We have isolated the human orthologue of mouse AID cDNA, which has an open reading frame of 198 residues containing a conserved cytidine deaminase motif. The amino acid sequence of human AID is 92% identical to that of mouse AID. RT-PCR analysis of 15 human tissues showed that AID mRNA is expressed strongly in lymph nodes and tonsils. The complete human AID gene consisting of five exons was isolated and mapped to chromosome 12p13 by fluorescence in situ hybridization.     

Citrus limonoids obacunone and limonin inhibit azoxymethane-induced colon carcinogenesis in rats

Obacunone and limonin are bitter limonoids in citrus. Their modifying effects on the development of aberrant crypt foci (ACF), the activity of detoxification enzymes, glutathione S-transferase (GST) and quinone reductase (QR), and cell proliferation activity were investigated in male F344 rats treated with azoxymethane (AOM). Obacunone and limonin were administered in the diet, during the initiation (for 4 weeks) or postinitiation phase (for 4 weeks) of AOM-induced tumorigenesis. Feeding of obacunone and limonin (0.02% or 0.05%) caused significant reduction (55-65% by "initiation" feeding and 28-42% by "postinitiation" feeding) in the yield of ACF. The ability to reduce the proliferating cell nuclear antigen-labeling index in crypts and correlated well with the prevention of ACF. In a subsequent long-term experiment (38 weeks), in which rats were initiated with AOM and fed 0.05% obacunone or 0.05% limonin during the initiation or post-initiation phase, both compounds in diet caused significant reduction (65%-92% inhibition) in the incidence of colonic adenocarcinoma. Thus, citrus bitter limonoids obacunone and limonin possess chemopreventive effects on chemically induced rat colon carcinogenesis.     

Cellular activities of 20K- and 22K-hGH do not necessarily correlate with their binding affinities for rat GH receptor

Even though 20K human growth hormone (20K-hGH) has 3-10% binding affinity for the rat liver and adipose tissue microsomes as compared to 22K-hGH, it was also reported that 20K-hGH has the same potency as 22K-hGH in the hypophysectomized rat weight gain assay. In order to investigate the reason why such controversial data exist, we have studied 20K- and 22K-hGH using the rat GH receptor extracellular domain (rGHR-ECD) and full-length rGHR. When we examined the complex formation of rGHR-ECD with 20K- and 22K-hGH in gel filtration assay, 20K-hGH formed no complex while 22K-hGH formed a 1:1 complex. Next, rGHR cDNA was introduced into Ba/F3 cells and CHO-K1 cells, and stable transfectants (Ba/F3-rGHR and CHO-rGHR) were established. In the proliferation of Ba/F3-rGHR cells, 20K-hGH had 10-fold lower activity than 22K-hGH, which is consistent with their affinities for rGHR. But surprisingly, in the Spi2.1 gene promoter activation in CHO-rGHR cells, 20K- and 22K-hGH had the same activity, which was found not only in stable CHO-rGHR clones but also in CHO-K1 cells transiently expressing rGHR. In conclusion, these results indicate that cellular activities of 20K- and 22K-hGH do not necessarily correlate with their binding affinities for rGHR.     

Induction of skin fibrosis in mice expressing a mutated fibrillin-1 gene

BACKGROUND: Tight skin mice (TSK) bear a mutated Fibrillin-1 (Fbn-1) gene. Genetic studies show that the TSK mutation is closely associated with the Fbn-1 locus (0-0.7 cM). A previous study showed two recombinants between the Fbn-1 locus and the TSK mutation. TSK mutation and mutated Fbn-1 gene cosegregate in F1 mice. MATERIALS AND METHODS: To elucidate the role of the mutated Fbn-1 gene in occurrence of TSK syndrome, we generated transgenic (Tg) mice expressing mutated Fbn-1 gene. In another set of experiments, we injected normal mice after birth with a plasmid bearing mutated Fbn-1 gene (pdFbn-1). RESULTS: Our results demonstrate that the pdFbn-1 Tg mice developed permanent cutaneous hyperplasia that was permanent. In mice injected as newborns with a plasmid bearing the sense pdFbn-1 gene, cutaneous hyperplasia was transient. In contrast to TSK mice, neither Tg nor mice injected with plasmid developed lung emphysema. The pdFbn-1 Tg and TSK mice spontaneously produced anti-topoisomerase I and anti-Fbn- antibodies, as do humans afflicted by scleroderma; whereas, those injected with a plasmid containing the pdFbn-1 gene produced only anti-Fbn-1 autoantibodies. CONCLUSIONS: The results suggest that, although cutaneous hyperplasia is due to mutated Fbn-1 gene, the TSK syndrome may be multifactorial.     

Mathematical models of action potentials in the periphery and center of the rabbit sinoatrial node

Mathematical models of the action potential in the periphery and center of the rabbit sinoatrial (SA) node have been developed on the basis of published experimental data. Simulated action potentials are consistent with those recorded experimentally: the model-generated peripheral action potential has a more negative takeoff potential, faster upstroke, more positive peak value, prominent phase 1 repolarization, greater amplitude, shorter duration, and more negative maximum diastolic potential than the model-generated central action potential. In addition, the model peripheral cell shows faster pacemaking. The models behave qualitatively the same as tissue from the periphery and center of the SA node in response to block of tetrodotoxin-sensitive Na(+) current, L- and T-type Ca(2+) currents, 4-aminopyridine-sensitive transient outward current, rapid and slow delayed rectifying K(+) currents, and hyperpolarization-activated current. A one-dimensional model of a string of SA node tissue, incorporating regional heterogeneity, coupled to a string of atrial tissue has been constructed to simulate the behavior of the intact SA node. In the one-dimensional model, the spontaneous action potential initiated in the center propagates to the periphery at approximately 0.06 m/s and then into the atrial muscle at 0.62 m/s.