Serotonylated fibronectin is elevated in pulmonary hypertension

Abstract

Serotonin (5-HT) and fibronectin (FN) have been associated with pulmonary hypertension (PH). We previously reported that FN is posttranslationally modified by tissue transglutaminase (TGase) to form serotonylated FN (s-FN) in pulmonary artery smooth muscle cells and that serotonylation stimulates their proliferation and migration, hallmarks of PH. We hypothesized that s-FN and its binding to TGase are elevated in human and experimental PH. To assess this hypothesis, FN isolation and electrophoretic, immunoblotting, and densitometric techniques were used. Mean ratio of serum s-FN to total FN level (s-FN/FN) was elevated in 19 consecutive pulmonary arterial hypertension (PAH) patients compared with 25 controls (0.3 Ϯ 0.18 vs. 0.05 Ϯ 0.07, P Ͻ 0.001). s-FN/FN also was increased in lungs of mice and rats with hypoxiainduced PH and in rats with monocrotaline-induced PH. In mice, the increase was detected at 1 wk of hypoxia, preceding the development of PH. Hypoxic rats had elevated serum s-FN/FN. Enhanced binding of TGase to its substrate FN occurred in serum from patients with PAH (mean 0.50 Ϯ 0.51 vs. 0.063 Ϯ 0.11, P ϭ 0.002) and s-FN/FN and TGase-bound FN were highly correlated (R 2 ϭ 0.77). TGasebound FN also was increased in experimental PH. We conclude that increased serotonylation of FN occurs in human and experimental PH and may provide a biomarker for the disease.serotonin; transglutaminase; transglutamidation; hypoxia-and monocrotaline-induced pulmonary hypertension STRONG LINES OF EVIDENCE FROM human and experimental animal models support a role for serotonin (5-HT) and the serotonin transporter (SERT) in the pathogenesis of pulmonary hypertension (PH). Herve et al. (11,12) first identified elevation of plasma 5-HT and reduced platelet 5-HT in association with pulmonary arterial hypertension (PAH) in patients with familial platelet storage disease. About this time it also became recognized that PH is associated with appetite-suppressing derivatives of fenfluramine (e.g., Ref. 1), which along with 5-HT is a substrate for the 5-HT transporter (SERT) (19,30). In the mid-1980s our laboratory reported that exposure of endothelial and smooth muscle cells (SMCs) to hypoxia enhanced cellular transcription of SERT and that this was related to increased cellular glycolysis (17,18). This observation fitted well with known hypoxia-induced PH, later reports of elevated plasma 5-HT in mice developing PH after hypoxic exposure (3) and elevated plasma levels of 5-HT in humans with the idiopathic form of PAH (15). Eddahibi and associates (6) carried these observations further with studies on transgenic mice in which SERT knockout animals failed to develop hypoxia-induced PH and animals selectively overexpressing vascular SERT with a SM22-targeted promoter spontaneously developed PH (9). Furthermore, these investigators reported elevated expression of SERT in cultured pulmonary artery SMCs from patients with PH. A promoter polymorphism in SERT has been described in humans, and the LL genotype has been associated with higher...

Calpain-1 regulates platelet function in a humanized mouse model of sickle cell disease

“…In the present study, we observed severe hypertrophy of the right and left ventricles of SS and SSCKO mice (Figures 5B – C), resulting in a normal Fulton ratio (Figure 5D). Despite the ventricular hypertrophy, SS and SSCKO mice displayed normal right ventricular systolic pressure (RVSP) (Figure 5E), a common measure of PAH [31, 32]. Thus, our results suggest that the Townes sickle mice might be a model of ventricular dysfunction but not PAH.…”

“…For PAH, steady state and H/R-treated mice were examined for right ventricular systolic pressure (RVSP) as previously described [31, 32]. …”

Tissue transglutaminase promotes serotonin-induced AKT signaling and mitogenesis in pulmonary vascular smooth muscle cells

“…Guilluy et al reported TGase-dependent Rho activation and depletion by 5-HT in vascular SMCs [15], and also elevation of serotonylated RhoA in platelets and vascular tissues of PAH patients [16]. Our own studies have shown elevated serotonylated fibronectin in the serum of PAH patients and in animal models of pulmonary hypertension that we have linked to TG2 [17]. Moreover, the TG2 inhibitor ERW1041E mitigates pulmonary hypertension in a rodent model [18].…”

Regulation of the activities of the mammalian transglutaminase family of enzymes

“…Indeed, this may be the mechanism for hypoxia induced, TG2 catalyzed serotonylation of fibronectin in rodent models of pulmonary hypertension. 20 In addition, and perhaps more importantly, selective recognition of TG2 by the protein cofactor thioredoxin 1 leads to highly efficient activation of oxidized TG2. 16 The precise mechanisms for thioredoxin secretion into the extracellular matrix remain to be established, although at least one pro-inflammatory signal has been identified.…”