Long non-coding RNA HOTAIR promotes UVB-induced apoptosis and inflammatory injury by up-regulation of PKR in keratinocytes

Molecular mechanism of lncRNAs in pathogenesis and diagnosis of auto-immune diseases, with a special focus on lncRNA-based therapeutic approaches

Autoimmune diseases are a diverse set of conditions defined by organ damage due to abnormal innate and acquired immune system responses. The pathophysiology of autoimmune disorders is exceedingly intricate and has yet to be fully understood. The study of long non-coding RNAs (lncRNAs), non-protein-coding RNAs with at least 200 nucleotides in length, has gained significant attention due to the completion of the human genome project and the advancement of high-throughput genomic approaches. Recent research has demonstrated how lncRNA alters disease development to different degrees. Although lncRNA research has made significant progress in cancer and generative disorders, autoimmune illnesses are a relatively new research area. Moreover, lncRNAs play crucial functions in differentiating various immune cells, and their potential relationships with autoimmune diseases have received growing attention. Because of the importance of Th17/Treg axis in auto-immune disease development, in this review, we discuss various molecular mechanisms by which lncRNAs regulate the differentiation of Th17/Treg cells. Also, we reviewed recent findings regarding the several approaches in the application of lncRNAs in the diagnosis and treatment of human autoimmune diseases, as well as current challenges in lncRNA-based therapeutic approaches to auto-immune diseases.

Correlation analysis of differentially expressed long non-coding RNA HOTAIR with PTEN/PI3K/AKT pathway and inflammation in patients with osteoarthritis and the effect of baicalin intervention

OBJECTIVE

This study aims to investigate the correlation of long non-coding RNA HOX transcript antisense RNA (lncRNA HOTAIR) with the PTEN/PI3K/AKT pathway and clinical-related indicators in osteoarthritis (OA) and determine the effect of baicalin intervention.

METHODS

The levels of clinical lipid metabolism indexes and immune-inflammatory indexes in OA patients and normal controls was detected. OA chondrocytes (OA-CHs) were induced with peripheral blood mononuclear cells (PBMCs), followed by baicalin treatment (50 ug/mL). RT-qPCR was performed to measure lncRNA HOTAIR expression. The levels of inflammatory cytokines and adiponectin were detected using ELISA kits. CCK-8 assay was used to assess the viability of CHs. The related protein expression was measured using Western blot analysis.

RESULTS

LncRNA HOTAIR might act as a biomarker of OA in vivo. LncRNA HOTAIR was positively correlated with TC, hs-CRP, IgA, TNF-α, and VAS score. Overexpression of lncRNA HOTAIR in vitro inhibited cell proliferation, reduced IL-10 and PTEN expression, but augmented TNF-α, p-PI3K, and p-AKT proteins in OA-CHs stimulated by OA-PBMCs. The changes of above indexes were also observed in OA-CHs stimulated by OA-PBMCs treated with si-lncRNA HOTAIR or baicalin, implying the synergistic effects of baicalin and lncRNA HOTAIR silencing on OA.

CONCLUSIONS

Conclusively, lncRNA HOTAIR was highly expressed in OA-CHs, which facilitated OA inflammatory responses by orchestrating inflammatory cytokines and the PTEN/PI3K/AKT pathway. Baicalin exerted therapeutic effects by inhibiting the expression of lncRNA HOTAIR, decreasing the protein levels of p-PI3K and p-AKT, and increasing the protein levels of PTEN, APN, and ADIPOR1.

Long noncoding RNA HOTAIR facilitates pulmonary vascular endothelial cell apoptosis via DNMT1 mediated hypermethylation of Bcl-2 promoter in COPD

BACKGROUND

To study the regulatory effect of Long non-coding RNA (LncRNA) HOX transcript antisense RNA (HOTAIR) on pulmonary vascular endothelial cell (HPVEC) apoptosis and determine whether the HOTAIR facilitate HPVEC apoptosis via DNMT1 mediated hypermethylation of Bcl-2 promoter in chronic obstructive pulmonary disease (COPD).

METHODS

LncRNA array was used to measure the differentially expressed lncRNAs in COPD and non-COPD lung tissues. Expression of HOTAIR in COPD patient lungs and cigarette smoke extract (CSE)-induced HPVEC was assessed by qRT-PCR. The location of HOTAIR was determined in COPD patient lungs and HPVEC by RNA in situ hybridization (RNA-ISH). The emphysema mouse model and HOTAIR knockdown mice were each established by inhaling cigarette smoke or intratracheal lentiviral vectors instillation. The dysregulation of DNA methyltransferase enzyme 1 (DNMT1), B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax) and Cleaved-caspase 3 protein expression were detected by Western blotting. HOTAIR, DNMT1, Bcl-2 and Bax mRNA expression were measured by quantitative real-time polymerase chain reaction. TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assays were used to assess apoptotic ratio in mice and CSE-induced HPVEC. Methylation-specific PCR (MSP) assay was conducted to observe the alterations in the methylation of the Bcl-2 promoter in specimens. RNA pull-down assay was used for analysis of the correlation between HOTAIR and DNMT1.

RESULTS

The expression levels of the HOTAIR were up-regulated in COPD patient lungs and CSE-induced HPVEC. HPVEC apoptosis with down-regulated Bcl-2 expression, increased promoter methylation, DNMT1, Bax and Cleaved-caspase 3 expression was found in emphysema mouse model and CSE-induced HPVEC. Knockdown HOTAIR can attenuate cell apoptosis and emphysema via DNMT1 mediated hypermethylation of Bcl-2 promoter in mice. In vitro, HOTAIR can aggravate the apoptosis of CSE-exposed HPVEC. DNMT1 was a target of HOTAIR and had a positive correlation with HOTAIR.

CONCLUSION

HOTAIR facilitates HPVEC apoptosis via DNMT1 mediated hypermethylation of Bcl-2 promoter in COPD, and attenuating the expression of HOTAIR may be a new therapy to prevent COPD.

HOTAIR beyond repression: In protein degradation, inflammation, DNA damage response, and cell signaling

Long noncoding RNAs (lncRNAs) are pervasively transcribed from the mammalian genome as transcripts that are usually >200 nucleotides long. LncRNAs generally do not encode proteins but are involved in a variety of physiological processes, principally as epigenetic regulators. HOX transcript antisense intergenic RNA (HOTAIR) is a well-characterized lncRNA that has been implicated in several cancers and in various other diseases. HOTAIR is a repressor lncRNA and regulates various repressive chromatin modifications. However, recent studies have revealed additional functions of HOTAIR in regulation of protein degradation, microRNA (miRNA) sponging, NF-κB activation, inflammation, immune signaling, and DNA damage response. Herein, we have summarized the diverse functions and modes of action of HOTAIR in protein degradation, inflammation, DNA repair, and diseases, beyond its established functions in gene silencing.

The Role of Epigenetic Factors in Psoriasis

Psoriasis is a chronic, systemic, immune-mediated disease with an incidence of approximately 2%. The pathogenesis of the disease is complex and not yet fully understood. Genetic factors play a significant role in the pathogenesis of the disease. In predisposed individuals, multiple trigger factors may contribute to disease onset and exacerbations of symptoms. Environmental factors (stress, infections, certain medications, nicotinism, alcohol, obesity) play a significant role in the pathogenesis of psoriasis. In addition, epigenetic mechanisms are considered result in modulation of individual gene expression and an increased likelihood of the disease. Studies highlight the significant role of epigenetic factors in the etiology and pathogenesis of psoriasis. Epigenetic mechanisms in psoriasis include DNA methylation, histone modifications and non-coding RNAs. Epigenetic mechanisms induce gene expression changes under the influence of chemical modifications of DNA and histones, which alter chromatin structure and activate transcription factors of selected genes, thus leading to translation of new mRNA without affecting the DNA sequence. Epigenetic factors can regulate gene expression at the transcriptional (via histone modification, DNA methylation) and posttranscriptional levels (via microRNAs and long non-coding RNAs). This study aims to present and discuss the different epigenetic mechanisms in psoriasis based on a review of the available literature.

Association of HOTAIR Polymorphisms with Susceptibility to Psoriasis in a Chinese Han Population

Psoriasis is a common disease in dermatology, but its etiology and pathogenesis have not been fully elucidated. In recent years, researchers have found that HOX transcript antisense RNA (HOTAIR) plays an important role in biological processes as an important long-chain noncoding RNA (lncRNA). The goal of this study was to investigate the association between HOTAIR polymorphisms and psoriasis in a Chinese Han population by screening key candidate single-nucleotide polymorphism (SNPs) sites in HOTAIR. A total of 269 patients diagnosed with psoriasis and 273 healthy control subjects were enrolled in this case-control study. Three SNPs of HOTAIR were genotyped: SNP1 (rs12826786), SNP2 (rs1899663), and SNP3 (rs4759314). All polymorphisms were in Hardy-Weinberg equilibrium in both the control and patient groups, and the SNPs were in linkage disequilibrium. The distribution of the rs4759314 genotype in the control group and case group was statistically significant according to all the models except the recessive model (adjusted p value < 0.05), and the CCG haplotype group had a significant difference (OR (95%CI) = 2.907 (1.344 - 6.289), adjusted p value = 0.0263). rs12826786 was associated with a risk of psoriasis according to the dominant model (C/T-T/T vs. C/C: OR (95%CI) = 0.70 (0.48 - 1.01), adjusted p value = 0.049) and overdominant model (C/T vs. C/C-T/T: OR (95%CI) = 0.69 (0.47 - 1.01), adjusted p value = 0.048). The current work showed that a genomic variant within HOTAIR was associated with a risk of psoriasis, and the clinical value of this study should be further evaluated in the future.

An update on the role of long non-coding RNAs in psoriasis

Increasing evidence suggests that long non-coding RNAs (lncRNAs) are of vital importance for various biological processes, and dysregulation of lncRNAs is frequently associated with various diseases such as psoriasis. LncRNAs modulate gene expression at the transcriptional, post-transcriptional, and translational levels; however, the specific regulatory mechanisms of lncRNAs in psoriasis remain largely unexplored. This review provides an overview of recent studies investigating mechanisms and functions of lncRNAs in psoriasis, especially focusing on the role of lncRNAs in keratinocytes, T cells, and dendritic cells.

The Role of Non-Coding RNAs as Prognostic Factor, Predictor of Drug Response or Resistance and Pharmacological Targets, in the Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (CSCC) is the most common keratinocyte-derived skin cancer in the Caucasian population. Exposure to UV radiations (UVRs) represents the main risk carcinogenesis, causing a considerable accumulation of DNA damage in epidermal keratinocytes with an uncontrolled hyperproliferation and tumor development. The limited and rarely durable response of CSCC to the current therapeutic options has led researchers to look for new therapeutic strategies. Recently, the multi-omics approaches have contributed to the identification and prediction of the key role of non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), circularRNAs (circRNAs) and long non-coding RNAs (lncRNAs) in the regulation of several cellular processes in different tumor types, including CSCC. ncRNAs can modulate transcriptional and post-transcriptional events by interacting either with each other or with DNA and proteins, such as transcription factors and RNA-binding proteins. In this review, the implication of ncRNAs in tumorigenesis and their potential role as diagnostic biomarkers and therapeutic targets in human CSCC are reported.

Long non‑coding RNA HOTAIR promotes burn wound healing by regulating epidermal stem cells

Local transplantation of epidermal stem cells (ESCs) exerts a therapeutic effect on burn wounds. However, cell viability can impede their clinical application. HOX antisense intergenic RNA (HOTAIR) is involved in regulating adult tissue stem cells, as well as in developmental patterning and pluripotency. However, little is known about its role in regulating ESCs. The present study was performed to investigate the effects of HOTAIR in the modulation of ESCs and wound repair. Firstly, reverse transcription‑quantitative PCR was used to detect the relative expression of HOTAIR during burn wound healing in mice to determine whether HOTAIR is associated with wound healing. Subsequently, ESCs derived from mouse skin were transfected with a lentiviral vector to overexpress or knockdown HOTAIR. The effects of HOTAIR on cell proliferation and differentiation were measured by 5‑bromodeoxyuridine and MTT assays, and by assessing NANOG mRNA expression. Lastly, mice with burns were administered a subcutaneous injection of HOTAIR‑overexpressing ESCs. Images were captured and histological analyses were performed to evaluate wound healing. The results revealed that the expression of HOTAIR gradually increased and peaked at day 7 post‑burn and maintained at relatively high levels until day 14 post‑burn during wound healing. Furthermore, overexpression of HOTAIR promoted ESC proliferation and maintained the stem cell state in vitro. By contrast, suppression of HOTAIR inhibited cell proliferation and cell stemness. It was also identified that HOTIR‑overexpressing ESCs accelerated re‑epithelialization and facilitated burn wound repair. In conclusion, the present findings confirmed an essential role of HOTAIR in the regulation of ESC proliferation and stemness. Therefore, targeting HOTAIR in ESCs may be a potentially promising therapy for burn wound healing.

The Potential Regulatory Roles of lncRNAs in DNA Damage Response in Human Lymphocytes Exposed to UVC Irradiation

Long noncoding RNAs (lncRNAs) are a class of noncoding RNAs that modulate gene expression, thereby participating in the regulation of various cellular processes. However, it is not clear about the expression and underlying mechanism of lncRNAs in irradiation-induced DNA damage response. In the present study, we performed integrative analysis of lncRNA-mRNA expression profile in human lymphocytes irradiated with ultraviolet-C (UVC). The results showed that exposure to UVC irradiation dose-dependently increased the fluorescence intensity of γ-H₂AX and induced cell death. Microarray analysis revealed that up-regulated lncRNAs were more common than down-regulated lncRNAs with the increase of radiation dose in UVC-radiated cells. Stem analysis demonstrated the relationship between lncRNA expression level and radiation dose. qPCR results confirmed that LOC338799 and its coexpressed genes such as LCE1F and ISCU showed the increase in expression levels with the increase of UVC radiation dose. We utilized Cytoscape to screen out 5 lncRNAs and 13 coexpressed genes linking to p53, which might participate in the regulation of DNA damage, cell cycle arrest, apoptosis, and cell death. These findings suggest that lncRNAs might play a role in UVC-induced DNA damage response through regulating expression of genes in p53 signaling pathway.

The Roles of lncRNA in Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma derives from keratinocytes and is the second most common cause of non-melanoma skin cancer. Cutaneous squamous cell carcinoma (cSCC) develops rapidly and is also the leading cause of death in non-melanoma cancers. Lymph node metastasis occurs in 5% of cSCC patients, and some patients may even metastasize to the viscera. Patients with regional lymphatic metastasis or distant metastases have a <20% 10-year survival rate, indicating the substantial challenge in treating advanced and metastatic cSCC. Some lncRNAs have been found to be abnormally overexpressed in many tumor tissues, so that they can be considered as potential new biomarkers or targets that can be used in the diagnosis and treatment of cSCC in the future. In this review, we summarize the role of lncRNA in cutaneous squamous cell carcinoma to make a better understanding of mutations in cSCC and lay the foundation for effective target therapy of cSCC.

The role of cigarette smoke-induced epigenetic alterations in inflammation

Background

Exposure to cigarette smoke (CS) is a major threat to human health worldwide. It is well established that smoking increases the risk of respiratory diseases, cardiovascular diseases and different forms of cancer, including lung, liver, and colon. CS-triggered inflammation is considered to play a central role in various pathologies by a mechanism that stimulates the release of pro-inflammatory cytokines. During this process, epigenetic alterations are known to play important roles in the specificity and duration of gene transcription.

Main text

Epigenetic alterations include three major modifications: DNA modifications via methylation; various posttranslational modifications of histones, namely, methylation, acetylation, phosphorylation, and ubiquitination; and non-coding RNA sequences. These modifications work in concert to regulate gene transcription in a heritable fashion. The enzymes that regulate these epigenetic modifications can be activated by smoking, which further mediates the expression of multiple inflammatory genes. In this review, we summarize the current knowledge on the epigenetic alterations triggered by CS and assess how such alterations may affect smoking-mediated inflammatory responses.

Conclusion

The recognition of the molecular mechanisms of the epigenetic changes in abnormal inflammation is expected to contribute to the understanding of the pathophysiology of CS-related diseases such that novel epigenetic therapies may be identified in the near future.

HOX transcript antisense RNA is elevated in gastric carcinogenesis and regulated by the NF-κB pathway

The expression pattern of HOX transcript antisense RNA (HOTAIR) in the progression of gastric cancer and the regulation of its expression are still unclear. In the current study, HOTAIR expressions in gastric tissues collected from patients with superficial gastritis, atrophic gastritis, atypical hyperplasia, and gastric cancer as well as normal controls was quantitatively examined. The results showed that the expression of HOTAIR was higher in gastric cancer than in normal tissues, but reached the highest level in atrophic gastritis, suggesting that HOTAIR may be involved in the molecular process of nonresolving inflammation. Then tumor necrosis factor-α-induced protein-8 like-2 (TIPE2), a known gene associated with nonresolving inflammation, was overexpressed and the results showed that the promotion in TIPE2 expression triggered HOTAIR reduction, this result was further verified by microarray analysis and TIPE2 knockout mice. Subsequently, the data obtained from HOTAIR knockdown experiment showed that it significantly enhanced colony forming capability and inhibited p27 expression in AGS cells. Furthermore, deletion constructs and luciferase-based activity assays indicated that the -475 to -443bp region of HOTAIR promoter contained a crucial regulatory element. Transcription factor prediction with software TRANSFAC revealed that nuclear factor-κB signaling protein p65 had a binding site in this region and might have roles in HOTAIR expression. The binding of phosphor-p65 to HOTAIR promoter was verified by chromatin immunoprecipitation, and succeeding experiment results demonstrated that p65 reduction by p65 small interfering RNA and TIPE2 overexpression also decreased HOTAIR expression. Conclusively, our results suggest that HOTAIR was associated with nonresolving inflammation, and its expression is regulated by p65.

PKR: A Kinase to Remember

Aging is a major risk factor for many diseases including metabolic syndrome, cancer, inflammation, and neurodegeneration. Identifying mechanistic common denominators underlying the impact of aging is essential for our fundamental understanding of age-related diseases and the possibility to propose new ways to fight them. One can define aging biochemically as prolonged metabolic stress, the innate cellular and molecular programs responding to it, and the new stable or unstable state of equilibrium between the two. A candidate to play a role in the process is protein kinase R (PKR), first identified as a cellular protector against viral infection and today known as a major regulator of central cellular processes including mRNA translation, transcriptional control, regulation of apoptosis, and cell proliferation. Prolonged imbalance in PKR activation is both affected by biochemical and metabolic parameters and affects them in turn to create a feedforward loop. Here, we portray the central role of PKR in transferring metabolic information and regulating cellular function with a focus on cancer, inflammation, and brain function. Later, we integrate information from open data sources and discuss current knowledge and gaps in the literature about the signaling cascades upstream and downstream of PKR in different cell types and function. Finally, we summarize current major points and biological means to manipulate PKR expression and/or activation and propose PKR as a therapeutic target to shift age/metabolic-dependent undesired steady states.

Retracted Article: Long noncoding RNA HOTAIR promotes cell apoptosis by sponging miR-221 in Parkinson's disease

Parkinson's disease (PD) is a common neurological disorder that is detrimental to the health of older people worldwide. Long noncoding RNAs (lncRNAs) have been reported to play essential roles in the pathogenesis and therapeutics of PD. LncRNA homeobox transcript antisense intergenic RNA (HOTAIR) is expressed in PD samples; however, the exact roles of HOTAIR and its mechanism remain largely unclear. Herein, the neurotoxins 1-methyl-4-phenylpyridine (MPP⁺) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were used to establish PD models in vitro and in vivo. The expressions of HOTAIR and microRNA-221 (miR-221) were measured by the quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability and apoptosis were detected by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay and western blot or flow cytometry, respectively. The interaction between HOTAIR and miR-221 was explored by luciferase activity and RNA immunoprecipitation (RIP). The tyrosine hydroxylase (TH)-positive cells in MPTP-treated-mouse midbrains were analyzed by immunohistochemistry. The HOTAIR expression was up-regulated and that of miR-221 was down-regulated in the serum of PD patients and MPP⁺-treated SH-SY5Y cells. Overexpression of HOTAIR inhibited cell viability and promoted apoptosis in MPP⁺-treated SH-SY5Y cells. However, the down-regulation of HOTAIR showed an opposite effect. Moreover, miR-221 was validated to be bound to HOTAIR, and its addition reversed the regulatory effect of HOTAIR on cell viability and apoptosis in MPP⁺-treated SH-SY5Y cells. Moreover, the knockdown of HOTAIR attenuated the degree of PD and cell apoptosis by regulating miR-221 in MPTP-treated mice. In conclusion, HOTAIR contributed to cell apoptosis by sponging miR-221 in PD. This study elucidates a new mechanism for understanding the pathogenesis of PD and provides a promising target for the treatment of PD.

Parkinson's disease (PD) is a common neurological disorder that is detrimental to the health of older people worldwide.