Platelets and platelet-derived serotonin promote tissue repair after normothermic hepatic ischemia in mice

The roles of liver sinusoidal endothelial cells in liver ischemia/reperfusion injury

Liver ischemia/reperfusion injury (IRI) is a major complication after partial hepatectomy and liver transplantation and during hypovolemic shock and hypoxia-related diseases. Liver IRI is a current research hotspot. The early stage of liver IRI is characterized by injury and dysfunction of liver sinusoidal endothelial cells (LSECs), which, along with hepatocytes, are the major cells involved in liver injury. In this review, we elaborate on the roles played by LSECs in liver IRI, including the pathological features of LSECs, LSECs exacerbation of the sterile inflammatory response, LSECs interactions with platelets and the promotion of liver regeneration, and the activation of LSECs autophagy. In addition, we discuss the study of LSECs as therapeutic targets for the treatment of liver IRI and the existing problems when applying LSECs in liver IRI research.

Platelet lifespan and mechanisms for clearance

PURPOSE OF REVIEW

Activated or aged platelets are removed from circulation under (patho)physiologic conditions, the exact mechanism of platelet clearance under such conditions remains unclear and are currently being investigated. This review focuses on recent findings and controversies regarding platelet clearance and the disruption of platelet life cycle.

RECENT FINDINGS

The platelet life span is determined by glycosylation of platelet surface receptors with sialic acid. Recently, it was shown that platelet activation and granule release leads to desialylation of glycans and accelerated clearance of platelets under pathological conditions. This phenomenon was demonstrated to be a main reason for thrombocytopenia being a complication in several infections and immune disorders.

SUMMARY

Although we have recently gained some insight into how aged platelets are cleared from circulation, we are still not seeing the full picture. Further investigations of the platelet clearance pathways under pathophysiologic conditions are needed as well as studies to unravel the connection between platelet clearance and platelet production.

Intravital Imaging of Thrombosis Models in Mice

Intravital microscopy is a powerful tool to study thrombosis in real time. The kinetics of thrombus formation and progression in vivo is studied after inflicting damage to the endothelium through mechanical, chemical, or laser injury. Mouse models of atherosclerosis are also used to induce thrombus formation. Vessels of different sizes and from different vascular beds such as carotid artery or vena cava, mesenteric or cremaster arterioles, can be targeted. Using fluorescent dyes, antibodies, or reporter mouse strains allows to visualize key cells and factors mediating the thrombotic processes. Here, we review the latest literature on using intravital microscopy to study thrombosis as well as thromboinflammation following transient middle cerebral artery occlusion, infection-induced immunothrombosis, and liver ischemia reperfusion.

Tyrosine phosphorylation of YAP-1 in biliary epithelial cells mediates posthepatectomy liver regeneration and is affected by serotonin

Experimental data suggested activation of yes-associated protein (YAP-1) as a critical regulator of liver regeneration (LR). Serotonin (5-HT) promotes LR in rodent models and has been proposed to act via YAP-1. How 5-HT affects LR is incompletely understood. A possible mechanism how 5-HT affects human LR was explored. Sixty-one patients were included. Tissue samples prior and 2 h after induction of LR were collected. Circulating levels of 5-HT and osteopontin (OPN) were assessed. YAP-1, its phosphorylation states, cytokeratin 19 (CK-19) and OPN were assessed using immunofluorescence. A mouse model of biliary epithelial cells (BECs) specific deletion of YAP/TAZ was developed. YAP-1 increased as early as 2 h after induction of LR (p = 0.025) predominantly in BECs. BEC specific deletion of YAP/TAZ reduced LR after 70% partial hepatectomy in mice (Ki67%, p < 0.001). SSRI treatment, depleting intra-platelet 5-HT, abolished YAP-1 and OPN induction upon LR. Portal vein 5-HT levels correlated with intrahepatic YAP-1 expression upon LR (R = 0.703, p = 0.035). OPN colocalized with YAP-1 in BECs and its circulating levels increased in the liver vein 2 h after induction of LR (p = 0.017). In the context of LR tyrosine-phosphorylated YAP-1 significantly increased (p = 0.042). Stimulating BECs with 5-HT resulted in increased YAP-1 activation via tyrosine-phosphorylation and subsequently increased OPN expression. BECs YAP-1 appears to be critical for LR in mice and humans. Our evidence suggests that 5-HT, at least in part, exerts its pro-regenerative effects via YAP-1 tyrosine-phosphorylation in BECs and subsequent OPN-dependent paracrine immunomodulation.

Transplantation of a human liver following 3 days of ex situ normothermic preservation

Current organ preservation methods provide a narrow window (usually <12 hours) to assess, transport and implant donor grafts for human transplantation. Here we report the transplantation of a human liver discarded by all centers, which could be preserved for several days using ex situ normothermic machine perfusion. The transplanted liver exhibited normal function, with minimal reperfusion injury and the need for only a minimal immunosuppressive regimen. The patient rapidly recovered a normal quality of life without any signs of liver damage, such as rejection or injury to the bile ducts, according to a 1-year follow up. This inaugural clinical success opens new horizons in clinical research and promises an extended time window of up to 10 days for assessment of viability of donor organs as well as converting an urgent and highly demanding surgery into an elective procedure.

Targeting the Hepatic Microenvironment to Improve Ischemia/Reperfusion Injury: New Insights into the Immune and Metabolic Compartments

Hepatic ischemia/reperfusion injury (IRI) is mainly characterized by high activation of immune inflammatory responses and metabolic responses. Understanding the molecular and metabolic mechanisms underlying development of hepatic IRI is critical for developing effective therapies for hepatic IRI. Recent advances in research have improved our understanding of the pathogenesis of IRI. During IRI, hepatocyte injury and inflammatory responses are mediated by crosstalk between the immune cells and metabolic components. This crosstalk can be targeted to treat or reverse hepatic IRI. Thus, a deep understanding of hepatic microenvironment, especially the immune and metabolic responses, can reveal new therapeutic opportunities for hepatic IRI. In this review, we describe important cells in the liver microenvironment (especially non-parenchymal cells) that regulate immune inflammatory responses. The role of metabolic components in the diagnosis and prevention of hepatic IRI are discussed. Furthermore, recent updated therapeutic strategies based on the hepatic microenvironment, including immune cells and metabolic components, are highlighted.

Association Between Platelet Levels on Admission and 90-day Mortality in Patients With Exertional Heatstroke, a 10 Years Cohort Study

Background: Heatstroke is a common clinical symptom in summer with high mortality requiring identification of appropriate and rapid methods of assessment.

Method: This is a retrospective study that included the recent 10 years clinical data of heatstroke patients. A total of n = 186 patients were included in this study and grouped based on platelet (PLT) abnormality observed on admission.

Results: In the study group, n = 120 patients (64.5%) patients had normal PLT and n = 66 patients (35.5%) had abnormal PLT. Compared with PLT-normal group, PLT-abnormal group had higher Acute Physiology and Chronic Health Evaluation II (APACHE II) scores [median 15.0 (IQR 11.5–21.5) vs. 9.0 (IQR 7.0–12.5)] and SOFA scores [median 6.0 (IQR 4.0–10.0) vs. 2.0 (IQR 2.0–4.0)], lower Sequential Organ Failure Assessment (GCS)[median 8.0 (IQR 5.0–12.0) vs. 13.0 (IQR 9.0–14.0)]. The PLT-abnormal group had severe organ damage, including damage to the coagulation system, liver, and kidney (all p < 0.05). Significant differences were noted in 90-day survival between the two groups even after correction for Age, GCS, White blood cell count (WBC), Neutrophil, International normalized ratio (INR), Activated partial thromboplastin time (APTT), Procalcitonin (PCT), Alanine aminotransferase (ALT), Creatine (CR), D-Dime (D-D) (Before correction P < 0.001; After correction P = 0.009).The area under the ROC curve for the prediction of mortality based on PLT was 80.7% (95% CI 0.726–0.888, P < 0.001), the optimal cutoff value was 94, the sensitivity was 77.3%, and the specificity was 82.6%.

Conclusion: Patients with heatstroke with platelet abnormalities during admission have more severe organ impairment and a lower 90-day survival rate even when adjusted for other factors.

A narrative review of liver regeneration-from models to molecular basis

Objective

To elucidate the characteristics of different liver regeneration animal models, understand the activation signals and mechanisms related to liver regeneration, and obtain a more comprehensive conception of the entire liver regeneration process.

Background

Liver regeneration is one of the most enigmatic and fascinating phenomena of the human organism. Despite suffering significant injuries, the liver still can continue to perform its complex functions through the regeneration system. Although advanced topics on liver regeneration have been proposed; unfortunately, complete regeneration of the liver has not been achieved until now. Therefore, increasing understanding of the liver regenerative process can help improve our treatment of liver failure. It will provide a new sight for the treatment of patients with liver injury in the clinic.

Methods

Literatures on liver regeneration animal models and involved basic research on molecular mechanisms were retrieved to analyze the characteristics of different models and those related to molecular basis.

Conclusions

The process of liver regeneration is complex and intricate, consisting of various and interactive pathways. There is sufficient evidence to demonstrate that liver regeneration is similar between humans and rodents. At the same time, many of the same cytokines, growth factors, and signaling pathways are relevant. There are many gaps in our current knowledge. Understanding of this knowledge will provide more supportive clinical treatment strategies, including small-scale liver transplantation and high-quality regenerative process after surgical resection, and offer possible targets to treat the dysregulation of regeneration that occurs in chronic hepatic diseases and tumors. Current research work, such as the use of animal models as in vivo vectors for high-quality human hepatocytes, represents a unique and significant cutting edge in the field of liver regeneration.

Attenuation of peripheral serotonin inhibits tumor growth and enhances immune checkpoint blockade therapy in murine tumor models

[Figure: see text].

Phenylalanine hydroxylase contributes to serotonin synthesis in mice

Serotonin is an important signaling molecule in the periphery and in the brain. The hydroxylation of tryptophan is the first and rate-limiting step of its synthesis. In most vertebrates, two enzymes have been described to catalyze this step, tryptophan hydroxylase (TPH) 1 and 2, with expression localized to peripheral and neuronal cells, respectively. However, animals lacking both TPH isoforms still exhibit about 10% of normal serotonin levels in the blood demanding an additional source of the monoamine. In this study, we provide evidence by the gain and loss of function approaches in in vitro and in vivo systems, including stable-isotope tracing in mice, that phenylalanine hydroxylase (PAH) is a third TPH in mammals. PAH contributes to serotonin levels in the blood, and may be important as a local source of serotonin in organs in which no other TPHs are expressed, such as liver and kidney.

Serotonin as a Mitogen in the Gastrointestinal Tract: Revisiting a Familiar Molecule in a New Role

Serotonin signaling is ubiquitous in the gastrointestinal (GI) system, where it acts as a neurotransmitter in the enteric nervous system (ENS) and influences intestinal motility and inflammation. Since its discovery, serotonin has been linked to cellular proliferation in several types of tissues, including vascular smooth muscle, neurons, and hepatocytes. Activation of serotonin receptors on distinct cell types has been shown to induce well-known intracellular proliferation pathways. In the GI tract, potentiation of serotonin signaling results in enhanced intestinal epithelial proliferation, and decreased injury from intestinal inflammation. Furthermore, activation of the type 4 serotonin receptor on enteric neurons leads to neurogenesis and neuroprotection in the setting of intestinal injury. It is not surprising that the mitogenic properties of serotonin are pronounced within the GI tract, where enterochromaffin cells in the intestinal epithelium produce 90% of the body's serotonin; however, these proliferative effects are attributed to increased serotonin signaling within the ENS compartment as opposed to the intestinal mucosa, which are functionally and chemically separate by virtue of the distinct tryptophan hydroxylase enzyme isoforms involved in serotonin synthesis. The exact mechanism by which serotonergic neurons in the ENS lead to intestinal proliferation are not known, but the activation of muscarinic receptors on intestinal crypt cells indicate that cholinergic signaling is essential to this signaling pathway. Further understanding of serotonin's role in mucosal and enteric nervous system mitogenesis may aid in harnessing serotonin signaling for therapeutic benefit in many GI diseases, including inflammatory bowel disease, malabsorptive conditions, and cancer.

Analysis of survival rates and prognosis of hepatoblastoma in children: a retrospective study from a single center in China

Hepatoblastoma (HB) is the most common liver cancer in children, this study aims at analyzing the prognostic factors affecting the survival rates and summarizing the treatment experience. In this study, we reviewed patients with primary HB under the age of 14 years who underwent complete tumor resection from June 1997 to March 2019. The data of 72 patients were collected. Survival analysis was performed by Kaplan-Meier, multivariate Cox proportional hazards regression and linear mixed model for repeated measures (LMMRM). The 5-year and the 10-year event-free survival (EFS) of all patients were 78.2% and 73%, respectively. Both the 5-year and 10-year overall survival (OS) were 85.7%. Kaplan-Meier survival analysis showed that patients with tumor capsule infiltration (TCI) and patients with surgical margin less than 1 cm may also have a good prognosis. The Cox proportional hazards regression model analysis results were similar to the Kaplan-Meier analysis results. LMMRM analysis showed that there were significant differences in platelet, alpha-fetoprotein, C-reactive protein and hemoglobin values after surgery in the metastasis group (P < 0.05). This study suggests that patients with TCI or narrow surgical margin (<1 cm) may also have a good prognosis, and the risk stratification of HB can be used as the latest grading standard to evaluate the prognosis of patients.

Perioperative Changes in Platelet Counts During Adult Liver Transplantation

OBJECTIVES

Thrombocytopenia is a common problem among liver transplant recipients. However, various patterns of change in platelet counts during adult liver transplant have been reported in the literature. This study aimed to evaluate alterations in platelet count according to the surgical phase (preanhepatic, anhepatic, after reperfusion) and during the early postoperative period of liver transplant.

MATERIALS AND METHODS

Perioperative data from 100 patients undergoing deceased donor liver transplant were reviewed, including platelet count-related data. Platelet counts were measured at predefined time points throughout the procedure: immediately before induction of anesthesia, at the early neo-hepatic stage (10 min after graft reperfusion), immediately after admission to the intensive care unit posttransplant, and 6 hours posttransplant. Platelet counts were then measured daily during stay in the intensive care unit.

RESULTS

Mean baseline platelet count before transplant and anesthesia was 97.92 × 109/L. A peak platelet count was seen in the early neo-hepatic stage. Platelet counts then decreased sharply in the first 6 hours after transplant. A slight decrease in platelet counts continued until the third day after the surgery; finally, on day 6 posttransplant, platelet counts increased significantly.

CONCLUSIONS

Our study showed a significant sudden increase in platelet counts during the early neo-hepatic phase in many liver transplant recipients. Therefore, our results suggest that it is reasonable to avoid platelet transfusion for most liver transplant recipients during transplant surgery.

Depletion of serotonin relieves concanavalin A-induced liver fibrosis in mice by inhibiting inflammation, oxidative stress, and TGF-β1/Smads signaling pathway

Serotonin exerts important functions in several liver pathophysiological processes. In this study, we investigated the role of serotonin in concanavalin A (Con A)-induced liver fibrosis (LF) in mice and the underlying mechanisms. To establish the mouse model of LF, mice of wild-type (WT) and tryptophan hydroxylase 1 (Tph1) knockout (serotonin depletion) received Con A for 8 successive weeks. Degree of fibrosis was assessed by Sirius red staining, as well as the measurements of alpha smooth muscle actin (α- SMA), hydroxyproline (Hyp) and type I collagen in liver tissues. To elucidate the potential mechanisms, we assessed the effect of serotonin depletion on inflammatory, oxidative stress as well as TGF-β1/Smads signaling pathway. We found that serotonin depletion significantly inhibited collagen deposition as evaluated by less collagenous fiber in Sirus Red staining and reduced contents of Hyp and type I collagen. In addition, the absence of serotonin significantly inhibited the release of several inflammatory cytokines, including interleukin-6 (IL-6), interferon-gamma (IFN-γ), tumor necrosis-alpha (TNF-α), and transforming growth factor β1 (TGF-β1). Oxidative stress was also largely mitigated in LF mice with serotonin deficiency as manifested by the decreases of oxidative stress markers (malonaldehyde (MDA) and myeloperoxidase (MPO)), as well as the increases of antioxidant stress indicators (glutathione (GSH), and GSH-px, catalase (CAT), superoxide dismutase (SOD)) in liver tissues. Moreover, the lack of serotonin may provide an antifibrotic role by inhibiting the intrahepatic expressions of TGF-β1, phosphorylated-smad2 (p-smad2), and phosphorylated-smad3 (p-smad3). These results indicated that, serotonin depletion attenuates Con A-induced LF through the regulation of inflammatory response, oxidative stress injury, and TGF-β1/Smads signaling pathway.

Platelets prevent the development of monocrotaline-induced liver injury in mice

Destruction of liver sinusoidal endothelial cells (LSECs) is an initial event in sinusoidal obstruction syndrome (SOS) that leads to accumulation of platelets in the liver. Herein, we explored the role of platelets during progression of experimental SOS induced by monocrotaline (MCT) in mice. Depletion of platelets using an anti-CD41 antibody or anti-thrombocyte serum exacerbated MCT-induced liver injury in C57BL/6 mice, as indicated by an increase in the alanine transaminase (ALT) level, which was associated with hemorrhagic necrosis. Thrombocytosis induced by thrombopoietin (TPO) or the TPO receptor agonist romiplostim (ROM) attenuated MCT-induced liver injury, as evidenced by lower levels of ALT and mRNA encoding matrix metalloproteinase (MMP) 9, and higher levels of mRNA encoding vascular endothelial growth factor receptor (VEGFR) 2 and VEGFR3. The level of activated hepatic platelets was higher in TPO- and ROM-treated mice than in saline-treated mice. Co-culture with a high number of platelets increased the viability of LSECs and their mRNA levels of CD31, VEGFR2, and VEGFR3, and decreased their mRNA level of MMP9. The level of VEGF-A was increased in the culture medium of LSECs co-cultured with platelets. These results indicate that platelets attenuate MCT-induced liver injury by minimizing damage to LSECs.

Platelets Boost Recruitment of CD133+ Bone Marrow Stem Cells to Endothelium and the Rodent Liver-The Role of P-Selectin/PSGL-1 Interactions

We previously demonstrated that clinical administration of mobilized CD133⁺ bone marrow stem cells (BMSC) accelerates hepatic regeneration. Here, we investigated the potential of platelets to modulate CD133⁺BMSC homing to hepatic endothelial cells and sequestration to warm ischemic livers. Modulatory effects of platelets on the adhesion of CD133⁺BMSC to human and mouse liver-sinusoidal- and micro- endothelial cells (EC) respectively were evaluated in in vitro co-culture systems. CD133⁺BMSC adhesion to all types of EC were increased in the presence of platelets under shear stress. This platelet effect was mostly diminished by antagonization of P-selectin and its ligand P-Selectin-Glyco-Ligand-1 (PSGL-1). Inhibition of PECAM-1 as well as SDF-1 receptor CXCR4 had no such effect. In a model of the isolated reperfused rat liver subsequent to warm ischemia, the co-infusion of platelets augmented CD133⁺BMSC homing to the injured liver with heightened transmigration towards the extra sinusoidal space when compared to perfusion conditions without platelets. Extravascular co-localization of CD133⁺BMSC with hepatocytes was confirmed by confocal microscopy. We demonstrated an enhancing effect of platelets on CD133⁺BMSC homing to and transmigrating along hepatic EC putatively depending on PSGL-1 and P-selectin. Our insights suggest a new mechanism of platelets to augment stem cell dependent hepatic repair.

Low Postoperative Platelet Counts Are Associated with Major Morbidity and Inferior Survival in Adult Recipients of Orthotopic Liver Transplantation

BACKGROUND

Platelets (PLT) play an essential functional role in cellular injury and liver regeneration following partial hepatectomy and orthotopic liver transplantation (OLT). Here, we investigated the association of postoperative PLT counts with short- and long-term outcomes in adult OLT recipients.

METHODS

Three hundred consecutive patients from our prospective OLT database were analyzed retrospectively (May 2010-November 2017). Ninety-day post-OLT complications were graded using the Clavien-Dindo (CD) classification and quantified by the comprehensive complication index (CCI). To determine the prognostic accuracy of PLT counts, the area under the receiver operating characteristic curve (AUROC) was calculated for major complications (CD ≥ 3b). Parametric and non-parametric tests were applied for subgroup analyses. Uni- and multivariable logistic regression analyses were performed to identify risk factors for major complications. Graft and patient survival were analyzed using the Kaplan-Meier method as well as uni- and multivariable Cox regression analyses.

RESULTS

Postoperative day 6 PLT counts < 70 × 10⁹/L (POD6-70) were identified as the best cutoff for predicting major complications (AUROC = 0.7; p < 0.001; Youden index 0.317). The stratification of patients into low- (n = 113) and high-PLT (n = 187) groups highlighted significant differences in major complications (CCI 68 ± 29 vs. 43 ± 28, p < 0.001); length of hospital and intensive care unit (ICU) stay (53 ± 43 vs. 31 ± 25, p < 0.001; 21 ± 29 vs. 7 ± 11, p < 0.001, respectively) and estimated procedural costs. POD6-70 was associated with inferior 5-year graft survival. Multivariable logistic regression analysis identified POD6-70 as an independent predictor of major complications (odds ratio 2.298, confidence intervals 1.179-4.478, p = 0.015).

CONCLUSION

In OLT patients, a PLT count on POD6 of less than 70 × 10⁹/L bears a prognostic significance warranting further investigations.

Dynamics of Platelet Behaviors as Defenders and Guardians: Accumulations in Liver, Lung, and Spleen in Mice

Systemic platelet behaviors in experimental animals are often assessed by infusion of isotope-labeled platelets and measuring them under anesthesia. However, such procedures alter, therefore may not reveal, real-life platelet behaviors. 5-Hydroxytryptamine (5HT or serotonin) is present within limited cell-types, including platelets. In our studies, by measuring 5HT as a platelet-marker in non-anesthetized mice, we identified stimulation- and time-dependent accumulations in liver, lung, and/or spleen as important systemic platelet behaviors. For example, intravenous, intraperitoneal, or intragingival injection of lipopolysaccharide (LPS, a cell-wall component of Gram-negative bacteria), interleukin (IL)-1, or tumor necrosis factor (TNF)-α induced hepatic platelet accumulation (HPA) and platelet translocation into the sinusoidal and perisinusoidal spaces or hepatocytes themselves. These events occurred "within a few hours" of the injection, caused hypoglycemia, and exhibited protective or causal effects on hepatitis. Intravenous injection of larger doses of LPS into normal mice, or intravenous antigen-challenge to sensitized mice, induced pulmonary platelet accumulation (PPA), as well as HPA. These reactions occurred "within a few min" of the LPS injection or antigen challenge and resulted in shock. Intravenous injection of 5HT or a catecholamine induced a rapid PPA "within 6 s." Intravenous LPS injection, within a minute, increased the pulmonary catecholamines that mediate the LPS-induced PPA. Macrophage-depletion from liver and spleen induced "day-scale" splenic platelet accumulation, suggesting the spleen is involved in clearing senescent platelets. These findings indicate the usefulness of 5HT as a marker of platelet behaviors, and provide a basis for a discussion of the roles of platelets as both "defenders" and "guardians."

Platelet and liver regeneration after liver surgery

The success of liver surgery, including resection and transplantation, is largely dependent on the ability of the liver to regenerate. Despite substantial improvement in surgical techniques and perioperative care, one of the main concerns is post-hepatectomy liver failure and early allograft dysfunction, both of which are associated with impaired liver regeneration. Recent studies have demonstrated the positive role of platelets in promoting liver regeneration and protecting hepatocytes; however, the underlying mechanisms responsible for these effects are not fully understood. In this review, we updated the accumulated evidence of the role of platelets in promoting liver regeneration, with a focus on liver resection and liver transplantation. The goal of these studies was to support the clinical implementation of platelet agents, such as thrombopoietin receptor agonists, to augment liver regeneration after liver surgery. This "platelet therapy" may become a treatment choice for post-hepatectomy liver failure and early allograft dysfunction.

Inhibition of serotonin synthesis: A novel therapeutic paradigm

The rate-limiting enzyme in serotonin synthesis is tryptophan hydroxylase (TPH). There are two independent serotonin systems in the body characterized by two isoforms of TPH, TPH1 and TPH2. While TPH2 synthesizes serotonin in the brain, TPH1 is expressed in the gut and in other peripheral tissues and supplies platelets in the circulation with serotonin. This duality of the serotonin system is enforced by the blood-brain barrier which is impermeable for serotonin. In the brain serotonin acts as neurotransmitter and is a main target for the treatment of psychiatric disorders. In the periphery it is released by platelets at the site of activation and elicits numerous physiological effects. TPH1 deficient mice were shown to be protected from diverse diseases including hemostatic, inflammatory, fibrotic, gastrointestinal, and metabolic disorders and therefore serotonin synthesis inhibition emerged as a reasonable therapeutic paradigm. Recently the first TPH inhibitor, telotristat ethyl, came on the market for the treatment of carcinoid syndrome. This review summarizes the state of development and the therapeutic opportunities of such compounds.

Circulating transforming growth factor-β1 facilitates remyelination in the adult central nervous system

Oligodendrocyte maturation is necessary for functional regeneration in the CNS; however, the mechanisms by which the systemic environment regulates oligodendrocyte maturation is unclear. We found that Transforming growth factor (TGF)-β1, which is present in higher levels in the systemic environment, promotes oligodendrocyte maturation. Oligodendrocyte maturation was enhanced by adult mouse serum treatment via TGF-β type I receptor. Decrease in circulating TGF-β1 level prevented remyelination in the spinal cord after toxin-induced demyelination. TGF-β1 administration promoted remyelination and restored neurological function in a multiple sclerosis animal model. Furthermore, TGF-β1 treatment stimulated human oligodendrocyte maturation. These data provide the therapeutic possibility of TGF-β for demyelinating diseases.

CD133+ bone marrow stem cells (BMSC) control platelet activation - Role of ectoNTPDase-1 (CD39)

BACKGROUND

We previously demonstrated CD133+ bone marrow stem cells (BMSC) to promote hepatic proliferation for liver regeneration. Here, we evaluated the capacity of CD133+BMSC to utilize platelets for homing to vasculature and concomitant controlling their aggregability upon ADP stimulation.

METHODS

CD133+BMSC and platelets were co-cultured along micro endothelial cells under variable flow conditions and tested for homing levels along vasculature. Aggregometry and FACS analysis were utilized to evaluate platelet reactivity following co-incubation ± CD133+BMSC. RT-PCR and FACS analyses served to characterize ADP degrading ectonucleoside triphosphate diphosphohydrolase-1 (ectoNTPDase-1/CD39) expression on various cell types.

RESULTS

Platelets attracted human CD133+BMSC to autologous micro endothelium under shear stress unaffected by ADP stimulation. However, CD133+BMSC inhibited ADP-mediated platelet activation and aggregation. Latter was dependent on ectoNTPDase-1 expression levels. Platelet aggregatory control was increased with CD133+BMSC compared to CD133+PHSC. Different effects of those stem cell subtypes positively correlated with their FACS-detected expression levels of ectoNTPDase-1.

CONCLUSION

We provide evidence that CD133+BMSC are capable of controlling ADP-dependent platelet aggregation and activation by direct interaction dependent on cellular expression of ectoNTPDase-1. Whether different capacities of BMSC modulate platelet-depending thrombogenicity at sites of regeneration impact effectiveness and adverse event profiles of regenerative treatment requires further evaluation.

Molecular Evolution of Tryptophan Hydroxylases in Vertebrates: A Comparative Genomic Survey

Serotonin is a neurotransmitter involved in various physiological processes in the central and peripheral nervous systems. Serotonin is also a precursor for melatonin biosynthesis, which mainly occurs in the pineal gland of vertebrates. Tryptophan hydroxylase (TPH) acts as the rate-limiting enzyme in serotonin biosynthesis and is the initial enzyme involved in the synthesis of melatonin. Recently, two enzymes-TPH1 and TPH2-were reported to form the TPH family in vertebrates and to play divergent roles in serotonergic systems. Here, we examined the evolution of the TPH family from 70 vertebrate genomes. Based on the sequence similarity, we extracted 184 predicted tph homologs in the examined vertebrates. A phylogenetic tree, constructed on the basis of these protein sequences, indicated that tph genes could be divided into two main clades (tph1 and tph2), and that the two clades were further split into two subgroups of tetrapods and Actinopterygii. In tetrapods, and some basal non-teleost ray-finned fishes, only two tph isotypes exist. Notably, tph1 in most teleosts that had undergone the teleost-specific genome duplication could be further divided into tph1a and tph1b. Moreover, protein sequence comparisons indicated that TPH protein changes among vertebrates were concentrated at the NH₂-terminal. The tertiary structures of TPH1 and TPH2 revealed obvious differences in the structural elements. Five positively selected sites were characterized in TPH2 compared with TPH1; these sites may reflect the functional divergence in enzyme activity and substrate specificity. In summary, our current work provides novel insights into the evolution of tph genes in vertebrates from a comprehensive genomic perspective.

Low platelet count: Predictor of death and graft loss after liver transplantation

BACKGROUND

The impact of platelets on liver transplantation (LT) is well recognized, but not completely understood. Platelets exert dichotomous effects on the graft and on the patient. On the one hand, they are essential for primary hemostasis and tissue repair and regeneration. On the other hand, they support ischemia/reperfusion injury and inflammatory processes. Recent evidence has shown a new role for platelet count (PC) in predicting outcomes after LT.

AIM

To evaluate if low PC is a predictor of short- and long-term outcomes after LT.

METHODS

Four hundred and eighty consecutive LT patients were retrospectively assessed. PC from the preoperative to the seventh postoperative day (POD) were considered. C-statistic analysis defined the ideal cutoff point for PC. Cox regression was performed to check whether low PC was a predictor of death, retransplantation or primary changes in graft function within one year after LT.

RESULTS

The highest median PC was 86 × 10⁹/L [interquartile range (IQR) = 65–100 × 10⁹/L] on seventh POD, and the lowest was 51 × 10⁹/L (IQR = 38–71 × 10⁹/L) on third POD. The C-statistic defined a PC < 70 × 10⁹/L on fifth POD as the ideal cutoff point for predicting death and retransplantation. In the multivariate analysis, platelets < 70 × 10⁹/L on 5POD was an independent risk factor for death at 12 mo after LT [hazard ratio (HR) = 2.01; 95% confidence interval (CI) 1.06-3.79; P = 0.031]. In the Cox regression, patients with PC < 70 × 10⁹/L on 5POD had worse graft survival rates up to one year after LT (HR = 2.76; 95%CI 1.52-4.99; P = 0.001).

CONCLUSION

PC < 70 × 10⁹/L on 5POD is an independent predictor of death in the first year after LT. These results are in agreement with other studies that indicate that low PC after LT is associated with negative outcomes.

The Platelet Response to Tissue Injury

In recent years, various studies have increasingly explained platelet functions not only in their central role as a regulator in cellular hemostasis and coagulation. In fact, there is growing evidence that under specific conditions, platelets act as a mediator between the vascular system, hemostasis, and the immune system. Therefore, they are essential in many processes involved in tissue remodeling and tissue reorganization after injury or inflammatory responses. These processes include the promotion of inflammatory processes, the contribution to innate and adaptive immune responses during bacterial and viral infections, the modulation of angiogenesis, and the regulation of cell apoptosis in steady-state tissue homeostasis or after tissue breakdown. All in all platelets may contribute to the control of tissue homeostasis much more than generally assumed. This review summarizes the current knowledge of platelets as part of the tissue remodeling network and seeks to provide possible translational implications for clinical therapy.

Association of Platelet Count and Platelet Transfusion With Serotonin Level During Living Donor Liver Transplantation: Possible Connection to Graft Regeneration

BACKGROUND

We recently showed that platelet counts and the amount of platelet transfusion during liver transplantation are positively associated with early graft regeneration. It was hypothesized that platelet-derived serotonin mediates liver regeneration.

OBJECTIVES

This study aimed to evaluate the association between intraoperative platelet count, platelet transfusion, and serum serotonin level.

METHODS

Thirty-two recipients undergoing living-donor liver transplantation were enrolled into this prospective observational study. Serum platelet counts and serotonin levels were measured at the following times: anesthetic induction, start of the anhepatic phase, before graft reperfusion, 5 minutes/1 hour/3 hours/5 hours after graft reperfusion, and before/after platelet transfusion. Serotonin was measured by using a liquid chromatography tandem mass spectrometry.

RESULTS

Serotonin level at the anesthetic induction was 24.5 μg/mL (interquartile range, 14.6 to 38.1 μg/mL). During surgery, serial changes in platelet counts and serotonin levels showed a similar trend: they decreased during the anhepatic phase, increased during the first hour after graft reperfusion, and thereafter gradually decreased. Serotonin level was positively correlated with platelet counts (correlation coefficient = 0.620, P < .001). Allogeneic platelet transfusion significantly increased platelet count from 22 (19-31) × 10⁹/L to 53 (50-81) × 10⁹/L (P = .008) and it also increased serum serotonin from 11.04 (6.41-15.34) μg/mL to 34.26 (25.86-41.94) μg/mL (P = .008).

CONCLUSIONS

Our findings indicate that allogeneic platelets could act as effector cells deriving serotonins. Also, our findings support the hypothesis that the association between platelets and post-transplantation graft regeneration is mediated by serotonin. Further studies are warranted regarding the respective role of serotonin and other platelet-derived molecules mediating liver regeneration.

Axis of serotonin -pERK-YAP in liver regeneration

BACKGROUND AND AIM

Serotonin and YAP exhibit a vital role in regulating cell proliferation and wound-healing response. The aim of the study was to investigate whether 5-HT could promote liver regeneration by activating YAP.

METHODS

PH models were established by WT and TPH1-/- mice. ELISA, RT-PCR, western blot, immunohistochemistry, flow cytometry and MTT assay were used to assess the level of 5-HT and YAP and proliferation after PH.

RESULTS

We found that 5-HT level was lower in the serum and liver of TPH1-/- mice. After PH, TPH1-/- mice, lacking in 5-HT, demonstrated worse regenerative ability and suffered more severe liver injury. Additionally, YAP expression was also lower in TPH1-/- mice. Moreover, we found that YAP expression was prominent within the first three days following PH. Similarly, 5-HT could promote cell proliferation by upregulating YAP expression in L-O2 cells. As predicted, using YAP-siRNA sharply reduced the proliferative capacity mediated by 5-HT. Further study also indicated that ERK participated in the regulation of YAP induced by 5-HT. By using an ERK inhibitor, the YAP expression and cell proliferation induced by 5-HT were both suppressed. Although YAP-siRNA was used to block YAP expression, pERK and ERK expression were not affected. Taken together, these data showed that 5-HT contributed to liver regeneration by regulating YAP expression, which at least in part, was by activation of pERK.

CONCLUSION

A role of the 5-HT-pERK-YAP axis in liver regeneration emerged from our study and might be a potential target to promote regeneration and injury repair.

Accumulation of myeloid lineage cells is mapping out liver fibrosis post injury: a targetable lesion using Ketanserin

Liver fibrosis is problematic after persistent injury. However, little is known about its response to an acute insult. Accumulation of myeloid lineage cells contributes into the promotion and resolution of inflammation and fibrosis. Using Cre-transgenic mice that specifically mark myeloid lineage cells with EYFP and burn as a model of acute systemic injury, we investigated the role of myeloid lineage cells in the liver after acute injury. Our data show that thermal injury in mice (30% total body surface area) induces fibrosis predominantly around portal venules whereas myeloid cells are enriched throughout the liver. The fibrosis peaks around 1-2 weeks post injury and resolves by week 3. Ablating myeloid cells led to lower fibrosis. Through FACS sorting, we isolated myeloid lineage cells (EYFP +ve cells) from injured animals and from the control uninjured animals and subjected the extracted RNA from these cells to microarray analysis. Microarray analysis revealed an inflammatory signature for EYFP +ve cells isolated from injured animals in comparison with control cells. Moreover, it showed modulation of components of the serotonin (5-HT) pathway in myeloid cells. Antagonizing the 5HT2A/2C receptor decreased fibrosis in thermally injured mice by skewing macrophages away from their pro-fibrotic phenotype. Macrophages conditioned with Ketanserin showed a lower pro-fibrotic phenotype in a co-culture system with mesenchymal cells. There is a spatiotemporal pattern in liver fibrosis post-thermal injury, which is associated with the influx of myeloid cells. Treating mice with a 5HT2A/2C receptor antagonist promotes an anti-fibrotic effect, through modulating the phenotype of macrophages.

Meta-analysis of the prognostic role of perioperative platelet count in posthepatectomy liver failure and mortality

BACKGROUND

Emerging evidence suggests that the perioperative platelet count (PLT) can predict posthepatectomy liver failure (PHLF). In this systematic review and meta-analysis, the impact of perioperative PLT on PHLF and mortality was evaluated.

METHODS

MEDLINE and Web of Science databases were searched systematically for relevant literature up to January 2018. All studies comparing PHLF or mortality in patients with a low versus high perioperative PLT were included. Study quality was assessed using methodological index for non-randomized studies (MINORS) criteria. Meta-analyses were performed using Mantel-Haenszel tests with a random-effects model, and presented as odds ratios (ORs) with 95 per cent confidence intervals.

RESULTS

Thirteen studies containing 5260 patients were included in the meta-analysis. Two different cut-off values for PLT were used: 150 and 100/nl. Patients with a perioperative PLT below 150/nl had higher PHLF (4 studies, 817 patients; OR 4·79, 95 per cent c.i. 2·89 to 7·94) and mortality (4 studies, 3307 patients; OR 3·78, 1·48 to 9·62) rates than patients with a perioperative PLT of 150/nl or more. Similarly, patients with a PLT below 100/nl had a significantly higher risk of PHLF (4 studies, 949 patients; OR 4·65, 2·60 to 8·31) and higher mortality rates (7 studies, 3487 patients; OR 6·35, 2·99 to 13·47) than patients with a PLT of 100/nl or greater.

CONCLUSION

A low perioperative PLT correlates with higher PHLF and mortality rates after hepatectomy.

Autocrine and paracrine regulatory functions of platelet serotonin

Platelets serotonin (5-hydroxytrytamine, 5-HT) uptake and storage in dense granules is tightly regulated by the serotonergic transport system in the blood. Several 5-HT transporters (5-HTTs) have been identified in the vasculature and blood cells, beyond them 5-HTT is the major 5-HT transporter in platelets. Abnormal 5-HT concentrations in the blood plasma or increased platelet 5-HT uptake or abnormal release contribute to the development of various diseases in the vasculature. Consequently, several clinical trials suggested the positive therapeutic effects of 5-HTT blockade in the circulation. Inhibition of 5-HT strongly attenuates autocrine and paracrine functions of platelets, influencing platelet aggregation, vascular contraction, permeability, tissue repair, wound healing, immunity and cancer. Here, we highlight the current state of basic biological research regarding the hemostatic and non-hemostatic functions of platelet-derived 5-HT in normal and disease conditions. We also describe the physiological consequences of targeting platelet 5-HT functions in thrombosis, stroke, inflammation and cancer to overcome common health problems.

Autonomic nervous system network and liver regeneration

To date, various signal transducers, cytokines, growth factors, and hormones have been reported to play an important role in homeostasis of various organs. Various cells and organs are involved in the hepatic regeneration process, which proceeds as a result of the coordination of many factors. While these factors are well known to be involved in the liver regeneration after the liver injury, however, as the details of such mechanisms have not been sufficiently elucidated, the practical applicability of hepatic regeneration based on the action of these and cytokines growth factors is still unclear. In terms of the involvement of the autonomic nervous system in hepatic regeneration, cell proliferation resulting from direct signal transduction to the liver has also been reported and recent studies focusing on the inter-organ communication via neural network opened a novel aspect of this field for therapeutic applicability. Therefore, the appropriate understanding of the relationship between autonomic neural network and liver regeneration through various organs including brain, afferent nerve, efferent nerve, etc. is essential. This mini-review explains the principle of neural system involved in the inter-organ communication and its contribution on the liver regeneration upon the liver injury reviewing recent progress in this field.

Peripheral Serotonin Synthesis as a New Drug Target

The first step in serotonin (5-HT) biosynthesis is catalyzed by tryptophan hydroxylase (TPH). There are two independent sources of the monoamine that have distinct functions: first, the TPH1-expressing enterochromaffin cells (ECs) of the gut; second, TPH2-expressing serotonergic neurons. TPH1-deficient mice revealed that peripheral 5-HT plays important roles in platelet function and in inflammatory and fibrotic diseases of gut, pancreas, lung, and liver. Therefore, TPH inhibitors were developed which cannot pass the blood-brain barrier to specifically block peripheral 5-HT synthesis. They showed therapeutic efficacy in several rodent disease models, and telotristat ethyl is the first TPH inhibitor to be approved for the treatment of carcinoid syndrome. We review this development and discuss further therapeutic options for these compounds.

The impact of depression and antidepressant usage on primary biliary cholangitis clinical outcomes

BACKGROUND

Depression is prevalent in primary biliary cholangitis (PBC) patients. Our aims were to examine the effects of depression and antidepressants on hepatic outcomes of PBC patients.

METHODS

We used the UK Health Improvement Network database to identify PBC patients between 1974 and 2007. Our primary outcome was one of three clinical events: decompensated cirrhosis, liver transplantation and death. We assessed depression and each class of antidepressant medication in adjusted multivariate Cox proportional hazards models to identify independent predictors of outcomes. In a sensitivity analysis, the study population was restricted to PBC patients using ursodeoxycholic acid (UDCA).

RESULTS

We identified 1,177 PBC patients during our study period. In our cohort, 86 patients (7.3%) had a depression diagnosis prior to PBC diagnosis, while 79 patients (6.7%) had a depression diagnosis after PBC diagnosis. Ten-year incidence of mortality, decompensated cirrhosis, and liver transplantation were 13.4%, 6.6%, and 2.0%, respectively. In our adjusted models, depression status was not a predictor of poor outcomes. After studying all classes of antidepressants, using the atypical antidepressant mirtazapine after PBC diagnosis was significantly protective (Adjusted HR 0.23: 95% CI 0.07-0.72) against poor liver outcomes (decompensation, liver transplant, mortality), which remained statistically significant in patients using UCDA (HR 0.21: 95% CI 0.05-0.83).

CONCLUSIONS

In our study, depression was not associated with poor clinical outcomes. However, using the antidepressant mirtazapine was associated with decreased mortality, decompensated cirrhosis and liver transplantation in PBC patients. These findings support further assessment of mirtazapine as a potential treatment for PBC patients.

Effect of Splenectomy on Serum Cytokine Profiles in Hepatitis B Virus-Related Cirrhosis Patients with Portal Hypertension

Emerging evidences showed the promoting role of spleen in the development of cirrhosis and hepatocellular carcinoma, in the context of portal hypertension and hypersplenism due to hepatitis B virus-related cirrhosis. In this study, we tried to explore the precise mechanism of how spleen regulates this process from the serum cytokines profile level. Compared with the 16 healthy subjects, the RayBio Human Cytokine Antibody Array identified 136 cytokines differentially expressed in 36 cirrhotic patients. Splenectomy resulted in significant changes in 28 cytokines. Differentially expressed cytokines were mainly involved in cellular processes, responses to stimuli, immune processes, binding, extracellular regions, and extracellular matrix. These cytokines were mainly enriched in cytokine-cytokine receptor interactions, Jak-STAT and MAPK signaling pathways, and pathways in cancer. These results may provide new clues to the function of the spleen, and modulation of cytokine expression maybe a potential alternative therapeutic strategy for these patients.

Effect of a neural relay on liver regeneration in mice: activation of serotonin release from the gastrointestinal tract

The development of therapeutic options to promote hepatic regeneration following severe liver injury is essential. While humoral factors have been reported as mechanisms of liver regeneration, the contributions of interorgan communication to liver regeneration have not been reported. In this study, we examined the effect of a neural relay on liver regeneration via activation of serotonin release from the gastrointestinal (GI) tract. Our results demonstrated that the afferent visceral nerve from the liver activates the efferent vagus nerve from the brain, leading to activation of serotonin release from the GI tract and contributing to liver regeneration. While it is difficult to apply these results directly to human health, we believe that this study may represent a step toward developing essential therapeutics to promote liver regeneration.

Enteric serotonin and oxytocin: endogenous regulation of severity in a murine model of necrotizing enterocolitis

Necrotizing enterocolitis (NEC), a gastrointestinal inflammatory disease of unknown etiology that may also affect the liver, causes a great deal of morbidity and mortality in premature infants. We tested the hypothesis that signaling molecules, which are endogenous to the bowel, regulate the severity of intestinal and hepatic damage in an established murine NEC model. Specifically, we postulated that mucosal serotonin (5-HT), which is proinflammatory, would exacerbate experimental NEC and that oxytocin (OT), which is present in enteric neurons and is anti-inflammatory, would oppose it. Genetic deletion of the 5-HT transporter (SERT), which increases and prolongs effects of 5-HT, was found to increase the severity of systemic manifestations, intestinal inflammation, and associated hepatotoxicity of experimental NEC. In contrast, genetic deletion of tryptophan hydroxylase 1 (TPH1), which is responsible for 5-HT biosynthesis in enterochromaffin (EC) cells of the intestinal mucosa, and TPH inhibition with LP-920540 both decrease the severity of experimental NEC in the small intestine and liver. These observations suggest that 5-HT from EC cells helps to drive the inflammatory damage to the gut and liver that occurs in the murine NEC model. Administration of OT decreased, while the OT receptor antagonist atosiban exacerbated, the intestinal inflammation of experimental NEC. Data from the current investigation are consistent with the tested hypotheses-that the enteric signaling molecules, 5-HT (positively) and OT (negatively) regulate severity of inflammation in a mouse model of NEC. Moreover, we suggest that mucosally restricted inhibition of 5-HT biosynthesis and/or administration of OT may be useful in the treatment of NEC.NEW & NOTEWORTHY Serotonin (5-HT) and oxytocin reciprocally regulate the severity of intestinal inflammation and hepatotoxicity in a murine model of necrotizing enterocolitis (NEC). Selective depletion of mucosal 5-HT through genetic deletion or inhibition of tryptophan hydroxylase-1 ameliorates, while deletion of the 5-HT uptake transporter, which increases 5-HT availability, exacerbates the severity of NEC. In contrast, oxytocin reduces, while the oxytocin receptor antagonist atosiban enhances, NEC severity. Peripheral tryptophan hydroxylase inhibition may be useful in treatment of NEC.

A new index predicts early allograft dysfunction following living donor liver transplantation: A propensity score analysis

OBJECTIVE/AIM

The aim of this study was to identify a new index to predict early allograft dysfunction following living donor liver transplantation.

METHODS

The study enrolled 260 adult living donor liver transplantation recipients. Postoperative laboratory variables were assessed for their association with the prevalence of early allograft dysfunction using the inverse probability of treatment weighting and propensity-score matching (n=93 pairs) analysis.

RESULTS

Forty-seven recipients (18.1%) developed early allograft dysfunction. In multivariable analysis, the alanine aminotransferase and gamma-glutamyl transpeptidase levels on postoperative day 1 were independent predictors of early allograft dysfunction. The alanine aminotransferase to gamma-glutamyl transpeptidase ratio (AGR) was developed. All cases were divided into two groups (Group 1 [AGR≥8.47, n=103] and Group 2 [AGR<8.47, n=157]). AGR≥8.47 (OR 10.345, 95%CI 4.502-23.772, p<0.001), hepatorenal syndrome (OR 3.016, 95%CI 1.119-8.125, p=0.029), and graft to recipient weight ratio <0.8% (OR 2.155, 95%CI 1.004-4.624, p=0.049) were independent risk factors for early allograft dysfunction. The prevalence of early allograft dysfunction was higher in group 1 (after adjusting for inverse probability of treatment weighting [n=39; 37.9% vs n=8; 5.1%] and propensity-score matching [n=33; 35.5% vs n=2; 2.2%]) than that in group 2 (p<0.001).

CONCLUSIONS

The postoperative AGR is a practical index for predicting early allograft dysfunction after living donor liver transplantation.

Association of interleukin-28B polymorphisms with platelet count and liver function recovery after liver transplant

The present genome-wide association study investigated the relationship of interleukin 28B (IL-28B) genetic variants with HBV susceptibility and prognosis of HBV-infected patients. This study aims to examine the role of IL-28B polymorphisms on transplant etiologies and the liver function recovery in Chinese liver transplant recipients.A total of 231 liver transplant recipients were enrolled in the study. The transplant etiologies included progressive HBV hepatitis, HBV-related liver cirrhosis (LC), HBV-related hepatocellular carcinoma (HCC), and non-HBV-related disease. All recipients were in stable condition before transplantation. Three single nucleotide polymorphisms (SNPs) of IL-28B (rs12979860, rs12980275, rs8099917) of recipients were analyzed by high-resolution melting (HRM) curve analysis. Liver function, blood cell count, and coagulation function were regularly tested before and for next 5 years after transplantation.No significant association was found between IL-28B gene polymorphisms and transplant etiologies. Peripheral platelet count in the third and fourth days after transplantation were significantly higher in recipients carrying IL-28B rs12979860 T allele, or rs8099917 C allele (P < .016666667), while there were no significant differences between these variants and International Normalized Ratio (INR) levels. In addition, gamma-glutamyltransferase (GGT) levels in recipients with rs12980275 G allele were higher than those in the wide-type recipients before transplantation (P < .016666667, respectively); nevertheless, no influence of these variants on GGT recovery was observed after transplantation.Genetic variations of IL-28B might impact on liver function recovery by influencing peripheral platelet counts and reducing liver inflammation, but have weak association with transplant etiologies.

5-HT2B receptor antagonists attenuate myofibroblast differentiation and subsequent fibrotic responses in vitro and in vivo

Pulmonary fibrosis is characterized by excessive accumulation of connective tissue, along with activated extracellular matrix (ECM)‐producing cells, myofibroblasts. The pathological mechanisms are not well known, however serotonin (5‐HT) and 5‐HT class 2 (5‐HT₂) receptors have been associated with fibrosis. The aim of the present study was to investigate the role of 5‐HT_2B receptors in fibrosis, using small molecular 5‐HT_2B receptor antagonists EXT5 and EXT9, with slightly different receptor affinity. Myofibroblast differentiation [production of alpha‐smooth muscle actin (α‐SMA)] and ECM synthesis were quantified in vitro, and the effects of the receptor antagonists were evaluated. Pulmonary fibrosis was also modeled in mice by subcutaneous bleomycin administrations (under light isoflurane anesthesia), and the effects of receptor antagonists on tissue density, collagen‐producing cells, myofibroblasts and decorin expression were investigated. In addition, cytokine expression was analyzed in serum. Lung fibroblasts displayed an increased α‐SMA (P < 0.05) and total proteoglycan production (P < 0.01) when cultured with TGF‐β1 together with 5‐HT, which were significantly reduced with both receptor antagonists. Following treatment with EXT5 or EXT9, tissue density, expression of decorin, number of collagen‐producing cells, and myofibroblasts were significantly decreased in vivo compared to bleomycin‐treated mice. Receptor antagonization also significantly reduced systemic levels of TNF‐α and IL‐1β, indicating a role in systemic inflammation. In conclusion, 5‐HT_2B receptor antagonists have potential to prevent myofibroblast differentiation, in vitro and in vivo, with subsequent effect on matrix deposition. The attenuating effects of 5‐HT_2B receptor antagonists on fibrotic tissue remodeling suggest these receptors as novel targets for the treatment of pulmonary fibrosis.

The Role of Serotonin Transporter in Human Lung Development and in Neonatal Lung Disorders

Introduction. Failure of the vascular pulmonary remodeling at birth often manifests as pulmonary hypertension (PHT) and is associated with a variety of neonatal lung disorders including a uniformly fatal developmental disorder known as alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV). Serum serotonin regulation has been linked to pulmonary vascular function and disease, and serotonin transporter (SERT) is thought to be one of the key regulators in these processes. We sought to find evidence of a role that SERT plays in the neonatal respiratory adaptation process and in the pathomechanism of ACD/MPV. Methods. We used histology and immunohistochemistry to determine the timetable of SERT protein expression in normal human fetal and postnatal lungs and in cases of newborn and childhood PHT of varied etiology. In addition, we tested for a SERT gene promoter defect in ACD/MPV patients. Results. We found that SERT protein expression begins at 30 weeks of gestation, increases to term, and stays high postnatally. ACD/MPV patients had diminished SERT expression without SERT promoter alteration. Conclusion. We concluded that SERT/serotonin pathway is crucial in the process of pulmonary vascular remodeling/adaptation at birth and plays a key role in the pathobiology of ACD/MPV.

Prognostic impact of postoperative low platelet count after liver transplantation

BACKGROUND

The positive impact of platelets has been recently implicated in liver transplantation (LT). The aim of this study was to determine the risk factors for graft loss and mortality after LT, focusing on perioperative platelet counts.

METHODS

We reviewed all deceased donor LT from 2000 to 2012 and enrolled 975 consecutive recipients. The risk factors for graft loss and mortality were analyzed by multivariate analysis, using Cox's regression model.

RESULTS

Using cutoff values acquired by receiver operating characteristics curve analysis, multivariate analyses determined that viral hepatitis C (hazard ratio [HR]=1.32), donor age >40 (HR=1.33), higher peak serum alanine aminotransferase (HR=1.01), reoperation within 30 days (HR=1.51), and platelet count <72 500/μL on postoperative day (POD) 5 (HR=1.30) were independent risk factors for graft loss. Viral hepatitis C (HR=1.33), reoperation within 30 days (HR=1.35), and platelet count <72 500/μL on POD 5 (HR=1.38) were independent risk factors for mortality.

CONCLUSION

A low platelet count on POD 5 was associated with graft loss and mortality after LT. Platelet count <72 500/μL on POD 5 can be a predictor of poor graft and overall survival. Maintaining higher postoperative platelet counts could potentially improve graft and overall survival rates.

Association of thrombocytopenia with outcome following adult living donor liver transplantation

This study aimed to evaluate the association of postoperative thrombocytopenia with outcome following adult living donor liver transplantation (LDLT) for end-stage liver disease (ESLD). It was a prospective study of 120 consecutive adult LDLT from September 2012 to May 2015. Preoperative platelet counts (PLTs) and postoperative PLTs were recorded at regular intervals till 3 months after LDLT. Univariate and multivariate analyses were performed. The median pretransplant PLT was 61 × 10(9) /l. The lowest median PLT after LDLT was observed on POD 3. Patients were stratified into low platelet group (n = 83) with PLT <30 × 10(9) /l and high platelet group (n = 37) with PLT ≥30 × 10(9) /l. Patients with PLT <30 × 10(9) /l had statistically significant higher grade III/IV complication (P = 0.001), early graft dysfunction (P = 0.01), sepsis (P = 0.001), and prolonged ascites drainage (P = 0.002). On multivariate analysis, PLT<30 × 10(9) /l was identified as an independent risk factor for grade III/IV complications (P = 0.005). Overall, patients survival was significantly different between two groups (P = 0.04), but this predictive value was lost in patients who survived more than 90 days (P = 0.37). Postoperative PLT of <30 × 10(9) /l was a strong predictor of major postoperative complications and is associated with early graft dysfunction, prolonged ascites drainage, and sepsis. The perioperative mortality rate was high in the thrombocytopenia group.

New approaches for fibrosis regression in alcoholic cirrhosis

Liver fibrosis is a dynamic process of fibrinogenesis and fibrinolysis. It is sequelae of recurrent injury and inflammation to the liver. Only recently has there been significant progress in understanding the pathophysiology behind liver fibrosis. This has allowed for the development of identifiable targets for potential therapies. In this article we will discuss the underlying general cellular mechanisms that play a key role in the pathway of fibrinogenesis and fibrinolysis and then focus on the mechanisms that are key in alcohol-induced liver fibrosis. Challenges in formulating potential fibrosis therapies as well as current potential targets for liver fibrosis will be reviewed as well.

Mechanisms of platelet-mediated liver regeneration

Platelets have multiple functions beyond their roles in thrombosis and hemostasis. Platelets support liver regeneration, which is required after partial hepatectomy and acute or chronic liver injury. Although it is widely assumed that platelets stimulate liver regeneration by local excretion of mitogens stored within platelet granules, definitive evidence for this is lacking, and alternative mechanisms deserve consideration. In-depth knowledge of mechanisms of platelet-mediated liver regeneration may lead to new therapeutic strategies to treat patients with failing regenerative responses.

Clopidogrel treatment may associate with worsening of endothelial function and development of new digital ulcers in patients with systemic sclerosis: results from an open label, proof of concept study

Background

Activated platelets release serotonin that binds 5-HT_2B receptor on fibroblasts leading to fibroblast activation. Clopidogrel, an inhibitor of ADP-dependent platelet activation prevents fibrosis in animal models of systemic sclerosis (SSc). We aimed at assessing whether i) ADP-dependent platelet activation is increased in patients with SSc compared to healthy subjects and patients with rheumatoid arthritis (RA) and ii) whether clopidogrel can effectively suppress ADP-dependent activation, reduce circulating serotonin levels and hence, favorably affect fibrosis or vasculopathy in patients with systemic sclerosis.

Methods

Thirteen patients with SSc were recruited. Platelet activation was assessed by aggregometry prior to and following 14 days of clopidogrel treatment. At the same time points serotonin and soluble vascular cell adhesion molecule 1 (s-VCAM1), a marker of endothelial dysfunction, were measured.

Results

ADP-dependent platelet activation was similar between patients with SSc (n = 13), patients with RA (n = 28) and healthy subjects (n = 22) (mean ± SEM AU*min: 392.1 ± 58.4, 535.5 ± 61.33 and 570.9 ± 42.9 in patients with SSc, patients with RA and healthy subjects respectively, p = 0.14). Clopidogrel treatment significantly reduced platelet activation in patients with SSc (mean ± SEM AU*min: 392.1 ± 58.4 vs 163.8 ± 51.7, p = 0.014). Clopidogrel treatment did not affect serotonin levels but led to a significant increase in s-VCAM1 (p = 0.03). Three patients developed new digital ulcers during the study. The potential association of the study drug with the development of new digital ulcers led to early termination of the study.

Conclusion

Clopidogrel may worsen markers of endothelial function and associate with development of new digital ulcers in patients with SSc.

Clinical trial registration

ISRCTN63206606. Registered 02/Dec/2014.