Induction of interleukin-1 and glucocorticoid hormones by HIV promotes viral replication and links human chromosome 2 to AIDS pathogenesis: genetic mechanisms and therapeutic implications

Human immunodeficiency virus may regulate its replication by stimulating the synthesis of interleukin-1. Interleukin-1, in turn, has the ability to stimulate the human immunodeficiency virus enhancer region. The human genes responsible for interleukin-1 and interleukin-1 receptor antagonist synthesis are located on the long arm of chromosome 2. Coincidentally, the trans-activation responsive ribonucleic acid element in the R region of the long terminal repeat of human immunodeficiency virus-1 has been found to interact directly with a factor present on the long arm of chromosome 2 to facilitate transactivation by the human immunodeficiency virus Tat protein. The human CD26 gene is also located on the long arm of chromosome 2. CD26 is a lymphocyte cell surface antigen that is stimulated by interleukin-1 and serves with CD4 as a coreceptor that interacts with the V3 loop in gp120 of human immunodeficiency virus. The human immunodeficiency virus-induced interleukin-1 excess, thus, serves human immunodeficiency virus by enhancing replication, and by increasing human immunodeficiency virus infectivity via activation of CD26. IL-1 also adversely affects acquired immune deficiency syndrome-related Kaposi's sarcoma. Several genetic treatments for human immunodeficiency virus infection are proposed.     

Solution structure of the transforming growth factor beta-binding protein-like module, a domain associated with matrix fibrils

Here we describe the high resolution nuclear magnetic resonance (NMR) structure of a transforming growth factor beta (TGF-beta)-binding protein-like (TB) domain, which comes from human fibrillin-1, the protein defective in the Marfan syndrome (MFS). This domain is found in fibrillins and latent TGF-beta-binding proteins (LTBPs) which are localized to fibrillar structures in the extracellular matrix. The TB domain manifests a novel fold which is globular and comprises six antiparallel beta-strands and two alpha-helices. An unusual cysteine triplet conserved in the sequences of TB domains is localized to the hydrophobic core, at the C-terminus of an alpha-helix. The structure is stabilized by four disulfide bonds which pair in a 1-3, 2-6, 4-7, 5-8 pattern, two of which are solvent exposed. Analyses of MFS-causing mutations and the fibrillin-1 cell-binding RGD site provide the first clues to the surface specificity of TB domain interactions. Modelling of a homologous TB domain from LTBP-1 (residues 1018-1080) suggests that hydrophobic contacts may play a role in its interaction with the TGF-beta1 latency-associated peptide.     

Protein-disulfide isomerase-mediated reduction of the A subunit of cholera toxin in a human intestinal cell line

A key step in the action of cholera toxin (CT) is the reduction of its A subunit to the A1 peptide. The latter is an ADP-ribosyltransferase, which activates the alpha-subunit of the stimulatory G protein of adenylyl cyclase. In this study, the enzymatic reduction of membrane-bound CT in CaCo-2 human intestinal epithelial cells was characterized. Whereas diphtheria toxin was found to be reduced by a cell surface population of protein-disulfide isomerase (PDI) and its cytotoxicity was inhibited by p-chloromercuribenzenesulfonic acid, bacitracin, or anti-PDI antibodies, these inhibitors had no effect on CT reduction or activity in intact cells. In contrast, the reduction of CT in vitro by either postnuclear supernatants (PNS) or microsomal membranes in the presence of Triton X-100 was significantly inhibited by p-chloromercuribenzenesulfonic acid and bacitracin. Anti-PDI monoclonal antibodies likewise inhibited the in vitro reduction of CT and also were effective in depleting reductase activity from PNS. Since inhibition and depletion were not observed in the absence of detergent, these results suggested that the reductase activity was a soluble component localized to the lumen of microsomal vesicles and correlated with the presence of protein-disulfide isomerase. This was further confirmed by showing a corresponding depletion of reductase activity and PDI in alkali-treated microsomes. This activity was restored when purified bovine PDI was added back to alkali-treated microsomes in a redox buffer that reflected conditions found in the lumen of the endoplasmic reticulum (ER). When the CT-related reductase activity was assayed in subcellular fractions of PNS-derived membranes isolated on a 9-30% Iodixanol gradient, the activity, as measured by CT-A1 peptide formation localized to those fractions containing PDI. Likewise CT-A1 peptide formed in intact cells co-localized to those membrane fractions containing the majority of cellular PDI. Furthermore, the banding density corresponded to a region of the gradient containing ER-derived membranes. These results indicated that CT was a substrate for PDI-catalyzed reduction in intact cells and supported the hypothesis that CT reduction and activation occurs in the ER.     

Further observations on histological changes at the ureteroileal junction in ileal conduits

Seventy-two ureteroileal anastomoses taken from ileal conduits removed from 62 patients were examined histologically to characterize the range of mucosal and stromal changes at these sites. All 72 demonstrated variable amounts of subepithelial chronic inflammation and fibrosis. Other histological features included: cystic spaces lined by transitional epithelium (N = 29; 40%; average diameter 1.2 mm); cystic spaces lined by mixed intestinal/transitional epithelium (N = 5; 7%; average diameter 0.77 mm); and cystically dilated intestinal glands (N = 21; 29%; average diameter 0.24 mm). The latter were associated with overgrowth by transitional epithelium, which had prevented mucus drainage. Twenty-one (29%) had mucus pools with no epithelial lining (average diameter 1.2 mm), and polypoidal protrusions into the lumen of the anastomosis were found containing mucus pools (N = 4; 6%; average diameter 1.4 mm), transitional-lined cysts (N = 5; 7%; average diameter 2.2 mm), and mixed intestinal/transitional-lined cysts (N = 2; 3%; average diameter 2.5 mm). Focal rupture of dilated intestinal glands with interstitial pooling of mucus was not uncommon, and marked dystrophic calcification was found in 1 case within a large collection of extracellular mucus. This series confirms that inflammation, fibrosis, and glandular overgrowth by transitional epithelium are common occurrences at ureteroileal anastomosis sites. Subsequent gland rupture may result in sizable accumulations of interstitial mucus, and rarely in marked dystrophic calcification.     

Aspirin therapy in nonarteritic anterior ischemic optic neuropathy

Swiss mice fed commercial or elemental diets and an oral short-chain fatty acid (SCFA) solution or saline were treated with the cytostatic drug Ara-C (cytarabine, 3.6 mg/mouse/day) for two or four days. Histopathological examination revealed less damage (atrophy, inflammation, or necrosis) to the small intestine and colon caused by Ara-C when SCFA was administered. Accordingly, protein and nucleotide concentrations in the intestinal mucosa were higher in the group receiving SCFA than in the group receiving a placebo of the same pH and osmolarity. Improvement by SCFA treatment was correlated with an increase in the height of the intestinal villi, with no alterations of the crypts. Furthermore, the number of intraepithelial lymphocytes was similar to normal values in animals receiving SCFA and Ara-C. When large doses of SCFA were administered, xanthomized enterocytes appeared, suggesting an accumulation of fatty acids in these cells. We conclude that oral administration of SCFA at close to physiological proportions reduces the inflammation and necrosis caused by Ara-C administration, thus representing a potential factor for the improvement of patients with mucositis caused by cancer treatment.     

Age differences in mental multiplication: evidence for peripheral but not central decrements

This study reports two mental multiplication experiments that were designed to measure age differences in central and peripheral processes. Experiment 1 varied task type (verification vs production), and Experiment 2 varied exposure duration (presentation until response, 600 ms, and 300 ms) on a production task. Neither experiment showed evidence of age differences in central processes (e.g., retrieval speed); however, there was some evidence of a peripheral-process (e.g., encoding) decrement for older adults. Specifically, there were no Age X Problem Size interactions for either experiment. Experiment 2 revealed decreasing age differences as problem difficulty increased. Indeed, for the 300-ms exposure duration, there were no age differences in RT or error rate. These results suggest that the magnitude of age differences in central processing speed are significantly less extreme than are age differences for peripheral processing speed for this type of mental arithmetic task. Also, older adults, in general, may have a higher skill level for basic fact retrieval in mental arithmetic than do young adults.     

Protease inhibitor and triple-drug therapy: cellular immune parameters are not restored in pediatric AIDS patients after 6 months of treatment

OBJECTIVE: To assess whether treatment of HIV-positive children by antiretroviral drugs for a 6-month period would improve immune function significantly. DESIGN AND METHODS: Immunological assessment of 89 HIV-positive children who received protease inhibitor monotherapy for 12-16 weeks as part of phase I/II studies, followed by triple antiretroviral therapy for an additional 12 weeks, was conducted. Immunological parameters were assessed in vitro at four time points (at enrollment, at weeks 2-4, at weeks 12-16, and at weeks 24-28). Assessments included: cytokine production by monocytes, T-cell proliferation to mitogen or recall antigens (including an HIV antigen) and apoptotic cell death. Plasma levels of tumor necrosis factor (TNF)-alpha and soluble TNF receptor (sTNF-R) were also measured, in addition to CD4+ T-lymphocyte counts and viral load. In addition, limited analyses were performed on samples from 17 children after 120 weeks of therapy, including 104 weeks of triple therapy. RESULTS: At enrollment, the 89 children exhibited severe immune defects. Antiretroviral therapy raised CD4+ T-lymphocyte counts significantly and decreased viral loads. In contrast, the in vitro immune parameters studied were not improved, except for plasma levels of sTNF-RII which decreased in parallel with the decrease in viral load. In addition, there was a trend towards increased skin test reactivity for the ritonavir-treated children. No differences were seen in the immune parameters whether the patients were treated with mono- or triple therapy. Results obtained after 120 weeks of therapy demonstrated that defective interleukin-12 production was not restored by long-term therapy. CONCLUSIONS: After 6 months of therapy, with the exception of decreased sTNF-RII levels, and a trend towards increased skin test reactivity, restoration of several defective cellular immune responses did not occur despite significantly decreased viral loads and increased CD4+ T-lymphocyte counts.     

Overexpression of the stathmin gene in a subset of human breast cancer

Stathmin is a highly conserved cytosolic phosphoprotein that destabilizes microtubules. Stathmin, which has been proposed as a relay protein integrating diverse cell signalling pathways, acts in vitro as a tubulin-sequestering protein, and its activity is dramatically reduced by phosphorylation. Interestingly, stathmin expression and phosphorylation are regulated during the control of cell growth and differentiation, and there is much evidence suggesting that in vivo stathmin plays a role in the control of microtubule dynamics during mitosis. Stathmin may thus be considered as one of the key regulators of cell division. We examined 50 human primary breast tumours for stathmin mRNA and protein expression and screened for abnormalities in the chromosome region harbouring the stathmin gene. Overexpression of stathmin was found in 15 tumours (30%). At the present stage, no clear correlation emerged between stathmin expression and several prognosis markers. Interestingly, perfect matching was observed between stathmin mRNA overexpression, protein overexpression and strong staining for stathmin on paraffin-embedded tumour sections when specimens were available. Furthermore, a tentative link between loss of heterozygosity (LOH) in the 1p32-1pter region and stathmin overexpression was observed. Our results suggest that stathmin might play a role in breast carcinogenesis and that stathmin-overexpressing tumours may represent a new subtype of breast cancer.