Working mechanism of Hic-5 in human and experimental NAFLD-related liver fibrosis

Non-alcoholic fatty liver disease (NAFLD) is characterized by a wide spectrum of pathological findings, ranging from simple steatosis to steatohepatitis which can progress to cirrhosis and hepatocellular carcinoma. Fibrosis severity is the main determinant of liver-related complications and mortality, therefore its regression is considered an important therapeutic endpoint in clinical trials evaluating pharmacological intervention in NAFLD. Activation of hepatic stellate cells (HSC) by transforming growth factor beta (TGFβ) is a well-established driver of liver fibrogenesis. Recently, a TGFβ-modulated protein, namely hydrogen peroxide-inducible clone 5 (Hic-5) has been proposed as a novel potential therapeutic target for liver fibrosis, since its knockdown attenuated experimental liver fibrosis in mice. However, limited data are available regarding its expression in human HSC, while no study has investigated its role in the setting of NAFLD so far. Based on these premises, the aim of my thesis was first to characterize Hic-5 expression in human HSC according to different hepatic microenvironment (healthy versus fibrotic); secondly to assess whether Hic-5 is expressed in human and experimental NAFLD. To investigate the first aim, primary human HSC were cultured in a new 3-dimensional (3D) culture model based on decellularized human liver extracellular matrix (ECM) scaffolds derived from healthy and cirrhotic livers. Compared to traditional 2D cultures, Hic-5 gene expression was significantly upregulated in HSC cultured in the 3D model. This effect was further enhanced upon TGFβ stimulation in healthy scaffolds. Moreover, higher Hic-5 mRNA levels were detected in HSC cultured in cirrhotic scaffolds compared to healthy scaffolds, suggesting that Hic-5 expression and its modulation by TGFβ are strongly affected by liver- and disease specific ECM features. Based on these preliminary in-vitro results, I decided to further investigate Hic-5 expression in human NAFLD samples obtained from obese patients undergoing bariatric surgery. Immunohistochemical staining showed an increased expression of Hic-5 in fibrotic liver tissue, which overlapped alpha smooth muscle actin (α-SMA) positive areas. In order to better elucidate the role of Hic-5 across NAFLD progression, a nutritional rat model of NAFLD, based on the administration of choline-deficient (CD) diet, was employed and hepatic Hic-5 expression analyzed at different time points. After 3 days of CD diet Hic-5 mRNA levels were not significantly upregulated, suggesting that fatty liver alone without associated liver fibrosis does not affect Hic-5 expression. Accordingly, no difference in α-SMA gene expression was observed compared to control diet. In contrast, administration of CD diet for 7 weeks led to increased mRNA expression of Hic-5 along with αSMA, TGFβ1 and collagen type 1A1. Upregulation of Hic-5 was further confirmed at the protein level by Western blot analysis. Similar findings were obtained when CD diet was given for 11 weeks. Interestingly, the administration of a triiodothyronine(T3)-supplemented diet for 1 week, which has been previously shown to revert rat fatty liver, was able to reduce the expression of Hic-5. The same effect of T3 on Hic-5 was seen on the microenvironment surrounding preneoplastic nodules during NASH-related experimental liver carcinogenesis. Since T3 administration was associated with regression of preneoplastic nodules not expressing Hic-5 or αSMA, we speculate that its antifibrotic effect may contribute to preneoplastic nodules regression. Taken together, these results highlight the role of Hic-5 in HSC activation in vitro and its association with NAFLD progression. Further studies are needed to clarify the molecular mechanisms regulating Hic-5 expression in NAFLD-related fibrosis and the effects of thyroid receptor’s agonists in order to identify potential anti-fibrotic therapie

Differential targeting of lysophosphatidic acid LPA1, LPA2, and LPA3 receptor signalling by tricyclic and tetracyclic antidepressants

We previously reported that in different cell types antidepressant drugs activate lysophosphatidic acid (LPA) LPA1 receptor to induce proliferative and prosurvival responses. Here, we further characterize this unique action of antidepressants by examining their effects on two additional LPA receptor family members, LPA2 and LPA3. Human LPA1-3 receptors were stably expressed in HEK-293 cells (HEK-LPA1, -LPA2 and -LPA3 cells) and their functional activity was determined by Western blot and immunofluorescence. LPA effectively stimulated the phosphorylation of extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) in HEK-LPA1, -LPA2, and -LPA3 cells. The tricyclic antidepressants amitriptyline, clomipramine, imipramine and desipramine increased phospho-ERK1/2 levels in HEK-LPA1 and -LPA3 cells but were relatively poor agonists in LPA2-expressing cells. The tetracyclic antidepressants mianserin and mirtazapine were active at all three LPA receptors. When combined with LPA, both amitriptyline and mianserin potentiated Gi/o-mediated phosphorylation of ERK1/2 induced by LPA in HEK-LPA1, -LPA2 and -LPA3 cells, CHO-K1 fibroblasts and HT22 hippocampal neuroblasts. This potentiation was associated with enhanced phosphorylation of CREB and S6 ribosomal protein, two molecular targets of activated ERK1/2. The antidepressants also potentiated LPA-induced Gq/11-mediated phosphorylation of AMP-activated protein kinase in HEK-LPA1 and -LPA3 cells. Conversely, amitriptyline and mianserin were found to inhibit LPA-induced Rho activation in HEK-LPA1 and LPA2 cells. These results indicate that tricyclic and tetracyclic antidepressants can act on LPA1, LPA2 and LPA3 receptor subtypes and exert differential effects on LPA signalling through these receptors

Lysophosphatidic Acid Stimulates Mitogenic Activity and Signaling in Human Neuroblastoma Cells through a Crosstalk with Anaplastic Lymphoma Kinase

Lysophosphatidic acid (LPA) is a well-documented pro-oncogenic factor in different cancers, but relatively little is known on its biological activity in neuroblastoma. The LPA effects and the participation of the tyrosine kinase receptor anaplastic lymphoma kinase (ALK) in LPA mitogenic signaling were studied in human neuroblastoma cell lines. We used light microscopy and [3H]-thymidine incorporation to determine cell proliferation, Western blot to study intracellular signaling, and pharmacological and molecular tools to examine the role of ALK. We found that LPA stimulated the growth of human neuroblastoma cells, as indicated by the enhanced cell number, clonogenic activity, and DNA synthesis. These effects were curtailed by the selective ALK inhibitors NPV-TAE684 and alectinib. In a panel of human neuroblastoma cell lines harboring different ALK genomic status, the ALK inhibitors suppressed LPA-induced phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2), which are major regulators of cell proliferation. ALK depletion by siRNA treatment attenuated LPA-induced ERK1/2 activation. LPA enhanced ALK phosphorylation and potentiated ALK activation by the ALK ligand FAM150B. LPA enhanced the inhibitory phosphorylation of the tumor suppressor FoxO3a, and this response was impaired by the ALK inhibitors. These results indicate that LPA stimulates mitogenesis of human neuroblastoma cells through a crosstalk with ALK

Role of Lysophosphatidic Acid in Neurological Diseases: From Pathophysiology to Therapeutic Implications

Lysophosphatidic acid (LPA), a bioactive lipid molecule, has been identified as a critical regulator of several cellular processes in the central nervous system, with significant impacts on neuronal function, synaptic plasticity, and neuroinflammatory responses. While Alzheimer's disease, Multiple Sclerosis, and Parkinson's disease have garnered considerable attention due to their incidence and socioeconomic significance, many additional neurological illnesses remain unclear in terms of underlying pathophysiology and prospective treatment targets. This review synthesizes evidence linking LPA's function in neurological diseases such as traumatic brain injury, spinal cord injury, cerebellar ataxia, cerebral ischemia, seizures, Huntington's disease, amyotrophic lateral sclerosis, Hutchinson-Gilford progeria syndrome, autism, migraine, and human immunodeficiency virus (HIV)-associated complications Despite recent advances, the specific mechanisms underlying LPA's actions in various neurological disorders remain unknown, and further research is needed to understand the distinct roles of LPA across multiple disease conditions, as well as to investigate the therapeutic potential of targeting LPA receptors in these pathologies. The purpose of this review is to highlight the multiple functions of LPA in the aforementioned neurological diseases, which frequently share the same poor prognosis due to a scarcity of truly effective therapies, while also evaluating the role of LPA, its receptors, and signaling as promising actors for the development of alternative therapeutic strategies to those proposed today

The Neurotrophin Receptor TrkC as a Novel Molecular Target of the Antineuroblastoma Action of Valproic Acid

Neurotrophins and their receptors are relevant factors in controlling neuroblastoma growth and progression. The histone deacetylase (HDAC) inhibitor valproic acid (VPA) has been shown to downregulate TrkB and upregulate the p75NTR/sortilin receptor complex. In the present study, we investigated the VPA effect on the expression of the neurotrophin-3 (NT-3) receptor TrkC, a favorable prognostic marker of neuroblastoma. We found that VPA induced the expression of both full-length and truncated (TrkC-T1) isoforms of TrkC in human neuroblastoma cell lines without (SH-SY5Y) and with (Kelly, BE(2)-C and IMR 32) MYCN amplification. VPA enhanced cell surface expression of the receptor and increased Akt and ERK1/2 activation by NT-3. The HDAC inhibitors entinostat, romidepsin and vorinostat also increased TrkC in SH-SY5Y, Kelly and BE(2)-C but not IMR 32 cells. TrkC upregulation by VPA involved induction of RUNX3, stimulation of ERK1/2 and JNK, and ERK1/2-mediated Egr1 expression. In SH-SY5Y cell monolayers and spheroids the exposure to NT-3 enhanced the apoptotic cascade triggered by VPA. Gene silencing of both TrkC-T1 and p75NTR prevented the NT-3 proapoptotic effect. Moreover, NT-3 enhanced p75NTR/TrkC-T1 co-immunoprecipitation. The results indicate that VPA upregulates TrkC by activating epigenetic mechanisms and signaling pathways, and sensitizes neuroblastoma cells to NT-3-induced apoptosis

Role of interferon lambda 4 and ALT levels in optimising treatment of HCV for patients with low-stage fibrosis

The use of new anti-HCV drugs is currently limited by high costs and dual therapy; pegylated interferon and ribavirin (peg-IFN+RBV) still represents the only affordable treatment in patients with low-stage fibrosis. We evaluated the role of Interferon lambda4 (IFNL4) polymorphisms and its combination with on-treatment alanine transaminase (ALT) modification in predicting sustained virological response (SVR) in HCV genotype 1 and 4 patients with low-stage fibrosis. We retrospectively analysed 124 patients with Metavir ≤F2, who received dual therapy at our centre. Genotyping for IFNL4 polymorphisms was assessed at baseline, as well as ALT levels (baseline and week 2, 4, 12 and 24 of therapy). Thirty patients (24%) were TT/TT, 74 (60%) TT/DG and 20 (16%) DG/DG. The SVR rate was significantly higher in TT/TT genotype compare to TT/DG and DG/DG (97% vs. 53% and 50%, respectively, p=0.001). Patients that achieved a 60% reduction of ALT baseline value after 4 weeks of therapy had a significantly higher SVR rate (94% vs. 52%, p<0.001). Factors significantly associated with SVR were TT/TT genotype (p=0.029), RVR (p=0.019) and 60% ALT reduction at 4 week of therapy (p=0.005). The absence of both TT/TT genotype and 60% ALT reduction were negative predictors of SVR (p<0.001). In conclusion, the combined use of IFNL4 polymorphisms and ALT reduction at 4 week of treatment is able to optimize candidates’ selection for peg-IFN+RBV, discriminating those that could still benefit from dual therapy from the ones that need the new regimen

Exploring the Role of Killer Cell Immunoglobulin-Like Receptors and Their HLA Class I Ligands in Autoimmune Hepatitis

Background Natural killer cells are involved in the complex mechanisms underlying autoimmune diseases but few studies have investigated their role in autoimmune hepatitis. Killer immunoglobulin-like receptors are key regulators of natural killer cell-mediated immune responses. Methods and Findings KIR gene frequencies, KIR haplotypes, KIR ligands and combinations of KIRs and their HLA Class I ligands were investigated in 114 patients diagnosed with type 1 autoimmune hepatitis and compared with a group of 221 healthy controls. HLA Class I and Class II antigen frequencies were compared to those of 551 healthy unrelated families representative of the Sardinian population. In our cohort, type 1 autoimmune hepatitis was strongly associated with the HLA-B18, Cw5, DR3 haplotype. The KIR2DS1 activating KIR gene and the high affinity HLA-C2 ligands were significantly higher in patients compared to controls. Patients also had a reduced frequency of HLA-Bw4 ligands for KIR3DL1 and HLA-C1 ligands for KIR2DL3. Age at onset was significantly associated with the KIR2DS1 activating gene but not with HLA-C1 or HLA-C2 ligand groups. Conclusions The activating KIR gene KIR2DS1 resulted to have an important predictive potential for early onset of type 1 autoimmune hepatitis. Additionally, the low frequency of the KIR-ligand combinations KIR3DL1/HLA-Bw4 and KIR2DL3/HLA-C1 coupled to the high frequency of the HLA-C2 high affinity ligands for KIR2DS1 could contribute to unwanted NK cell autoreactivity in AIH-1