Interaction of antibodies to proteinase 3 (classic anti-neutrophil cytoplasmic antibody) with human renal tubular epithelial cells: impact on signaling events and inflammatory mediator generation

PR3-ANCA in Wegener's granulomatosis prime human mononuclear cells for enhanced activation via TLRs and NOD1/2

Background

Anti-neutrophil cytoplasmic antibodies (ANCA) is autoantibodies characteristic of vasculitis diseases. A connection between ANCA and Wegener's granulomatosis was well established. The interaction of both ANCA phenotypes (PR3-ANCA and MPO-ANCA) with leukocytes provoked cell activation, which might be involved in the pathogenesis of ANCA-related Wegener's granulomatosis.

Methods

In this study, we examined whether PR3-ANCA sera and purified immunoglobulins from patients with Wegener's granulomatosis prime human monocytic cells for enhanced responses to microbial components in terms of production of proinflammatory cytokines.

Results

Flow cytometry demonstrated that stimulation with antibodies to proteinase 3 enhanced the expression of TLR2, 3, 4, 7, and 9, NOD1, and NOD2 in human mononuclear cells. The sera and purified immunoglobulins significantly primed human mononuclear cells to secrete interleukin-8 in response to microbial components via TLRs and NODs. Priming effects were also observed for the production of interleukin-6, monocyte chemoattractant protein-1, and tumor necrosis factor-α. On the other hand, PR3-ANCA-negative sera from patients with polyarteritis nodosa which possibly related to MPO-ANCA and aortitis syndrome as well as control sera from a healthy volunteer did not have any priming effects on PBMCs.

Conclusion

In conclusion, PR3-ANCA prime human mononuclear cells to produce cytokines upon stimulation with various microbial components by up-regulating the TLR and NOD signaling pathway, and these mechanisms may partially participate in the inflammatory process in Wegener's granulomatosis.

Antibodies to proteinase 3 prime human oral, lung, and kidney epithelial cells to secrete proinflammatory cytokines upon stimulation with agonists to various Toll-like receptors, NOD1, and NOD2

Antineutrophil cytoplasmic antibodies (ANCA) are autoantibodies, the detection of which in serum can be used in the diagnosis of Wegener's granulomatosis (WG). Proteinase 3 (PR3) is a major target antigen of ANCA in WG patients, and the interaction of PR3 ANCA with leukocytes causes a debilitating autoimmune disease. The first signs and symptoms in WG patients are observed in the oral cavity, lungs, and kidneys. Human epithelial cells generally do not secrete proinflammatory cytokines upon stimulation with pathogen-associated molecular patterns (PAMPs). In this study, anti-PR3 antibodies (Abs) and PR3 ANCA-containing sera from WG patients endowed human oral, lung, and kidney epithelial cells with responsiveness to PAMPs in terms of the production of proinflammatory cytokines, such as interleukin-6 (IL-6), IL-8, monocyte chemoattractant protein-1, and tumor necrosis factor alpha. Protease-activated receptor-2 (PAR-2) agonist peptides mimicked the priming effects of PR3 ANCA against PAMPs. Furthermore, the anti-PR3 Ab-mediated cell activation was significantly abolished by RNA interference targeting PAR-2 and NF-kappaB. This is the first report of priming effects of anti-PR3 Abs (PR3 ANCA) on epithelial cells. The results suggest that anti-PR3 Abs (PR3 ANCA) prime human epithelial cells to produce cytokines upon stimulation with various PAMPs, and these mechanisms may be involved in severe chronic inflammation in WG.

Bone Marrow–Derived Cells Are Sufficient and Necessary Targets to Mediate Glomerulonephritis and Vasculitis Induced by Anti-Myeloperoxidase Antibodies

Clinical and experimental evidence indicate that ANCA cause pauci-immune necrotizing and crescentic glomerulonephritis (NCGN) and systemic small vessel vasculitis in humans. One of the major target antigens for ANCA is myeloperoxidase (MPO). An animal model that closely resembles the human disease is induced by intravenous injection of anti-MPO IgG into mice. The likely primary pathogenic targets for the anti-MPO IgG are circulating neutrophils and monocytes, although other cells have been implicated, including endothelial cells and epithelial cells. Herein is reported a new model for anti-MPO-mediated glomerulonephritis and vasculitis that further documents the pathogenic potential of ANCA and demonstrates that bone marrow (BM)-derived cells are sufficient targets to cause anti-MPO disease in the absence of MPO in other cell type. MPO knockout (Mpo-/-) mice that were immunized with mouse MPO were exposed to irradiation and received a transplant of Mpo+/+ or Mpo-/- BM. Engraftment in mice with circulating anti-MPO resulted in development of pauci-immune NCGN in all mice and pulmonary capillaritis and splenic necrotizing arteritis in some. Anti-MPO IgG also was introduced intravenously into chimeric mice by transplantation of Mpo+/+ BM into irradiated Mpo-/- mice or Mpo-/- BM into irradiated Mpo+/+ mice. Chimeric Mpo-/- mice with circulating MPO-positive neutrophils developed NCGN, whereas chimeric Mpo+/+ mice with circulating MPO-negative neutrophils did not, thereby indicating that BM-derived cells are not only sufficient but also necessary for induction of anti-MPO disease. This novel animal model further documents ANCA IgG interactions with neutrophils as a cause of ANCA-associated glomerulonephritis and vasculitis.

Proinflammatory Cytokines Induce Proteinase 3 as Membrane-Bound and Secretory Forms in Human Oral Epithelial Cells and Antibodies to Proteinase 3 Activate the Cells through Protease-Activated Receptor-2

Anti-neutrophil cytoplasmic Abs targeting proteinase 3 (PR3) have been detected in relation to a wide range of inflammatory conditions such as periodontitis, and interaction of anti-PR3 Abs with endothelial and epithelial cells provokes cell activation, although the underlying mechanism has been unclear. The present study showed that human oral epithelial cells expressed PR3 mRNA after treatment with proinflammatory cytokines such as IL-1alpha, TNF-alpha, IFN-alpha, IFN-beta, and IFN-gamma. A 29-kDa PR3 was expressed on the cell surface and released into culture supernatants by the cells upon stimulation with these cytokines. The membrane and supernatant fractions of oral epithelial cells exhibited enzymatic activity, which was inhibited by serine proteinase inhibitors, but not by a cysteine proteinase inhibitor or secretory leukocyte protease inhibitor. Addition of anti-PR3 Abs to cytokine-primed oral epithelial cells in culture induced remarkable secretion of IL-8 and monocyte chemoattractant protein 1 and aggregation of PR3 on the cells. RNA interference targeted to protease-activated receptor-2 mRNA and intracellular Ca2+ mobilization assays revealed that anti-PR3 Abs activated the epithelial cells through protease-activated receptor-2, a family of G protein-coupled receptors. The anti-PR3 Ab-mediated cell activation was completely abolished by RNA interference targeted to PR3 mRNA and by inhibition of phospholipase C and NF-kappaB. Immunohistochemistry showed that inflamed oral epithelium actually expresses PR3 protein. These results suggest that oral epithelial cells express functional PR3 in the inflamed sites and respond to anti-PR3 Abs detected in diseased sera, and that these mechanisms may actively participate in the inflammatory process, including periodontitis.

Action of EGF and PGE2on basolateral organic anion uptake in rabbit proximal renal tubules and hOAT1 expressed in human kidney epithelial cells

We recently showed that, in a proximal tubule cell line (opossum kidney cells), epithelial growth factor (EGF) stimulates basolateral organic anion transport (OAT) via ERK1/2, arachidonic acid, phospholipase A2, and generation of prostaglandins. PGE2binds the prostanoid receptor and, thus, activates adenylate cyclase and PKA, which stimulate basolateral organic anion uptake. In the present study, we investigated whether this regulatory cascade is also true 1) for ex vivo conditions in isolated renal proximal (S2) tubules from rabbit and 2) in a human renal epithelial cell line stably expressing human OAT1 (IHKE-hOAT1). EGF activated ERK1/2 in S2 tubules and IHKE-hOAT1, and, in both cases, inhibition of ERK activation (by U-0126) abolished this stimulation. In S2 tubules and IHKE-hOAT1, EGF led to an increase of organic anion uptake, which again was inhibited by U-0126. PGE2stimulated basolateral organic anion uptake in rabbit S2 tubules and IHKE-hOAT1. EGF- and PGE2-mediated stimulation of organic anion uptake was abolished by inhibition of PKA in rabbit S2 tubules and IHKE-hOAT1, respectively. We conclude that 1) stimulation of basolateral organic anion uptake by EGF or PGE2is a widespread (if not general) regulatory mechanism, 2) the signal transduction pathway involved seems to be general, 3) stimulation of basolateral organic anion uptake by EGF or PGE2is also present under ex vivo conditions and, thus, is not a cell culture artifact, 4) activation of OAT1 is sufficient to explain the stimulatory effects of EGF and PGE2in opossum kidney cells and rabbit S2 segments, and 5) stimulation of basolateral OAT1 by EGF or PGE2is also important in humans and, thus, may have clinical implications.

Short-Term Regulation of Basolateral Organic Anion Uptake in Proximal Tubular Opossum Kidney Cells: Prostaglandin E2 Acts via Receptor-Mediated Activation of Protein Kinase A

ABSTRACT. It was shown previously that EGF induces release of the important prostanoid prostaglandin E2 (PGE2) in proximal tubular opossum kidney (OK) cells and PGE2 then stimulates initial basolateral uptake of organic anions (OA) dose dependently. PGE2 is a receptor agonist and a known substrate for the basolateral exchanger mediating OA uptake (OAT1 and/or OAT3). This study investigated the mechanism of short-term PGE2 action on initial basolateral OA uptake in OK cells. PGE2 stimulation of OA uptake was abolished by selective inhibition of adenylate cyclase (by MDL-12, 330A) or protein kinase A (PKA; by H89). PGE2 stimulation of OA uptake persisted after preloading the cells with glutarate and was still abolished by inhibition of PKA. Selective activation of adenylate cyclase by forskolin led to identical results. These data contradicted the hypothesis that PGE2 action on OA uptake is due to its action as a counter ion. Therefore, we tested whether the PGE2 receptors (EP1 to 4) are involved in stimulation of OA uptake in OK cells by PGE2. Because of their intracellular signaling profile, EP1 and EP3 were not taken into account as possible receptors for mediation of PGE2-induced OA uptake. With the use of selective agonists (11-deoxy PGE1 and butaprost), EP4 was pharmacologically identified as the receptor responsible for PGE2-mediated stimulation of OA uptake. By reverse transcription–PCR, cloning, and subsequent sequencing, a homologue fragment to EP4 was identified in OK cells. EGF-induced stimulation of basolateral organic anion uptake was abolished by inhibition of adenylate cyclase or PKA. This indicates that EGF action is mediated by generation of PGE2. The following model is proposed: PGE2 generated in the cells does not act as a counter ion but activates adenylate cyclase. This is mediated by a homologue of EP4 receptor. cAMP then activates PKA, which stimulates initial basolateral uptake of OA in OK cells by a not-yet-known mechanism. PGE2 is an organic anion, a potential stimulator of organic anion excretion, and an important mediator of inflammation all at once. Thus, the mechanism presented here may contribute to a limitation of inflammatory events in the kidney cortex interstitium.