Hydroxyurea attenuates hepatic stellate cell proliferation in vitro and liver fibrogenesis in vivo

Liver fibrosis results from excessive proliferation of, and collagen production by hepatic stellate cells (HSCs) that is caused by chronic liver injury. No drugs are available to cure liver fibrosis. Hydroxyurea is an anti-proliferative drug that is used in benign and malignant disorders. Here, we studied the effect of hydroxyurea on primary HSCs and its anti-fibrotic effect in the CCl4 mouse model of liver fibrosis. Primary rat HSCs were cultured in the absence or presence of hydroxyurea (0.1-1.0 mmol/L). CCl4 or vehicle was administered to C57BL/6/J mice for 4 weeks, with or without hydroxyurea (100 mg/kg/day) co-treatment. We used real-time cell proliferation analysis, Oil Red O (lipid droplet) staining, immunohistochemistry, Acridine Orange staining (apoptosis), Sytox green staining (necrosis), RT-qPCR, ELISA, and Western Blotting for analysis. Hydroxyurea dose-dependently suppressed lipid droplet-loss and mRNA levels of Col1α1 and Acta2 in transdifferentiating HSCs. In fully-activated HSCs, hydroxyurea dose-dependently attenuated PCNA protein levels and BrdU incorporation, but did not reverse Col1α1 and Acta2 mRNA expression. Hydroxyurea did not induce apoptosis or necrosis in HSCs or hepatocytes. Hydroxyurea suppressed accumulation of desmin-positive HSCs and hepatic collagen deposition after CCl4 treatment. CCl4 -induced regenerative hepatocyte proliferation, Col1α1 and Acta2 mRNA expression and α-SMA protein levels were not affected. This study demonstrates that hydroxyurea inhibits HSC proliferation in vitro and attenuates early development of liver fibrosis in vivo, while preserving hepatocyte regeneration after toxic insults by CCl4. Thus, hydroxyurea may have therapeutic value against liver fibrosis.

A Quick Guide to CAF Subtypes in Pancreatic Cancer

Pancreatic cancer represents one of the most desmoplastic malignancies and is characterized by an extensive deposition of extracellular matrix. The latter is provided by activated cancer-associated fibroblasts (CAFs), which are abundant cells in the pancreatic tumor microenvironment. Many recent studies have made it clear that CAFs are not a singular cellular entity but represent a multitude of potentially dynamic subgroups that affect tumor biology at several levels. As mentioned before, CAFs significantly contribute to the fibrotic reaction and the biomechanical properties of the tumor, but they can also modulate the local immune environment and the response to targeted, chemo or radiotherapy. As the number of known and emerging CAF subgroups is steadily increasing, it is becoming increasingly difficult to keep up with these developments and to clearly discriminate the cellular subsets identified so far. This review aims to provide a helpful overview that enables readers to quickly familiarize themselves with field of CAF heterogeneity and to grasp the phenotypic, functional and therapeutic distinctions of the various stromal subpopulations.

Role of B Cell-Activating Factor in Fibrosis Progression in a Murine Model of Non-Alcoholic Steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease all over the world. Therapeutic strategies targeting its multidirectional pathways are required. Particularly, fibrosis is closely associated with its prognosis. We previously found that B cell-activating factor (BAFF) is associated with severity of NAFLD. Here, we determined the direct in vivo role of BAFF in the development of liver fibrosis. Histological and biochemical analyses were performed using wild-type and BAFF-deficient mice. We established a murine model of non-alcoholic steatohepatitis (NASH) using carbon tetrachloride injection accompanied by high-fat/high-cholesterol diet feeding. Additionally, in vitro analysis using mouse macrophage-like cell line RAW264.7 and primary hepatic stellate cells was performed. Hepatic steatosis and inflammation, and most importantly, the progression of liver fibrosis, were ameliorated in BAFF-deficient mice compared to those wild-type mice in our model. Additionally, BAFF deficiency reduced the number of CD11c⁺ M1-type macrophages in the liver. Moreover, BAFF stimulated RAW264.7 cells to secrete nitric oxide and tumor necrosis factor α, which drove the activation of hepatic stellate cells. This indicates that BAFF plays a crucial role in NASH development and may be a promising therapeutic target for NASH.

Watching Living Cells in Action in the Exocrine Pancreas: The Palade Prize Lecture

George Palade's pioneering electron microscopical studies of the pancreatic acinar cell revealed the intracellular secretory pathway from the rough endoplasmic reticulum at the base of the cell to the zymogen granules in the apical region. Palade also described for the first time the final stage of exocytotic enzyme secretion into the acinar lumen. The contemporary studies of the mechanism by which secretion is acutely controlled, and how the pancreas is destroyed in the disease acute pancreatitis, rely on monitoring molecular events in the various identified pancreatic cell types in the living pancreas. These studies have been carried out with the help of high-resolution fluorescence recordings, often in conjunction with patch clamp current measurements. In such studies we have gained much detailed information about the regulatory events in the exocrine pancreas in health as well as disease, and new therapeutic opportunities have been revealed.

Metabolic reprogramming of tumor-associated macrophages by collagen turnover promotes fibrosis in pancreatic cancer

A hallmark of pancreatic tumors is their highly desmoplastic stroma composed of fibroblasts, immune cells, and a dense network of collagen fibers. Tumor-associated macrophages are one of the most abundant immune cell populations in the pancreatic tumor stroma. Their protumorigenic function has been attributed predominantly to their capacity to promote immune evasion and metastasis. Tumor-assoc iated macrophages are also well known for their role in the remodeling of the stroma via collagen production and degradation, with the latter being mediated by mannose receptor (MRC1)-dependent endocytosis of collagen. Here we show that MRC1-mediated collagen internalization and subsequent lysosomal degradation by macrophages harboring a tumor-associated phenotype are accompanied by the accumulation of collagen-derived intracellular free amino acids and increased arginine biosynthesis. The resulting increase in intracellular arginine levels leads to the up-regulation of inducible nitric oxide synthase and the production of reactive nitrogen species. Furthermore, reactive nitrogen species derived from internalized and degraded collagen promotes a profibrotic phenotype in pancreatic stellate cells resulting in enhanced intratumoral collagen deposition. Overall, our findings identify a role for extracellular matrix remodeling in the functional modulation of tumor-associated macrophages via metabolic rewiring.

Honokiol Acts as a Potent Anti-Fibrotic Agent in the Liver through Inhibition of TGF-β1/SMAD Signaling and Autophagy in Hepatic Stellate Cells

Chronic liver injury may result in hepatic fibrosis, which can progress to cirrhosis and eventually liver failure. There are no drugs that are specifically approved for treating hepatic fibrosis. The natural product honokiol (HNK), a bioactive compound extracted from Magnolia grandiflora, represents a potential tool in the management of hepatic fibrosis. Though HNK has been reported to exhibit suppressive effects in a rat fibrosis model, the mechanisms accounting for this suppression remain unclear. In the present study, the anti-fibrotic effects of HNK on the liver were evaluated in vivo and in vitro. In vivo studies utilized a murine liver fibrosis model, in which fibrosis is induced by treatment with carbon tetrachloride (CCl₄). For in vitro studies, LX-2 human hepatic stellate cells (HSCs) were treated with HNK, and expression of markers of fibrosis, cell viability, the transforming growth factor-β (TGF-β1)/SMAD signaling pathway, and autophagy were analyzed. HNK was well tolerated and significantly attenuated CCl₄-induced liver fibrosis in vivo. Moreover, HNK decreased HSC activation and collagen expression by downregulating the TGF-β1/SMAD signaling pathway and autophagy. These results suggest that HNK is a new potential candidate for the treatment of hepatic fibrosis through suppressing both TGF-β1/SMAD signaling and autophagy in HSCs.

Development of the Entorhinal Cortex Occurs via Parallel Lamination During Neurogenesis

The entorhinal cortex (EC) is the spatial processing center of the brain and structurally is an interface between the three layered paleocortex and six layered neocortex, known as the periarchicortex. Limited studies indicate peculiarities in the formation of the EC such as early emergence of cells in layers (L) II and late deposition of LIII, as well as divergence in the timing of maturation of cell types in the superficial layers. In this study, we examine developmental events in the entorhinal cortex using an understudied model in neuroanatomy and development, the pig and supplement the research with BrdU labeling in the developing mouse EC. We determine the pig serves as an excellent anatomical model for studying human neurogenesis, given its long gestational length, presence of a moderate sized outer subventricular zone and early cessation of neurogenesis during gestation. Immunohistochemistry identified prominent clusters of OLIG2+ oligoprogenitor-like cells in the superficial layers of the lateral EC (LEC) that are sparser in the medial EC (MEC). These are first detected in the subplate during the early second trimester. MRI analyses reveal an acceleration of EC growth at the end of the second trimester. BrdU labeling of the developing MEC, shows the deeper layers form first and prior to the superficial layers, but the LV/VI emerges in parallel and the LII/III emerges later, but also in parallel. We coin this lamination pattern parallel lamination. The early born Reln+ stellate cells in the superficial layers express the classic LV marker, Bcl11b (Ctip2) and arise from a common progenitor that forms the late deep layer LV neurons. In summary, we characterize the developing EC in a novel animal model and outline in detail the formation of the EC. We further provide insight into how the periarchicortex forms in the brain, which differs remarkably to the inside-out lamination of the neocortex.

Excitatory granule neuron precursors orchestrate laminar localization and differentiation of cerebellar inhibitory interneuron subtypes

GABAergic interneurons migrate long distances through stereotyped migration programs toward specific laminar positions. During their migration, GABAergic interneurons are morphologically alike but then differentiate into a rich array of interneuron subtypes critical for brain function. How interneuron subtypes acquire their final phenotypic traits remains largely unknown. Here, we show that cerebellar molecular layer GABAergic interneurons, derived from the same progenitor pool, use separate migration paths to reach their laminar position and differentiate into distinct basket cell (BC) and stellate cell (SC) GABAergic interneuron subtypes. Using two-photon live imaging, we find that SC final laminar position requires an extra step of tangential migration supported by a subpopulation of glutamatergic granule cells (GCs). Conditional depletion of GCs affects SC differentiation but does not affect BCs. Our results reveal how timely feedforward control of inhibitory interneuron migration path regulates their terminal differentiation and, thus, establishment of the local inhibitory circuit assembly.

Purinergic Signaling in Liver Pathophysiology

Extracellular nucleosides and nucleotides activate a group of G protein-coupled receptors (GPCRs) known as purinergic receptors, comprising adenosine and P2Y receptors. Furthermore, purinergic P2X ion channels are activated by ATP. These receptors are expressed in liver resident cells and play a critical role in maintaining liver function. In the normal physiology, these receptors regulate hepatic metabolic processes such as insulin responsiveness, glycogen and lipid metabolism, and bile secretion. In disease states, ATP and other nucleotides serve as danger signals and modulate purinergic responses in the cells. Recent studies have demonstrated that purinergic receptors play a significant role in the development of metabolic syndrome associated non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), fibrosis, hepatocellular carcinoma (HCC) and liver inflammation. In this concise review, we dissect the role of purinergic signaling in different liver resident cells involved in maintaining healthy liver function and in the development of the above-mentioned liver pathologies. Moreover, we discuss potential therapeutic strategies for liver diseases by targeting adenosine, P2Y and P2X receptors.

Development of a cost-effective automated platform to produce human liver spheroids for basic and applied research

Liver disease represents an increasing cause of global morbidity and mortality. Currently, liver transplant is the only treatment curative for end-stage liver disease. Donor organs cannot meet the demand and therefore scalable treatments and new disease models are required to improve clinical intervention. Pluripotent stem cells represent a renewable source of human tissue. Recent advances in three-dimensional cell culture have provided the field with more complex systems that better mimic liver physiology and function. Despite these improvements, current cell-based models are variable in performance and expensive to manufacture at scale. This is due, in part, to the use of poorly defined or cross-species materials within the process, severely affecting technology translation. To address this issue, we have developed an automated and economical platform to produce liver tissue at scale for modelling disease and small molecule screening. Stem cell derived liver spheres were formed by combining hepatic progenitors with endothelial cells and stellate cells, in the ratios found within the liver. The resulting tissue permitted the study of human liver biology 'in the dish' and could be scaled for screening. In summary, we have developed an automated differentiation system that permits reliable self-assembly of human liver tissue for biomedical application. Going forward we believe that this technology will not only serve as anin vitroresource, and may have an important role to play in supporting failing liver function in humans.

Inhibition of Renal Stellate Cell Activation Reduces Renal Fibrosis

Interstitial fibrosis is a common feature of chronic kidney disease, and platelet-derived growth factor receptor-β (PDGFR-β)-positive mesenchymal cells are reportedly the major source of scar-producing myofibroblasts. We had previously demonstrated that albumin and its derivative R-III (a retinol-binding protein-albumin domain III fusion protein) inhibited the transdifferentiation/activation of hepatic stellate cells (HSCs) to myofibroblasts and that R-III administration reduced liver fibrosis. In this study, we isolated cells (referred to as renal stellate cells, RSCs) from rat kidney tissues using the HSC isolation protocol and compared their morphological and biochemical characteristics with those of HSCs. RSCs shared many characteristics with HSCs, such as storage of vitamin A-containing lipid droplets and expression of HSC markers as well as pericyte markers. RSCs underwent spontaneous transdifferentiation into myofibroblasts in in vitro culture, which was inhibited by albumin expression or R-III treatment. We also evaluated the therapeutic effects of R-III in unilateral ureteral obstruction (UUO)-induced renal fibrosis in mice. Injected R-III localized predominantly in cytoglobin/stellate cell activation-associated protein (Cygb/STAP)-positive cells in the kidney and reduced renal fibrosis. These findings suggest that RSCs can be recognized as the renal counterparts of HSCs and that RSCs represent an attractive therapeutic target for anti-fibrotic therapy.

The Role of Insulin Resistance and Diabetes in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) consists of the entire spectrum of fatty liver disease in patients without significant alcohol consumption, ranging from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH) to cirrhosis, with NASH recently shown as an important cause of hepatocellular carcinoma (HCC). There is a close relationship between insulin resistance (IR) and NAFLD, with a five-fold higher prevalence of NAFLD in patients with type 2 diabetes (T2DM) compared to that in patients without T2DM. IR is involved in the progression of disease conditions such as steatosis and NASH, as well as hepatic fibrosis progression. The mechanisms underlying these processes involve genetic factors, hepatic fat accumulation, alterations in energy metabolism, and inflammatory signals derived from various cell types including immune cells. In NASH-associated fibrosis, the principal cell type responsible for extracellular matrix production is the hepatic stellate cell (HSC). HSC activation by IR involves “direct” and “indirect” pathways. This review will describe the molecular mechanisms of inflammation and hepatic fibrosis in IR, the relationship between T2DM and hepatic fibrosis, and the relationship between T2DM and HCC in patients with NAFLD.

Angiogenesis in the progression of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent liver disease worldwide, and an increasing cause of liver cirrhosis and hepatocellular carcinoma. Angiogenesis, the formation of new blood vessels from pre-existing ones, is a key pathophysiological mechanism contributing to NAFLD progression. Major triggers for angiogenesis in NAFLD include tissue hypoxia, structural and dynamic endothelial cell dysfunction, stellate cell activation and macrophage-mediated inflammation. In turn, angiogenesis drives inflammation and is closely linked to the progression of liver fibrosis and the development of liver cancer. In particular, the molecular crosstalk between pro-angiogenic endothelial cells and activated stellate cells can result in a positive feedback loop in which angiogenesis and fibrosis develop in parallel. In this review, we highlight the molecular mechanisms, drivers and consequences of angiogenesis in the progression of NAFLD to NASH, fibrosis and hepatocellular carcinoma. Evidence from animal and clinical studies suggests that mediators of angiogenesis and endothelial dysfunction are promising disease biomarkers, and that inhibiting angiogenesis may improve the course of NAFLD.

Specialized stellate cells offer a privileged route for rapid water flux in Drosophila renal tubule

Insects are highly successful, in part through an excellent ability to osmoregulate. The renal (Malpighian) tubules can secrete fluid faster on a per-cell basis than any other epithelium, but the route for these remarkable water fluxes has not been established. In Drosophila melanogaster, we show that 4 genes of the major intrinsic protein family are expressed at a very high level in the fly renal tissue: the aquaporins (AQPs) Drip and Prip and the aquaglyceroporins Eglp2 and Eglp4 As predicted from their structure, and by their transport function by expressing these proteins in Xenopus oocytes, Drip, Prip, and Eglp2 show significant and specific water permeability, whereas Eglp2 and Eglp4 show very high permeability to glycerol and urea. Knockdowns of any of these genes result in impaired hormone-induced fluid secretion. The Drosophila tubule has 2 main secretory cell types: active cation-transporting principal cells, wherein the aquaglyceroporins localize to opposite plasma membranes, and small stellate cells, the site of the chloride shunt conductance, with these AQPs localizing to opposite plasma membranes. This suggests a model in which osmotically obliged water flows through the stellate cells. Consistent with this model, fluorescently labeled dextran, an in vivo marker of membrane water permeability, is trapped in the basal infoldings of the stellate cells after kinin diuretic peptide stimulation, confirming that these cells provide the major route for transepithelial water flux. The spatial segregation of these components of epithelial water transport may help to explain the unique success of the higher insects in regulating their internal environments.

Stellate Cells, Hepatocytes, and Endothelial Cells Imprint the Kupffer Cell Identity on Monocytes Colonizing the Liver Macrophage Niche

Macrophages are strongly adapted to their tissue of residence. Yet, little is known about the cell-cell interactions that imprint the tissue-specific identities of macrophages in their respective niches. Using conditional depletion of liver Kupffer cells, we traced the developmental stages of monocytes differentiating into Kupffer cells and mapped the cellular interactions imprinting the Kupffer cell identity. Kupffer cell loss induced tumor necrosis factor (TNF)- and interleukin-1 (IL-1) receptor-dependent activation of stellate cells and endothelial cells, resulting in the transient production of chemokines and adhesion molecules orchestrating monocyte engraftment. Engrafted circulating monocytes transmigrated into the perisinusoidal space and acquired the liver-associated transcription factors inhibitor of DNA 3 (ID3) and liver X receptor-α (LXR-α). Coordinated interactions with hepatocytes induced ID3 expression, whereas endothelial cells and stellate cells induced LXR-α via a synergistic NOTCH-BMP pathway. This study shows that the Kupffer cell niche is composed of stellate cells, hepatocytes, and endothelial cells that together imprint the liver-specific macrophage identity.

Adipose tissue-derived stem cells prevent fibrosis in murine steatohepatitis by suppressing IL-17-mediated inflammation

BACKGROUND AND AIM

The pathological features of non-alcoholic steatohepatitis (NASH) have not been determined, so fundamental treatment has not been established. Adipose-tissue-derived stromal/stem cells (ADSCs) are beneficial for repair/regenerative therapy of impaired organs because of their immuno-modulatory capability. In this study, we assessed how liver damage progresses during the early development phase of the murine NASH model and investigated whether ADSCs are preventatively efficacious against the fibrosis progression of NASH.

METHODS

C57BL/6J mice were fed with atherogenic high fat or high-fat diet 60 developing into NASH or simple steatosis. Their hepatic inflammatory cells (HICs) were analyzed by cDNA microarray. NASH mice were treated with ADSCs injected into spleen when hepatic inflammation was initially observed, and liver samples were analyzed. The effect of ADSCs on the mice hepatic stellate cell (HSC) line stimulated by recombinant IL-17 and HICs from NASH mice was analyzed.

RESULTS

The gene expression features of HICs implicated as humoral cytokine mediators of lymphoid cells during NASH development, compared with a simple steatosis model. One of the featured cytokines was IL-17. The development of hepatic fibrosis was alleviated when NASH mice were treated with ADSCs as well as treated with anti-IL-17 antibody, and the frequency of IL-17-secreting HICs decreased. NASH-HICs enhanced proliferation of HSCs, in which proliferation was sensitive to IL-17 stimulation. The stimulatory effect of NASH-HICs on the activation of HSCs was attenuated by co-culture with ADSCs.

CONCLUSION

ADSCs treatment prevented progression of NASH fibrosis by suppressing IL-17-mediated inflammation, which was associated with HSCs activation.

Cerebellar Stellate Cell Excitability Is Coordinated by Shifts in the Gating Behavior of Voltage-Gated Na+ and A-Type K+ Channels

Neuronal excitability in the vertebrate brain is governed by the coordinated activity of both ligand- and voltage-gated ion channels. In the cerebellum, spontaneous action potential (AP) firing of inhibitory stellate cells (SCs) is variable, typically operating within the 5- to 30-Hz frequency range. AP frequency is shaped by the activity of somatodendritic A-type K⁺ channels and the inhibitory effect of GABAergic transmission. An added complication, however, is that whole-cell recording from SCs induces a time-dependent and sustained increase in membrane excitability making it difficult to define the full range of firing rates. Here, we show that whole-cell recording in cerebellar SCs of both male and female mice augments firing rates by reducing the membrane potential at which APs are initiated. AP threshold is lowered due to a hyperpolarizing shift in the gating behavior of voltage-gated Na⁺ channels. Whole-cell recording also elicits a hyperpolarizing shift in the gating behavior of A-type K⁺ channels which contributes to increased firing rates. Hodgkin–Huxley modeling and pharmacological experiments reveal that gating shifts in A-type K⁺ channel activity do not impact AP threshold, but rather promote channel inactivation which removes restraint on the upper limit of firing rates. Taken together, our work reveals an unappreciated impact of voltage-gated Na⁺ channels that work in coordination with A-type K⁺ channels to regulate the firing frequency of cerebellar SCs.

Fibrosis reversal after hepatitis C virus elimination

PURPOSE OF REVIEW

Hepatitis C virus (HCV) infection has been the leading cause of cirrhosis in the United States now for the last several decades. With the introduction of highly effective direct acting antiviral (DAA) drugs, cure rates are now almost 100%. With this explosion of effective therapy, it is possible that many patients with HCV may have reversion in fibrosis. The purpose of this review is, therefore, to report on recent findings in this field.

RECENT FINDINGS

Older data that examined the effect of interferon-based HCV therapy indicate that fibrosis reverses after HCV eradication. More recent work in the DAA era similarly indicates that fibrosis is reversible. A caveat is that DAA therapy causes rapid viral clearance, and appears to lead to rapid reductions in inflammation. Some tools (such as transient elastography), which may also reflect the inflammatory response, and thus may 'overestimate' of fibrosis reversal. However, emerging data suggesting improved outcomes in patients with cirrhosis after HCV clearance support the concept that even cirrhosis reverses in some patients.

SUMMARY

Fibrosis (and cirrhosis) reversion, to some extent, occurs after HCV clearance. This topic is vitally important and information continues to emerge; more data on this subject are expected and needed.

MSP-RON Signaling Is Activated in the Transition From Pancreatic Intraepithelial Neoplasia (PanIN) to Pancreatic Ductal Adenocarcinoma (PDAC)

Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest epithelial malignancies and remains difficult to treat. Pancreatic intraepithelial neoplasias (PanINs) represent the majority of the pre-cancer lesions in the pancreas. The PDAC microenvironment consists of activated pancreatic stellate cells (PSCs) and immune cells, which are thought to contribute to neoplastic transformation. However, the signaling events involved in driving the transition from the neoplastic precursor to the more advanced and aggressive forms in the pancreas are not well understood. Recepteur d’Origine Nantais (RON) is a c-MET family receptor tyrosine kinase that is implicated in playing a role in cell proliferation, migration and other aspects of tumorigenesis. Macrophage stimulating protein (MSP) is the ligand for RON and becomes activated upon proteolytic cleavage by matriptase (also known as ST14), a type II transmembrane serine protease. In the current study, by immunohistochemistry (IHC) analysis of human pancreatic tissues, we found that the expression levels MSP and matriptase are drastically increased during the transition from the preneoplastic PanIN stages to the more advanced and aggressive PDAC. Moreover, RON is highly expressed in both PDAC and in cancer-associated stellate cells. In contrast, MSP, RON, and matriptase are expressed at low levels, if any, in normal pancreas. Our study underscores an emerging role of MSP-RON autocrine and paracrine signaling events in driving malignant progression in the pancreas.

Electrophysiological Characterization of Networks and Single Cells in the Hippocampal Region of a Transgenic Rat Model of Alzheimer's Disease

The hippocampus and entorhinal cortex (EC) are areas affected early and severely in Alzheimer’s disease (AD), and this is associated with deficits in episodic memory. Amyloid-β (Aβ), the main protein found in amyloid plaques, can affect neuronal physiology and excitability, and several AD mouse models with memory impairments display aberrant network activity, including hyperexcitability and seizures. In this study, we investigated single cell physiology in EC and network activity in EC and dentate gyrus (DG) in the McGill-R-Thy1-APP transgenic rat model, using whole-cell patch clamp recordings and voltage-sensitive dye imaging (VSDI) in acute slices. In slices from transgenic animals up to 4 months of age, the majority of the principal neurons in Layer II of EC, fan cells and stellate cells, expressed intracellular Aβ (iAβ). Whereas the electrophysiological properties of fan cells were unaltered, stellate cells were more excitable in transgenic than in control rats. Stimulation in the DG resulted in comparable patterns in both groups at three and nine months, but at 12 months, the elicited responses in the transgenic group showed a significant preference for the enclosed blade, without any change in overall excitability. Only transient changes in the local network activity were seen in the medial EC (MEC). Although the observed changes in the McGill rat model are subtle, they are specific, pointing to a differential and selective involvement of specific parts of the hippocampal circuitry in Aβ pathology.

Conophylline suppresses pancreatic cancer desmoplasia and cancer-promoting cytokines produced by cancer-associated fibroblasts

Despite recent advances in cancer treatment, pancreatic cancer is a highly malignant tumor type with a dismal prognosis and it is characterized by dense desmoplasia in the cancer tissue. Cancer-associated fibroblasts (CAF) are responsible for this fibrotic stroma and promote cancer progression. We previously reported that a novel natural compound conophylline (CnP) extracted from the leaves of a tropical plant reduced liver and pancreatic fibrosis by suppression of stellate cells. However, there have been no studies to investigate the effects of CnP on CAF, which is the aim of this work. Here, we showed that CAF stimulated indicators of pancreatic cancer malignancy, such as proliferation, invasiveness, and chemoresistance. We also showed that CnP suppressed CAF activity and proliferation, and inhibited the stimulating effects of CAF on pancreatic cancer cells. Moreover, CnP strongly decreased the various cytokines involved in cancer progression, such as interleukin (IL)-6, IL-8, C-C motif chemokine ligand 2 (CCL2), and C-X-C motif chemokine ligand 12 (CXCL12), secreted by CAF. In vivo, CAF promoted tumor proliferation and desmoplastic formation in a mouse xenograft model, CnP reduced desmoplasia of tumors composed of pancreatic cancer cells + CAF, and combination therapy of CnP with gemcitabine remarkably inhibited tumor proliferation. Our findings suggest that CnP is a promising therapeutic strategy of combination therapy with anticancer drugs to overcome refractory pancreatic cancers.

The plant alkaloid conophylline inhibits matrix formation of fibroblasts

Conophylline is a Vinca alkaloid from leaves of the tropical plant Ervatamia microphylla and has been shown to mimic the effect of the growth and differentiation factor activin A on pancreatic progenitor cells. However, activin A stimulates fibrosis of pancreatic stellate cells, whereas conophylline inhibits it, suggesting that this compound may serve as an antifibrotic drug. Here we investigated the effects of conophylline on human foreskin fibroblasts, especially focusing on extracellular matrix (ECM) proteins. A gene microarray analysis revealed that conophylline remarkably suppressed expression of the gene for hyaluronan synthase 2 (HAS2) and of its antisense RNA, whereas the expression of collagen genes was unaffected. Of note, immunostaining experiments revealed that conophylline substantially inhibits incorporation of versican and collagens into the ECM in cells treated with transforming growth factor β (TGFβ), which promotes collagen synthesis, but not in cells not treated with TGFβ. Moreover, a protein biosynthesis assay disclosed that conophylline decreases collagen biosynthesis, concomitant with a decrease in total protein biosynthesis, indicating that conophylline-mediated inhibition of fibrosis is not specific to collagen synthesis. Conophylline affected neither TGFβ-induced nuclear translocation of SMAD family member 2/3 (SMAD2/3) nor phosphorylation of SMAD2. However, conophylline substantially inhibited phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), suggesting that conophylline inhibits HAS2 expression via TGFβ-mediated activation of the ERK1/2 pathway. Taken together, our results indicate that conophylline may be a useful inhibitor of ECM formation in fibrosis.

A Map-like Micro-Organization of Grid Cells in the Medial Entorhinal Cortex

How the topography of neural circuits relates to their function remains unclear. Although topographic maps exist for sensory and motor variables, they are rarely observed for cognitive variables. Using calcium imaging during virtual navigation, we investigated the relationship between the anatomical organization and functional properties of grid cells, which represent a cognitive code for location during navigation. We found a substantial degree of grid cell micro-organization in mouse medial entorhinal cortex: grid cells and modules all clustered anatomically. Within a module, the layout of grid cells was a noisy two-dimensional lattice in which the anatomical distribution of grid cells largely matched their spatial tuning phases. This micro-arrangement of phases demonstrates the existence of a topographical map encoding a cognitive variable in rodents. It contributes to a foundation for evaluating circuit models of the grid cell network and is consistent with continuous attractor models as the mechanism of grid formation.

Non-parenchymal hepatic cell lipotoxicity and the coordinated progression of non-alcoholic fatty liver disease and atherosclerosis

PURPOSE OF REVIEW

Non-alcoholic fatty liver disease (NAFLD) appears to be independently associated with the development of atherosclerosis. The biological mechanisms underlying this association are complex, and likely involve liver-resident cell types other than hepatocytes. Thus, we review recent evidence that non-parenchymal hepatic cell responses to lipid excess contribute to the pathogenesis of both NAFLD and atherosclerosis.

RECENT FINDINGS

Significant independent associations between NAFLD and atherosclerosis have been identified through cross-sectional studies and meta-analyses. Mechanistic studies in cell cultures and in rodent models suggest that liver-resident macrophages, activated hepatic stellate cells (HSC) and liver sinusoidal endothelial cells (LSEC) mount lipotoxic responses under NAFLD conditions which can contribute to the progression of both NAFLD and atherosclerosis.

SUMMARY

Non-parenchymal hepatic cell types exhibit some similarity in their responses to lipid excess, and in their pathogenic mechanisms, which likely contribute to the coordinated progression of NAFLD and atherosclerosis. In response to lipotoxic conditions, macrophages, Kupffer cells and HSC initiate robust inflammatory responses, whereas LSEC generate excess reactive oxygen species (ROS). The extent to which inflammatory cytokines and ROS produced by non-parenchymal cells contribute to the progression of both NAFLD and atherosclerosis warrants further investigation.

Stellate Cells in Tissue Repair, Inflammation, and Cancer

Stellate cells are resident lipid-storing cells of the pancreas and liver that transdifferentiate to a myofibroblastic state in the context of tissue injury. Beyond having roles in tissue homeostasis, stellate cells are increasingly implicated in pathological fibrogenic and inflammatory programs that contribute to tissue fibrosis and that constitute a growth-permissive tumor microenvironment. Although the capacity of stellate cells for extracellular matrix production and remodeling has long been appreciated, recent research efforts have demonstrated diverse roles for stellate cells in regulation of epithelial cell fate, immune modulation, and tissue health. Our present understanding of stellate cell biology in health and disease is discussed here, as are emerging means to target these multifaceted cells for therapeutic benefit.

Evidence-based complementary treatment of pancreatic cancer: a review of adjunct therapies including paricalcitol, hydroxychloroquine, intravenous vitamin C, statins, metformin, curcumin, and aspirin

Despite new and exciting research and renewed optimism about future therapy, current statistics of survival from pancreatic cancer remains dismal. Patients seeking alternative or complementary treatments should be warned to avoid the hype and instead look to real science. A variety of relatively safe and inexpensive treatment options that have shown success in preclinical models and/or retrospective studies are currently available. Patients require their physicians to provide therapeutic guidance and assistance in obtaining and administrating these various therapies. Paricalcitol, an analog of vitamin D, has been shown by researchers at the Salk Institute for Biological Studies to break though the protective stroma surrounding tumor cells. Hydroxychloroquine has been shown to inhibit autophagy, a process by which dying cells recycle injured organelles and internal toxins to generate needed energy for survival and reproduction. Intravenous vitamin C creates a toxic accumulation of hydrogen peroxide within cancer cells, hastening their death. Metformin inhibits mitochondrial oxidative metabolism utilized by cancer stem cells. Statins inhibit not only cholesterol but also other factors in the same pathway that affect cancer cell growth, protein synthesis, and cell cycle progression. A novel formulation of curcumin may prevent resistance to chemotherapy and inhibit pancreatic cancer cell proliferation. Aspirin therapy has been shown to prevent pancreatic cancer and may be useful to prevent recurrence. These therapies are all currently available and are reviewed in this paper with emphasis on the most recent laboratory research and clinical studies.

"Talking": Differential Autocrine Inflammatory Networks in Isolated Primary Hepatic Stellate Cells and Hepatocytes under Hypoxic Stress

We hypothesized that isolated primary mouse hepatic stellate cells (HSC) and hepatocytes (HC) would elaborate different inflammatory responses to hypoxia with or without reoxygenation. We further hypothesized that intracellular information processing (“thinking”) differs from extracellular information transfer (“talking”) in each of these two liver cell types. Finally, we hypothesized that the complexity of these autocrine responses might only be defined in the absence of other non-parenchymal cells or trafficking leukocytes. Accordingly, we assayed 19 inflammatory mediators in the cell culture media (CCM) and whole cell lysates (WCLs) of HSC and HC during hypoxia with and without reoxygenation. We applied a unique set of statistical and data-driven modeling techniques including Two-Way ANOVA, hierarchical clustering, Principal Component Analysis (PCA) and Network Analysis to define the inflammatory responses of these isolated cells to stress. HSC, under hypoxic and reoxygenation stresses, both expressed and secreted larger quantities of nearly all inflammatory mediators as compared to HC. These differential responses allowed for segregation of HSC from HC by hierarchical clustering. PCA suggested, and network analysis supported, the hypothesis that above a certain threshold of cellular stress, the inflammatory response becomes focused on a limited number of functions in both HSC and HC, but with distinct characteristics in each cell type. Network analysis of separate extracellular and intracellular inflammatory responses, as well as analysis of the combined data, also suggested the presence of more complex inflammatory “talking” (but not “thinking”) networks in HSC than in HC. This combined network analysis also suggested an interplay between intracellular and extracellular mediators in HSC under more conditions than that observed in HC, though both cell types exhibited a qualitatively similar phenotype under hypoxia/reoxygenation. Our results thus suggest that a stepwise series of computational and statistical analyses may help decipher how cells respond to environmental stresses, both within the cell and in its secretory products, even in the absence of cooperation from other cells in the liver.

Nitric oxide signals are interlinked with calcium signals in normal pancreatic stellate cells upon oxidative stress and inflammation

The mammalian diffuse stellate cell system comprises retinoid-storing cells capable of remarkable transformations from a quiescent to an activated myofibroblast-like phenotype. Activated pancreatic stellate cells (PSCs) attract attention owing to the pivotal role they play in development of tissue fibrosis in chronic pancreatitis and pancreatic cancer. However, little is known about the actual role of PSCs in the normal pancreas. These enigmatic cells have recently been shown to respond to physiological stimuli in a manner that is markedly different from their neighbouring pancreatic acinar cells (PACs). Here, we demonstrate the capacity of PSCs to generate nitric oxide (NO), a free radical messenger mediating, for example, inflammation and vasodilatation. We show that production of cytosolic NO in PSCs is unambiguously related to cytosolic Ca²⁺ signals. Only stimuli that evoke Ca²⁺ signals in the PSCs elicit consequent NO generation. We provide fresh evidence for the striking difference between signalling pathways in PSCs and adjacent PACs, because PSCs, in contrast to PACs, generate substantial Ca²⁺-mediated and NOS-dependent NO signals. We also show that inhibition of NO generation protects both PSCs and PACs from necrosis. Our results highlight the interplay between Ca²⁺ and NO signalling pathways in cell–cell communication, and also identify a potential therapeutic target for anti-inflammatory therapies.

Neuroligins Are Selectively Essential for NMDAR Signaling in Cerebellar Stellate Interneurons

Neuroligins are postsynaptic cell-adhesion molecules that contribute to synapse specification. However, many other postsynaptic cell-adhesion molecules are known and the relative contributions of neuroligins versus other such molecules in different types of synapses and neurons remains largely unknown. Here, we have studied the role of neuroligins in cerebellar stellate interneurons that participate in a well defined circuit that converges on Purkinje cells as the major output neurons of cerebellar cortex. By crossing triple conditional knock-out (cKO) mice targeting all three major neuroligins [neuroligin-1 to neuroligin-3 (NL123)] with parvalbumin-Cre (PV-Cre) transgenic mice, we deleted neuroligins from inhibitory cerebellar interneurons and Purkinje cells, allowing us to study the effects of neuroligin deletions on cerebellar stellate cell synapses by electrophysiology in acute slices. PV-Cre/NL123 cKO mice did not exhibit gross alterations of cerebellar structure or cerebellar interneuron morphology. Strikingly, electrophysiological recordings in stellate cells from these PV-Cre/NL123 cKO mice revealed a large decrease in NMDAR-mediated excitatory synaptic responses, which, in stellate cells, are largely extrasynaptic, without a change in AMPA-receptor-mediated responses. Parallel analyses in PV-Cre/NL1 mice that are single NL1 cKO mice uncovered the same phenotype, demonstrating that NL1 is responsible for recruiting extrasynaptic NMDARs. Moreover, we observed only a modest impairment in inhibitory synaptic responses in stellate cells lacking NL123 despite a nearly complete suppression of inhibitory synaptic transmission in Purkinje cells by the same genetic manipulation. Our results suggest that, unlike other types of neurons investigated, neuroligins are selectively essential in cerebellar stellate interneurons for enabling the function of extrasynaptic NMDARs.

SIGNIFICANCE STATEMENT

Neuroligins are postsynaptic cell-adhesion molecules genetically linked to autism. However, the contributions of neuroligins to interneuron functions remain largely unknown. Here, we analyzed the role of neuroligins in cerebellar stellate interneurons. We deleted neuroligin-1, neuroligin-2, and neuroligin-3, the major cerebellar neuroligin isoforms, from stellate cells in triple NL123 conditional knock-out mice and analyzed synaptic responses by acute slice electrophysiology. We find that neuroligins are selectively essential for extrasynaptic NMDAR-mediated signaling, but dispensable for both AMPAR-mediated and inhibitory synaptic transmission. Our results reveal a critical and selective role for neuroligins in the regulation of NMDAR responses in cerebellar stellate interneurons.

Postnatal Migration of Cerebellar Interneurons

Due to its continuing development after birth, the cerebellum represents a unique model for studying the postnatal orchestration of interneuron migration. The combination of fluorescent labeling and ex/in vivo imaging revealed a cellular highway network within cerebellar cortical layers (the external granular layer, the molecular layer, the Purkinje cell layer, and the internal granular layer). During the first two postnatal weeks, saltatory movements, transient stop phases, cell-cell interaction/contact, and degradation of the extracellular matrix mark out the route of cerebellar interneurons, notably granule cells and basket/stellate cells, to their final location. In addition, cortical-layer specific regulatory factors such as neuropeptides (pituitary adenylate cyclase-activating polypeptide (PACAP), somatostatin) or proteins (tissue-type plasminogen activator (tPA), insulin growth factor-1 (IGF-1)) have been shown to inhibit or stimulate the migratory process of interneurons. These factors show further complexity because somatostatin, PACAP, or tPA have opposite or no effect on interneuron migration depending on which layer or cell type they act upon. External factors originating from environmental conditions (light stimuli, pollutants), nutrients or drug of abuse (alcohol) also alter normal cell migration, leading to cerebellar disorders.

Temporal integration and 1/f power scaling in a circuit model of cerebellar interneurons

Inhibitory interneurons interconnected via electrical and chemical (GABA_A receptor) synapses form extensive circuits in several brain regions. They are thought to be involved in timing and synchronization through fast feedforward control of principal neurons. Theoretical studies have shown, however, that whereas self-inhibition does indeed reduce response duration, lateral inhibition, in contrast, may generate slow response components through a process of gradual disinhibition. Here we simulated a circuit of interneurons (stellate and basket cells) of the molecular layer of the cerebellar cortex and observed circuit time constants that could rise, depending on parameter values, to >1 s. The integration time scaled both with the strength of inhibition, vanishing completely when inhibition was blocked, and with the average connection distance, which determined the balance between lateral and self-inhibition. Electrical synapses could further enhance the integration time by limiting heterogeneity among the interneurons and by introducing a slow capacitive current. The model can explain several observations, such as the slow time course of OFF-beam inhibition, the phase lag of interneurons during vestibular rotation, or the phase lead of Purkinje cells. Interestingly, the interneuron spike trains displayed power that scaled approximately as 1/f at low frequencies. In conclusion, stellate and basket cells in cerebellar cortex, and interneuron circuits in general, may not only provide fast inhibition to principal cells but also act as temporal integrators that build a very short-term memory.NEW & NOTEWORTHY The most common function attributed to inhibitory interneurons is feedforward control of principal neurons. In many brain regions, however, the interneurons are densely interconnected via both chemical and electrical synapses but the function of this coupling is largely unknown. Based on large-scale simulations of an interneuron circuit of cerebellar cortex, we propose that this coupling enhances the integration time constant, and hence the memory trace, of the circuit.

STAT3 Inhibition Suppresses Hepatic Stellate Cell Fibrogenesis: HJC0123, a Potential Therapeutic Agent for Liver Fibrosis

Hepatic Stellate Cells (HSCs) are the major source of the excessive extracellular matrix (ECM) production that replaces liver parenchyma with fibrous tissue during liver fibrosis. The signal transducer and activator of transcription 3 (STAT3) promotes HCSs survival, proliferation, and activation contributing to fibrogenesis. We have previously used a fragment-based drug design approach and have discovered a novel STAT3 inhibitor, HJC0123. Here, we explored the biological effects of HJC0123 on the fibrogenic properties of HSCs. HJC0123 treatment resulted in the inhibition of HSCs proliferation at submicromolar concentrations. HJC0123 reduced the phosphorylation, nuclear translocation, and transcriptional activity of STAT3. It decreased the expression of STAT3-regulated proteins, induced cell cycle arrest, promoted apoptosis and downregulated SOCS3. HJC0123 treatment inhibited HSCs activation and downregulated ECM protein fibronectin and type I collagen expression. In addition, HJC0123 increased IL-6 production and decreased TGF-β induced Smad2/3 phosphorylation. These results demonstrate that HJC0123 represents a novel STAT3 inhibitor that suppresses the fibrogenic properties of HSCs, suggesting its therapeutic potential in liver fibrosis.

Cell-Type Specific Phase Precession in Layer II of the Medial Entorhinal Cortex

The identity of phase-precessing cells in the entorhinal cortex is unknown. Here, we used a classifier derived from cell-attached recordings to separate putative pyramidal cells and putative stellate cells recorded extracellularly in layer II of the medial entorhinal cortex in rats. Using a novel method to identify single runs as temporal periods of elevated spiking activity, we find that both cell types show phase precession but putative stellate cells show steeper slopes of phase precession and larger phase ranges. As the two classes of cells have different projection patterns, phase precession is differentially passed on to different subregions of the hippocampal formation.

SIGNIFICANCE STATEMENT

It is a great challenge for neuroscience to reveal the cellular basis of cognitive functions. One such function is the ability to learn and recollect temporal sequences of events. The representation of sequences in the brain is thought to require temporally structured activity of nerve cells. How different types of neurons generate temporally structured activity is currently unknown. In the present study, we use a computational classification procedure to separate different cell types and find that a subpopulation of cells, so-called stellate neurons, exhibits clear temporal coding. Contrary to the stellate cells, pyramidal cells show weaker temporal coding. This discovery sheds light on the cellular basis of temporal coding in the brain.

Cytoglobin as a Marker of Hepatic Stellate Cell-derived Myofibroblasts

Myofibroblasts play important roles in inflammation, fibrosis and tumorigenesis in chronically inflamed liver. Liver myofibroblasts originate from hepatic stellate cells, portal fibroblasts or mesothelial cells, and they are localized in and around fibrotic septum and portal tracts. Liver myofibroblasts are the source of extracellular matrix materials, including type I collagen and multiple fibrogenic growth factors, such as transforming growth factor-β and vascular endothelial growth factor. Although a detailed characterization of the function of individual myofibroblasts has not been conducted, owing to the lack of appropriate cell markers, recent lineage-tracing technology has revealed the limited contribution of myofibroblasts that are derived from portal fibroblasts to various types of liver fibrosis, as compared with the contribution of hepatic stellate cells. In addition, cytoglobin, which is the fourth globin in mammals and function as a local gas sensor, provides a new perspective on the involvement of stellate cells in fibrosis and carcinogenesis, possibly through its anti-oxidative properties and is a promising new marker that discriminates between myofibroblasts derived from stellate cells and those from portal fibroblasts.

Conophylline suppresses hepatic stellate cells and attenuates thioacetamide-induced liver fibrosis in rats

BACKGROUND & AIMS

Conophylline (CnP) is a vinca alkaloid purified from a tropical plant and inhibits activation of pancreatic stellate cells. We investigated the effect of CnP on hepatic stellate cells (HSC) in vitro. We also examined whether CnP attenuates hepatic fibrosis in vivo.

METHOD

We examined the effect of CnP on the expression of α-smooth muscle actin (α-SMA) and collagen-1, DNA synthesis and apoptosis in rat HSC and Lx-2 cells. We also examined the effect of CnP on hepatic fibrosis induced by thioacetamide (TAA).

RESULTS

In rat HSC and Lx-2 cells, CnP reduced the expression of α-SMA and collagen-1. CnP inhibited DNA synthesis induced by serum. CnP also promoted activation of caspase-3 and induced apoptosis as assessed by DNA ladder formation and TUNEL assay. In contrast, CnP did not induce apoptosis in AML12 cells. We then examined the effect of CnP on TAA-induced cirrhosis. In TAA-treated rats, the surface of the liver was irregular and multiple nodules were observed. Histologically, formation of pseudolobules surrounded by massive fibrous tissues was observed. When CnP was administered together with TAA, the surface of the liver was smooth and liver fibrosis was markedly inhibited. Collagen content was significantly reduced in CnP-treated liver.

CONCLUSION

Conophylline suppresses HSC and induces apoptosis in vitro. CnP also attenuates formation of the liver fibrosis induced by TAA in vivo.

Membrane potential-dependent integration of synaptic inputs in entorhinal stellate neurons

Stellate cells (SCs) of the medial entorhinal cortex exhibit robust spontaneous membrane-potential oscillations (MPOs) in the theta (4-12 Hz) frequency band as well as theta-frequency resonance in their membrane impedance spectra. Past experimental and modeling work suggests that these features may contribute to the phase-locking of SCs to the entorhinal theta rhythm and may be important for forming the hexagonally tiled grid cell place fields exhibited by these neurons in vivo. Among the major biophysical mechanisms contributing to MPOs is a population of persistent (non-inactivating or slowly inactivating) sodium channels. The resulting persistent sodium conductance (GNaP ) gives rise to an apparent increase in input resistance as the cell approaches threshold. In this study, we used dynamic clamp to test the hypothesis that this increased input resistance gives rise to voltage-dependent, and thus MPO phase-dependent, changes in the amplitude of excitatory and inhibitory post-synaptic potential (PSP) amplitudes. We find that PSP amplitude depends on membrane potential, exhibiting a 5-10% increase in amplitude per mV depolarization. The effect is larger than-and sums quasi-linearly with-the effect of the synaptic driving force, V - Esyn . Given that input-driven MPOs 10 mV in amplitude are commonly observed in MEC stellate cells in vivo, this voltage- and phase-dependent synaptic gain is large enough to modulate PSP amplitude by over 50% during theta-frequency MPOs. Phase-dependent synaptic gain may therefore impact the phase locking and phase precession of grid cells in vivo to ongoing network oscillations. © 2014 Wiley Periodicals, Inc.

Caffeine attenuates liver fibrosis via defective adhesion of hepatic stellate cells in cirrhotic model

BACKGROUND AND AIM

Several epidemiological studies have shown that coffee intake attenuates the progression of liver fibrosis; however, the mechanism is unclear.

AIMS

We investigated the direct effects of caffeine on hepatic stellate cells (HSCs) and assessed whether caffeine attenuated intrahepatic fibrosis in rat model of liver cirrhosis.

METHODS

Human hepatic stellate cell line, an immortalized human HSCs line, was used in in vitro assay system. Cell migration and proliferation were assessed in presence of various caffeine concentrations (0, 1, 5, and 10 mmol), and levels of procollagen type Ic and α-smooth muscle actin (α-SMA) were measured by Western blot. Severity of liver inflammation and fibrosis were compared between thioacetamide-treated rats with and without caffeine supplementation.

RESULTS

Caffeine increased HSCs apoptosis and intracellular F-actin and cyclic adenosine monophosphate expression. Caffeine also inhibited procollagen type Ic and α-SMA expression in a dose- and time-dependent manner. In rat model, caffeine decreased periportal inflammation, levels of inflammatory cells (1.4 ± 0.52 vs 2.6 ± 0.46, P < 0.05), and fibrosis (2.1 ± 0.35 vs 2.9 ± 0.84, P < 0.05). Transforming growth factor-β and α-SMA expressions were also reduced by caffeine.

CONCLUSION

Caffeine attenuates the progression of liver fibrosis by inhibiting HSCs adhesion and activation.

Modulated discharge of Purkinje and stellate cells persists after unilateral loss of vestibular primary afferent mossy fibers in mice

Cerebellar Purkinje cells are excited by two afferent pathways: climbing and mossy fibers. Climbing fibers evoke large "complex spikes" (CSs) that discharge at low frequencies. Mossy fibers synapse on granule cells whose parallel fibers excite Purkinje cells and may contribute to the genesis of "simple spikes" (SSs). Both afferent systems convey vestibular information to folia 9c-10. After making a unilateral labyrinthectomy (UL) in mice, we tested how the discharge of CSs and SSs was changed by the loss of primary vestibular afferent mossy fibers during sinusoidal roll tilt. We recorded from cells identified by juxtacellular neurobiotin labeling. The UL preferentially reduced vestibular modulation of CSs and SSs in folia 8-10 contralateral to the UL. The effects of a UL on Purkinje cell discharge were similar in folia 9c-10, to which vestibular primary afferents project, and in folia 8-9a, to which they do not project, suggesting that vestibular primary afferent mossy fibers were not responsible for the UL-induced alteration of SS discharge. UL also induced reduced vestibular modulation of stellate cell discharge contralateral to the UL. We attribute the decreased modulation to reduced vestibular modulation of climbing fibers. In summary, climbing fibers modulate CSs directly and SSs indirectly through activation of stellate cells. Whereas vestibular primary afferent mossy fibers cannot account for the modulated discharge of SSs or stellate cells, the nonspecific excitation of Purkinje cells by parallel fibers may set an operating point about which the discharges of SSs are sculpted by climbing fibers.

Cicletanine stimulates eNOS phosphorylation and NO production via Akt and MAP kinase/Erk signaling in sinusoidal endothelial cells

The function of the endothelial isoform of nitric oxide synthase (eNOS) and production of nitric oxide (NO) is altered in a number of disease states. Pharmacological approaches to enhancing NO synthesis and thus perhaps endothelial function could have substantial benefits in patients. We analyzed the effect of cicletanine, a synthetic pyridine with potent vasodilatory characteristics, on eNOS function and NO production in normal (liver) and injured rat sinusoidal endothelial cells, and we studied the effect of cicletanine-induced NO on stellate cell contraction and portal pressure in an in vivo model of liver injury. Sinusoidal endothelial cells were isolated from normal and injured rat livers. After exposure to cicletanine, eNOS phosphorylation, NO synthesis, and the signaling pathway regulating eNOS activation were measured. Cicletanine led to an increase in eNOS (Ser¹¹⁷⁷) phosphorylation, cytochrome c reductase activity, L-arginine conversion to L-citrulline, as well as NO production. The mechanism of the effect of cicletanine appeared to be via the protein kinase B (Akt) and MAP kinase/Erk signaling pathways. Additionally, cicletanine improved NO synthesis in injured sinusoidal endothelial cells. NO production induced by cicletanine in sinusoidal endothelial cells increased protein kinase G (PKG) activity as well as relaxation of stellate cells. Finally, administration of cicletanine to mice with portal hypertension induced by bile duct ligation led to reduction of portal pressure. The data indicate that cicletanine might improve eNOS activity in injured sinusoidal endothelial cells and likely activates hepatic stellate cell NO/PKG signaling. It raises the possibility that cicletanine could improve intrahepatic vascular function in portal hypertensive patients.

The compartmental restriction of cerebellar interneurons

The Purkinje cells (PC's) of the cerebellar cortex are subdivided into multiple different molecular phenotypes that form an elaborate array of parasagittal stripes. This array serves as a scaffold around which afferent topography is organized. The ways in which cerebellar interneurons may be restricted by this scaffolding are less well-understood. This review begins with a brief survey of cerebellar topography. Next, it reviews the development of stripes in the cerebellum with a particular emphasis on the embryological origins of cerebellar interneurons. These data serve as a foundation to discuss the hypothesis that cerebellar compartment boundaries also restrict cerebellar interneurons, both excitatory [granule cells, unipolar brush cells (UBCs)] and inhibitory (e.g., Golgi cells, basket cells). Finally, it is proposed that the same PC scaffold that restricts afferent terminal fields to stripes may also act to organize cerebellar interneurons.

An undifferentiated embryonal sarcoma of the liver containing adipophilin-positive vesicles in an adult with massive sinusoidal invasion

Undifferentiated embryonal sarcoma of the liver (UESL) is a malignant mesenchymal tumor that occurs typically in children and rarely in adults. Here we describe a case of UESL in a 51-year-old woman who presented with a cystic lesion in the liver. Because it grew slowly, the anterior segment of the liver was resected to check the lesion. Histologically, the lesion looked like a telangiectatic hepatic adenoma. Two years after resection, the tumor recurred, and she died 3 years later due to liver failure. The autopsy revealed that these lesions were UESL with massive sinusoidal invasion, and a review of the case indicated the primary lesion was also UESL. We also confirmed these tumor cells by staining with CD56, alpha-smooth muscle actin (SMA), and adipophilin, suggesting that they have a character similar to that of stellate cells in the space of Disse. The histological result of our patient revealed atypical UESL. Therefore, UESL should be considered when a hepatic lesion with degeneration is seen, even in an adult. In addition, the immunohistochemical appearance of this case implies that UESL is perhaps derived from stellate cells or stellate cells with myofibroblast differentiation in the space of Disse.

Epidemiology, risk factors, and the promotion of pancreatic cancer: role of the stellate cell

There are approximately 277,000 new cases of pancreatic cancer and 266,000 deaths from pancreatic cancer annually, indicating a mortality rate of 96% of the cases diagnosed. Because of the ineffectiveness of therapies, a major emphasis needs to be placed on prevention. This paper reviews the epidemiology and risk factors for pancreatic cancer, and uses this information to propose plausible research directions for determining the biological mechanisms mediating the effects of risk factors on the promotion of pancreatic cancer, with a focus on the pancreatic stellate cell.

Possible role of acetylcholine in regulating spatial novelty effects on theta rhythm and grid cells

Existing pharmacological and lesion data indicate that acetylcholine plays an important role in memory formation. For example, increased levels of acetylcholine in the hippocampal formation are known to be associated with successful encoding while disruption of the cholinergic system leads to impairments on a range of mnemonic tasks. However, cholinergic signaling from the medial septum also plays a central role in generating and pacing theta-band oscillations throughout the hippocampal formation. Recent experimental results suggest a potential link between these distinct phenomena. Environmental novelty, a condition associated with strong cholinergic drive, has been shown to induce an expansion in the firing pattern of entorhinal grid cells and a reduction in the frequency of theta measured from the LFP. Computational modeling suggests the spatial activity of grid cells is produced by interference between neuronal oscillators; scale being determined by theta-band oscillations impinging on entorhinal stellate cells, the frequency of which is modulated by acetylcholine. Here we propose that increased cholinergic signaling in response to environmental novelty triggers grid expansion by reducing the frequency of the oscillations. Furthermore, we argue that cholinergic induced grid expansion may enhance, or even induce, encoding by producing a mismatch between expanded grid cells and other spatial inputs to the hippocampus, such as boundary vector cells. Indeed, a further source of mismatch is likely to occur between grid cells of different native scales which may expand by different relative amounts.

Mechanisms of hepatic fibrogenesis

Multiple etiologies of liver disease lead to liver fibrosis through integrated signaling networks that regulate the deposition of extracellular matrix. This cascade of responses drives the activation of hepatic stellate cells (HSCs) into a myofibroblast-like phenotype that is contractile, proliferative and fibrogenic. Collagen and other extracellular matrix (ECM) components are deposited as the liver generates a wound-healing response to encapsulate injury. Sustained fibrogenesis leads to cirrhosis, characterized by a distortion of the liver parenchyma and vascular architecture. Uncovering the intricate mechanisms that underlie liver fibrogenesis forms the basis for efforts to develop targeted therapies to reverse the fibrotic response and improve the outcomes of patients with chronic liver disease.

B7-H4 mediates inhibition of T cell responses by activated murine hepatic stellate cells

Liver fibrosis is mediated by the transformation of hepatic stellate cells (HSC) from a quiescent to an activated state. To understand the role of HSC in liver immunity, we investigated the effect of this transition on T cell stimulation in vitro. Unlike quiescent HSC, activated HSC did not induce proliferation of antigen-specific T cells. Phenotypic analysis of quiescent and activated HSC revealed that activated HSC expressed the coinhibitory molecule B7-H4. Silencing B7-H4 by small interfering RNA (siRNA) in activated HSC restored the ability of T cells to proliferate, differentiate, and regain effector recall responses. Furthermore, expression of B7-H4 on HSC inhibits early T cell activation and addition of exogenous interleukin (IL)-2 reversed the T cell anergy induced by activated HSC.

CONCLUSION

These studies reveal a novel role for activated HSC in the attenuation of intrahepatic T cell responses by way of expression of the coinhibitory molecule B7-H4, and may provide fundamental insight into intrahepatic immunity during liver fibrogenesis.

Macrophages: master regulators of inflammation and fibrosis

Macrophages are found in close proximity with collagen-producing myofibroblasts and indisputably play a key role in fibrosis. They produce profibrotic mediators that directly activate fibroblasts, including transforming growth factor-beta1 and platelet-derived growth factor, and control extracellular matrix turnover by regulating the balance of various matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases. Macrophages also regulate fibrogenesis by secreting chemokines that recruit fibroblasts and other inflammatory cells. With their potential to act in both a pro- and antifibrotic capacity, as well as their ability to regulate the activation of resident and recruited myofibroblasts, macrophages and the factors they express are integrated into all stages of the fibrotic process. These various, and sometimes opposing, functions may be performed by distinct macrophage subpopulations, the identification of which is a growing focus of fibrosis research. Although collagen-secreting myofibroblasts once were thought of as the master "producers" of fibrosis, this review will illustrate how macrophages function as the master "regulators" of fibrosis.

Value of α-smooth muscle actin and glial fibrillary acidic protein in predicting early hepatic fibrosis in chronic hepatitis C virus infection

INTRODUCTION

α-Smooth muscle actin (α-SMA)-positive hepatic stellate cells (HSCs) are pericytes responsible for fibrosis in chronic liver injury. The glial fibrillary acidic protein (GFAP), commonly expressed by astrocytes in the central nervous system, is expressed in vivo in the liver in a subpopulation of quiescent stellate cells. The reports concerning GFAP expression in human liver are still conflicting. The aim of the study is investigation the utility of GFAP compared to α-SMA as an indicator of early activated HSCs, in predicting fibrosis in chronic hepatitis C (CHC) patients.

MATERIAL AND METHODS

With immunohistochemistry and a semi-quantitative scoring system, the expressions of α-SMA and GFAP on HSCs in liver biopsies from patients with pure CHC (n = 34), hepatitis C virus-induced cirrhosis (n = 24), mixed CHC/schistosomiasis (n = 11) and normal controls (n = 10) were analysed.

RESULTS

The immunoreactivity of α-SMA and GFAP in perisinusoidal, periportal and pericentral areas was assessed. α-Smooth muscle actin and GFAP-positive HSCs were significantly increased in all diseased groups compared with normal controls. In pure CHC with or without cirrhosis, perisinusoidal α-SMA-positive HSCs were predominant in relation to GFAP-positive cells. On the other hand, GFAP-positive cells were predominant in the group of schistosomiasis as compared with the other diseased groups. It was noticed that expression of GFAP on perisinusoidal HSCs in CHC patients sequentially decreased with the progression of fibrosis.

CONCLUSIONS

Glial fibrillary acidic protein could represent a more useful marker than α-SMA of early activation of HSCs in CHC patients and seems to be an early indicator of hepatic fibrogenesis.

Endothelin antagonism in portal hypertensive mice: implications for endothelin receptor-specific signaling in liver disease

Endothelin-1 (ET-1), a potent vasoactive peptide, plays an important role in the pathogenesis of liver disease and portal hypertension. Two major endothelin receptors (ET-A and ET-B) mediate biological effects, largely on the basis of their known downstream signaling pathways. We hypothesized that the different receptors are likely to mediate divergent effects in portal hypertensive mice. Liver fibrosis and cirrhosis and portal hypertension were induced in 8-wk-old male BALB/c mice by gavage with carbon tetrachloride (CCl4). Portal pressure was recorded acutely during intravenous infusion of endothelin receptor antagonists in normal or portal hypertensive mice. In vivo microscopy was used to monitor sinusoidal dynamics. Additionally, the effect of chronic exposure to endothelin antagonists was assessed in mice during induction of fibrosis and cirrhosis with CCl4 for 8 wk. Intravenous infusion of ET-A receptor antagonists into normal and cirrhotic mice reduced portal pressure whereas ET-B receptor antagonism increased portal pressure. A mixed endothelin receptor antagonist also significantly reduced portal pressure. Additionally, the ET-A receptor antagonist caused sinusoidal dilation, whereas the ET-B receptor antagonist caused sinusoidal constriction. Chronic administration of each the endothelin receptor antagonists during the induction of fibrosis and portal hypertension led to reduced fibrosis, a significant reduction in portal pressure, and altered sinusoidal dynamics relative to controls. Acute effects of endothelin receptor antagonists are likely directly on the hepatic and sinusoidal vasculature, whereas chronic endothelin receptor antagonism appears to be more complicated, likely affecting fibrogenesis and the hepatic microcirculation. The data imply a relationship between hepatic fibrogenesis or fibrosis and vasomotor responses.

Current and future anti-fibrotic therapies for chronic liver disease

Chronic injury results in a wound healing response that eventually leads to fibrosis. The response is generalized, with features common among multiple organ systems. In the liver, various different types of injury lead to fibrogenesis, implying a common pathogenesis. Although several specific therapies for patients who have different liver diseases have been successfully developed, including antiviral therapies for those who have hepatitis B and hepatitis C virus infection, specific and effective antifibrotic therapy remains elusive. Over the past 2 decades, great advances in the understanding of fibrosis have been made and multiple mechanisms underlying hepatic fibrogenesis uncovered. Elucidation of these mechanisms has been of fundamental importance in highlighting novel potential therapies. Preclinical studies have indicated several putative therapies that might abrogate fibrogenesis. This article emphasizes mechanisms underlying fibrogenesis and reviews available and future therapeutics.