Cytolytically inactive terminal complement complex causes transendothelial migration of polymorphonuclear leukocytes in vitro and in vivo

Abstract

Intravital microscopy was used to monitor leukocyte traffic across rat mesenteric postcapillary venules induced by the inactive terminal complement (C) complex (iTCC) topically applied to ileal mesentery. Leukocytes started rolling within 15 minutes from the administration of iTCC, and by 1 hour they adhered almost completely to the endothelium emigrating from the vessels in the next 3 hours. C5a caused a similar, though less marked, effect, whereas boiled iTCC was inactive, excluding the contribution of contaminating lipopolysaccharide. The complex stimulated the migration of polymorphonuclear neutrophils (PMNs) across endothelial cells (ECs) in a transwell system after a 4-hour incubation of ECs with iTCC added to the lower chamber of the transwell, whereas a 30-minute incubation was sufficient for C5a and interleukin (IL)-8 to induce the passage of PMNs. C5a was not responsible for the effect of iTCC because this complex had no chemotactic activity and contained too small an amount of C5a to account for the transen- IntroductionTerminal complement (C) complex (TCC) represents the end product of the C-activation cascade and is formed by the assembly of the 5 late components of the C system. The best-known function of this complex is to insert into the phospholipid bilayer of the cell target as membrane attack complex (MAC) causing cytolysis. However, evidence collected in the last 2 decades has convincingly proved that MAC in sublytic amounts is also able to induce noncytolytic effects on several target cells. 1,2 An early manifestation of cell activation induced by MAC is the rise in Ca ϩϩ caused by the rapid influx of these ions from an extracellular source and their cytoplasmic redistribution from intracellular stores. 1 The endothelium is a potential target of MAC that can be formed directly on the cell membrane as a result of C activation triggered by cell-bound antibodies. Alternatively, MAC starts assembling in the circulation and subsequently interacts with endothelial cells (ECs). Cells attacked by MAC may undergo cytolysis, but, more frequently, they release and express on their surfaces molecules involved in important biologic functions. Mobilization of P-selectin, 3 enhancement of tumor necrosis factor (TNF)-␣-induced expression of adhesion molecules, 4 release of chemokines, monocyte chemotactic protein-1 (MCP-1), and interleukin (IL)-8, 5 and platelet-activating factor 6 are examples of pro-inflammatory effects stimulated by MAC on ECs. Moreover, MAC triggers the coagulation process, stimulating ECs to express tissue factor 7 and to shed MAC-enriched vesicles that support the formation of a prothrombinase complex. 8 Finally, MAC has been shown to create interendothelial gaps, causing structural changes of the endothelium, 9 and it contributes to the modification of vascular tone by promoting the release of the vasodilator prostaglandin I 2 10 and the vasoconstrictor thromboxane A 2 from ECs. 11 These noncytotoxic effects on ECs require the complex to insert into the cytoplasmic membrane to signa...

CD59a Deficiency Exacerbates Accelerated Nephrotoxic Nephritis in Mice

“…First, MAC has been shown to cause proliferation of glomerular mesangial, endothelial, and epithelial cells in vitro and therefore may be directly involved in inducing a increase in intrinsic cell number (17,21,44,45). Additionally, there are data indicating that MAC can induce the synthesis and/or secretion of a number of proinflammatory cytokines such as TNF-␣ and IL-1 (22,44), adhesion molecules such as ICAM-1 and E selectin (23), and chemokines such as IL-8 (46) and that these effects may play a role in the infiltration of cells to the glomerulus. We have also demonstrated that later in the progression of ANTN, mCd59a deficiency, by allowing unregulated MAC deposition, exacerbates glomerular thrombosis.…”

Decidual endothelial cells express surface-bound C1q as a molecular bridge between endovascular trophoblast and decidual endothelium

“…mAb M89D3 to CD31 was kindly provided by M.R. Zocchi (San Raffaele Hospital, Milan, Italy) (Dobrina et al, 2002). Mouse IgG1 isotype control was from Sigma-Aldrich (Milano, Italy) and mAb MEM-G9 anti-human leukocyte antigen G (HLA-G) was a kind gift of P. Le Bouteiller (Toulouse, France).…”

“…Expression of adhesion molecules and tissue factor, release of chemokines, increased permeability are some of the responses of ECs to these factors (Bossi et al, 2004;Dobrina et al, 2002;Kilgore et al, 1996;Selvan et al, 1998) and both C5a and SC5b-9 have been shown to promote transendothelial migration of PMN (Dobrina et al, 2002). However, under normal conditions the endothelium is protected from the stimulating effect of C activation products that induce a pro-inflammatory and pro-coagulant state by the regulatory proteins CD46, CD55 and CD59 expressed on their surface and the fluid phase regulator Factor H that binds to ECs (Asch et al, 1986;Hamilton et al, 1990;Jokiranta et al, 2005;McNearney et al, 1989).…”

The Neutrophil-Activating Protein of Helicobacter pylori Crosses Endothelia to Promote Neutrophil Adhesion In Vivo

“…HP-NAP (1 M) was added to the lower chamber, and after 45 min of incubation at 37°C, the PMNs were added to the endothelial layer and left for 30 min at 37°C. The adherent PMNs were fixed and processed for scanning microscopy, as described previously (28).…”