Toward unraveling the complexity of simple epithelial keratins in human disease

Glial fibrillary acidic protein is pathologically modified in Alexander disease

Here we describe pathological events potentially involved in the disease pathogenesis of Alexander disease (AxD). This is a primary genetic disorder of astrocyte caused by dominant gain-of-function mutations in the gene coding for an intermediate filament protein glial fibrillary acidic protein (GFAP). Pathologically, this disease is characterized by up-regulation of GFAP and its accumulation as Rosenthal fibers. Although the genetic basis linking GFAP mutations with Alexander disease has been firmly established, the initiating events that promote GFAP accumulation and the role of Rosenthal fibers (RFs) in the disease process remain unknown. Here, we investigate the hypothesis that disease-associated mutations promote GFAP aggregation through aberrant post-translational modifications. We found high molecular weight GFAP species in the RFs of AxD brains, indicating abnormal GFAP crosslinking as a prominent pathological feature of this disease. In vitro and cell-based studies demonstrate that cystine-generating mutations promote GFAP crosslinking by cysteine-dependent oxidation, resulting in defective GFAP assembly and decreased filament solubility. Moreover, we found GFAP was ubiquitinated in Rosenthal fibers of AxD patients and rodent models, supporting this modification as a critical factor linked to GFAP aggregation. Finally, we found that arginine could increase the solubility of aggregation-prone mutant GFAP by decreasing its ubiquitination and aggregation. Our study suggests a series of pathogenic events leading to AxD, involving interplay between GFAP aggregation and abnormal modifications by GFAP ubiquitination and oxidation. More important, our findings provide a basis for investigating new strategies to treat AxD by targeting abnormal GFAP modifications.

Transcriptomic profiling analysis of the effect of palmitic acid on 3D spheroids of β-like cells derived from induced pluripotent stem cells

Type 2 diabetes (T2D) is posing a serious public health concern with a considerable impact on human life and health expenditures worldwide. The disease develops when insulin plasma level is insufficient for coping insulin resistance, caused by the decline of pancreatic β-cell function and mass. In β-cells, the lipotoxicity exerted by saturated free fatty acids in particular palmitate (PA), which is chronically elevated in T2D, plays a major role in β-cell dysfunction and mass. However, there is a lack of human relevant in vitro model to identify the underlying mechanism through which palmitate induces β-cell failure. In this frame, we have previously developed a cutting-edge 3D spheroid model of β-like cells derived from human induced pluripotent stem cells. In the present work, we investigated the signaling pathways modified by palmitate in β-like cells derived spheroids. When compared to the 2D monolayer cultures, the transcriptome analysis (FDR set at  0.1) revealed that the 3D spheroids upregulated the pancreatic markers (such as GCG, IAPP genes), lipids metabolism and transporters (CD36, HMGSC2 genes), glucose transporter (SLC2A6). Then, the 3D spheroids are exposed to PA 0.5 mM for 72 h. The differential analysis demonstrated that 32 transcription factors and 135 target genes were mainly modulated (FDR set at  0.1) including the upregulation of lipid and carbohydrates metabolism (HMGSC2, LDHA, GLUT3), fibrin metabolism (FGG, FGB), apoptosis (CASP7). The pathway analysis using the 135 selected targets extracted the fibrin related biological process and wound healing in 3D PA treated conditions. An overall pathway gene set enrichment analysis, performed on the overall gene set (with pathway significance cutoff at 0.2), highlighted that PA perturbs the citrate cycle, FOXO signaling and Hippo signaling as observed in human islets studies. Additional RT-PCR confirmed induction of inflammatory (IGFBP1, IGFBP3) and cell growth (CCND1, Ki67) pathways by PA. All these changes were associated with unaffected glucose-stimulated insulin secretion (GSIS), suggesting that they precede the defect of insulin secretion and death induced by PA. Overall, we believe that our data demonstrate the potential of our spheroid 3D islet-like cells to investigate the pancreatic-like response to diabetogenic environment.

Improved diagnostic accuracy with three lung tumor markers compared to six-marker panel

Background

Combining multiple tumor markers increases sensitivity for lung cancer diagnosis in the cost of false positive. However, some would like to check as many as tumor markers in the fear of missing cancer. We though to propose a panel of fewer tumor markers for lung cancer diagnosis.

Methods

Patients with suspected lung cancer who simultaneously underwent all six tests [carcinoembryonic antigen (CEA), cytokeratin-19 fragment (CYFRA), squamous cell carcinoma-associated antigen (SCC), neuron-specific enolase (NSE), pro-gastrin-releasing peptide (ProGRP), and sialyl Lewis-X antigen (SLX)] were included. Tumor markers with significant impact on the lung cancer in a logistic regression model were included in our panel. Area under the curve (AUC) was compared between our panel and the panel of all six.

Results

We included 1,733 [median 72 years, 1,128 men, 605 women, 779 (45%) confirmed lung cancer]. Logistic regression analysis suggested CEA, CYFRA, and NSE were independently associated with the lung cancer diagnosis. The panel of these three tumor markers [AUC =0.656, 95% confidence interval (CI): 0.630-0.682, sensitivity 0.650, specificity 0.662] had better (P<0.001) diagnostic performance than six tumor markers (AUC =0.575, 95% CI: 0.548-0.602, sensitivity 0.829, specificity 0.321).

Conclusions

Compared to applying all six markers (at least one marker above the upper limit of normal), the panel with three markers (at least one marker above the upper limit of normal) led to a better predictive value by lowering the risk of false positives.

Lineage tracing reveals transient phenotypic adaptation of tubular cells during acute kidney injury

Tubular injury is the hallmark of acute kidney injury (AKI) with a tremendous impact on patients and health-care systems. During injury, any differentiated proximal tubular cell (PT) may transition into a specific injured phenotype, so-called "scattered tubular cell" (STC)-phenotype. To understand the fate of this specific phenotype, we generated transgenic mice allowing inducible, reversible, and irreversible tagging of these cells in a murine AKI model, the unilateral ischemia-reperfusion injury (IRI). For lineage tracing, we analyzed the kidneys using single-cell profiling during disease development at various time points. Labeled cells, which we defined by established endogenous markers, already appeared 8 h after injury and showed a distinct expression set of genes. We show that STCs re-differentiate back into fully differentiated PTs upon the resolution of the injury. In summary, we show the dynamics of the phenotypic transition of PTs during injury, revealing a reversible transcriptional program as an adaptive response during disease.

High KRT17 expression in tumour budding indicates immunologically 'hot' tumour budding and predicts good survival in patients with colorectal cancer

Objectives

Emerging evidence has demonstrated that tumour budding (TB) is negatively associated with T-lymphocyte infiltration in CRC. Despite extensive research, the molecular characteristics of immunologically 'hot' TB remain poorly understood.

Methods

We quantified the number of TB by haematoxylin-eosin (H&E) sections and the densities of CD3+ and CD8+ T-lymphocytes by immunohistochemistry in a CRC cohort of 351 cases who underwent curative resection. We analysed the differential expression and T-lymphocyte infiltration score of 37 human epithelial keratins in CRC using RNA sequencing from the TCGA dataset. In 278 TB-positive cases, KRT17 expression was evaluated in tumour centre (TC) and TB with a staining score. Patient demographic, clinicopathological features and survival rates were analysed.

Results

In a CRC cohort of 351 cases, low-grade TB was associated with high CD3+ and CD8+ T-cell densities in the invasive margin (IM) but not in the TC. Of 37 human epithelial keratins, only KRT17 expression in TB had an apparent association with TB-grade and T-lymphocyte infiltration. In 278 TB-positive cases, high KRT17 expression in TB (KRT17TB) was negatively associated with low-grade TB and positively associated with high CD3+ and CD8+ T-cell densities in IM. High KRT17TB predicted early tumour grade, absence of lymph node metastasis and absence of tumour deposits. Additionally, patients with high KRT17TB had good overall survival and disease-free survival. Notably, low KRT17TB can specifically identify those patients with a poor prognosis among colorectal cancer patients with low TB and high T-lymphocyte infiltration.

Conclusions

KRT17 can be employed as a new indicator for distinguishing different immunological TBs.

Differential distribution of intermediate filament proteins in the bovine and ovine tongues

Intermediate filaments constitute the most heterogeneous class among the major classes of cytoskeletal proteins of mammalian cells. The 40 or more intermediate filament proteins have been classified into five types which show very specific rules of expression in specialized cell types. This study aimed to investigate the immunohistochemical distribution of cytokeratins (CKs) 8, 18, and 19 as well as the intermediate filaments vimentin, laminin, and desmin in bovine and ovine tongues. Immunohistochemical staining was performed for CKs 8, 18, 19, vimentin, laminin, and desmin. Our results revealed similar immunostaining intensity and distribution among various CKs, contrasting with distinct patterns for vimentin, laminin, and desmin. Immunoreactions were primarily localized in serous acini and ductal epithelium for cytokeratins, while vimentin and laminin were evident in connective tissue, endothelium, serous acini, and desmin in striated and smooth muscles. This study highlighted the absence of CKs 8, 18, 19, vimentin, and desmin in the lingual epithelium of bovine and ovine tongues. These findings enabled the classification of epithelial cells based on their specific cytokeratin patterns. Furthermore, vimentin was identified in mesodermal tissues and organs, desmin in muscle tissue, and laminin played crucial roles in basement membrane formation, nerve tissue regeneration, innervation of epithelial taste buds, and tissue separation and connection. Our findings provide essential insights into intermediate filament dynamics at the cellular and tissue levels. They serve as a foundation for future studies using systematic molecular biological techniques in this field.

Regulation of epithelial transitional states in murine and human pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive scarring disease arising from impaired regeneration of the alveolar epithelium after injury. During regeneration, type 2 alveolar epithelial cells (AEC2s) assume a transitional state that upregulates multiple keratins and ultimately differentiate into AEC1s. In IPF, transitional AECs accumulate with ineffectual AEC1 differentiation. However, whether and how transitional cells cause fibrosis, whether keratins regulate transitional cell accumulation and fibrosis, and why transitional AECs and fibrosis resolve in mouse models but accumulate in IPF are unclear. Here, we show that human keratin 8 (KRT8) genetic variants were associated with IPF. Krt8-/- mice were protected from fibrosis and accumulation of the transitional state. Keratin 8 (K8) regulated the expression of macrophage chemokines and macrophage recruitment. Profibrotic macrophages and myofibroblasts promoted the accumulation of transitional AECs, establishing a K8-dependent positive feedback loop driving fibrogenesis. Finally, rare murine transitional AECs were highly senescent and basaloid and may not differentiate into AEC1s, recapitulating the aberrant basaloid state in human IPF. We conclude that transitional AECs induced and were maintained by fibrosis in a K8-dependent manner; in mice, most transitional cells and fibrosis resolved, whereas in human IPF, transitional AECs evolved into an aberrant basaloid state that persisted with progressive fibrosis.

Hepatic Macrophages as Targets for the MSC-Based Cell Therapy in Non-Alcoholic Steatohepatitis

Non-alcoholic steatohepatitis (NASH) is a serious public health issue associated with the obesity pandemic. Obesity is the main risk factor for the non-alcoholic fatty liver disease (NAFLD), which progresses to NASH and then to end-stage liver disease. Currently, there are no specific pharmacotherapies of NAFLD/NASH approved by the FDA or other national regulatory bodies and the treatment includes lifestyle adjustment and medicines for improving lipid metabolism, enhancing sensitivity to insulin, balancing oxidation, and counteracting fibrosis. Accordingly, further basic research and development of new therapeutic approaches are greatly needed. Mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles prevent induced hepatocyte death in vitro and attenuate NASH symptoms in animal models of the disease. They interact with hepatocytes directly, but also target other liver cells, including Kupffer cells and macrophages recruited from the blood flow. This review provides an update on the pathogenesis of NAFLD/NASH and the key role of macrophages in the development of the disease. We examine in detail the mechanisms of the cross-talk between the MSCs and the macrophages, which are likely to be among the key targets of MSCs and their derivatives in the course of NAFLD/NASH cell therapy.

Variability of serum CYFRA 21 - 1 and its susceptibility to clinical characteristics in individuals without cancer: a 4-year retrospective analysis

BACKGROUND

CYFRA 21 - 1 is a useful marker for diagnosing and monitoring lung cancer. However, its stability remains unclear. Moreover, while its applicability to screening is now being investigated, CYFRA 21 - 1 levels in individuals without cancer, who are targets for cancer screening, have not yet been the focus of research. Therefore, the present study investigated variability in and the factors increasing serum CYFRA 21 - 1 levels.

METHODS

This retrospective study recruited 951 individuals undergoing annual medical examinations for six years. We used data obtained in the first four years. Variability in serum CYFRA 21 - 1 levels over a period of four years were investigated. CYFRA 21 - 1 was categorized as normal (≤ 3.5 ng/ml) or elevated (> 3.5 ng/ml). The rate of an elevated level in one visit and the transition from an elevated to normal level between visits were visualized. A multiple logistic regression model was used to study the relationships between the frequency of elevated CYFRA 21 - 1 levels and clinical characteristics, such as age, sex, body mass index, weight changes, and the smoking status.

RESULTS

Approximately 5% of subjects had elevated CYFRA 21 - 1 levels once in five tests over four years, while 15% had elevated CYFRA 21 - 1 levels once or more. Among subjects with elevated CYFRA 21 - 1 levels in one blood test, between 63 and 72% had normal levels in the next test. The median CYFRA 21 - 1 level in subjects with elevations in one blood test significantly decreased in the next test at all four time points. The frequency of elevated CYFRA 21 - 1 levels was associated with an older age [odds ratio (OR) = 6.99, 95% confidence interval (CI) = 3.01-16.2], current heavy smoking (OR = 3.46, 95% CI = 1.52-7.9), and weight loss (OR = 1.86, 95% CI = 1.07-3.24).

CONCLUSIONS

Variability in and the factors increasing serum CYFRA 21 - 1 levels beyond the cut-off value need to be considered when interpretating CYFRA 21 - 1 test results. The future application of CYFRA 21 - 1 to lung cancer screening may require more than a single measurement.

Role of microRNA in non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH): a comprehensive review

Non-alcoholic fatty liver disease (NAFLD) is a prevalent liver condition that affects people who do not overconsume alcohol. Uncertainties exist over how microRNAs (miRNAs) in the blood and liver relate to NAFLD. The aim of this narrative review was to investigate the role of miRNAs in the onset and progression of non-alcoholic steatohepatitis (NASH) from NAFLD, and explore their potential as diagnostic tools and treatment targets for NAFLD patients. Liver miRNA-34a levels were found to accurately represent the degree of liver damage, with lower levels suggesting more damage. In patients with NAFLD and severe liver fibrosis, higher levels of miRNA-193a-5p and miRNA-378d were found. Moreover, miRNA-34a, miRNA-122, and miRNA-192 levels might aid in differentiating NASH from NAFLD. Similar to this, miRNA-21 and miRNA-27 levels in rats were able to distinguish between steatosis and steatohepatitis. High-fat diets enhanced the expression of 15 distinct miRNAs in rats, and there were substantial differences in the miRNA expression patterns between obese and lean people. The results from the present review imply that miRNA microarrays and sequencing may be helpful diagnostic tools, and miRNAs may be a possible treatment target for patients with NAFLD.

Keratin 7 expression in different anatomical parts of colonic epithelium in inflammatory bowel diseases and its prognostic value: a 3-year follow-up study

The diagnosis of inflammatory bowel diseases (IBD) may be challenging and their clinical course, characterized by relapses and spontaneous or drug-induced remissions, is difficult to predict. Novel prognostic biomarkers are needed. Keratin 7 (K7) is a cytoskeletal intermediate filament protein which is not normally expressed in the colonic epithelium. It was recently shown that K7 expression in the colonic epithelium is associated with ulcerative colitis and Crohn's disease, the two main subtypes of IBD. Here we investigated IBD associated K7 neo-expression in different regions of colon and terminal ileum. The correlation of the K7 expression with the inflammatory activity of the epithelium was analyzed in each region. The prognostic value of K7 was estimated by comparing the clinical disease activity after 3 years with the K7 expression at the time of enrollment. Our data shows that the level of K7 expression in inflamed epithelium varies depending on the anatomical region and it is the most pronounced in ascending and descending colon, but it did not predict the severity of IBD for the following 3 years. These results warrant future studies focusing on the biological role of K7 in colon and its utilization as potential IBD biomarker.

Deacetylation via SIRT2 prevents keratin-mutation-associated injury and keratin aggregation

Keratin (K) and other intermediate filament (IF) protein mutations at conserved arginines disrupt keratin filaments into aggregates and cause human epidermolysis bullosa simplex (EBS; K14-R125C) or predispose to mouse liver injury (K18-R90C). The challenge for more than 70 IF-associated diseases is the lack of clinically utilized IF-targeted therapies. We used high-throughput drug screening to identify compounds that normalized mutation-triggered keratin filament disruption. Parthenolide, a plant sesquiterpene lactone, dramatically reversed keratin filament disruption and protected cells and mice expressing K18-R90C from apoptosis. K18-R90C became hyperacetylated compared with K18-WT and treatment with parthenolide normalized K18 acetylation. Parthenolide upregulated the NAD-dependent SIRT2, and increased SIRT2-keratin association. SIRT2 knockdown or pharmacologic inhibition blocked the parthenolide effect, while site-specific Lys-to-Arg mutation of keratin acetylation sites normalized K18-R90C filaments. Treatment of K18-R90C-expressing cells and mice with nicotinamide mononucleotide had a parthenolide-like protective effect. In 2 human K18 variants that associate with human fatal drug-induced liver injury, parthenolide protected K18-D89H- but not K8-K393R-induced filament disruption and cell death. Importantly, parthenolide normalized K14-R125C-mediated filament disruption in keratinocytes and inhibited dispase-triggered keratinocyte sheet fragmentation and Fas-mediated apoptosis. Therefore, keratin acetylation may provide a novel therapeutic target for some keratin-associated diseases.

Acute alcohol-associated hepatitis: Latest findings in non-invasive biomarkers and treatment

Acute alcohol-associated hepatitis (AH) is a syndrome that occurs in heavy and long-term drinkers and results in severe jaundice and liver failure. The mortality rate in severe cases is 20%-50% at 28 days, and in cases that do not improve despite appropriately timed corticosteroid therapy, the mortality rate reaches 70% at 6 months. The only curative treatment is early liver transplantation, but less than 2% of patients with severe AH are eligible. In order to improve the prognosis, diagnostic tools are needed to detect appropriate cases at risk of severe conditions, and new therapies need to be developed that can replace corticosteroids. Recent research has revealed that the pathogenesis of AH involves a complex of factors, including changes in the gut microbiota, inflammatory and cytokine signalling, oxidative stress and mitochondrial dysfunction, and abnormalities in the hepatic regenerative capacity. Non-invasive diagnostic tools focusing on these specific pathologies have been reported in recent years. In addition, several novel agents targeting specific pathways are currently being developed and tested in clinical trials. This review will provide an overview of alcohol-associated hepatitis and focus on the latest diagnostic tools, particularly non-invasive biomarkers, and novel therapies.

Dialog beyond the Grave: Necrosis in the Tumor Microenvironment and Its Contribution to Tumor Growth

Damage-associated molecular patterns (DAMPs) are endogenous molecules released from the necrotic cells dying after exposure to various stressors. After binding to their receptors, they can stimulate various signaling pathways in target cells. DAMPs are especially abundant in the microenvironment of malignant tumors and are suspected to influence the behavior of malignant and stromal cells in multiple ways often resulting in promotion of cell proliferation, migration, invasion, and metastasis, as well as increased immune evasion. This review will start with a reminder of the main features of cell necrosis, which will be compared to other forms of cell death. Then we will summarize the various methods used to assess tumor necrosis in clinical practice including medical imaging, histopathological examination, and/or biological assays. We will also consider the importance of necrosis as a prognostic factor. Then the focus will be on the DAMPs and their role in the tumor microenvironment (TME). We will address not only their interactions with the malignant cells, frequently leading to cancer progression, but also with the immune cells and their contribution to immunosuppression. Finally, we will emphasize the role of DAMPs released by necrotic cells in the activation of Toll-like receptors (TLRs) and the possible contributions of TLRs to tumor development. This last point is very important for the future of cancer therapeutics since there are attempts to use TLR artificial ligands for cancer therapeutics.

Emerging Biomarkers in Alcohol-associated Hepatitis

Alcohol-associated hepatitis (AH) is a clinical syndrome of jaundice, abdominal pain, and anorexia due to prolonged heavy alcohol intake. AH is associated with changes in gene expression, cytokines, immune response, and the gut microbiome. There are limited biomarkers to diagnose and prognosticate in AH, but several non-invasive biomarkers are emerging. In this review, clinical risk-stratifying algorithms, promising AH biomarkers like cytokeratin-18 fragments, genetic polymorphisms, and microRNAs will be reviewed.

PP2 protects from keratin mutation-associated liver injury and filament disruption via SRC kinase inhibition in male but not female mice

BACKGROUND AND AIMS

Hepatocyte keratin polypeptides 8/18 (K8/K18) are unique among intermediate filaments proteins (IFs) in that their mutation predisposes to, rather than causes, human disease. Mice that overexpress human K18 R90C manifest disrupted hepatocyte keratin filaments with hyperphosphorylated keratins and predisposition to Fas-induced liver injury. We hypothesized that high-throughput screening will identify compounds that protect the liver from mutation-triggered predisposition to injury.

APPROACH AND RESULTS

Using A549 cells transduced with a lentivirus K18 construct and high-throughput screening, we identified the SRC-family tyrosine kinases inhibitor, PP2, as a compound that reverses keratin filament disruption and protects from apoptotic cell death caused by K18 R90C mutation at this highly conserved arginine. PP2 also ameliorated Fas-induced apoptosis and liver injury in male but not female K18 R90C mice. The PP2 male selectivity is due to its lower turnover in male versus female livers. Knockdown of SRC but not another kinase target of PP2, protein tyrosine kinase 6, in A549 cells abrogated the hepatoprotective effect of PP2. Phosphoproteomic analysis and validation showed that the protective effect of PP2 associates with Ser/Thr but not Tyr keratin hypophosphorylation, and differs from the sex-independent effect of the Ser/Thr kinase inhibitor PKC412. Inhibition of RAF kinase, a downstream target of SRC, by vemurafenib had a similar protective effect to PP2 in A549 cells and male K18 R90C mice.

CONCLUSIONS

PP2 protects, in a male-selective manner, keratin mutation-induced mouse liver injury by inhibiting SRC-triggered downstream Ser/Thr phosphorylation of K8/K18, which is phenocopied by RAF kinase inhibitor vemurafenib. The PP2/vemurafenib-associated findings, and their unique mechanisms of action, further support the potential role of select kinase inhibition as therapeutic opportunities for keratin and other IF-associated human diseases.

Keratin 80 Promotes Migration and Invasion of Non-Small Cell Lung Cancer Cells by Regulating the TGF-β/SMAD Pathway

Upregulation of keratin 80 (KRT80) expression levels and carcinogenic function has been found in several types of tumors. However, its contribution and mechanism in NSCLC remain to be outlined. In this study, bioinformatic investigation from the TCGA dataset revealed that KRT80 was confirmed to be elevated in human NSCLC tissues. The results of qRT-PCR and Western blot assays disclosed that KRT80 was uplifted in NSCLC cells. Data from CCK-8 and colony formation assays exhibited that depletion of KRT80 restrained NSCLC cell proliferation. Findings from Transwell and Western blot assays illustrated that downregulation of KRT80 inhibited NSCLC cell migration, invasion, and EMT. Further mechanism exploration implied that KRT80 may be included within the regulation of EMT of NSCLC cells by affecting the TGF-β/SMAD pathway. Moreover, depletion of KRT80 attenuated xenograft tumor growth and the expressions of KRT80, Ki-67, and TGFBR1. In conclusion, depletion of KRT80 repressed NSCLC cell proliferation, invasion, and EMT, possibly mediated by the TGF-β/SMAD signaling pathway, indicating that KRT80 may be a potentially useful target for NSCLC.

A TGFβR inhibitor represses keratin-7 expression in 3D cultures of human salivary gland progenitor cells

Salivary gland tissue engineering offers an attractive alternative for the treatment of radiation-induced xerostomia. Key to the success of this approach is the maintenance and expansion of secretory acinar cells in vitro. However, recent studies revealed that in vitro culture of primary salivary gland epithelial cells led to undesirable upregulation of the expression of keratin-7 (K7), a marker of ductal phenotype and frequently associated with cellular stress. We have previously shown that hyaluronic acid (HA)-based, RGDSP-decorated hydrogels support the 3D growth and assembly of primary human salivary gland stem/progenitor cells (hS/PCs). Here, we investigate whether the RGDSP culture also promotes K7 expression, and if so, what factors govern the K7 expression. Compared to hS/PCs maintained in blank HA gels, those grown in RGDSP cultures expressed a significantly higher level of K7. In other tissues, various transforming growth factor-β (TGF-β) superfamily members are reported to regulate K7 expression. Similarly, our immunoblot array and ELISA experiments confirmed the increased expression of TGF-β1 and growth/differentiation factor-15 (GDF-15) in RGDSP cultures. However, 2D model studies show that only TGF-β1 is required to induce K7 expression in hS/PCs. Immunocytochemical analysis of the intracellular effectors of TGF-β signaling, SMAD 2/3, further confirmed the elevated TGF-β signaling in RGDSP cultures. To maximize the regenerative potential of h/SPCs, cultures were treated with a pharmacological inhibitor of TGF-β receptor, A83-01. Our results show that A83-01 treatment can repress K7 expression not only in 3D RGDSP cultures but also under 2D conditions with exogenous TGF-β1. Collectively, we provide a link between TGF-β signaling and K7 expression in hS/PC cultures and demonstrate the effectiveness of TGF-β inhibition to repress K7 expression while maintaining the ability of RGDSP-conjugated HA gels to facilitate the rapid development of amylase expressing spheroids. These findings represent an important step towards regenerating salivary function with a tissue-engineered salivary gland.

Roles of Keratins in Intestine

Keratins make up a major portion of epithelial intermediate filament proteins. The widely diverse keratins are found in both the small and large intestines. The human intestine mainly expresses keratins 8, 18, 19, and 20. Many of the common roles of keratins are for the integrity and stability of the epithelial cells. The keratins also protect the cells and tissue from stress and are biomarkers for some diseases in the organs. Although an increasing number of studies have been performed regarding keratins, the roles of keratin in the intestine have not yet been fully understood. This review focuses on discussing the roles of keratins in the intestine. Diverse studies utilizing mouse models and samples from patients with intestinal diseases in the search for the association of keratin in intestinal diseases have been summarized.

MiR-4268 suppresses gastric cancer genesis through inhibiting keratin 80

Gastric cancer (GC) affects a large proportion of cancer patients worldwide, and the prediction of potential biomarkers can greatly improve its diagnosis and treatment. Here, miR-4268 and keratin 80 (KRT80) expression in GC tissues and cell lines was determined. The effect of downregulating miR-4268 and interfering with KRT80 expression on the viability, proliferation, apoptosis, and migration of GC cells were evaluated. The interaction between miR-4268 and KRT80 was studied using luciferase reporter and RNA pull-down assays. The western blot, CCK-8, BrdU, caspase-3 activity, Transwell assays were performed for the functional characterization. In GC tissues and cells, KRT80 expression was found to be significantly higher, while that of miR-4268 was significantly lower than the respective expressions in normal tissues and cells. Interference with KRT80 expression inhibited the viability, proliferation, and migration of GC cells and facilitated cell apoptosis in vitro. We further demonstrated that miR-4268 targeted KRT80 and negatively regulated its expression, and miR-4268 inhibitor alleviated the inhibitory effects of KRT80 downregulation on GC cell growth. Finally, miR-4268 may function as tumor suppressor through inhibiting PI3K/AKT/JNK pathways by targeting KRT80 in GC. Collectively, our present results indicate that the miR-4268/KRT80 axis acts as a potential therapeutic target for patients with GC.AbbreviationsGastric cancer (GC); MicroRNAs (miRNAs); Keratin 80 (KRT80); differentially expressed genes (DEGs); chemoradiotherapy (CRT); negative nonsense sequence (NC); radioimmunoprecipitation assay (RIPA); polyvinylidene fluoride (PVDF).

Targeted deletion of keratin 8 in intestinal epithelial cells disrupts tissue integrity and predisposes to tumorigenesis in the colon

Keratin 8 (K8) is the main intestinal epithelial intermediate filament protein with proposed roles for colonic epithelial cell integrity. Here, we used mice lacking K8 in intestinal epithelial cells (floxed K8 and Villin-Cre1000 and Villin-CreERt2) to investigate the cell-specific roles of intestinal epithelial K8 for colonocyte function and pathologies. Intestinal epithelial K8 deletion decreased K8 partner proteins, K18-K20, 75-95%, and the remaining keratin filaments were located at the colonocyte apical regions with type II K7, which decreased 30%. 2-Deoxy-2-[18F]-fluoroglucose positron emission tomography in vivo imaging identified a metabolic phenotype in the lower gut of the conditional K8 knockouts. These mice developed intestinal barrier leakiness, mild diarrhea, and epithelial damage, especially in the proximal colon. Mice exhibited shifted differentiation from enterocytes to goblet cells, displayed longer crypts and an increased number of Ki67 + transit-amplifying cells in the colon. Significant proproliferative and regenerative signaling occurred in the IL-22, STAT3, and pRb pathways, with minor effects on inflammatory parameters, which, however, increased in aging mice. Importantly, colonocyte K8 deletion induced a dramatically increased sensitivity to azoxymethane-induced tumorigenesis. In conclusion, intestinal epithelial K8 plays a significant role in colonocyte epithelial integrity maintenance, proliferation regulation and tumor suppression.

Keratin 80 regulated by miR-206/ETS1 promotes tumor progression via the MEK/ERK pathway in ovarian cancer

Introduction: Keratin 80 (KRT80) is a type II epithelial keratin protein that plays an important role in cell differentiation and tumor progression. However, its role and mechanisms in ovarian cancer remain unclear. Methods: The effect of KRT80 on the survival and prognosis of patients with ovarian cancer was determined using immunohistochemistry. Cell lines overexpressing KRT80 and with KRT80 knockdown were established to study its effect on the malignant behavior of ovarian cancer cells. Western blotting was used to detect changes in related molecules, and in the MEK/ERK signal transduction pathway. ChIP assay was used to confirm that ETS1 regulates KRT80 at the transcriptional level. A double luciferase assay was used to confirm the target of miR-206. Results: The expression levels of KRT80 were high in ovarian cancer tissue, and were related to survival and prognosis. KRT80 expression is an independent prognostic factor in patients with ovarian cancer. KRT80 overexpression promotes the proliferation of ovarian cancer cells, the transition from G1 phase to S phase, invasion, and migration. KRT80 overexpression increased the expression of BCL2/BAX, CyclinD1, MMP2, MMP9, and N-cadherin, decreased the expression of E-cadherin, and increased the phosphorylation of MEK and ERK. ETS1 binds to the upstream promoter sequence of KRT80 and regulates KRT80 expression at the transcriptional level. ETS1 is a direct target of miR-206 in ovarian cancer cells. Conclusion: KRT80 regulated by miR-206/ETS1 promotes tumor progression via the MEK/ERK pathway in ovarian cancer, and KRT80 may have applications as a screening biomarker and potential therapeutic target for ovarian cancer.

UV induced changes in proteome of rats plasma are reversed by dermally applied cannabidiol

UV radiation is known to induce a multiple changes in the metabolism of skin-building cells, what can affect the functioning not only neighboring cells, but also, following signal transduction releasing into the blood vessels, the entire body. Therefore, the aim of this study was to analyze the proteomic disturbances occurred in plasma of chronically UVA/UVB irradiated rats and define the effect on these changes of skin topically applied cannabidiol (CBD). Obtained results showed significant changes in the expression of numerous anti-inflammatory and signaling proteins including: NFκB inhibitor, 14-3-3 protein, protein kinase C, keratin, and protein S100 after UV irradiation and CBD treatment. Moreover, the effects of UVA and UVB were manifested by increased level of lipid peroxidation products-protein adducts formation. CBD partially prevented all of these changes, but in a various degree depending on the UV radiation type. Moreover, topical treatment with CBD resulted in the penetration of CBD into the blood and, as a consequence, in direct modifications to the plasma protein structure by creating CBD adducts with molecules, such as proline-rich protein 30, transcription factor 19, or N-acetylglucosamine-6-sulfatase, what significantly changed the activity of these proteins. In conclusion, it may be suggested that CBD applied topically may be an effective compound against systemic UV-induced oxidative stress, but its effectiveness requires careful analysis of CBD's effects on other tissues of the living organism.

Assembly and recognition of keratins: A structural perspective

Keratins are one of the major components of cytoskeletal network and assemble into fibrous structures named intermediate filaments (IFs), which are important for maintaining the mechanical properties of cells and tissues. Over the past decades, evidence has shown that the functions of keratins go beyond providing mechanical support for cells, they interact with multiple cellular components and are widely involved in the pathways of cell proliferation, differentiation, motility and death. However, the structural details of keratins and IFs are largely missing and many questions remain regarding the mechanisms of keratin assembly and recognition. Here we briefly review the current structural models and assembly of keratins as well as the interactions of keratins with the binding partners, which may provide a structural view for understanding the mechanisms of keratins in the biological activities and the related diseases.

Loss of FAM83H promotes cell migration and invasion in cutaneous squamous cell carcinoma via impaired keratin distribution

BACKGROUNDS

FAM83H is essential for amelogenesis, but recent reports implicate that FAM83H is involved in the tumorigenesis. We previously clarified that TRIM29 binds to FAM83H to regulate keratin distribution and squamous cell migration. However, little is known about FAM83H in normal/malignant skin keratinocytes.

OBJECTIVE

To investigate the expression of FAM83H in cutaneous squamous cell carcinoma (SCC) and its physiological function.

METHODS

Immunohistochemical analysis and RT-PCR of human SCC tissues were performed. Next, we examined the effect of FAM83H knockdown/overexpression in SCC cell lines using cell proliferation, migration, and invasion assay. To investigate the molecular mechanism, immunoprecipitation of FAM83H was examined. Further, Immunofluorescence staining was performed. Finally, we examined the correlation between the expressions of FAM83H and the keratin distribution.

RESULTS

FAM83H expression was lower in SCC lesions than in normal epidermis and correlated with differentiation grade. The mRNA expression levels of FAM83H in SCC tumors were also lower than in normal epidermis. The knockdown of FAM83H enhanced SCC cell migration and invasion, whereas the overexpression of FAM83H led to decreases in both. Furthermore, the knockdown of FAM83H enhanced the cancer cell metastasis in vivo. FAM83H formed a complex with TRIM29 and keratins. The knockdown of FAM83H altered keratin distribution and solubility. Clinically, the loss of FAM83H correlates with an altered keratin distribution.

CONCLUSION

Our findings reveal a critical function for FAM83H in regulating keratin distribution, as well as in the migration/invasion of cutaneous SCC, suggesting that FAM83H could be a crucial molecule in the tumorigenesis of cutaneous SCC.

Current and Future Biomarkers in Alcoholic Hepatitis

Alcoholic hepatitis (AH) is a clinical syndrome of jaundice, abdominal pain, and anorexia due to prolonged heavy alcohol intake, and is associated with alterations in gene expression, cytokines, immune response, and the gut microbiome. Currently, we have limited biomarkers to diagnose and prognosticate in AH, but there are many novel noninvasive biomarkers under development. We evaluate the currently used algorithms to risk-stratify in AH (such as the Maddrey modified discriminant function), and discuss novel biomarkers in development, such as breath biomarkers, microRNAs, cytokeratin-18 fragments, and the AshTest. We also review the characteristics of an ideal biomarker in AH.

Keratin 8 mutations in transgenic mice predispose to lung injury

Keratin 8 (K8) is the cytoskeletal intermediate filament protein of simple-type epithelia. Mutations in K8 predispose the affected individual and transgenic mouse to liver disease. However, the role of K8 in the lung has not been reported in mutant transgenic mouse models. Here, we investigated the susceptibility of two different transgenic mice expressing K8 Gly62-Cys (Gly62 replaced with Cys) or Ser74-Ala (Ser74 replaced with Ala) to lung injury. The mutant transgenic mice were highly susceptible to two independent acute and chronic lung injuries compared with control mice. Both K8 Gly62-Cys mice and K8 Ser74-Ala mice showed markedly increased mouse lethality (∼74% mutant mice versus ∼34% control mice) and more severe lung damage, with increased inflammation and apoptosis, under L-arginine-mediated acute lung injury. Moreover, the K8 Ser74-Ala mice had more severe lung damage, with extensive hemorrhage and prominent fibrosis, under bleomycin-induced chronic lung injury. Our study provides the first direct evidence that K8 mutations predispose to lung injury in transgenic mice.

Keratin 7 Is a Constituent of the Keratin Network in Mouse Pancreatic Islets and Is Upregulated in Experimental Diabetes

Keratin (K) 7 is an intermediate filament protein expressed in ducts and glands of simple epithelial organs and in urothelial tissues. In the pancreas, K7 is expressed in exocrine ducts, and apico-laterally in acinar cells. Here, we report K7 expression with K8 and K18 in the endocrine islets of Langerhans in mice. K7 filament formation in islet and MIN6 β-cells is dependent on the presence and levels of K18. K18-knockout (K18^‒/‒) mice have undetectable islet K7 and K8 proteins, while K7 and K18 are downregulated in K8^‒/‒ islets. K7, akin to F-actin, is concentrated at the apical vertex of β-cells in wild-type mice and along the lateral membrane, in addition to forming a fine cytoplasmic network. In K8^‒/‒ β-cells, apical K7 remains, but lateral keratin bundles are displaced and cytoplasmic filaments are scarce. Islet K7, rather than K8, is increased in K18 over-expressing mice and the K18-R90C mutation disrupts K7 filaments in mouse β-cells and in MIN6 cells. Notably, islet K7 filament networks significantly increase and expand in the perinuclear regions when examined in the streptozotocin diabetes model. Hence, K7 represents a significant component of the murine islet keratin network and becomes markedly upregulated during experimental diabetes.

Spaceflight decelerates the epigenetic clock orchestrated with a global alteration in DNA methylome and transcriptome in the mouse retina

Astronauts exhibit an assortment of clinical abnormalities in their eyes during long-duration spaceflight. The purpose of this study was to determine whether spaceflight induces epigenomic and transcriptomic reprogramming in the retina or alters the epigenetic clock. The mice were flown for 37 days in animal enclosure modules on the International Space Station; ground-based control animals were maintained under similar housing conditions. Mouse retinas were isolated and both DNA methylome and transcriptome were determined by deep sequencing. We found that a large number of genes were differentially methylated with spaceflight, whereas there were fewer differentially expressed genes at the transcriptome level. Several biological pathways involved in retinal diseases such as macular degeneration were significantly altered. Our results indicated that spaceflight decelerated the retinal epigenetic clock. This study demonstrates that spaceflight impacts the retina at the epigenomic and transcriptomic levels, and such changes could be involved in the etiology of eye-related disorders among astronauts.

Developmental cell programs are co-opted in inflammatory skin disease

The skin confers biophysical and immunological protection through a complex cellular network established early in embryonic development. We profiled the transcriptomes of more than 500,000 single cells from developing human fetal skin, healthy adult skin, and adult skin with atopic dermatitis and psoriasis. We leveraged these datasets to compare cell states across development, homeostasis, and disease. Our analysis revealed an enrichment of innate immune cells in skin during the first trimester and clonal expansion of disease-associated lymphocytes in atopic dermatitis and psoriasis. We uncovered and validated in situ a reemergence of prenatal vascular endothelial cell and macrophage cellular programs in atopic dermatitis and psoriasis lesional skin. These data illustrate the dynamism of cutaneous immunity and provide opportunities for targeting pathological developmental programs in inflammatory skin diseases.

Targeting the cytoskeleton against metastatic dissemination

Cancer is a pathology characterized by a loss or a perturbation of a number of typical features of normal cell behaviour. Indeed, the acquisition of an inappropriate migratory and invasive phenotype has been reported to be one of the hallmarks of cancer. The cytoskeleton is a complex dynamic network of highly ordered interlinking filaments playing a key role in the control of fundamental cellular processes, like cell shape maintenance, motility, division and intracellular transport. Moreover, deregulation of this complex machinery contributes to cancer progression and malignancy, enabling cells to acquire an invasive and metastatic phenotype. Metastasis accounts for 90% of death from patients affected by solid tumours, while an efficient prevention and suppression of metastatic disease still remains elusive. This results in the lack of effective therapeutic options currently available for patients with advanced disease. In this context, the cytoskeleton with its regulatory and structural proteins emerges as a novel and highly effective target to be exploited for a substantial therapeutic effort toward the development of specific anti-metastatic drugs. Here we provide an overview of the role of cytoskeleton components and interacting proteins in cancer metastasis with a special focus on small molecule compounds interfering with the actin cytoskeleton organization and function. The emerging involvement of microtubules and intermediate filaments in cancer metastasis is also reviewed.

Hepatocyte-Derived Igκ Exerts a Protective Effect against ConA-Induced Acute Liver Injury

Immunoglobulin (Igκ) has been reported to be expressed in sorted liver epithelial cells of μMT mice, and the sequence characteristics of hepatocyte-derived Igκ were different from those of classical B-cell-derived Igκ. However, the physiological function of hepatocyte-derived Igκ is still unclear. The expression of Igκ was firstly identified in primary hepatocytes and normal liver cell line (NCTC1469), and hepatocyte-derived Igκ expression was elevated and displayed unique localization in hepatocytes of concanavalin A (ConA)-induced hepatitis model. Moreover, Igκ knockout mice were more sensitive to ConA-induced hepatitis and had higher serum aspartate aminotransferase (AST) levels, more severe histological injury and a greater number of terminal deoxynucleotide transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL)-positive cells as compared with littermate controls. Furthermore, knockdown of Igκ in primary hepatocytes and NCTC1469 cells led to accelerated activation of the mitochondrial death pathway and caspase-3 cleavage in vitro, which might be related to inhibition of NF-κB signaling pathway and activation of JNK via the cytoskeleton dynamics. Taken together, these results indicate that hepatocyte-derived Igκ mediates cellular resistance to ConA-induced liver injury by inhibiting activation of caspase-3 and the mitochondrial death pathway, suggesting that Igκ plays an important role in hepatocyte survival and exerts a protective effect against ConA-induced liver injury in mice.

Small interfering RNA-mediated knockdown of KRT80 suppresses colorectal cancer proliferation

Colorectal cancer (CRC) is the third most common cancer in the world and its development is associated with oncogenic dysfunction. Therefore, the present study aimed to identify differentially expressed genes (DEGs) in CRC tissues and to determine the role of keratin 80 (KRT80) in CRC cell proliferation. DEGs were initially screened in 32 paired CRC tissues and matched adjacent normal tissues from RNA-Seq datasets in The Cancer Genome Atlas database using the limma package in R software. In total, 2,114 DEGs were identified, of which KRT80 was discovered to be the most upregulated in CRC tissues. Moreover, increased KRT80 expression levels were confirmed in tissues collected from 50 patients with CRC using reverse transcription-quantitative PCR, and its increased expression levels were significantly associated with increased lymph node and distant metastasis and a higher pathological stage. Furthermore, KRT80 knockdown using siRNA decreased the viability and proliferation of CRC cells. Finally, pathway analysis revealed that the proteins co-expressed with KRT80 in CRC were enriched in the cell cycle, DNA replication, immune system, metabolism of protein and RNA, signal transduction and other cellular processes. Among them, the cell cycle and DNA replication pathways contained the highest number of the proteins identified. In conclusion, the findings of the present study suggested that KRT80 may be overexpressed in CRC tissues. Furthermore, KRT80 may be involved in the proliferation of CRC cells, which is likely through its ability to regulate the cell cycle and DNA replication pathways, thus it may serve as a potential therapeutic target for patients with CRC.

Time-Course Changes of Serum Keratin Concentrations after Liver Transplantation: Contrasting Results of Keratin-18 and Keratin-19 Fragments

Objective

Under normal conditions, adult hepatocytes express only keratin-8 (K8) and keratin-18 (K18), whereas cholangiocytes also express K19. In this study, we delineate the pattern of normal time-course changes in serum K19 and K18 levels after liver transplantation. Patients and Methods. Serum levels of the K19 fragment CYFRA 21-1 and the K18 fragments tissue polypeptide specific antigen (TPS) and M30 (a neoepitope that is generated after caspase cleavage during apoptosis) were measured at baseline and at regular intervals (up to 6 months) after liver transplantation in 11 adult patients.

Results

There was a gradual decrease in serum K19 concentrations from baseline values after transplantation, following a time-course pattern similar to that of serum bilirubin. In contrast, serum concentrations of K18 fragments increased markedly shortly after transplantation and gradually decreased thereafter, following a time-course pattern similar to that of serum transaminases. The increase in TPS tended to occur earlier than that in M30, suggesting an initial predominance of hepatocyte necrosis followed by a predominance of apoptosis in the first days after transplantation. Five patients presented posttransplant complications (acute rejection in three cases and HCV recurrence in two cases). An early increase in serum K19 concentrations was observed in all cases. An increase in serum concentrations of K18 fragments (M30 and TPS) was observed in the two cases with HCV recurrence and was more variable in the three cases with acute rejection.

Conclusions

Serum concentrations of K19 and K18 fragments follow a dissimilar pattern of time-course changes after liver transplantation. The diagnostic value of variations in these normal patterns should be addressed in future studies.

Keratin intermediate filaments in the colon: guardians of epithelial homeostasis

Keratin intermediate filament proteins are major cytoskeletal components of the mammalian simple layered columnar epithelium in the gastrointestinal tract. Human colon crypt epithelial cells express keratins 18, 19 and 20 as the major type I keratins, and keratin 8 as the type II keratin. Keratin expression patterns vary between species, and mouse colonocytes express keratin 7 as a second type II keratin. Colonic keratin patterns change during cell differentiation, such that K20 increases in the more differentiated crypt cells closer to the central lumen. Keratins provide a structural and mechanical scaffold to support cellular stability, integrity and stress protection in this rapidly regenerating tissue. They participate in central colonocyte processes including barrier function, ion transport, differentiation, proliferation and inflammatory signaling. The cell-specific keratin compositions in different epithelial tissues has allowed for the utilization of keratin-based diagnostic methods. Since the keratin expression pattern in tumors often resembles that in the primary tissue, it can be used to recognize metastases of colonic origin. This review focuses on recent findings on the biological functions of mammalian colon epithelial keratins obtained from pivotal in vivo models. We also discuss the diagnostic value of keratins in chronic colonic disease and known keratin alterations in colon pathologies. This review describes the biochemical properties of keratins and their molecular actions in colonic epithelial cells and highlights diagnostic data in colorectal cancer and inflammatory bowel disease patients, which may facilitate the recognition of disease subtypes and the establishment of personal therapies in the future.

Characterisation of the novel spontaneously immortalized and invasively growing human skin keratinocyte line HaSKpw

We here present the spontaneously immortalised cell line, HaSKpw, as a novel model for the multistep process of skin carcinogenesis. HaSKpw cells were established from the epidermis of normal human adult skin that, without crisis, are now growing unrestricted and feeder-independent. At passage 22, clonal populations were established and clone7 (HaSKpwC7) was further compared to the also spontaneously immortalized HaCaT cells. As important differences, the HaSKpw cells express wild-type p53, remain pseudodiploid, and show a unique chromosomal profile with numerous complex aberrations involving chromosome 20. In addition, HaSKpw cells overexpress a pattern of genes and miRNAs such as KRT34, LOX, S100A9, miR21, and miR155; all pointing to a tumorigenic status. In concordance, HaSKpw cells exhibit reduced desmosomal contacts that provide them with increased motility and a highly migratory/invasive phenotype as demonstrated in scratch- and Boyden chamber assays. In 3D organotypic cultures, both HaCaT and HaSKpw cells form disorganized epithelia but only the HaSKpw cells show tumorcell-like invasive growth. Together, HaSKpwC7 and HaCaT cells represent two spontaneous (non-genetically engineered) “premalignant” keratinocyte lines from adult human skin that display different stages of the multistep process of skin carcinogenesis and thus represent unique models for analysing skin cancer development and progression.

Systemic inflammation is associated with circulating cell death released keratin 18 fragments in colorectal cancer

Systemic inflammation is a stage-independent marker of poor prognosis in colorectal cancer (CRC), activated in a complex, multifactorial process. It has been proposed that one of the main factors driving systemic inflammation may be tumor necrosis. Keratin 18 (KRT18) fragments are released from dead cells and their serum levels are markers for apoptotic and necrotic cell death. In CRC, high KRT18 levels associate with advanced disease, but their relationship with tumor necrosis and systemic inflammation is unknown. In this study, serum total soluble KRT18 (tKRT18) and apoptosis-related, caspase-cleaved fragment (aKRT18) levels were measured preoperatively from 328 CRC patients, and their difference was calculated to assess necrosis related KRT18 (nKRT18) levels. The relationships of these markers with tumor necrosis, clinicopathologic features, systemic inflammation markers (C-reactive protein, albumin, and 13 cytokines), and survival were analyzed. High serum tKRT18, aKRT18, and nKRT18 levels showed association with a higher extent of tumor necrosis, distant metastasis, and increased levels of several markers of systemic inflammation, including CXCL8. High serum tKRT18 (multivariable HR 1.94, 95% CI 1.28-2.95, p = .002) and nKRT18 (multivariable HR 1.87, 95% CI 1.24-2.82, p = .003) levels were associated with poor overall survival independent of potential confounding factors. Our results show that tumor necrosis in CRC contributes to serum levels of KRT18 fragments, and both necrosis and KRT18 levels associate with systemic inflammation. Moreover, we show that serum tKRT18 and nKRT18 levels have independent prognostic value in CRC. Our observations confirm the link between cell death and systemic inflammation.

Leukamenin E Induces K8/18 Phosphorylation and Blocks the Assembly of Keratin Filament Networks Through ERK Activation

Leukamenin E is a natural ent-kaurane diterpenoid isolated from Isodon racemosa (Hemsl) Hara that has been found to be a novel and potential keratin filament inhibitor, but its underlying mechanisms remain largely unknown. Here, we show that leukamenin E induces keratin filaments (KFs) depolymerization, largely independently of microfilament (MFs) and microtubules (MTs) in well-spread cells and inhibition of KFs assembly in spreading cells. These effects are accompanied by keratin phosphorylation at K8-Ser73/Ser431 and K18-Ser52 via the by extracellular signal-regulated kinases (ERK) pathway in primary liver carcinoma cells (PLC) and human umbilical vein endothelial cells (HUVECs). Moreover, leukamenin E increases soluble pK8-Ser73/Ser431, pK18-Ser52, and pan-keratin in the cytoplasmic supernatant by immunofluorescence imaging and Western blotting assay. Accordingly, leukamenin E inhibits the spreading and migration of cells. We propose that leukamenin E-induced keratin phosphorylation may interfere with the initiation of KFs assembly and block the formation of a new KFs network, leading to the inhibition of cell spreading. Leukamenin E is a potential target drug for inhibition of KFs assembly.

Morphology, Motility, and Cytoskeletal Architecture of Breast Cancer Cells Depend on Keratin 19 and Substrate

Cancer cells gain motility through events that accompany modulation of cell shape and include altered expression of keratins. However, the role of keratins in change of cancer cell architecture is not well understood. Therefore, we ablated the expression of keratin 19 (K19) in breast cancer cells of the MDA-MB-231 cell line and found that cells lacking K19 become more elongated in culture, with morphological reversion toward the parental phenotype upon transduction of KRT19. Also, the number of actin stress fibers and focal adhesions were significantly reduced in KRT19 knockout (KO) cells. The altered morphology of KRT19 KO cells was then characterized quantitatively using digital holographic microscopy (DHM), which not only confirmed the phenotypic change of KRT19 KO cells but also identified that the K19-dependent morphological change is dependent on the substrate type. A new quantitative method of single cell analysis from DHM, via average phase difference maps, facilitated evaluation of K19-substrate interactive effects on cell morphology. When plated on collagen substrate, KRT19 KO cells were less elongated and resembled parental cells. Assessing single cell motility further showed that while KRT19 KO cells moved faster than parental cells on a rigid surface, this increase in motility became abrogated when cells were plated on collagen. Overall, our study suggests that K19 inhibits cell motility by regulating cell shape in a substrate-dependent manner. Thus, this study provides a potential basis for the altered expression of keratins associated with change in cell shape and motility of cancer cells. © 2020 International Society for Advancement of Cytometry.

Elevated Serum Level of Cytokeratin 18 M65ED Is an Independent Indicator of Cardiometabolic Disorders

BACKGROUND

Recent studies have suggested that cell death might be involved in the pathophysiology of metabolic disorders. The cytokeratin 18 (CK18) fragment, as a cell death marker, plays an important role in nonalcoholic fatty liver disease (NAFLD). However, only a limited number of studies have found elevated serum levels of CK18 in patients with type 2 diabetes. Moreover, no studies have been conducted yet to investigate the role of CK18 in hypertension or dyslipidemia. In particular, CK18 M65ED is a more sensitive marker of cell death, and its role in cardiometabolic disorders has not been revealed yet.

METHODS

A total of 588 subjects were enrolled from the local communities of Shanghai. Serum CK18 M65ED were determined using the enzyme-linked immunosorbent assay. A cardiometabolic disorder was identified by the presence of at least one of the components including overweight or central obesity, diabetes, dyslipidemia, and hypertension.

RESULTS

Subjects with cardiometabolic disorders exhibited significantly higher serum levels of CK18 M65ED than those without cardiometabolic disorders (197.36 (121.13-354.50) U/L versus 83.85 (52.80-153.75) U/L, respectively, P < 0.001). Increased serum CK18 M65ED quartiles were associated with the increased prevalence of cardiometabolic disorders and its components (P < 0.001 for all components). Multiple stepwise regression analysis also revealed that diastolic blood pressure, glycated hemoglobin A1c, alanine transaminase, and high-density lipoprotein cholesterol were independently correlated with serum CK18 M65ED levels (all P < 0.01). In addition, logistic regression analysis showed that the serum CK18 M65ED levels were positively correlated with cardiometabolic disorders and in an independent manner. Further, CK18 M65ED was revealed to be an indicator of cardiometabolic disorders in a NAFLD-independent manner.

CONCLUSIONS

Elevated levels of CK18 M65ED, a sensitive cell death marker, were independently and positively correlated with cardiometabolic disorders, even after the adjustment for the presence of NAFLD and other cardiovascular risk factors.

CK19 Promotes Ovarian Cancer Development by Impacting on Wnt/β-Catenin Pathway

Background

Epithelial ovarian cancer (EOC) is the most common type of ovarian cancer and is the most lethal gynecologic malignancy. Cytokeratin 19 (CK19) is a small type I cytokeratin. The aim of this study is to explore the functional role of CK19 and its underlying mechanism in EOC.

Methods

The expression levels of CK19 in EOC tissues were identified by Western blotting and RT-PCR assay. Transwell assay and CCK-8 proliferation assay were used to assess the invasion, migration and proliferation abilities of overexpressed or knockdown CK19 of ovarian cancer cells. We also detected the related genes of Wnt/β-catenin signal pathway, including β-catenin, TCF7, LEF1, c-MYC and cyclin D1 in the transfected ovarian cancer cells by Western blotting and RT-PCR assay.

Results

The results demonstrated that CK19 was upregulated in EOC tissue. CK19 was verified to promote the invasion, proliferation and migration of ovarian cancer cells. Additionally, CK19 activates the Wnt/β-catenin signaling pathway by upregulated β-catenin, TCF7, LEF1, c-MYC and cyclin D1.

Conclusions

In summary, this is the first study to investigate the role of CK19 in EOC. These findings provide a potential new therapeutic target for the clinical diagnosis and treatment of ovarian cancer.

Crystal Structure of Keratin 1/10(C401A) 2B Heterodimer Demonstrates a Proclivity for the C-Terminus of Helix 2B to Form Higher Order Molecular Contacts

We previously determined the crystal structure of the wild-type keratin 1/10 helix 2B heterodimer at 3.3 Å resolution. We proposed that the resolution of the diffraction data was limited due to the crystal packing effect from keratin 10 (K10) residue Cys401. Cys401K10 formed a disulfide-linkage with Cys401 from another K1/10 heterodimer, creating an "X-shaped" structure and a loose crystal packing arrangement. We hypothesized that mutation of Cys401K10 to alanine would eliminate the disulfide-linkage and improve crystal packing thereby increasing resolution of diffraction and enabling a more accurate side chain electron density map. Indeed, when a K10 Cys401Ala 2B mutant was paired with its native keratin 1 (K1) 2B heterodimer partner its x-ray crystal structure was determined at 2.07 Å resolution; the structure does not contain a disulfide linkage. Superposition of the K1/K10(Cys401Ala) 2B structure onto the wild-type K1/10 2B heterodimer structure had a root-mean-square-deviation of 1.88 Å; the variability in the atomic positions reflects the dynamic motion expected in this filamentous coiled-coil complex. The electrostatic, hydrophobic, and contour features of the molecular surface are similar to the lower resolution wild-type structure. We postulated that elimination of the disulfide linkage in the K1/K10(Cys401Ala) 2B structure could allow for the 2B heterodimers to bind/pack in the A22 tetramer configuration associated with mature keratin intermediate filament assembly. Analysis of the crystal packing revealed a half-staggered anti-parallel tetrameric complex of 2B heterodimers; however, their register is not consistent with models of the A22 mode of tetrameric alignment or prior biochemical cross-linking studies.

Pathophysiology of NAFLD and NASH in Experimental Models: The Role of Food Intake Regulating Peptides

Obesity, diabetes, insulin resistance, sedentary lifestyle, and Western diet are the key factors underlying non-alcoholic fatty liver disease (NAFLD), one of the most common liver diseases in developed countries. In many cases, NAFLD further progresses to non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and to hepatocellular carcinoma. The hepatic lipotoxicity and non-liver factors, such as adipose tissue inflammation and gastrointestinal imbalances were linked to evolution of NAFLD. Nowadays, the degree of adipose tissue inflammation was shown to directly correlate with the severity of NAFLD. Consumption of higher caloric intake is increasingly emerging as a fuel of metabolic inflammation not only in obesity-related disorders but also NAFLD. However, multiple causes of NAFLD are the reason why the mechanisms of NAFLD progression to NASH are still not well understood. In this review, we explore the role of food intake regulating peptides in NAFLD and NASH mouse models. Leptin, an anorexigenic peptide, is involved in hepatic metabolism, and has an effect on NAFLD experimental models. Glucagon-like peptide-1 (GLP-1), another anorexigenic peptide, and GLP-1 receptor agonists (GLP-1R), represent potential therapeutic agents to prevent NAFLD progression to NASH. On the other hand, the deletion of ghrelin, an orexigenic peptide, prevents age-associated hepatic steatosis in mice. Because of the increasing incidence of NAFLD and NASH worldwide, the selection of appropriate animal models is important to clarify aspects of pathogenesis and progression in this field.

Encapsulation of the cytoskeleton: towards mimicking the mechanics of a cell

The cytoskeleton of a cell controls all the aspects of cell shape changes and motility from its physiological functions for survival to reproduction to death. The structure and dynamics of the cytoskeletal components: actin, microtubules, intermediate filaments, and septins - recently regarded as the fourth member of the cytoskeleton family - are conserved during evolution. Such conserved and effective control over the mechanics of the cell makes the cytoskeletal components great candidates for in vitro reconstitution and bottom-up synthetic biology studies. Here, we review the recent efforts in reconstitution of the cytoskeleton in and on membrane-enclosed biomimetic systems and argue that co-reconstitution and synergistic interplay between cytoskeletal filaments might be indispensable for efficient mechanical functionality of active minimal cells. Further, mechanical equilibrium in adherent eukaryotic cells is achieved by the formation of integrin-based focal contacts with extracellular matrix (ECM) and the transmission of stresses generated by actomyosin contraction to ECM. Therefore, a minimal mimic of such balance of forces and quasi-static kinetics of the cell by bottom-up reconstitution requires a careful construction of contractile machineries and their link with adhesive contacts. In this review, in addition to cytoskeletal crosstalk, we provide a perspective on reconstruction of cell mechanical equilibrium by reconstitution of cortical actomyosin networks in lipid membrane vesicles adhered on compliant substrates and also discuss future perspectives of this active research area.

Fatty Liver Disease: A Practical Approach

CONTEXT.—

Fatty liver disease is now one of the most commonly encountered entities in the practice of liver pathology. Distinguishing simple steatosis from steatohepatitis is critical because the latter requires follow-up because of long-term risks that include cirrhosis and hepatocellular carcinoma. An organized approach for evaluating liver biopsies with steatosis is recommended to capture all of the relevant features: (1) degree of steatosis, (2) presence or absence of ballooning degeneration, (3) lobular inflammation, and (4) fibrosis. Herein, we provide a stepwise approach that readers can use to evaluate liver biopsies with steatosis, including examples, pitfalls, differential diagnostic considerations, and suggested diagnostic phrasing.

OBJECTIVE.—

To provide a stepwise approach for the evaluation of liver biopsies showing significant steatosis (involving ≥5% of liver parenchyma).

DATA SOURCES.—

Biopsies demonstrating fatty liver disease encountered in our daily practice were examined as well as recent literature.

CONCLUSIONS.—

Effective evaluation of liver biopsies with steatosis requires careful histologic examination and correlation with clinical history, particularly regarding medications, nutrition status, and alcohol use. Examples of uniform reporting, including appropriate use of the nonalcoholic steatohepatitis Clinical Research Network Activity Score, are provided.

Keratins regulate Hsp70-mediated nuclear localization of p38 mitogen-activated protein kinase

Intermediate filament protein keratin 8 (K8) binds to heat shock protein 70 (Hsp70) and p38 MAPK, and is phosphorylated at Ser74 by p38α (MAPK14, hereafter p38). However, a p38 binding site on K8 and the molecular mechanism of K8-p38 interaction related to Hsp70 are unknown. Here, we identify a p38 docking site on K8 (Arg148/149 and Leu159/161) that is highly conserved in other intermediate filaments. A docking-deficient K8 mutation caused increased p38-Hsp70 interaction and enhanced p38 nuclear localization, indicating that the p38 dissociated from mutant K8 makes a complex with Hsp70, which is known as a potential chaperone for p38 nuclear translocation. Comparison of p38 MAPK binding with keratin variants associated with liver disease showed that the K18 I150V variant dramatically reduced binding with p38, which is similar to the effect of the p38 docking-deficient mutation on K8. Because the p38 docking site on K8 (Arg148/149 and Leu159/161) and the K18 Ile150 residue are closely localized in the parallel K8/K18 heterodimer, the K18 I150V mutation might interfere with K8-p38 interaction. These findings show that keratins, functioning as cytoplasmic anchors for p38, modulate p38 nuclear localization and thereby might affect a number of p38-mediated signal transduction pathways.

Serum keratin-18 fragments as cell death biomarker in association with disease progression and prognosis in hepatitis B virus-related cirrhosis

Extensive hepatocyte death leads to hepatic inflammation and contributes to systemic inflammation in decompensated cirrhosis. We aimed to investigate the prognostic value of serum cell death markers in patients with hepatitis B virus (HBV)-related acute decompensation (AD) of cirrhosis with and without acute-on-chronic liver failure (ACLF). We studied two cohorts-cohort 1: 201 outpatients with stable chronic hepatitis B (49 cirrhosis); cohort 2: 232 inpatients with HBV-related cirrhosis admitted for AD. Cell death was determined with serum keratin-18 (K18) for total death and serum caspase-cleaved-K18 (cK18) for apoptosis. Survival analyses were performed using competing risk method. We found that serum K18 and cK18 were significantly (P < 0.001) higher in patients from cohort 2 than those from cohort 1. Among cohort 2, ACLF patients had significantly (P < 0.001) increased K18 and cK18 comparing to those without ACLF. Increased K18 and cK18 were mainly attributed to HBV flare and were associated with liver and coagulation failure. HBV-AD patients without ACLF who admitted with upper tertile of K18 or cK18 were at higher risk of developing ACLF during follow-up. Baseline serum K18 or cK18 was significantly associated with transplant-free 90-day survival independent of leucocytes, HBV DNA, bacterial infection, encephalopathy and severity scores. The combination of cell death biomarkers significantly improved the prognostic value of the currently established prognostic scores. The reduction of cell death level after standard treatment was associated with increased short-term survival. In conclusion, measurements of serum K18 or cK18 in HBV decompensated cirrhosis are a promising tool for predicting ACLF and risk stratification of short-term outcome.

Identification of Keratin 23 as a Hepatitis C Virus-Induced Host Factor in the Human Liver

Keratin proteins form intermediate filaments, which provide structural support for many tissues. Multiple keratin family members are reported to be associated with the progression of liver disease of multiple etiologies. For example, keratin 23 (KRT23) was reported as a stress-inducible protein, whose expression levels correlate with the severity of liver disease. Hepatitis C virus (HCV) is a human pathogen that causes chronic liver diseases including fibrosis, cirrhosis, and hepatocellular carcinoma. However, a link between KRT23 and hepatitis C virus (HCV) infection has not been reported previously. In this study, we investigated KRT23 mRNA levels in datasets from liver biopsies of chronic hepatitis C (CHC) patients and in primary human hepatocytes experimentally infected with HCV, in addition to hepatoma cells. Interestingly, in each of these specimens, we observed an HCV-dependent increase of mRNA levels. Importantly, the KRT23 protein levels in patient plasma decreased upon viral clearance. Ectopic expression of KRT23 enhanced HCV infection; however, CRIPSPR/Cas9-mediated knockout did not show altered replication efficiency. Taken together, our study identifies KRT23 as a novel, virus-induced host-factor for hepatitis C virus.