Contribution of peptidyl prolyl isomerase (Pin1) to development of pulmonary hypertension via pulmonary vascular endothelial cell dysfunction

Background

Endothelial dysfunction is thought to be a major contributor to overall pathogenesis of vasculopathy seen in pulmonary hypertension (PH), which is manifested by the impaired release of nitric oxide (NO) generated through endothelial nitric oxide synthase (eNOS) in endothelial cells. Activation of human eNOS is regulated by phosphorylation at multiple sites including Thr33 and Ser114, which residues are followed by Pro. The peptidyl isomerase Pin1 specifically isomerizes the phospho-protein having Ser/Thr-Pro bond and regulates their activity. Pin1 is involved in proliferation, cell cycle, and apoptosis in cancer, by isomerizing some functional molecules such as JNK, JUN, cyclin D, BAX, etc. However, it is controversial whether direct interaction of Pin1 with eNOS and how eNOS activity is altered by Pin1, especially in PH.

Purpose

We aimed to clarify whether Pin1 contributes to the PH development using Pin1 knockout mice and Pin1 affects the expression of phosphorylated eNOS (p-eNOS) molecule and pulmonary arterial endothelial cell (PAEC) apoptosis.

Methods and results

Wild (WT) and Pin1-deficient mice (KO) were exposed to hypoxia (10% O2) or normoxia for 3 weeks to generate hypoxia-induced PH. Hypoxia-inducible factor (HIF1α) expression in lungs was significantly enhanced in WT-hypoxia (WH, n=6) and KO-hypoxia (KH, n=6), suggesting that hypoxic response was certainly occurred in these mice. Pulmonary arterial pressure did not elevate in KH compared with KO-normoxia (KN, n=6) and WT-normoxia (WN, n=6), it was significantly increased only in WH (P<0.01), indicating that KO did not develop PH by hypoxia. The gain of RV weight was parallel to the increase of pulmonary arterial pressure. Western blot showed that p-eNOS expression in lungs was significantly decreased in WH compared to WN, however, the expression was not different between KH and KN. It suggests that Pin1 plays a regulatory role in p-eNOS expression in hypoxic response. In cultured PAECs, the expression of p-eNOS and eNOS was markedly increased by siRNA-mediated Pin1 knockdown. Immunoprecipitation study showed the possibility of Pin1 binding to p-eNOS molecule. Apoptosis evaluated by caspase-3/7 activity by fluorescent assay and cleaved caspase-3 expression by Western blot was significantly increased by Pin1 overexpression in PAECs; however, it was significantly decreased by Pin1 knockdown. Moreover, the exaggeration of apoptosis induced by doxorubicin was markedly increased by Pin1 overexpression compared with control in PAECs; however, it was clearly suppressed by Pin1 knockdown.

Conclusion

This study suggests that endogenous Pin1 contributes to the development of PH partly via the dysfunction of PAECs, that is, by the interference with p-eNOS expression and by the increase of apoptosis inducibility to external stimuli.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): JSPS KAKENHI

Serum immunoglobulin G antibody titer to Fusobacterium nucleatum is associated with unfavorable outcome after stroke

Stroke can be a cause of death, while in non-fatal cases it is a common cause of various disabilities resulting from associated brain damage. However, whether a specific periodontal pathogen is associated with increased risk of unfavorable outcome after stroke remains unknown. We examined risk factors for unfavorable outcome following stroke occurrence, including serum antibody titers to periodontal pathogens. The enrolled cohort included 534 patients who had experienced an acute stroke, who were divided into favorable (n = 337) and unfavorable (n = 197) outcome groups according to modified ranking scale (mRS) score determined at 3 months after onset (favorable = score 0 or 1; unfavorable = score 2-6). The associations of risk factors with unfavorable outcome, including serum titers of IgG antibodies to 16 periodontal pathogens, were examined. Logistic regression analysis showed that the initial National Institutes of Health stroke scale score [odds ratio (OR) = 1·24, 95% confidence interval (CI) = 1·18-1·31, P < 0·001] and C-reactive protein (OR = 1·29, 95% CI = 1·10-1·51, P = 0·002) were independently associated with unfavorable outcome after stroke. Following adjustment with those, detection of the antibody for Fusobacterium nucleatum ATCC 10953 in serum remained an independent predictor of unfavorable outcome (OR = 3·12, 95% CI = 1·55-6·29, P = 0·002). Determination of the antibody titer to F. nucleatum ATCC 10953 in serum may be useful as a predictor of unfavorable outcome after stroke.

P6012Active selexipag metabolite MRE-269 increases endothelin receptors in pulmonary artery smooth muscle cells

Background

The pathology of pulmonary arterial hypertension (PAH) indicates the abnormal outgrowth of pulmonary artery smooth muscle cells (PASMCs) of the media. Abundant expression of endothelin 1 (ET-1) is observed in vessels of PAH, and has been considered to play a pathogenic role. There are several endothelin receptors including ETA, ETB. Compared to ETA, ETB mRNA is less expressed in PASMCs from control individuals, and is reported to be increased in those from PAH patients. However, how ETB is involved in PAH remains unclear. Selexipag, a non-prostanoid IP receptor agonist, was recently authorized for treating PAH. Compared to selexipag, the active metabolite MRE-269 has a higher affinity for the IP receptor. Initial combination therapy come to be accepted as a standard strategy for this disease, although the interaction of each drug has not been discussed enough.

Purpose

To assess the effect of selexipag on ET-1 receptors in PASMCs.

Methods

We stimulated purchased human PASMCs and endothelial cells by MRE-269 (300 nM), ET-1 (100 nM) or combination of them in vitro. Quantitative PCR was performed to quantify mRNA expressions. Cell proliferation was assessed by CCK8 cell proliferation assay kit. BQ123, A192621, bosentan was used as blocker against ETA, ETB, or both, respectively.

Results

In PASMCs, MRE-269 increased ETA and ETB expressions 2- and 7-fold, respectively. On the other hand, it increased ETB 1.2-fold in pulmonary artery endothelial cells; ETA was not detected in those cells. After pretreatment by MRE-269, ET-1 accelerated the proliferation of PASMCs. A192621 and bosentan abrogated this proliferation. In contrast, BQ123 did not abrogate it.

Conclusions

In PASMCs, active selexipag metabolite MRE-269 increases ETB more strongly than ETA, resulting in accelerated cell proliferation by ET-1 predominantly via ETB. These data call for further study focused on the choice of ET-1 receptor antagonists in the case of combination therapy with selexipag.

Enhancement of Saltiness Perception by Monosodium Glutamate Taste and Soy Sauce Odor: A Near-Infrared Spectroscopy Study

Previous studies have reported that the umami taste of monosodium l-glutamate (MSG) and salty-smelling odors (e.g., soy sauce, bacon, sardines) enhance the perception of saltiness. This study aimed to investigate the neural basis of the enhancement of saltiness in human participants using functional near-infrared spectroscopy (fNIRS). University students who had passed a taste panel test participated in this study. Sodium chloride solutions were presented with or without either 0.10% MSG or the odor of soy sauce. The participants were asked to drink a cup of the stimulus and to evaluate only saltiness intensity in Experiment 1, as well as other sensory qualities in Experiment 2, and temporal brain activity was measured using fNIRS. In Experiment 3, the participants were asked to evaluate saltiness intensity using the time-intensity (TI) method, and the response of the parotid salivary glands was measured using fNIRS. The fNIRS data showed that the added MSG and soy sauce enhanced the hemodynamic response in temporal brain regions, including the frontal operculum, but no effect on the hemodynamic salivary responses was detected. These results indicate that the perceived enhancement of saltiness occurs in the brain region that is involved in central gustatory processing. Furthermore, the results of the sensory evaluations suggest that enhancement of saltiness by the addition of MSG is mainly based on fusion of the salty-like property of MSG and saltiness of NaCl, whereas enhancement by the addition of soy sauce odor is mainly based on modulation of the temporal dynamics of saltiness perception.

Observation of the flexoelectricity of a SrTiO3 single crystal by x-ray absorption and emission spectroscopies

Flexoelectricity, defined as the spontaneous electric polarization in a dielectric material induced by a strain gradient, is investigated from the microscopic viewpoint by x-ray spectroscopy. A single crystal SrTiO₃ sample was used as a test system in order to reveal the appearance of the electric dipole moment by simple bending of the crystal. The spectral change characteristic of ferroelectric transition in SrTiO₃ was not observed in the Ti K-edge absorption spectra. Instead, the gradual decrease (increase) of the post-edge feature (pre-edge structure) by bending was qualitatively explained using theoretical calculations that assumed the presence of oxygen vacancies and a slight crystal distortion. This assumption is also supported by the broadening of a tiny charge-transfer peak in the Ti Kβ resonant emission spectra. Therefore, it was revealed that the flexoelectric effect in SrTiO₃ is easily drowned out through local imperfection induced by crystal deformations and cracks.

The identification of raft-derived tau-associated vesicles that are incorporated into immature tangles and paired helical filaments

AIMS

Neurofibrillary tangles (NFTs), a cardinal pathological feature of neurodegenerative disorders, such as Alzheimer's disease (AD) are primarily composed of hyper-phosphorylated tau protein. Recently, several other molecules, including flotillin-1, phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2] and cyclin-dependent kinase 5 (CDK5), have also been revealed as constituents of NFTs. Flotillin-1 and PtdIns(4,5)P2 are considered markers of raft microdomains, whereas CDK5 is a tau kinase. Therefore, we hypothesized that NFTs have a relationship with raft domains and the tau phosphorylation that occurs within NFTs.

METHODS

We investigated six cases of AD, six cases of other neurodegenerative diseases with NFTs and three control cases. We analysed the PtdIns(4,5)P2-immunopositive material in detail, using super-resolution microscopy and electron microscopy to elucidate its pattern of expression. We also investigated the spatial relationship between the PtdIns(4,5)P2-immunopositive material and tau kinases through double immunofluorescence analysis.

RESULTS

Pretangles contained either paired helical filaments (PHFs) or PtdIns(4,5)P2-immunopositive small vesicles (approximately 1 μm in diameter) with nearly identical topology to granulovacuolar degeneration (GVD) bodies. Various combinations of these vesicles and GVD bodies, the latter of which are pathological hallmarks observed within the neurons of AD patients, were found concurrently in neurons. These vesicles and GVD bodies were both immunopositive not only for PtdIns(4,5)P2, but also for several tau kinases such as glycogen synthase kinase-3β and spleen tyrosine kinase.

CONCLUSIONS

These observations suggest that clusters of raft-derived vesicles that resemble GVD bodies are substructures of pretangles other than PHFs. These tau kinase-bearing vesicles are likely involved in the modification of tau protein and in NFT formation.