Mechanisms by which the N-terminal 24 amino acids of the p55 regulatory subunit of phosphatidylinositol 3-kinase affect endotoxin-induced cytokine release in human keratinocytes

KMT2C Induced by FABP5P3 Aggravates Keratinocyte Hyperproliferation and Psoriasiform Skin Inflammation by Upregulating the Transcription of PIK3R3

The extensive involvement of lysine methyltransferase 2C (KMT2C) in the inflammatory response is well-documented. However, little is known about the role of KMT2C in psoriasis. We identified that KMT2C was significantly upregulated in the epidermis of psoriatic skin lesions and the psoriasiform cell model. KMT2C knockdown diminished keratinocyte proliferation and the secretion of IL-6, IL-8, CCL20, and S100A9 in vitro and in vivo. In psoriasiform keratinocytes, KMT2C promoted the transcription of PIK3R3 by regulating the enrichment of histone H3 lysine 4 trimethylation at the PIK3R3 promoter and histone 3 lysine 4 monomethylation at the enhancer. The PIK3R3/protein kinase B/NF-κB pathway is a vital step in KMT2C-mediated alleviation of cytokine-primed inflammation. The long noncoding RNA FABP5P3 sustained KMT2C mRNA stability by recruiting human antigen R. Furthermore, inhibition of KMT2C attenuated epidermal hyperplasia and skin inflammation in mice with psoriasis. Taken together, our findings indicated a link between KMT2C and psoriasis and opened the possibility of using KMT2C as a potential therapeutic target for psoriasis treatment.

Regulation of circADAMTS6-miR-324-5p-PIK3R3 ceRNA pathway may be a novel mechanism of IL-1β-induced osteoarthritic chondrocytes

INTRODUCTION

A disintegrin and metallopeptidase with thrombospondin type 1 motif 6 (ADAMTS6)-derived circular RNA (circADAMTS6; hsa_circ_0008667) is a novel regulator in interleukin (IL)-1β-induced apoptosis of human chondrocytes (HCs). Here, we planned to probe into its role and mechanism underlying HCs injury in osteoarthritis.

MATERIALS AND METHODS

Real time-quantitative PCR and immunoblotting estimated the abundance of RNA and protein, respectively. Cell proliferation and apoptosis were measured by WST-8, EdU, fluorescein isothiocyanate, and caspase3/7 activity assays. Levels of inflammatory cytokines (IL-6 and tumor necrosis factor-α), apoptosis-related proteins (Bcl-2 and Bcl-2-associated X protein), extracellular matrix (ECM)-related proteins (matrix metalloproteinase-13 and collagen type II alpha-1), and PI3K/AKT/mTOR signaling pathway-related proteins (AKT, mTOR, phosphorylated-AKT, and phosphorylated-mTOR) were evaluated by enzyme-linked immunosorbent assays and immunoblotting. Target relationship was confirmed by dual-luciferase reporter, Argonaute-2 immunoprecipitation and RNA pull-down assays.

RESULTS

Abundances of circADAMTS6 and phosphoinositide-3-kinase regulatory subunit 3 (PIK3R3) were underexpressed, and microRNA (miR)-324-5p was elevated in human osteoarthritic tissues and IL-1β-induced HCs. Overexpressing circADAMTS6 and inhibiting miR-324-5p enhanced proliferation and ECM synthesis, but suppressed apoptosis and inflammatory response in IL-1β-challenged HCs. Besides, silencing circADAMTS6 caused similar effects of IL-1β stress on HCs. Mechanically, there was a direct interaction between miR-324-5p and circADAMTS6 or PIK3R3, and IL-1β-induced activation of PI3K/AKT/mTOR signaling pathway was suppressed by circADAMTS6 overexpression and miR-324-5p silencing. Furthermore, counteractive effects of miR-324-5p upregulation on circADAMTS6 overexpression and PIK3R3 knockdown on miR-324-5p silencing were observed.

CONCLUSION

CircADAMTS6-miR-324-5p-PIK3R3 axis might participate in IL-1β-induced HCs dysfunction via competing endogenous RNA mechanism and the PI3K/AKT/mTOR signaling pathway.

p55PIK deficiency and its NH2-terminal derivative inhibit inflammation and emphysema in COPD mouse model

Chronic obstructive pulmonary disease (COPD) is composed of chronic airway inflammation and emphysema. Recent studies show that Class IA phosphatidylinositol 3-kinases (PI3Ks) play an important role in the regulation of inflammation and emphysema. However, there are few studies on their regulatory subunits. p55PIK is a regulatory subunit of Class IA PI3Ks, and its unique NH₂-terminal gives it special functions. p55PIK expression in the lungs of nonsmokers, smokers, and patients with COPD was examined. We established a fusion protein TAT-N15 from the NH₂-terminal effector sequence of p55PIK and TAT (the transduction domain of HIV transactivator protein) and investigated the effects of silencing p55PIK or adding TAT-N15 on cigarette smoke exposure at the cellular and animal level. p55PIK expression was increased in patients with COPD. p55PIK deficiency and TAT-N15 significantly inhibited the cigarette smoke extract-induced IL-6, IL-8, and activation of the Akt and the NF-κB pathway in BEAS-2B. p55PIK deficiency and TAT-N15 intranasal administration prevented emphysema and the lung function decline in mice exposed to smoke for 6 mo. p55PIK deficiency and TAT-N15 significantly inhibited lung inflammatory infiltration, reduced levels of IL-6 and KC in mice lung homogenate, and inhibited activation of the Akt and the NF-κB signaling in COPD mice lungs. Our studies indicate that p55PIK is involved in the pathogenesis of COPD, and its NH₂-terminal derivative TAT-N15 could be an effective drug in the treatment of COPD by inhibiting the activation of the Akt and the NF-κB pathway.

A cell-permeable peptide inhibitor of p55PIK signaling alleviates ocular inflammation in mouse models of uveitis

PURPOSE

Previously we developed TAT-N24 as a synthetic cell-permeable peptide inhibitor of p55PIK signaling and demonstrated its anti-inflammatory effects. This study aimed to evaluate the potential of TAT-N24 as a new agent for the treatment of ocular inflammatory diseases.

METHODS

The endotoxin-induced uveitis (EIU) model was established by intravitreal injection of lipopolysaccharide (LPS) in BALB/c mice and experimental autoimmune uveitis (EAU) model was established by subcutaneous injection of a peptide spanning amino acid residues 161-180 of interphotoreceptor retinoid binding protein (IRBP161-180) with complete Freund's adjuvant (CFA) in B10.RIII mice. TAT-N24 was topically administered in EIU model and intraperitoneally administered in EAU model. The severity levels of uveitis were assessed by clinical and histopathological scores. The mRNA levels of inflammatory cytokines in iris-ciliary body (ICB) and retina were analyzed by reverse transcription quantitative polymerase chain reaction (RT-qPCR). The protein levels of inflammatory factors were determined by ELISA or Western blotting.

RESULTS

The results showed that TAT-N24 alleviated clinical signs, decreased inflammatory cell infiltration and the expression of inflammatory cytokines in both EIU and EAU models. Furthermore, protein levels of tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) in aqueous humor and mRNA and protein levels of NF-κB p65 in the ICB significantly decreased in EIU model. In EAU model, TAT-N24 application induced a significant decrease of IFN-gamma (IFN-γ) and interleukin-17 (IL-17) in the retina, which were secreted by Th1 and Th17 cells, respectively.

CONCLUSION

In conclusion, TAT-N24 suppressed intraocular inflammation in both EIU and EAU models, and the anti-inflammatory effects were mediated by suppressing the expression of inflammatory cytokines by PI3K/NF-κB signaling pathway. TAT-N24 could be potential candidate for the treatment of ocular inflammatory diseases.

P55PIK Regulates P53-Dependent Apoptosis in Cancer Cells by Interacting with P53 DNA-Specific Domain

Purpose

Phosphatidylinositol 3-kinase (PI3K) plays an important role in tumorigenesis by cross-talking with several signaling pathways. p55PIK is a unique regulatory subunit of PI3K and contains an extra 24-residue N-terminal domain (N24). This study aimed to explore the interaction of p55PIK with p53 and the role of p55PIK in regulating p53-dependent apoptosis in cancer cells.

Materials and Methods

The expression of p55PIK was detected in cancer cells, and the interaction of p55PIK with p53 was examined by immunoprecipitation and pull-down assay. The expression of p53-dependent apoptosis-related genes was detected by PCR.

Results

N24 domain of p55PIK interacted with DNA-specific binding domain (DBD) of p53. The increase or decrease of p55PIK expression led to the change of the expression of p53 and p53-regulated genes in cancer cells. Moreover, N24 peptide led to the change of the expression of p53-regulated genes. Moreover, a membrane-permeable N24 peptide enhanced p53-dependent apoptosis induced by methyl methanesulfonate.

Conclusion

Our results reveal a novel mechanism that regulates p53-dependent apoptosis in cancer cells via p55PIK-p53 interaction.

Ashwagandha root extract exerts anti‑inflammatory effects in HaCaT cells by inhibiting the MAPK/NF‑κB pathways and by regulating cytokines

A paste composed of the boiled leaves and roots of the Ashwagandha plant is used to cure ulcer and swelling in Ayurvedic medicine. However, the effects of the hot water extract of Ashwagandha roots (ASH‑WEX), which is also used in Ayurveda, on skin have not been fully elucidated. Therefore, the present study investigated the anti‑inflammatory activity of ASH‑WEX on skin, by using the human keratinocyte cell line HaCaT. The results indicated that ASH‑WEX significantly inhibited mRNA expression of inflammatory cytokines, including interleukin (IL)‑8, IL‑6, tumor necrosis factor (TNF‑α), IL‑1β and IL‑12, and promoted the mRNA expression of the anti‑inflammatory cytokine transforming growth factor (TGF)‑β1 in HaCaT cells. In addition, ASH‑WEX inhibited the lipopolysaccharide‑induced phosphorylation of p38 and c‑Jun N‑terminal kinase, as well as the nuclear translocation of nuclear factor (NF)‑κB p65. Downregulation of TNF‑α mRNA and upregulation of TGF‑β1 mRNA were also observed in vivo following ASH‑WEX treatment of mouse skin. In conclusion, the present study demonstrated that the anti‑inflammatory effect of ASH‑WEX may be due to its ability to suppress the NF‑κB and mitogen‑activated protein kinase pathways, and to modulate cytokine expression. These results suggest that ASH‑WEX can potentially protect against skin inflammation.