The Adhesion G-Protein-Coupled Receptor GPR115/ADGRF4 Regulates Epidermal Differentiation and Associates with Cytoskeletal KRT1.

Among the 33 human adhesion G-protein-coupled receptors (aGPCRs), a unique subfamily of GPCRs, only ADGRF4, encoding GPR115, shows an obvious skin-dominated transcriptomic profile, but its expression and function in skin is largely unknown. Here, we report that GPR115 is present in a small subset of basal and in most suprabasal, noncornified keratinocytes of the stratified epidermis, supporting epidermal transcriptomic data. In psoriatic skin, characterized by hyperproliferation and delayed differentiation, the expression of GPR115 and KRT1/10, the fundamental suprabasal keratin dimer, is delayed. The deletion of ADGRF4 in HaCaT keratinocytes grown in an organotypic mode abrogates KRT1 and reduces keratinocyte stratification, indicating a role of GPR115 in epidermal differentiation. Unexpectedly, endogenous GPR115, which is not glycosylated and is likely not proteolytically processed, localizes intracellularly along KRT1/10-positive keratin filaments in a regular pattern. Our data demonstrate a hitherto unknown function of GPR115 in the regulation of epidermal differentiation and KRT1.

Effects of PPAR-γ and RXR-α on mouse meibomian gland epithelial cells during inflammation induced by latanoprost.

The purpose of this study is to investigate the effects of latanoprost on the secretion of cytokines and chemokines from meibomian gland epithelial cells, and to evaluate the modulation of peroxisome proliferator-activated receptor γ (PPAR-γ) and retinoid X receptor α (RXR-α) during latanoprost-induced inflammation. Mouse meibomian gland epithelial cells were cultured in proliferation and differentiation medium, respectively. Cells were exposed to latanoprost, rosiglitazone (PPAR-γ agonist), or LG100268 (RXR-α agonist), respectively. The expression of IL-6, IL-1ß, TNF-α, MMP-9, MCP-1, and CCL-5 were detected by real-time PCR and ELISA. The effect of latanoprost, rosiglitazone, LG100268, and inflammatory cytokines on the differentiation of meibocyte were evaluated by related gene expression and lipid staining. The expression of Keratin-1, 6, 17 protein was detected by western immunoblotting. The results showed that the above cytokines could be induced by latanoprost in meibomian gland epithelial cells. LG100268 and rosiglitazone could inhibit the production of IL-6 and TNF-α induced by latanoprost, respectively. Latanoprost suppressed the expression of differentiation-related mRNA through a positive feedback loop by enhancement of COX-2 expression via FP receptor-activated ERK signaling. The expression of Keratin-17 was upregulated by rosiglitazone and suppressed by LG100268. The application of IL-6 and TNF-α showed negative effects on lipid accumulation in meibomian gland epithelial cells. These results demonstrated that latanoprost could induce inflammation and suppress differentiation of mouse meibomian gland epithelial cells. The activation of PPAR-γ and RXR-α showed an anti-inflammatory effect, showing a potential role to antagonize the effect of latanoprost eyedrops on meibomian gland epithelial cells.

Effect of mutations on the hydrophobic interactions of the hierarchical molecular structure and mechanical properties of epithelial keratin 1/10.

Human epithelial keratin is an intermediate filament protein that serves as a backbone to maintain the stability of the cell nucleus and mechanical stability of the whole cells. The present study focused on two point mutations, F231L and S233L, of the 1B domain of keratin K 1/10 related to the rare genetic skin disease palmoplantar keratoderma (PPK). We used molecular dynamics simulation to study the effects of the mutations on various hierarchical structures, including heterodimers, tetramers, and octamers of the K1/10 1B domain at the atomic scale. The initial results demonstrated that the wild type and mutant proteins were highly similar at the dimer level but had different microstructures and mechanics at a higher-level assembly. A decrease in the hydrophobic interactions and hydrogen bonds at the terminus resulted in weakened mechanical properties of the tetramer and octamer of the F231L mutant. The asymmetrical structure of the S233L tetramer with an uneven distribution of the hydrogen bonds decreased its mechanical properties. However, the S233L mutation provided extra hydrophobic interactions between these mutated amino acid residues in the octamer, leading to improved mechanical properties. The results of the present study provided a deeper understanding of how the differences in point mutations induced the changes in the configuration and mechanical properties at the molecular scale. The differences in these properties may influence keratin assembly at the microscopic scale and ultimately cause diseases at the macroscopic scale.

Nuclear IL-33 Plays an Important Role in IL-31‒Mediated Downregulation of FLG, Keratin 1, and Keratin 10 by Regulating Signal Transducer and Activator of Transcription 3 Activation in Human Keratinocytes.

IL-33, a chromatin-associated multifunctional cytokine, is implicated in the pathogenesis of atopic dermatitis (AD), an inflammatory skin disorder characterized by skin barrier dysfunction. IL-33 accumulates in the nuclei of epidermal keratinocytes (KCs) in AD lesions. However, it is unclear whether nuclear IL-33 directly contributes to the pathogenesis of AD. IL-31, a pruritogenic cytokine primarily produced by T helper type 2 cells, is elevated in AD lesions and promotes AD development by suppressing KC differentiation and inducing itching. In this study, we investigated the involvement of nuclear IL-33 in IL-31‒mediated suppression of KC differentiation. In monolayer cultures and living skin equivalent, IL-31 increased the expression of full-length IL-33 and the phosphorylation of signal transducer and activator of transcription 3 (STAT3) in the nuclei of human KCs, which in turn downregulated the expression of differentiation markers. We found that IL-31 and IL-4/IL-13 use very similar mechanisms to inhibit KC differentiation: nuclear IL-33 combines with phosphorylated STAT3 and functions as a STAT3 transcription cofactor, promoting phosphorylated STAT3 binding to the FLG promoter to inhibit its transcription; moreover, the nuclear IL-33/phosphorylated STAT3 complex drives the downregulation of keratin 1 and keratin 10 by reducing the availability of the transcription factor RunX1. Therefore, nuclear IL-33 plays an important role in IL-31‒mediated differentiation suppression by regulating STAT3 activation in human KCs.

IL-22 Downregulates Peptidylarginine Deiminase-1 in Human Keratinocytes: Adding Another Piece to the IL-22 Puzzle in Epidermal Barrier Formation.

Increased presence of IL-22+ cells in the skin is a characteristic finding in skin barrier defects, such as psoriasis and atopic dermatitis. However, mechanistic insight into effects of IL-22 on epidermal functioning is yet to be elucidated. One crucial step during epidermal differentiation is deimination or citrullination. Here, we show reduced levels of peptidylarginine deiminase 1, an enzyme that converts peptidylarginine into citrulline in lesional psoriatic skin. IL-22 signaling through the IL-22 receptor complex was found to suppress expression of peptidylarginine deiminase 1 in epidermal keratinocytes. Subsequently, total peptidylarginine deiminase activity and extent of protein deimination in keratinocytes treated with IL-22 were reduced together with a significant decrease in deimination of keratin 1 and FLG, both important for epidermal differentiation. Vitamin D and acitretin partly restored the peptidylarginine deiminase 1 defect caused by IL-22. Collectively, we show that IL-22 downregulates deimination, thus identifying a potential target for treatment of skin barrier defects.

Keratin 1 as a cell-surface receptor in cancer.

Keratins are fibrous proteins that take part in several important cellular functions, including the formation of intermediate filaments. In addition, keratins serve as epithelial cell markers, which has made their role in cancer progression, diagnosis, and treatment an important focus of research. Keratin 1 (K1) is a type II keratin whose structure is comprised of a coiled-coil central domain flanked by flexible, glycine-rich loops in the N- and C-termini. While the structure of cytoplasmic K1 is established, the structure of cell-surface K1 is not known. Several transformed cells, such as cancerous cells and cells that have undergone oxidative stress, display increased levels of overall and/or cell-surface K1 expression. Cell-surface keratins (CSKs) may be modified or truncated, and their role is yet to be fully elucidated. Current studies suggest that CSKs are involved in receptor-mediated endocytosis and immune evasion. In this Review, we discuss findings relating to K1 structure, overexpression, and cell-surface expression in the context of utilizing CSK1 as a receptor for targeted drug delivery to cancer cells, and other strategies to develop novel treatments for cancer.

Keratin 1 maintains the intestinal barrier in ulcerative colitis.

BACKGROUND: The intestinal mechanical barrier plays a key role in the pathogenesis of ulcerative colitis (UC). Our previous study showed keratin 1 (KRT1) was downregulated in UC, but the mechanism by which KRT1 affects the intestinal barrier remains unknown. OBJECTIVES: To explore the mechanism of KRT1 in the intestinal barrier in UC. METHODS: Colonic tissues were collected from 20 UC patients before and after mucosal healing (MH) and 15 healthy controls. The expression of KRT1 was measured by PCR, western blotting and immunohistochemistry (IHC). A dextran sulfate sodium (DSS)-induced colitis model was established in krt1 transgenic (TG) mice, and the mice were treated with methylprednisolone (MP) to explore the role of KRT1 in the intestinal barrier. Inflammation was evaluated through the DAI score, colon, spleen and H&E. The expression of KRT1 and tight junction (TJ) proteins in mouse was analysed by the same methods. RESULTS: The transcription and expression of KRT1 in UC was decreased and recovered after MH but did not reach the level of the healthy controls. Similar to the clinical results, the expression of krt1 was decreased in DSS-induced colitis and upregulated after MP. Moreover, the krt1 TG group exhibited less inflammation than wild-type (WT) group. The expression of Occludin and ZO-1 decreased after DSS induction, the decreases in Occludin and ZO-1 in the krt1 TG group were lower than WT group, which was significantly increased after MP, while the expression of Claudin-2 exhibited the opposite effect. CONCLUSIONS: Keratin 1 maintains the intestinal barrier by upregulating TJ proteins in UC.

Post Zygotic, Somatic, Deletion in KERATIN 1 V1 Domain Generates Structural Alteration of the K1/K10 Dimer, Producing a Monolateral Palmar Epidermolytic Nevus.

Palmoplantar keratodermas (PPKs) are characterized by thickness of stratum corneum and epidermal hyperkeratosis localized in palms and soles. PPKs can be epidermolytic (EPPK) or non epidermolytic (NEPPK). Specific mutations of keratin 16 (K16) and keratin 1 (K1) have been associated to EPPK, and NEPPK. Cases of mosaicism in PPKs due to somatic keratin mutations have also been described in scientific literature. We evaluated a patient presenting hyperkeratosis localized monolaterally in the right palmar area, characterized by linear yellowish hyperkeratotic lesions following the Blaschko lines. No other relatives of the patient showed any dermatological disease. Light and confocal histological analysis confirmed the presence of epidermolityic hyperkeratosis. Genetic analysis performed demonstrates the heterozygous deletion NM_006121.4:r.274_472del for a total of 198 nucleotides, in KRT1 cDNA obtained by a palmar lesional skin biopsy, corresponding to the protein mutation NP_006112.3:p.Gly71_Gly137del. DNA extracted from peripheral blood lymphocytes did not display the presence of the mutation. These results suggest a somatic mutation causing an alteration in K1 N-terminal variable domain (V1). The deleted sequence involves the ISIS subdomain, containing a lysine residue already described as fundamental for epidermal transglutaminases in the crosslinking of IF cytoskeleton. Moreover, a computational analysis of the wild-type and V1-mutated K1/K10 keratin dimers, suggests an unusual interaction between these keratin filaments. The mutation taster in silico analysis also returned a high probability for a deleterious mutation. These data demonstrate once again the importance of the head domain (V1) of K1 in the formation of a functional keratinocyte cytoskeleton. Moreover, this is a further demonstration of the presence of somatic mutations arising in later stages of the embryogenesis, generating a mosaic phenotype.

Primary cutaneous carcinosarcoma: clinical, histological, and immunohistochemical analysis of eight cases.

BACKGROUND: Cutaneous carcinosarcoma is a rare biphasic tumor comprising malignant epithelial and heterologous mesenchymal elements. Data on the clinical and histopathologic characteristics of this tumor are scarce. The objective of this study was to describe the clinicopathologic and immunohistochemical features of cutaneous carcinosarcoma. METHODS: A descriptive retrospective study was conducted in a tertiary care hospital from Spain. We reviewed the records of eight patients with cutaneous carcinosarcoma who were diagnosed from 2009 to 2019. RESULTS: The mean patient age at diagnosis was 72.13 years (range 44-91 years), and there was a male predilection (6 cases). The most common site of cutaneous carcinosarcoma was the head and neck (5 cases). Carcinosarcomas demonstrated variable histopathological and immunohistochemical features. Follow-up was available for 7-8 patients. There were two cases of local recurrence and one case of metastasis. Two patients died from the tumor during the entire follow-up. CONCLUSIONS: Although the number of cases in this study was limited, our results provide valuable insight into the clinical, histopathologic, and immunohistochemical characteristics of primary cutaneous carcinosarcoma.

Annular epidermolytic ichthyosis with palmoplantar keratosis: a unique phenotype associated with interfamilial phenotypic heterogeneity.

BACKGROUND: Annular epidermolytic ichthyosis (AEI) is a rare autosomal dominant ichthyosis that was recently described in 10 separate families in the English literature. There are no reports on the phenotypic heterogeneity of AEI. OBJECTIVES: We investigated, for the first time, a large Chinese AEI pedigree exhibiting interfamilial phenotypic heterogeneity. MATERIALS AND METHODS: We collected clinical data and DNA from the members of the family, and skin lesions were obtained from two patients with different phenotypes. Skin imaging examinations were performed. Whole-exome sequencing (WES) and Sanger sequencing were used to detect gene mutations. RESULTS: The characteristic features of granular layer degeneration in the two biopsies were verified via histological methods. The missense mutation c.1436T > C in KRT1 was detected in all nine patients. CONCLUSION: This study demonstrates that AEI may present with different clinical phenotypes and that mutation analysis for suspected cases is necessary to obtain a precise diagnosis.

Serum lipids, retinoic acid and phenol red differentially regulate expression of keratins K1, K10 and K2 in cultured keratinocytes.

Abnormal keratinocyte differentiation is fundamental to pathologies such as skin cancer and mucosal inflammatory diseases. The ability to grow keratinocytes in vitro allows the study of differentiation however any translational value is limited if keratinocytes get altered by the culture method. Although serum lipids (SLPs) and phenol red (PR) are ubiquitous components of culture media their effect on differentiation is largely unknown. We show for the first time that PR and SLP themselves suppress expression of differentiation-specific keratins K1, K10 and K2 in normal human epidermal keratinocytes (NHEK) and two important cell lines, HaCaT and N/TERT-1. Removal of SLP increased expression of K1, K10 and K2 in 2D and 3D cultures, which was further enhanced in the absence of PR. The effect was reversed for K1 and K10 by adding all-trans retinoic acid (ATRA) but increased for K2 in the absence of PR. Furthermore, retinoid regulation of differentiation-specific keratins involves post-transcriptional mechanisms as we show KRT2 mRNA is stabilised whilst KRT1 and KRT10 mRNAs are destabilised in the presence of ATRA. Taken together, our results indicate that the presence of PR and SLP in cell culture media may significantly impact in vitro studies of keratinocyte differentiation.

Gut commensal derived-valeric acid protects against radiation injuries.

BACKGROUND: Hematopoietic and intestinal systems side effects are frequently found in patients who suffered from accidental or medical radiation exposure. In this case, we investigated the effects of gut microbiota produced-valeric acid (VA) on radiation-induced injuries. METHODS: Mice were exposed to total body irradiation (TBI) or total abdominal irradiation (TAI) to mimic accidental or clinical scenarios. High-performance liquid chromatography (HPLC) was performed to assess short-chain fatty acids (SCFAs) in fecal pellets. Oral gavage with VA was used to mitigate radiation-induced toxicity. Gross examination was performed to assess tissue injuries of thymus, spleen and small intestine. High-throughput sequencing was used to characterize the gut microbiota profile. Isobaric tags for relative and absolute quantitation (iTRAQ) were performed to analyze the difference of protein profile. Hydrodynamic-based gene delivery assay was performed to silence KRT1 in vivo. RESULTS: VA exerted the most significant radioprotection among the SCFAs. In detail, VA replenishment elevated the survival rate of irradiated mice, protected hematogenic organs, improved gastrointestinal (GI) tract function and intestinal epithelial integrity in irradiated mice. High-throughput sequencing and iTRAQ showed that oral gavage of VA restored the enteric bacteria taxonomic proportions, reprogrammed the small intestinal protein profile of mice following TAI exposure. Importantly, keratin 1 (KRT1) played a pivotal role in the radioprotection of VA. CONCLUSIONS: Our findings provide new insights into gut microbiota-produced VA and underpin that VA might be employed as a therapeutic option to mitigate radiation injury in pre-clinical settings.

Silencing of keratin 1 inactivates the Notch signaling pathway to inhibit renal interstitial fibrosis and glomerular sclerosis in uremia.

Renal interstitial fibrosis is a key factor in the development of chronic renal diseases, possibly leading to uremia. The present study conducted aimed to assess the hypothesis whether keratin 1 (KRT1) silencing could suppress kidney interstitial fibrosis and glomerular sclerosis via the Notch pathway to alleviate uremic symptoms. Differentially expressed genes associated with uremia were identified using the gene expression omnibus (GEO) database. Uremic rat models were established, in which short hairpin-RNA against KRT1, activators, and inhibitors of the Notch pathway were transfected. To further validate the mechanism of KRT1 in uremia, KRT1 expression, cell apoptosis, glomerular area (GA), and glomerular capillary volume (GV), the score of glomerular sclerosis, and tubulointerstitial injury were assayed and investigated. GEO database revealed that KRT1 was upregulated in uremia and regulated the Notch pathway. GA, GV, cell apoptosis, glomerular sclerosis, and tubulointerstitial injury were typically located in more elevated levels of uremia in rats. KRT1 silencing and Notch pathway inhibition decreased the expression of Jagged1, Notch1, NICD1, Hey1, Hes1, α-SMA, and FN, which further resulted in decreased cell apoptosis, GA, GV, the score of glomerular sclerosis, and tubulointerstitial injury. Subsequently, the effect of KRT1 silencing on uremia was no longer evident once the Notch pathway was activated. The co-localization of high expression KRT1 and Notch1 was found in uremia. In summary, the results identified KRT1 as a key regulator in uremia progression, and KRT1 silencing can suppress glomerular sclerosis and tubulointerstitial injury via inactivation of the Notch pathway in uremic rats.

Side-by-Side Comparison of Skin Biopsies and Skin Tape Stripping Highlights Abnormal Stratum Corneum in Atopic Dermatitis.

Skin biopsies are commonly used for the assessment of skin pathology in various skin diseases, including atopic dermatitis (AD). However, because of the invasive nature of skin biopsies, many patients, particularly children, decline participation. This can lead to potential subject sampling bias as data could be skewed toward more severe, older patients who are willing to have biopsies. Recently, researchers have begun studying the skin with a minimal, noninvasive technique using skin tape stripping (STS) to profile the epidermal transcriptome, proteins, and lipids in the skin. However, side-by-side comparisons of skin biopsies with STS have not been done to assess epidermal penetration. Therefore, 20 STS were collected from the volar surface of forearms from healthy nonatopic subjects and patients with AD, following this skin biopsies were collected from adjacent nontaped and taped areas of the skin. Using hematoxylin and eosin staining and immunostaining, we demonstrated that 20 STS reached the upper granular layer of the epidermis. Additionally, we found that the expression of terminal differentiation markers in samples from STS procedure positively correlated with the expression level of these markers in matching skin biopsies. Therefore, STS is a noninvasive and reliable approach to evaluate the expression of skin terminal differentiation markers, which are defective in AD skin.

Human keratin 1/10-1B tetramer structures reveal a knob-pocket mechanism in intermediate filament assembly.

To characterize keratin intermediate filament assembly mechanisms at atomic resolution, we determined the crystal structure of wild-type human keratin-1/keratin-10 helix 1B heterotetramer at 3.0 Å resolution. It revealed biochemical determinants for the A11 mode of axial alignment in keratin filaments. Four regions on a hydrophobic face of the K1/K10-1B heterodimer dictated tetramer assembly: the N-terminal hydrophobic pocket (defined by L227K1, Y230K1, F231K1, and F234K1), the K10 hydrophobic stripe, K1 interaction residues, and the C-terminal anchoring knob (formed by F314K1 and L318K1). Mutation of both knob residues to alanine disrupted keratin 1B tetramer and full-length filament assembly. Individual knob residue mutant F314AK1, but not L318AK1, abolished 1B tetramer formation. The K1-1B knob/pocket mechanism is conserved across keratins and many non-keratin intermediate filaments. To demonstrate how pathogenic mutations cause skin disease by altering filament assembly, we additionally determined the 2.39 Å structure of K1/10-1B containing a S233LK1 mutation linked to epidermolytic palmoplantar keratoderma. Light scattering and circular dichroism measurements demonstrated enhanced aggregation of K1S233L/K10-1B in solution without affecting secondary structure. The K1S233L/K10-1B octamer structure revealed S233LK1 causes aberrant hydrophobic interactions between 1B tetramers.

Significance of Cytokeratin-1 Single-Nucleotide Polymorphism and Protein Level in Susceptibility to Vocal Leukoplakia and Laryngeal Squamous Cell Carcinoma.

OBJECTIVE: To investigate the association between the cytokeratin (CK)-1 single-nucleotide polymorphism (SNP), the protein level of CK-1 and the risk of vocal leukoplakia and laryngeal squamous cell carcinoma (LSCC). METHODS: In this case-control study, 155 patients with vocal leukoplakia, 323 patients with LSCC, and 266 healthy controls were genotyped for the CK-1 (SNP RS14024) gene using pyrosequencing. The protein expression level of CK-1 was analyzed in vocal leukoplakia, LSCC, and vocal polyp patients by immunohistochemistry (IHC). RESULTS: Of the CK-1 RS14024 polymorphism, the heterozygote AG and homozygote GG genotype exhibited a significantly increased risk of LSCC (AG: OR = 2.16, p = 0.014; GG: OR = 2.15, p = 0.018) compared to normal controls. A higher protein expression level of CK-1 was detected in patients with LSCC compared to vocal leukoplakia and polyps (both p < 0.001), and a significant increasing trend of CK-1 protein expression level from mild-moderate dysplasia to moderate-severe dysplasia in vocal leukoplakia patients was also observed (p = 0.006). CONCLUSIONS: This study demonstrates that the CK-1 SNP and high protein expression levels are associated with vocal leukoplakia and LSCC and promote the transformation from vocal leukoplakia to LSCC in a Chinese Han population.

Ginnalin B induces differentiation markers and modulates the proliferation/differentiation balance via the upregulation of NOTCH1 in human epidermal keratinocytes.

The red maple and sugar maple (Acer rubrum and A. saccharum, respectively) contain acertannins (ginnalins and maplexins), galloylated derivatives of 1,5-anhydro-d-glucitol (1,5-AG, 1). These compounds have a variety of potential medicinal properties and we have shown that some of them promote the expression of ceramide synthase 3. We now report on the beneficial effects of ginnalin B, (6-O-galloyl-1,5-AG, 5), leading to acceleration of skin metabolism and reduction of the turnover time. Ginnalin B dose-dependently increased the relative amount of keratin 10, keratin 1, and filaggrin gene, with maximal increase of 1.7-, 2.9, and 5.2-fold at 100 µM, respectively. The validation study showed that it had superior capacity to induce multiple stages of keratinocyte differentiation and significantly elevated the immunostaining site of keratin 10 and filaggrin in a 3-dimensional cultured human skin model, by 1.2 and 2.8-fold, respectively. Furthermore, ginnalin B caused the arrest of proliferation at the G0/G1 phase but it did not induce apoptotic cell death in normal human keratinocytes. Molecular studies revealed that ginnalin B up-regulated the levels of NOTCH1 and a concomitant increase p21 expression. Ginnalin B, therefore, represents a new class of promising functional and medical cosmetic compound and it could contribute to the maintenance of homeostasis of the epidermis.

Extracellular FABP4 uptake by endothelial cells is dependent on cytokeratin 1 expression.

AIMS: The aim of this study is to determine the physical and functional interplay between fatty acid-binding protein 4 (FABP4) and its membrane receptor-like candidate protein, cytokeratin 1 (CK1), and to determine the effect of hindering CK1-mediated FABP4 cellular uptake on non-disturbed or metabolically stressed endothelial cells. METHODS: We monitored the direct interaction between FABP4 and CK1 using surface plasmon resonance, and the effects of blocking exogenous FABP4 (eFABP4) cellular uptake were determined by using specific siRNA to knock down the expression of CK1 in human umbilical vein endothelial cells (HUVECs). The expression and nuclear translocation of transcription factors involved in oxidative stress (NRF2) and inflammation (p65 subunit of NF-ĸB transcription factor) were determined by Western blotting analysis. RESULTS: Our data showed that FABP4 and CK1 bind to each other and that the putative FABP4 binding domain would be within the 151GIQEVTINQSLLQPLNVEID170 CK1 sequence. We determined that in non-disturbed or metabolically stressed endothelial cells, eFABP4 regulates the cellular response to oxidative stress. In addition, we also found that in the presence of palmitate, eFABP4 increases the pro-inflammatory effects induced by palmitate per se, probably due to an increase in the transport of palmitate inside cells, suggesting that these FABP4-mediated pro-oxidative and pro-inflammatory effects are dependent on CK1 expression. CONCLUSIONS: We demonstrated that CK1 facilitates eFABP4 cellular uptake in endothelial cells. Therefore, the CK1-targeted inhibition of exogenous FABP4 cellular uptake might be a potential therapeutic strategy to protect endothelial cells against FABP4-induced activation of inflammation and oxidative stress.

KRT1 gene silencing ameliorates myocardial ischemia-reperfusion injury via the activation of the Notch signaling pathway in mouse models.

Myocardial ischemia and reperfusion injury (MIRI) includes major drawbacks, such as excessive formation of free radicals and also overload of calcium, which lead to cell death, tissue scarring, and remodeling. The current study aims to explore whether KRT1 silencing may ameliorate MIRI via the Notch signaling pathway in mouse models. Myocardial tissues were used for the determination of the positive rate of KRT1 protein expression, apoptosis of myocardial cells, creatine kinase (CK) and lactate dehydrogenase (LDH) expression, expression of related biomarkers as well as myocardial infarction area. The transfected myocardial cells were treated with KRT1-siRNA, Jagged1, and DAPT (inhibitor of Notch-1 signaling pathway). The expression of KRT1, NICD, Hes1, Bcl-2, and Bax protein was detected. The MTT assay was applied for cell proliferation and flow cytometry was used for cell apoptosis. Mice with MIRI had a higher positive rate of KRT1 protein expression, apoptosis of myocardial cells, CK and LDH expression, myocardial infarction area, increased expression of MDA, NO, SDH, IL-1, IL-6, TNF-α, CRP, KRT1, Bax protein, CK, and LDH, and decreased expression of SOD, NICD, Hes1, and Bcl-2. The downregulation of KRT1 led to decreased expression of KRT1 and Bax protein, increased expression of NICD, Hes1, and Bcl-2, decreased cell apoptosis, and improved cell proliferation. The inhibition of the Notch signaling pathway leads to reduced expression of Bax, increased expression of NICD, Hes1, and Bcl 2, and also decreased cell apoptosis and increased cell proliferation. Our data conclude that KRT1 silencing is able to make MIRI better by activating the Notch signaling pathway in mice.

Nail abnormalities identified in an ageing study of 30 inbred mouse strains.

In a large-scale ageing study, 30 inbred mouse strains were systematically screened for histologic evidence of lesions in all organ systems. Ten strains were diagnosed with similar nail abnormalities. The highest frequency was noted in NON/ShiLtJ mice. Lesions identified fell into two main categories: acute to chronic penetration of the third phalangeal bone through the hyponychium with associated inflammation and bone remodelling or metaplasia of the nail matrix and nail bed associated with severe orthokeratotic hyperkeratosis replacing the nail plate. Penetration of the distal phalanx through the hyponychium appeared to be the initiating feature resulting in nail abnormalities. The accompanying acute to subacute inflammatory response was associated with osteolysis of the distal phalanx. Evaluation of young NON/ShiLtJ mice revealed that these lesions were not often found, or affected only one digit. The only other nail unit abnormality identified was sporadic subungual epidermoid inclusion cysts which closely resembled similar lesions in human patients. These abnormalities, being age-related developments, may have contributed to weight loss due to impacts upon feeding and should be a consideration for future research due to the potential to interact with other experimental factors in ageing studies using the affected strains of mice.