Glomerular endothelial injury associated with free radical production induced by a fungal cell wall component, (1-->3) beta-D glucan

Thrombotic Microangiopathy Due to Progressive Disseminated Histoplasmosis in a Child With Down Syndrome and Acute Lymphoblastic Leukemia

Histoplasmosis, a common mycosis in the south-central United States, may be life threatening in immunocompromised patients. We describe a 4-year-old female with Down syndrome and acute lymphoblastic leukemia who developed hemolytic anemia, thrombocytopenia, and renal failure, consistent with thrombotic microangiopathy. Bone marrow biopsy revealed non-necrotizing granulomas with GMS staining demonstrating budding yeast. Serum Histoplasma antigen testing was positive, providing further evidence for the diagnosis of progressive disseminated histoplasmosis. Treatment with amphotericin B, plasma exchange, and ventilator, vasopressor, and renal replacement support led to a full recovery. Providers should have a low threshold for histoplasmosis testing in ill immunocompromised patients, who are at greater risk for infection-related morbidity.

Immunomodulatory activities and subacute toxicity of a novel β-glucan from Paenibacillus polymyxa JB115 in rats

Subacute toxicity and immunopharmacological activities of β-glucan from P. polymyxa JB115 was evaluated in a 28-day feeding study in rats. The white blood cell count, red blood cell count, hematocrit, hemoglobin, thrombocytes (THR) and thrombocytocrit were significantly higher in male fed with β-glucan than control rats and the insignificant lower eosinophil count, mean corpuscular volume, mean cell hemoglobin and uninfected THR (uTHR) levels were observed in male whereas no marked changes in female rats. No other significant differences in serum chemistry and liver, kidney, and spleen weights were observed. The pathological changes and other abnormal indicators were not detected in urine. Female rats fed with diet supplemented with 0.01% β-glucan also showed marked increase in the percentage of blood cytotoxic T-lymphocytes compared to that of the control group while not significant differences in the percentage of blood B-lymphocytes. No adverse effects on general condition and behavior, growth, feed and water consumption and feed conversion efficiency were found. The results suggest that consumption of the novel β-1, 3/1, 6-glucan from P. polymyxa JB115 was not associated with any obvious toxic effects in rats, indicating its safety as a potential immunostimulant or as an adjuvant of some animal vaccines.

Uremic toxins of organic anions up-regulate PAI-1 expression by induction of NF-kappaB and free radical in proximal tubular cells

BACKGROUND

Uremic toxins have been suggested to promote progression of chronic renal failure. We have shown that organic anion transporter-mediated uptake of uremic toxins induces oxidative stress in opossum kidney renal tubular cells overexpressing the transporter. Plasminogen activator inhibitor-1 (PAI-1) and nuclear factor-kappa B (NF-kappaB) are major factors known to promote tubulointerstitial fibrosis. The present study examined the signaling pathway that is activated by uremic toxins to induce PAI-1 and activate NF-kappaB in human renal proximal tubular cells (HK-2).

METHODS

Uremic toxins in the form of organic anion were examined their ability to induce oxidative stress, PAI-1 gene expression, and NF-kappaB activation in HK-2. PAI-1 expression was measured by enzyme-linked immunosorbent assay (ELISA) and the Northern blotting. Human PAI-1 promoter activity was estimated by luciferase reporter gene (NKkappaB-luc) assay. NF-kappaB activation was measured by the pNFkappaB-luc reporter gene and electrophretic gel mobility shift assay.

RESULTS

Among organic anion species tested, indoxyl sulfate and indoleacetic acid induced free radical production in HK-2. A nonspecific transporter inhibitor (probenecid) suppressed the IS-stimulated radical production. Indoxyl sulfate and indoleacetic acid dose dependently increased the expressions of PAI-1 mRNA and protein in these cells. The luciferase reporter gene assay revealed that indoxyl sulfate and indoleacetic acid dose dependently activated NF-kappaB and PAI-1 promoter. Activation of NF-kappaB was also confirmed by an electrophoretic gel mobility shift assay. Both antioxidant and NF-kappaB inhibitors dose dependently inhibited the activation of PAI-1 promoter by indoxyl sulfate.

CONCLUSION

Uremic toxins induce free radical production by renal tubular cells and activate NF-kappaB which, in turn, up-regulates PAI-1 expression. Thus, progression of chronic renal failure may be promoted by PAI-1 up-regulation induced by uremic toxins.

Synergistic action of beta-glucan and platelets on interleukin-8 production by human peripheral blood leukocytes

The effects of human platelets on interleukin (IL)-8 production from human peripheral blood mononuclear cells (PBMCs) and polymorphonuclear leukocytes (PMNs) stimulated with the fungal (1-->3)-beta-D-glucan schizophyllan (SPG) were examined using ELISA. PBMCs/PMNs in the presence of platelets and SPG enhanced IL-8 production in comparison with those in the presence of either platelets or SPG. IL-8 production was dependent on the concentration of platelets and incubation time, and the activity reached the maximal level at 18 h of incubation. These activities were also observed with the addition of platelets prestimulated with SPG to PBMCs. Addition of SPG directly enhanced expression of P-selectin on platelet membrane surfaces. These results suggest that platelets play a key role in the cytokine production of leukocytes induced by fungal (1-->3)-beta-D-glucans and might be mediated, at least in part, by P-selectin.

Effect of D-glucose on nitric oxide release from glomerular endothelial cells

BACKGROUND

Altered glomerular production of nitric oxide (NO) may be involved in hyperfiltration in early diabetic nephropathy. However little is known as to the role of glomerular endothelial cells (GECs) in diabetic hyperfiltration and their ability to release NO in response to hyperglycemia.

METHODS

Using an established cell line, we directly monitored NO release from GECs in response to various concentrations of D-glucose, D-mannitol, and L-arginine, an NO synthase (NOS) agonist. L-Arginine-induced NO release was examined in the cells pretreated for different periods up to 24 h with 10 or 30 mM D-glucose. We also measured serially the accumulation of nitrite, the stable metabolite of NO, produced by the cells incubated for up to 24 h under 10 or 30 mM D-glucose conditions in the presence or absence of the NOS inhibitor, L-NAME.

RESULTS

Direct measurement of NO demonstrated that D-glucose, but not D-mannitol, stimulation resulted in a rapid and dose-dependent increase in NO release by the cells. However, L-arginine-induced NO release was attenuated significantly in the cells preincubated for more than 12 h with 30 mM D-glucose compared to 10 mM D-glucose. The L-NAME-inhibitable production of nitrite in the media was significantly increased 1.5--2.0-fold until 6 h after incubation with 30 mM D-glucose compared to 10 mM D-glucose.

CONCLUSIONS

We conclude that D-glucose, but not D-mannitol, produces a rapid and dose-dependent increase in NO release, whereas exposure to high D-glucose for more than 12 h may blunt NOS activity and/or NO stability in the GECs. These observations may therefore be important for glomerular endothelial dysfunction induced by hyperglycemia that is still tentative and may have a role in diabetic nephropathy.