HIV type 1 glycoprotein 120 inhibits human B cell chemotaxis to CXC chemokine ligand (CXCL) 12, CC chemokine ligand (CCL)20, and CCL21

We analyzed the modulation of human B cell chemotaxis by the gp120 proteins of various HIV-1 strains. X4 and X4/R5 gp120 inhibited B cell chemotaxis toward CXCL12, CCL20, and CCL21 by 40-50%, whereas R5 gp120 decreased inhibition by 20%. This gp120-induced inhibition was strictly dependent on CXCR4 or CCR5 and lipid rafts but not on CD4 or V(H)3-expressing BCR. Inhibition did not impair the expression or ligand-induced internalization of CCR6 and CCR7. Our data suggest that gp120/CXCR4 and gp120/CCR5 interactions lead to the cross-desensitization of CCR6 and CCR7 because gp120 does not bind CCR6 and CCR7. Unlike CXCL12, gp120 did not induce the activation of phospholipase Cbeta3 and PI3K downstream from CXCR4, whereas p38 MAPK activation was observed. Similar results were obtained if gp120-treated cells were triggered by CCL21 and CCL20. Our results are consistent with a blockade restricted to signaling pathways using phosphatidylinositol-4,5-bisphosphate as a substrate. X4 and X4/R5 gp120 induced the cleavage of CD62 ligand by a mechanism dependent on matrix metalloproteinase 1 and 3, CD4, CXCR4, Galpha(i), and p38 MAPK, whereas R5 gp120 did not. X4 and X4/R5 gp120 also induced the relocalization of cytoplasmic CD95 to the membrane and a 23% increase in CD95-mediated apoptosis. No such effects were observed with R5 gp120. The gp120-induced decrease in B cell chemotaxis and CD62 ligand expression, and increase in CD95-mediated B cell apoptosis probably have major deleterious effects on B cell responsiveness during HIV infection and in vaccination trials.     

Supplementation with undenatured whey protein during diabetes mellitus improves the healing and closure of diabetic wounds through the rescue of functional long-lived wound macrophages

Long and persistent uncontrolled diabetes tends to degenerate the immune system and increase the incidence of infections in diabetic patients. A serious complication of diabetes is impaired healing, which diminishes physical activity and, in some cases, leads to chronic wounds and limb amputation. Whey proteins (WPs) enhance immunity during early development and have a protective role in some immune disorders. The effect of camel WPs on wound healing in a streptozotocin-induced type 1 diabetic mice model was investigated. Sixty male mice were equally distributed into 3 experimental groups: group 1, non-diabetic control mice; group 2, diabetic mice; and group 3, diabetic mice that were orally supplemented with undenatured WP (100 mg/kg body weight/day for 1 month through oral gavage). We observed that the diabetic mice exhibited delayed wound closure characterized by a significant reduction in collagen deposition, prolonged elevation in inflammatory cytokines, aberrant activation of STAT3 and reduction in the activation of Akt and NF-κB when compared with the control mice. Moreover, in the diabetic mice, the wound-resident macrophages were dysfunctional and demonstrated increased apoptosis, a significant reduction in their phagocytotic ability, aberrant activation of STAT3 and a marked reduction in the activation of Akt. Interestingly, the supplementation of diabetic mice with WP significantly enhanced the collagen deposition, limited the inflammatory stimuli, restored the activation of STAT3, Akt and NF-κB and greatly improved the closure of diabetic wounds compared with the control mice. Most important, the supplementation of diabetic mice with WP rescued functional, long-lived wound-resident macrophages. Our data reveal the benefits of WP supplementation in improving the healing and closure of diabetic wounds.     

Corruption of human follicular B-lymphocyte trafficking by a B-cell superantigen

Protein A (SpA) of Staphylococcus aureus is known to target the paratope of immunoglobulins expressing V_H3 genes, and to delete marginal zone B cells and B-1a in vivo. We have discovered that SpA endows S. aureus with the potential to subvert B-cell trafficking in the host. We found that SpA, whose Fc-binding site has been inactivated, binds essentially to naïve B cells and induces a long-lasting decrease in CXCR4 expression and in B-cell chemotaxis to CXCL12. Competition experiments indicated that SpA does not interfere with binding of CXCR4 ligands and does not directly bind to CXCR4. This conclusion is strongly supported by the inability of SpA to modulate clathrin-mediated CXCR4 internalization, which contrasts with the potent effect of anti-immunoglobin M (IgM) antibodies. Microscopy and biochemical experiments confirmed that SpA binds to the surface IgM/IgD complex and induces its clathrin-dependent internalization. Concomitantly, the SpA-induced signaling leads to protein kinase C–dependent CXCR4 downmodulation, suggesting that SpA impairs the recycling of CXCR4, a postclathrin process that leads to either degradation into lysozomes or de novo expression at the cell surface. In addition to providing novel insight into disruption of B-cell trafficking by an infectious agent, our findings may have therapeutic implications. Because CXCR4 has been associated with cancer metastasis and with certain autoimmune diseases, SpA behaves as an evolutionary tailored highly specific, chemokine receptor inhibitor that may have value in addition to conventional cytotoxic therapy in patients with various malignancies and immune-mediated diseases.     

Circadian rhythm of DNA synthesis and mitotic activity in tongue keratinocytes

Tongue keratinocytes have a high mitotic index (MI) with an evident circadian variation. Our study set out to compare and contrast two phases of the cell cycle: DNA synthesis (S-phase), with inmunocytochemical detection by bromodeoxyuridine (BrdU), and mitosis (M-phase), by the colchicine-arrest of metaphase method, exploring both the dorsal and ventral surfaces of the mouse tongue throughout a circadian period. Adult male mice standardized for light periodicity used for MI experiment were injected intraperitoneally with colchicine. Other animals were injected intraperitoneally with 5-BrdU for S-phase determination. Animals given both treatments were divided into six groups and killed at 4 h intervals until 20:00 h. Tongue samples were processed for histology and immuno-histochemistry. S and M indices were expressed as labelled nuclei or colchicine metaphases, respectively, per 1000 nuclei. Peak MI occurred at 12:00, with the minimum value at 20:00 on dorsal and ventral tongue surfaces. Peak S-phase was at 04:00, whereas the minimum value was at 16:00 for both surfaces. These results show that the proliferative activity of the tongue epithelium is of similar intensity and temporal distribution on both surfaces.     

Aflatoxicosis in rabbits: Effectiveness of Egyptian raw bentonite in prevention or diminution the detrimental effects of naturally aflatoxin contaminated diets

Thirty five females and 15 males of New Zealand White mature rabbits about 6 months of age, were assigned to 1–5 dietary treatments (7 does+3 bucks for each): uncontaminated control diet, naturally aflatoxin contaminated diet without or with 1,2 and 3% bentonite. Rabbit fed with the aflatoxin-diet had a decreased (P<0.01 or 0.05) physical semen characteristics of bucks and a reproductive performance traits of does. The values of conception rate (%), gestation length (days), litter size (n) and litter weights (g) at birth and viability (%) of litters of doe rabbits, fed with the aflatoxin-diet, recorded, respectively: 64.5; 31.0; 4.4; 275.0 and 57.1 versus 85.6; 30.3; 7.9; 508.0; and 100 for those fed with the uncontaminated diet. Addition of bentonite to the aflatoxin contaminated diet improved in general the physical semen characteristics of buck and reproductive performance traits of doe rabbits. The results of the study demonstrate that adding 1% of Egyptian raw bentonite to the naturally aflatoxin contaminated rabbit diets can provide an effective, cheap and safe practical technique for preventing the aflatoxicosis in mature rabbits.