Excessive release of neutrophil extracellular traps (NETs) is associated with disease severity and contributes to tissue injury, followed by severe organ damage. Pharmacological or genetic inhibition of NET release reduces pathology in multiple inflammatory disease models, indicating that NETs are potential therapeutic targets. Here, we demonstrate using a preclinical basket approach that our therapeutic anti-citrullinated protein antibody (tACPA) has broad therapeutic potential. Treatment with tACPA prevents disease symptoms in various mouse models with plausible NET-mediated pathology, including inflammatory arthritis (IA), pulmonary fibrosis, inflammatory bowel disease and sepsis. We show that citrulline residues in the N-termini of histones 2A and 4 are specific targets for therapeutic intervention, whereas antibodies against other N-terminal post-translational histone modifications have no therapeutic effects. Because citrullinated histones are generated during NET release, we investigated the ability of tACPA to inhibit NET formation. tACPA suppressed NET release from human neutrophils triggered with physiologically relevant human diseaserelated stimuli. Moreover, tACPA diminished NET release and potentially initiated NET uptake by macrophages in vivo, which was associated with reduced tissue damage in the joints of a chronic arthritis mouse model of IA. To our knowledge, we are the first to describe an antibody with NET-inhibiting properties and thereby propose tACPA as a drug candidate for NET-mediated inflammatory diseases, as it eliminates the noxious triggers that lead to continued inflammation and tissue damage in a multidimensional manner.

The synthetic matrix metalloproteinase inhibitor batimastat was tested for its ability to inhibit growth and metastatic spread of the B16-BL6 murine melanoma in syngeneic C57BL/6N mice. Intraperitoneal administration of batimastat resulted in a significant inhibition in the number of lung colonies produced by B16-BL6 cells injected i.v. The effect of batimastat on spontaneous metastases was examined in mice inoculated in the hind footpad with B16-BL6 melanoma. The primary tumor was removed surgically after 26-28 days. Batimastat was administered twice a day from day 14 to day 28 (pre-surgery) or from day 26 to day 44 (post-surgery). With both protocols, the median number of lung metastases was not significantly affected, but there was a significant reduction in the weight of the metastases. Finally, the effect of batimastat was examined on s.c. growth of B16-BL6 melanoma. Batimastat administered daily, starting at day of tumor transplantation, resulted in a significant growth delay, whereas treatment starting at advanced stage tumor only reduced tumor growth marginally. Our results indicate that a matrix metalloproteinase inhibitor can not only prevent the colonization of secondary organs by B16-BL6 cells but also limit the growth of solid tumors.

No abstract

The neuronal protein tyrosine phosphatases encoded by mouse gene Ptprr (PTPBR7, PTP-SL, PTPPBSc-42 and PTPPBSc-37) have been implicated in mitogen-activated protein (MAP) kinase deactivation on the basis of transfection experiments. To determine their physiological role in vivo, we generated mice that lack all PTPRR isoforms. The cerebellum is the major centre of fine motor coordination in the central nervous system, and in addition serves in cognitive processing and sensory discrimination. Abbreviations used: DUSP, dual-specificity phosphatase; ERK, extracellular signal-regulated kinase; KIM, kinase interaction motif; MAPK, mitogen-activated protein kinase; PTP, protein tyrosine phosphatase.

Citrullinated histone epitopes are involved in the very early stages of inflammatory responses. An important early event is the activation of neutrophils. It has been shown that Peptidyl Arginine Deiminase (PAD) expression levels increase upon pro-inflammatory signalling followed by activation of neutrophils. Subsequently, PAD enzymes cause histone citrullination in the activated neutrophils. Histone citrullination is involved in various processes. One of the most important is NETosis, which results in the release of citrullinated histones to the extracellular space. There, they are involved in Neutrophil Extracellular Trap (NET) formation, which intensifies the inflammatory response. The central role of citrullinated histones in early inflammation makes NETs an attractive target for inflammatory disease intervention. Moreover, the safety profile is expected to be superior to immune-suppressing biologicals, like anti-Tumour Necrosis Factor (TNF) drugs. It is anticipated that shielding citrullinated histone epitopes from the immune system, as well as interfering with their putative roles in the inflammatory response, will have a broad applicability in preventing and treating various inflammatory diseases, including multiple sclerosis.

We have developed a novel antibody-based treatment for rheumatoid arthritis. In a collagen antibody-induced arthritis mouse model, anti-citrullinated protein antibodies (ACPAs) prevent the onset and/or exacerbation of inflammation, and prevent or strongly reduce joint damage. For the development of this novel therapy, we focussed on rheumatoid arthritis-specific citrullinated peptide epitopes. A growing number of studies indicate that modifications of arginines into citrulline residues are responsible for the initial triggering of autoimmunity and the breaking of tolerance. We identified a subset of human recombinant ACPAs that prevent the onset of inflammation in both collagen-induced arthritis and collagen antibody-induced arthritis mouse models for rheumatoid arthritis. Therapeutic administration of these antibodies resulted in the arrest of the inflammation and prevented a further increase of the inflammatory response. Prophylactic administration significantly prevented the onset of inflammation. Histological analysis of inflamed joints from ACPA treated mice revealed a significant decrease in joint damage, as compared to control animals. To identify the differentiating therapeutic epitope recognized by the therapeutic ACPA (tACPA), we performed comparative immunoprecipitations with therapeutic and non-therapeutic ACPAs using human PAD4deiminated HEK-293 cell lysates, followed by mass spectrometry analysis. The differentiating peptide epitope that is recognized by tACPAs only, is a citrullinated domain of Histone-2A. A second generation of antibodies was selected against this domain by means of phage display and by hybridoma generation. The second generation of tACPAs was comprised of even more potent inhibitors of the inflammatory response. Here, we describe the identification of a series of antibodies directed against a citrullinated epitope present in murine and human histone-2A. In mouse models for rheumatoid arthritis we demonstrate that these tACPAs exhibit a strong anti-inflammatory activity and prevent the occurrence of swelling and joint damage. We propose anti-histone-2A tACPA as a novel therapeutic treatment for rheumatoid arthritis patients.

Dimerisation of receptor-type protein tyrosine phosphatases (RPTPs) represents an appealing mechanism to regulate their enzymatic activity. Studies thus far mostly concern the dimerisation behaviour of RPTPs possessing two tandemly oriented catalytic PTP domains. Mouse gene Ptprr encodes four different protein isoforms (i.e. PTPBR7, PTP-SL and PTPPBSgamma-42/37) that contain a single PTP domain. Using selective membrane permeabilisation we here demonstrate that PTP-SL, like PTPBR7, is a single membrane-spanning RPTP. Furthermore, these two receptor-type PTPs constitutively formed homo- and hetero-meric complexes as witnessed in chemical cross-linking and co-immunoprecipitation experiments, in sharp contrast to the cytosolic PTPPBSgamma-42 and PTPPBSgamma-37 PTPRR isoforms. This multimerisation occurs independently of the PTP domain and requires the transmembrane domain and/or the proximal hydrophobic region. Using overexpression of a PTPBR7 mutant that essentially lacks the intracellular PTP domain-containing segment, a monomer-mimicking state was forced upon full-length PTPBR7 immunoprecipitates. This resulted in a significant increase in the enzymatic activity of the PTPRR PTP domain, which strengthens the notion that multimerisation represents a general mechanism to tone down RPTP catalytic activity.

The interleukin-1alpha(IL-1) gene was introduced by retroviral gene transfer into the A375P human melanoma cell line. Two hygromycin-resistant colonies, colony 3 and colony 6, which respectively do not and do express and release IL-1, were selected on the basis of Northern blot and ELISA. Both colonies adhered to resting human endothelial cells (EC) to the same extent. Pre-treatment of EC for 6 hr with conditioned medium (CM) from colony 6, but not from colony 3, increased the adhesion of A375P melanoma and HT-29 colon-carcinoma cells to EC. This increase was blocked by adding interleukin-l-receptor antagonist (IL-1ra) to the EC monolayer. Treatment of EC with colony-6-CM increased the expression of intercellular-adhesion molecule I (ICAM-1), vascular-cell-adhesion molecule I (VCAM-1) and E-selectin. Co-cultivation of colony-6 but not colony-3 melanoma cells with EC caused time-dependent increased expression of these adhesion proteins, reflecting their kinetics of expression on EC. Treating the EC with monoclonal antibodies to VCAM-1 and E-selectin abolished the colony-6-CM-induced increase in adhesion respectively to A375P melanoma and HT-29 colon-carcinoma cells. In vivo, i.v. injection of colony-6 cells in nude mice increased the expression of VCAM-1 on lung microvascular EC. The retention of radiolabeled A375P melanoma cells in the lung was increased in nude mice primed with colony-6 cells, but not with colony-3 cells, injected 6 hr earlier. These results demonstrate that IL-1 produced constitutively by transformed A375P melanoma cells is functionally active, inducing adhesion molecules on EC that enhance their adhesiveness for tumor cells and increase tumor-cell retention in the lung of nude mice.