Browsing by Author "Maiers, Jessica L."

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    Coordinated signaling of activating transcription factor 6α and inositol-requiring enzyme 1α regulates hepatic stellate cell-mediated fibrogenesis in mice
    (American Physiological Society, 2021) Xue, Fei; Lu, Jianwen; Buchl, Samuel C.; Sun, Liankang; Shah, Vijay H.; Malhi, Harmeet; Maiers, Jessica L.; Medicine, School of Medicine
    Liver injury and the unfolded protein response (UPR) are tightly linked, but their relationship differs with cell type and injurious stimuli. UPR initiation promotes hepatic stellate cell (HSC) activation and fibrogenesis, but the underlying mechanisms are unclear. Despite the complexity and overlap downstream of UPR transducers inositol-requiring protein 1α (IRE1α), activating transcription factor 6α (ATF6α), and protein kinase RNA-like ER kinase (PERK), previous research in HSCs primarily focused on IRE1α. Here, we investigated the fibrogenic role of ATF6α or PERK in vitro and HSC-specific UPR signaling in vivo. Overexpression of ATF6α, but not the PERK effector activating transcription factor 4 (ATF4), promoted HSC activation and fibrogenic gene transcription in immortalized HSCs. Furthermore, ATF6α inhibition through Ceapin-A7, or Atf6a deletion, disrupted transforming growth factor β (TGFβ)-mediated activation of primary human hepatic stellate cells (hHSCs) or murine hepatic stellate cells (mHSCs), respectively. We investigated the fibrogenic role of ATF6α in vivo through conditional HSC-specific Atf6a deletion. Atf6aHSCΔ/Δ mice displayed reduced fibrosis and HSC activation following bile duct ligation (BDL) or carbon tetrachloride (CCl4)-induced injury. The Atf6aHSCΔ/Δ phenotype differed from HSC-specific Ire1a deletion, as Ire1aHSCΔ/Δ mice showed reduced fibrogenic gene transcription but no changes in fibrosis compared with Ire1afl/fl mice following BDL. Interestingly, ATF6α signaling increased in Ire1aΔ/Δ HSCs, whereas IRE1α signaling was upregulated in Atf6aΔ/Δ HSCs. Finally, we asked whether co-deletion of Atf6a and Ire1a additively limits fibrosis. Unexpectedly, fibrosis worsened in Atf6aHSCΔ/ΔIre1aHSCΔ/Δ mice following BDL, and Atf6aΔ/ΔIre1aΔ/Δ mHSCs showed increased fibrogenic gene transcription. ATF6α and IRE1α individually promote fibrogenic transcription in HSCs, and ATF6α drives fibrogenesis in vivo. Unexpectedly, disruption of both pathways sensitizes the liver to fibrogenesis, suggesting that fine-tuned UPR signaling is critical for regulating HSC activation and fibrogenesis. NEW & NOTEWORTHY: ATF6α is a critical driver of hepatic stellate cell (HSC) activation in vitro. HSC-specific deletion of Atf6a limits fibrogenesis in vivo despite increased IRE1α signaling. Conditional deletion of Ire1α from HSCs limits fibrogenic gene transcription without impacting overall fibrosis. This could be due in part to observed upregulation of the ATF6α pathway. Dual loss of Atf6a and Ire1a from HSCs worsens fibrosis in vivo through enhanced HSC activation.
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    ER Disposal Pathways in Chronic Liver Disease: Protective, Pathogenic, and Potential Therapeutic Targets
    (Frontiers, 2022-01) Duwaerts, Caroline C.; Maiers, Jessica L.; Medicine, School of Medicine
    The endoplasmic reticulum is a central player in liver pathophysiology. Chronic injury to the ER through increased lipid content, alcohol metabolism, or accumulation of misfolded proteins causes ER stress, dysregulated hepatocyte function, inflammation, and worsened disease pathogenesis. A key adaptation of the ER to resolve stress is the removal of excess or misfolded proteins. Degradation of intra-luminal or ER membrane proteins occurs through distinct mechanisms that include ER-associated Degradation (ERAD) and ER-to-lysosome-associated degradation (ERLAD), which includes macro-ER-phagy, micro-ER-phagy, and Atg8/LC-3-dependent vesicular delivery. All three of these processes are critical for removing misfolded or unfolded protein aggregates, and re-establishing ER homeostasis following expansion/stress, which is critical for liver function and adaptation to injury. Despite playing a key role in resolving ER stress, the contribution of these degradative processes to liver physiology and pathophysiology is understudied. Analysis of publicly available datasets from diseased livers revealed that numerous genes involved in ER-related degradative pathways are dysregulated; however, their roles and regulation in disease progression are not well defined. Here we discuss the dynamic regulation of ER-related protein disposal pathways in chronic liver disease and cell-type specific roles, as well as potentially targetable mechanisms for treatment of chronic liver disease.
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    Melatonin-MT1 Signaling Axis Ameliorates the Phenotypes of Primary Sclerosing Cholangitis
    (2023-03) Ceci, Ludovica; Alpini, Gianfranco; Francis, Heather; Ekser, Burcin; Dong, Charlie X.; Maiers, Jessica L.
    Background: Primary Sclerosing Cholangitis (PSC) is characterized by hepatic fibrosis and portal inflammation. Melatonin is synthesized by arylalkylamine N-acetyltransferase (AANAT) in cholangiocytes. We found that: (i) the MT1 receptor is primarily expressed in cholangiocytes; (ii) melatonin reduces biliary proliferation via MT1 receptor signaling; and (iii) melatonin treatment for 1 wk decreases ductular reaction (DR) and liver fibrosis in cholestatic rats by downregulation of MT1 and clock genes. Melatonin administration to male Mdr2-/- mice (PSC model) reduces angiogenesis and portal inflammation via decreased miR-200b. Downregulation of maspin triggers angiogenesis during tumorigenesis by interaction with glutathione S-transferase (GST). We aimed to evaluate the effects of long-term melatonin treatment and MT1 signaling on PSC phenotypes in Mdr2-/- mice. Methods: Male FVB/NJ and Mdr2-/- mice had access ad libitum to drinking water with/without melatonin for 3 months. Immortilized-SV40-cholangiocytes isolated from human liver samples (control and PSC) were treated with melatonin (10-3 mol/L) for 24 hr. Male C3H-Hej (WT for MT1-/-), FVB/NJ (WT for Mdr2-/-), MT1-/-, Mdr2-/- mice and MT1-/-/Mdr2-/- mice were euthanized at 12 wk. We analyzed liver damage, PSC phenotypes, angiogenesis and AANAT, melatonin receptors and clock genes by immunohistochemistry, immunofluorescence, ELISA and western blots in liver samples and isolated cholangiocytes. Melatonin signaling was evaluated in human control and PSC samples. Results: Long-term melatonin treatment and inhibition of MT1 receptor ameliorates cholestatic liver phenotypes in Mdr2-/-mice by decreasing the immunoreactivity of melatonin enzymes and clock genes. GST activity and maspin expression decreased in Mdr2-/- mice and human PSC samples compared to controls; the phenotypes were reversed by melatonin. Conclusion: Chronic melatonin treatment improves liver histology and restores biliary circadian rhythm by interaction with MT1. Suppression of MT1 ameliorates biliary/liver phenotypes through changes in clock genes and melatonin enzymes. Restoration of the circadian rhythm by modulation of melatonin/MT1 signaling may be key for PSC management.
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    Stress and Liver Fibrogenesis: Understanding the Role and Regulation of Stress Response Pathways in Hepatic Stellate Cells
    (Elsevier, 2023) Hanquier, Zachary; Misra, Jagannath; Baxter, Reese; Maiers, Jessica L.; Medical and Molecular Genetics, School of Medicine
    Stress response pathways are crucial for cells to adapt to physiological and pathologic conditions. Increased transcription and translation in response to stimuli place a strain on the cell, necessitating increased amino acid supply, protein production and folding, and disposal of misfolded proteins. Stress response pathways, such as the unfolded protein response (UPR) and the integrated stress response (ISR), allow cells to adapt to stress and restore homeostasis; however, their role and regulation in pathologic conditions, such as hepatic fibrogenesis, are unclear. Liver injury promotes fibrogenesis through activation of hepatic stellate cells (HSCs), which produce and secrete fibrogenic proteins to promote tissue repair. This process is exacerbated in chronic liver disease, leading to fibrosis and, if unchecked, cirrhosis. Fibrogenic HSCs exhibit activation of both the UPR and ISR, due in part to increased transcriptional and translational demands, and these stress responses play important roles in fibrogenesis. Targeting these pathways to limit fibrogenesis or promote HSC apoptosis is a potential antifibrotic strategy, but it is limited by our lack of mechanistic understanding of how the UPR and ISR regulate HSC activation and fibrogenesis. This article explores the role of the UPR and ISR in the progression of fibrogenesis, and highlights areas that require further investigation to better understand how the UPR and ISR can be targeted to limit hepatic fibrosis progression.
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    The Cellular, Molecular, and Pathologic Consequences of Stress on the Liver
    (Elsevier, 2023) Maiers, Jessica L.; Chakraborty, Sanjukta; Medicine, School of Medicine
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    Traf2 and NCK Interacting Kinase Is a Critical Regulator of Procollagen I Trafficking and Hepatic Fibrogenesis in Mice
    (Wiley, 2022-03) Buchl, Samuel C.; Hanquier, Zachary; Haak, Andrew J.; Thomason, Yvonne M.; Huebert, Robert C.; Shah, Vijay H.; Maiers, Jessica L.; Medicine, School of Medicine
    Hepatic fibrosis is driven by deposition of matrix proteins following liver injury. Hepatic stellate cells (HSCs) drive fibrogenesis, producing matrix proteins, including procollagen I, which matures into collagen I following secretion. Disrupting intracellular procollagen processing and trafficking causes endoplasmic reticulum stress and stress-induced HSC apoptosis and thus is an attractive antifibrotic strategy. We designed an immunofluorescence-based small interfering RNA (siRNA) screen to identify procollagen I trafficking regulators, hypothesizing that these proteins could serve as antifibrotic targets. A targeted siRNA screen was performed using immunofluorescence to detect changes in intracellular procollagen I. Tumor necrosis factor receptor associated factor 2 and noncatalytic region of tyrosine kinase-interacting kinase (TNIK) was identified and interrogated in vitro and in vivo using the TNIK kinase inhibitor NCB-0846 or RNA interference-mediated knockdown. Our siRNA screen identified nine genes whose knockdown promoted procollagen I retention, including the serine/threonine kinase TNIK. Genetic deletion or pharmacologic inhibition of TNIK through the small molecule inhibitor NCB-0846 disrupted procollagen I trafficking and secretion without impacting procollagen I expression. To investigate the role of TNIK in liver fibrogenesis, we analyzed human and murine livers, finding elevated TNIK expression in human cirrhotic livers and increased TNIK expression and kinase activity in both fibrotic mouse livers and activated primary human HSCs. Finally, we tested whether inhibition of TNIK kinase activity could limit fibrogenesis in vivo. Mice receiving NCB-0846 displayed reduced CCl4-induced fibrogenesis compared to CCl4 alone, although α-smooth muscle actin levels were unaltered. Conclusions: Our siRNA screen effectively identified TNIK as a key kinase involved in procollagen I trafficking in vitro and hepatic fibrogenesis in vivo.
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    Transcriptomic Analysis Reveals the Messenger RNAs Responsible for the Progression of Alcoholic Cirrhosis
    (Wolters Kluwer, 2022) Yang, Zhihong; Han, Sen; Zhang, Ting; Kusumanchi, Praveen; Huda, Nazmul; Tyler, Kelsey; Chandler, Kristina; Skill, Nicholas J.; Tu, Wanzhu; Shan, Mu; Jiang, Yanchao; Maiers, Jessica L.; Perez, Kristina; Ma, Jing; Liangpunsakul, Suthat; Medicine, School of Medicine
    Alcohol-associated liver disease is the leading cause of chronic liver disease. We hypothesized that the expression of specific coding genes is critical for the progression of alcoholic cirrhosis (AC) from compensated to decompensated states. For the discovery phase, we performed RNA sequencing analysis of 16 peripheral blood RNA samples, 4 healthy controls (HCs) and 12 patients with AC. The DEGs from the discovery cohort were validated by quantitative polymerase chain reaction in a separate cohort of 17 HCs and 48 patients with AC (17 Child-Pugh A, 16 Child-Pugh B, and 15 Child-Pugh C). We observed that the numbers of differentially expressed messenger RNAs (mRNAs) were more pronounced with worsening disease severity. Pathway analysis for differentially expressed genes for patients with Child-Pugh A demonstrated genes involved innate immune responses; those in Child-Pugh B belonged to genes related to oxidation and alternative splicing; those in Child-Pugh C related to methylation, acetylation, and alternative splicing. We found significant differences in the expression of heme oxygenase 1 (HMOX1) and ribonucleoprotein, PTB binding 1 (RAVER1) in peripheral blood of those who died during the follow-up when compared to those who survived. Conclusion: Unique mRNAs that may implicate disease progression in patients with AC were identified by using a transcriptomic approach. Future studies to confirm our results are needed, and comprehensive mechanistic studies on the implications of these genes in AC pathogenesis and progression should be further explored.