Adhesion molecules in iris biopsy specimens from patients with uveitis

BACKGROUND/AIMS—Earlier studies on intraocular tissue have demonstrated that T lymphocytes play a major role in the pathogenesis of uveitis. Adhesion molecules are immunoregulatory molecules for the interaction between T lymphocytes and vascular endothelium and they play an important role in the recruitment of specific T lymphocytes from the circulation into inflamed tissue. In uveitis an increased expression of some of these adhesion molecules may be expected.
METHODS—The presence of adhesion molecules was investigated in iris biopsy specimens from 11 patients with uveitis and eight controls (patients with primary open angle glaucoma) immunohistochemically with a panel of monoclonal antibodies: LECAM (CD 62L), ICAM-1 (CD 54), LFA-1 (CD 11a/18), VCAM-1 (CD 106), VLA-4 (CD 49d), and HECA-452, a marker for high endothelial venules.
RESULTS—Positive staining for ICAM-1, LFA-1 and VCAM-1 was found in the iris in a significantly higher number of uveitis patients than in controls. The remaining adhesion molecules were also found in a higher number of uveitis patients than in controls, but this difference did not reach statistical significance.
CONCLUSION—An increased expression of adhesion molecules was found in the iris of patients with uveitis, indicating an immunoregulatory function for adhesion molecules in the pathogenesis of uveitis.

Keywords: adhesion molecules; uveitis; iris     

Effects of the color additive caramel color III and 2-acetyl-4(5)-tetrahydroxybutylimidazole (THI) on the immune system of rats.

Administration of ammonia caramel color (AC) to rats may decrease blood lymphocyte counts, specifically in rats fed a diet low in vitamin B6. This effect is associated with 2-acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)imidazole (THI). To characterize and compare the effects of AC and THI and to study the influence of dietary pyridoxine, two studies in rats were conducted. Weanling rats fed a diet containing 2-3 ppm pyridoxine and exposed to 4% AC or 5.72 ppm THI in drinking water for 4 weeks showed reduced cell numbers in spleen and popliteal lymph nodes, as well as in the blood. Flow cytometric analyses demonstrated a comparable reduction in B and T lymphocytes. In blood, spleen, and popliteal lymph nodes, CD4+ lymphocytes were more reduced than CD8+ cells. The number of bone marrow cells was not affected. Although thymus weight and cell number were not affected either, a decreased cortex over medulla area ratio and an increase in medullary cell density largely due to an increase in CD4+ thymocytes was observed. Decreased numbers of ED2+ macrophages were observed in the thymic cortex and in the spleen red pulp. All effects observed were either less pronounced or absent in a study with rats fed a diet containing 11-12 ppm pyridoxine. The effects of AC and THI on the immune system were similar. Whereas AC exposure was associated with changes in vitamin B6 status, THI did not induce obvious effects on vitamin B6 parameters. It is proposed that the effects of AC and THI on the immune system are not caused by a disturbance of vitamin B6 metabolism, but may in fact result from a disturbance of a specific PLP-dependent process.     

The role of alkalizing and neutral potassium salts in urinary bladder carcinogenesis in rats

Using an initiation-promotion rat model, we have previouslyshown that the alkalizing salt KHCO₃ is a strong and the neutralsalt KCl a weak promoter of urinary bladder carcinogenesis.We have now studied the effects of these salts on rat urinarybladder epithelium without prior exposure to a bladder tumourinitiator. In four studies ranging in duration from 4 to 130weeks, (equimolar) amounts of K⁺ were administered in the dietto male and female rats (85 rats/sex/ group) as KHCO3 or KCl.Comparable increases in urinary volume and potassium levelswere found with both KHCO₃ and KCl, but only KHCO₃ induced anelevated urinary pH. The feeding of KHCO₃ resulted in simpleepithelial hyper-plasia and, after prolonged administration,in papillary/ nodular hyperplasia, papillomas and transitionalcell carcinomas of the urinary bladder. With KCl, only a slightincrease in proliferative urothelial lesions was found; onemale showed papillary hyperplasia and one female exhibited nodularhyperplasia and a papilloma. Our results allow the conclusionthat KHCO₃, a strong promoter of bladder carcinogenesis, iscapable of inducing urinary bladder cancer in rats without priorapplication of an initiator, whereas KCl, a weak tumour promoter,induced only a few (pre)neoplastic lesions.     

Postoperative and long-term results of ileal pouch-anal anastomosis for ulcerative colitis and familial polyposis coli

The immediate postoperative and long-term functional results of 51 ulcerative colitis patients and 21 familial polyposis patients who underwent ileal J-pouch-anal anastomosis were compared in this study. The incidence of postoperative complications requiring reoperation was not statistically different in both groups. The mean daily stool frequency was significantly higher in colitis patients. Pouchitis occurred in 44% of colitis patients but not in polyposis patients (P<0.005). Symptoms of pouchitis included bloody diarrhea, urgency, abdominal pain, weight loss, fever, and arthritis. Six colitis patients required pouch excision because of intractable pouchitis. The overall pouch excision rate was 22% in ulcerative colitis patients and 5% in familial polyposis patients. Patient satisfaction was good in 46% of ulcerative colitis patients and 76% of polyposis patients (P<0.05). Our data demonstrate that the long-term outcome of ileal pouch-anal anastomosis is more favorable in polyposis patients than in colitis patients. Pouchitis is a major long-term complication occurring exclusively in colitis patients.     

Hermansky–Pudlak syndrome type 2: Aberrant pre‐mRNA splicing and mislocalization of granule proteins in neutrophils

Hermansky–Pudlak syndrome type 2 (HPS2) is a syndrome caused by mutations in the beta‐3A subunit of the adaptor protein (AP)‐3 complex (AP3B1 gene). We describe five unreported cases with four novel mutations, one of which caused aberrant pre‐mRNA splicing. A point mutation c.2702C>G in exon 23 of the AP3B1 gene caused deletion of 112 bp in the mRNA in two siblings. This mutation activates a cryptic donor splice site that overrules the wild‐type donor splice site of this exon. Three other novel mutations in AP3B1 were identified, that is, a nonsense mutation c.716G>A (p.Trp239Ter), a 1‐bp and a 4‐bp deletion c.177delA and c.1839_1842delTAGA, respectively, both causing frameshift and premature termination of translation. Mass spectrometry in four of these HPS2 patients demonstrated the (near) absence of all AP‐3 complex subunits. Immunoelectron microscopy on the neutrophils of two of these patients showed abnormal granule formation. We found clear mislocalization of myeloperoxidase in the neutrophils even though the content of this protein but not the activity seemed to be present at normal levels. In sum, HPS2 is the result of the absence of the entire AP‐3 complex, which results in severe neutropenia with a defect in granule formation as the major hematological finding.     

Granulocyte colony-stimulating factor inhibits the mitochondria-dependent activation of caspase-3 in neutrophils.

The exact mechanism of apoptosis in neutrophils (PMNs) and the explanation for the antiapoptotic effect of granulocyte colony-stimulating factor (G-CSF) in PMNs are unclear. Using specific fluorescent mitochondrial staining, immunofluorescent confocal microscopy, Western blotting, and flow cytometry, this study found that PMNs possess an unexpectedly large number of mitochondria, which are involved in apoptosis. Spontaneous PMN apoptosis was associated with translocation of the Bcl-2-like protein Bax to the mitochondria and subsequent caspase-3 activation, but not with changes in the expression of Bax. G-CSF delayed PMN apoptosis and prevented both associated events. These G-CSF effects were inhibited by cycloheximide. The general caspase inhibitor z-Val-Ala-DL-Asp-fluoromethylketone (zVAD-fmk) prevented caspase-3 activation and apoptosis in PMNs, but not Bax redistribution. PMN-derived cytoplasts, which lack a nucleus, granules, and mitochondria, spontaneously underwent caspase-3 activation and apoptosis (phosphatidylserine exposure), without Bax redistribution. zVAD-fmk inhibited both caspase-3 activation and phosphatidylserine exposure in cultured cytoplasts. Yet, G-CSF prevented neither caspase-3 activation nor apoptosis in cytoplasts, confirming the need for protein synthesis in the G-CSF effects. These data demonstrate that (at least) 2 routes regulate PMN apoptosis: one via Bax-to-mitochondria translocation and a second mitochondria-independent pathway, both linked to caspase-3 activation. Moreover, G-CSF exerts its antiapoptotic effect in the first, that is, mitochondria-dependent, route and has no impact on the second.     

Effects of rectal mobilization and lateral ligaments division on colonic and anorectal function

PURPOSE: Colonic and anorectal function are altered after posterior rectopexy. The aim of this randomized, prospective study was to evaluate the effects of rectal mobilization and division of the lateral ligaments on colonic and anorectal function. METHODS: Posterior rectopexy was performed in 18 patients with complete rectal prolapse. Anal manometry and measurement of rectal compliance, total and segmental colonic transit time, constipation score, and defecation frequency were performed preoperatively and three months postoperatively. Ligaments were divided in ten patients. RESULTS: Mean preoperative total transit time was similar between the two patient groups and doubled postoperatively (P=0.03). Mean postoperative segmental transit time increased by a factor of 1.7 in segments I (ascending colon) and II (descending colon) and by a factor of 2.3 in segment III (rectosigmoid). The same pattern was found in both groups. Mean resting pressure decreased after division of the lateral ligaments and increased after preservation. Mean rectal compliance decreased after division of the ligaments and increased when they were preserved. Mean postoperative constipation score differed little from the preoperative score. Mean defecation frequency was decreased in the group with the ligaments preserved and increased in the group with the ligaments divided. None of the effects of rectal mobilization or division of the lateral ligaments on anorectal function reached statistical significance. CONCLUSION: Rectal mobilization had a statistically significant effect on colonic function. Total and segmental colonic transit times doubled. The effects on anorectal function were not significant. Division of the lateral ligaments did not significantly influence postoperative functional outcome.     

Contribution of platelet glycoprotein VI to the thrombogenic effect of collagens in fibrous atherosclerotic lesions

Collagens (types I and III) are among the strongest thrombus-forming components of the vascular subendothelium. We compared the thrombogenic effects of four collagen-containing advanced atherosclerotic lesions with those of purified types I and III collagen fibers. Cell-free homogenates from the human plaques effectively promoted platelet adhesion and aggregate formation under high-shear flow conditions, as well as exposure of procoagulant phosphatidylserine (PS) on platelets. With all plaques, blocking of the glycoprotein VI (GPVI) receptor for collagen abolished aggregation and PS exposure. Blocking of platelet ADP receptors resulted in similar, but less complete inhibitory effects. Type I collagen was more potent than type III collagen in inducing aggregation and PS exposure under flow, via stimulation of GPVI and ADP receptors. Type I collagen also more strongly enhanced thrombin generation with platelets and tissue factor, again via GPVI activation and PS exposure. The plaque material enhanced thrombin generation, partly due to the presence of tissue factor and partly via GPVI and ADP receptors. Together, these results indicate that in advanced plaques collagen type I is a major trigger of thrombus formation and PS exposure, acting via GPVI and ADP release, while tissue factor directly enhances coagulation.