Ultimate discrimination between specific and unspecific effects would require further benchmarking with other S1P1 competitive antagonists

Ultimate discrimination between specific and unspecific effects would require further benchmarking with other S1P1 competitive antagonists. Overall, the present study suggests that, in the rat, specific competitive S1P1 antagonism-induced disruption of S1P1-dependent homeostasis of vascular permeability is associated with a concomitant disruption in the S1P1-dependent control of pleural permeability. provoked by NIBR-0213 treatments in rats. Mean body and organ weights in rats after 2 weeks of oral treatment with NIBR-0213 at 30, 100 or 300 mg/kg QD, or its vehicle. Results are mean s.e.m (n = 10/group/sex). *p<0.05(DOC) pone.0168252.s003.doc (70K) GUID:?A1E6E0AF-4303-4585-BEEA-A4518F230ACA S4 Table: Microscopic findings in lungs and heart of rats treated with NIBR-0213 over 2 weeks. Individual severity GRADES (- = none; 1 = minimal/very few and small; 2 = slight/few/small; 3 = moderate/moderate number and size; 4 = marked/many/ large) of the microscopic findings in lungs and heart of rats treated with NIBR-0213 or its vehicle. For each group, the Grades are indicated under the same the rat-order.(DOC) pone.0168252.s004.doc (63K) GUID:?6CD11041-EE31-416F-B253-53887DFD597B Data Availability StatementAll relevant data are within the paper and its Supporting Information files.NIBR-0213 is available upon requests and signature of Material Transfer Agreement. Abstract Rational Homeostasis of vascular barriers depends upon sphingosine 1-phosphate (S1P) signaling via the S1P1 receptor. Piperlongumine Accordingly, S1P1 competitive antagonism is known to reduce vascular barrier integrity with still unclear pathophysiological consequences. This was explored in the present study using NIBR-0213, a potent and selective S1P1 competitive antagonist. Results NIBR-0213 was tolerated at the efficacious oral dose of 30 mg/kg BID in the rat adjuvant-induced arthritis (AiA) model, with no sign of labored breathing. However, it induced dose-dependent acute vascular pulmonary leakage and pleural effusion that fully resolved within 3C4 days, as evidenced by Piperlongumine MRI monitoring. At the supra-maximal oral dose of 300 mg/kg QD, NIBR-0213 impaired lung function (with increased breathing rate and reduced tidal volume) within the first 24 hrs. Two weeks of NIBR-0213 oral dosing at 30, 100 and 300 mg/kg QD induced moderate pulmonary changes, characterized by alveolar wall thickening, Piperlongumine macrophage accumulation, fibrosis, micro-hemorrhage, edema and necrosis. In addition to this picture of chronic inflammation, perivascular edema and myofiber degeneration observed in the heart were also indicative of vascular leakage Piperlongumine and its consequences. Conclusions Overall, these observations suggest that, in the rat, the lung is the main target organ for the S1P1 competitive antagonism-induced acute vascular leakage, which appears first as transient and asymptomatic but could lead, upon chronic dosing, to lung remodeling with functional impairments. Hence, this not only raises the question of organ specificity in the homeostasis of vascular barriers, but also provides insight into the pre-clinical evaluation of a potential safety window for S1P1 competitive antagonists as drug candidates. Introduction Sphingosine 1-phosphate (S1P) in blood contributes to the homeostasis of vascular barriers by maintaining a balanced signaling at the level of specific S1P1, S1P2 and S1P3 receptors on the vascular endothelium [1,2,3,4]. On the one side, tonic S1P1 signaling stabilizes the adherence and tight junctions between cells [5,6] and causes persistent activation of eNOS with NO production and activation of the soluble guanylate cyclase to maintain patency of the vessels [6]. On the other side, S1P2 and/or Piperlongumine S1P3 signaling is associated with a disruption of adherent junctions and an increase in paracellular permeability [5,7,8]. This has been clearly substantiated by studies demonstrating that selective pharmacological antagonism at the level of S1P1 receptors could disrupt the physiologic S1P-signaling to become S1P2/S1P3-dominant and result in a marked loss of capillary integrity and vascular leakage [9,10]. Similar observations were made with all S1P1-selective FSCN1 competitive antagonists described thus far [11]. Although the molecular mechanisms involved in the vascular leakage resulting from S1P1 competitive antagonism are well understood, little is known about their pathophysiological consequences. Observations have thus far been limited to acute pulmonary edema [9,12,13,14,15], raising important questions concerning the reasons for such an apparent lung selective phenomenon, as well as about its duration and relevance. Hence, the primary goal of the present study was to refine our understanding on the acute long term impacts of S1P1 competitive antagonism mediated barrier changes with the help of NIBR-0213, a potent and selective S1P1 competitive antagonist which had previously demonstrated lung leakage effect but also good oral efficacy and tolerability in a mouse model of autoimmune disease [15]. The Medicinal Chemistry program that invented NIBR-0213 [14,16] was initiated upon demonstration that the pharmacological activity of FTY720/fingolimod, the well well-established S1P1 agonist now widely approved for the treatment of relapsing-remitting multiple sclerosis (MS) [17], was dependent upon S1P1 receptor internalization/degradation resulting in a so-called functional antagonism of receptor signaling, with abrogation of S1P-driven egress of peripheral blood lymphocytes (PBL) from lymph nodes [18,19,20]. This.