Markers of immunologic injury in progressive alopecia areata

In a selected group of 8 patients with progressive alopecia areata (AA) leading to AA universalis, immunological aspects (in the peripheral blood and the tissue) were studied during the period of the intitial attack of the disease. The peripheral T-cell helper/suppressor ratio appeared not to be a reliable parameter for the disease activity. The intrabulbar and peribulbar distribution of T-cells, Langerhans cells and of HLA-DR expression in and around the anagen hair follicles in the progressive areas of the disease (region of exclamation-mark hairs) may suggest a T-cell-mediated injury primarily in the peribulbar regions of the follicles. The data presented tend to support the possibility that in the early development of AA, the dermal pailla (capillary network?) may be the prime target of immunologic injury.     

Kupffer cell depletion in vivo results in clearance of large-sized IgA aggregates in rats by liver endothelial cells.

We investigated the clearance kinetics and tissue distribution of different sized IgA in normal and macrophage-depleted rats. Rats were injected iv with liposomes containing dichloromethylene diphosphonate (DMDP). DMDP treatment resulted in complete depletion of liver macrophages 24-48 h after administration. Normal and macrophage depleted rats were injected intravenously with monomeric, dimeric, polymeric or aggregated polymeric IgA (AIgA) and assessed for blood clearance and tissue distribution. In normal rats, clearance of IgA was size dependent, i.e. a faster clearance with increasing size. No differences in clearance kinetics were observed of the different sized IgA between normal and DMDP-treated rats. TCA non-precipitable radioactivity, a measure for degradation of IgA, was found in the circulation of normal and DMDP-treated rats after AIgA administration. The liver was the main organ responsible for the clearance of IgA in normal and DMDP-treated rats. Immunofluorescence studies on liver biopsies indicated that AIgA was associated with Kupffer cells in normal rats. Electron microscopical studies revealed that the AIgA was internalized and located in vesicles in Kupffer cells. In DMDP-treated rats the AIgA was associated with endothelial cells and electron microscopy studies showed that this AIgA was taken up by endothelial cells. These data show that rat liver endothelial cells are able to bind, internalize and degrade AIgA in situations where Kupffer cells are absent, and that these cells may play an important role in the handling of AIgA and IgA-immune complexes.     

Handling of asymmetrical dimethylarginine and symmetrical dimethylarginine by the rat kidney under basal conditions and during endotoxaemia.

BACKGROUND: Asymmetrical dimethylarginine (ADMA) is capable of inhibiting nitric oxide synthase enzymes, whereas symmetrical dimethylarginine (SDMA) competes with arginine transport. The potential role of inflammation in the metabolism of ADMA has been elucidated in an in vitro model using tumour necrosis factor-alpha, resulting in a decreased activity of the ADMA-degrading enzyme dimethylarginine dimethylaminohydrolase (DDAH). The kidney probably plays a crucial role in the metabolism of ADMA by both urinary excretion and degradation by DDAH. We aimed to further elucidate the role of the kidney in a rat model under basal conditions and during endotoxaemia. METHODS: Twenty-five male Wistar rats weighing 275-300 g were used for this study. The combination of arteriovenous concentration differences and kidney blood flow allowed calculation of net organ fluxes. Blood flow was measured using radiolabelled microspheres according to the reference sample method. Concentrations of ADMA, SDMA and arginine were measured by high-performance liquid chromatography. RESULTS: The kidney showed net uptake of both ADMA and SDMA and fractional extraction rates were 35% and 31%, respectively. Endotoxaemia resulted in a lower systemic ADMA concentration (P = 0.01), which was not explained by an increased net renal uptake. Systemic SDMA concentrations increased during endotoxaemia (P = 0.007), which was accompanied by increased creatinine concentrations. CONCLUSIONS: The rat kidney plays a crucial role in the regulation of concentrations of dimethylarginines, as both ADMA and SDMA were eliminated from the systemic circulation in substantial amounts. Furthermore, evidence for the role of endotoxaemia in the metabolism of dimethylarginines was obtained as plasma levels of ADMA were significantly lower in endotoxaemic rats.     

Reduced insulin secretion after short-term food deprivation in rats plays a key role in the adaptive interaction of glucose and free fatty acid utilization

The present study was undertaken to investigate the effects of short-term fasting periods up to 24 hr on insulin secretory responses of the B-cell to glucose and the consequences for FFA and glucose availability in the circulation. Conscious male rats provided with permanently implanted heart catheters received glucose infusions at midday, lasting for 20 min, in the nearly ad lib condition (i.e., 6 hr of non feeding during daytime) and after extending the fasting period to 12, 18 and 24 hr. Basal preinfusion insulin levels and insulin responses to glucose decreased gradually during these fasting periods. Basal blood glucose dropped only significantly after 24 hr of fasting whereas basal FFA levels increased gradually from 6 hr of fasting onwards. After prolonged fasting insulin released during glucose infusion became more effective in suppressing plasma FFA levels. While our data suggest that the sensitivity to the antilipolytic action of insulin is increased, the decreased responsiveness of the B-cell after moderate fasting periods may result in a drop of basal insulin levels. This facilitates the switch from glucose to FFA metabolism for most tissues already, when the first meals are missed. The results suggest that this physiological process is important to save the glycogen stores as long as possible as fuel for the central nervous system, and also to support basic energy requiring processes adequately.     

The pathophysiology of protein-overload proteinuria.

Alterations in glomerular function and structure were studied in protein-overload nephrosis in the rat induced by intraperitoneal administration of bovine serum albumin (BSA). Fractional clearance (C/GFR) studies using inulin and tracer proteins of different molecular size and charge revealed in proteinuric rats 1) unchanged glomerular filtration rate and renal plasma flow; 2) a 34-fold increase in C/GFR of rat serum albumin, reaching values similar to BSA; 3) a 2-fold increase in C/GFR for anionic horse radish peroxidase (HRP), but normal values for neutral and cationic HRP, and 4) an 11- and 3-fold increase for heterologous IgG and IgM, respectively. Glomerular epithelial cells showed degenerative changes, but the distribution of anionic sites in the glomerular basement membrane was found to be unaltered, as determined by polyethyleneimine binding studies. In summary, an elevation of serum albumin concentration resulted in an increased transcapillary albumin transport. This was found to lead to degenerative changes of glomerular epithelial cells with development of large pore defects, which were completely reversible.     

Polycystin-1, the product of the polycystic kidney disease 1 gene, co-localizes with desmosomes in MDCK cells

Polycystin-1 is a novel protein predicted to be a large membrane-spanning glycoprotein with an extracellular N-terminus and an intracellular C-terminus, harboring several structural motifs. To study the subcellular localization, antibodies raised against various domains of polycystin-1 and against specific adhesion complex proteins were used for two-color immunofluorescence staining. In Madine Darby canine kidney (MDCK) cells, polycystin-1 was detected in the cytoplasm as well as co-localizing with desmosomes, but not with tight or adherens junctions. Using confocal laser scanning and immunoelectron microscopy we confirmed the desmosomal localization. By performing a calcium switch experiment, we demonstrated the sequential reassembly of tight junctions, subsequently adherens junctions and finally desmosomes. Polycystin-1 only stained the membrane after incorporation of desmoplakin into the desmosomes, suggesting that membrane-bound polycystin-1 may be important for cellular signaling or cell adhesion, but not for the assembly of adhesion complexes.     

Sequential Measurements of Chemokines in Urosepsis and Experimental Endotoxemia

Chemokines are a superfamily of small chemotactic proteins. While increased levels of interleukin-8 have been measured in serum and urine during urinary tract infection, little is known about other chemokines in this condition. Monocyte chemoattractant protein (MCP)–1, macrophage inflammatory protein (MIP)–1, MIP-1 and interferon- inducible protein (IP)–10 were measured in 30 patients with culture-proven urosepsis during a 3-day follow-up and in 11 healthy humans after intravenous injection of endotoxin (4 ng/kg). Urine and serum levels of MCP-1, MIP-1, and IP-10, but not of MIP-1, were elevated in patients on admission, and decreased after initiation of antibiotic treatment. Endotoxin administration to healthy subjects induced increases in plasma and urine concentrations of all four chemokines. These data indicate that clinical and experimental gram-negative infection in humans is associated with enhanced production of chemokines that act mainly on mononuclear cells and that these chemokines are at least in part locally produced.