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Polyreactive antibodies are a major component of the natural antibody repertoire and are capable of binding a variety of structurally unrelated antigens. Many of the properties attributed to natural antibodies, in fact, are turning out to be due to polyreactive antibodies. In humans, each day, billions of cells undergo apoptosis. In the present experiments, we show by ImageStream technology that although polyreactive antibodies do not bind to live T cells they bind to both the plasma membrane and cytoplasm of late apoptotic cells, fix complement, generate the anaphylatoxin C5a and increase by as much as 5 fold complement-mediated phagocytosis by macrophages. Of particular importance, T cells undergoing apoptosis following infection with HIV also bind polyreactive antibodies and are phagocytosed. We conclude that the polyreactive antibodies in the natural antibody repertoire contribute in a major way to the clearance of cells made apoptotic by a variety of natural and infectious processes [ABSTRACT FROM AUTHOR]

Oversulfated chondroitin sulfate (OSCS) has become the subject of multidisciplinary investigation as a non-traditional contaminant in the heparin therapeutic preparations that were linked to severe adverse events. In this study, it was found that OSCS inhibited complement fixation on bacteria and bacterial lysis mediated by the complement classical pathway. The inhibition of complement by OSCS is not due to interference with antibody/antigen interaction or due to consumption of C3 associated with FXII-dependent contact system activation. However, OSCS complement inhibition is dependent on C1 inhibitor (C1inh) since the depletion of C1inh from either normal or FXII-deficient complement plasma prevents OSCS inhibition of complement activity. Surface plasmon resonance measurements revealed that immobilized C1inhibitor bound greater than 5-fold more C1s in the presence of OSCS than in presence of heparin. Although heparin can also inhibit complement, OSCS and OSCS contaminated heparin are more potent inhibitors of complement. Furthermore, polysulfated glycosaminoglycan (PSGAG), an anti-inflammatory veterinary medicine with a similar structure to OSCS, also inhibited complement in the plasma of dogs and farm animals. This study provides a new insight that in addition to the FXII- dependent activation of contact system, oversulfated and polysulfated chondroitin-sulfate can inhibit complement activity by potentiating the classical complement pathway regulator C1inh. This effect on C1inh may play a role in inhibiting inflammation as well as impacting bacterial clearance. [ABSTRACT FROM AUTHOR]

Activation of kinin-kallikrein and complement pathways by oversulfated-chondroitin-sulfate (OSCS) has been linked with recent heparin-associated adverse clinical events. Given the fact that the majority of patients who received contaminated heparin did not experience an adverse event, it is of particular importance to determine the circumstances that increase the risk of a clinical reaction. In this study, we demonstrated by both the addition and affinity depletion of C1inh from normal human plasma, that the level of C1inh in the plasma has a great impact on the OSCS-induced kallikrein activity and its kinetics. OSCS-induced kallikrein activity was dramatically increased after C1inh was depleted, while the addition of C1inh completely attenuated kallikrein activity. In addition, actual clinical infection can lead to increased C1inh levels. Plasma from patients with sepsis had higher average levels of functional C1inh and decreased OSCS-induced kallikrein activity. Lastly, descriptive data on adverse event reports suggest cases likely to be associated with contaminated heparin are inversely correlated with infection. Our data suggest that low C1inh levels can be a risk factor and high levels can be protective. The identification of risk factors for contact system-mediated adverse events may allow for patient screening and clinical development of prophylaxis and treatments. [ABSTRACT FROM AUTHOR]

It has been reported that diabetic vascular dysfunction is associated with impaired function of large conductance Ca-activated K (BK) channels. However, it is unclear whether impaired BK channel directly participates in regulating diabetic vascular remodeling by altering cell growth in response to hyperglycemia. In the present study, we investigated the specific role of BK channel in controlling apoptosis and proliferation under high glucose concentration (25 mM). The cDNA encoding the α+β1 subunit of BK channel, hSloα+β1, was transiently transfected into human embryonic kidney 293 (HEK293) cells. Cloned BK currents were recorded by both whole-cell and cell-attached patch clamp techniques. Cell apoptosis was assessed with immunocytochemistry and analysis of fragmented DNA by agarose gel electrophoresis. Cell proliferation was investigated by flow cytometry assays, MTT test, and immunocytochemistry. In addition, the expression of anti-apoptotic protein Bcl-2, intracellular Ca, and mitochondrial membrane potential (Δψm) were also examined to investigate the possible mechanisms. Our results indicate that inhibition of cloned BK channels might be responsible for hyperglycemia-altered apoptosis and proliferation in HEK- hSloα+β1 cells. However, activation of BK channel by NS1619 or Tamoxifen significantly induced apoptosis and suppressed proliferation in HEK- hSloα+β1 cells under hyperglycemia condition. When rat cerebral smooth muscle cells were cultured in hyperglycemia, similar findings were observed. Moreover, the possible mechanisms underlying the activation of BK channel were associated with decreased expression of Bcl-2, elevation of intracellular Ca, and a concomitant depolarization of Δψm in HEK- hSloα+β1 cells. In conclusion, cloned BK channel directly regulated apoptosis and proliferation of HEK293 cell under hyperglycemia condition. J. Cell. Physiol. 226: 1660-1675, 2011. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]