Daeho So

Sirtuin 1 attenuates nasal polypogenesis by suppressing epithelial-to-mesenchymal transition

BACKGROUND Nasal polyps (NPs) imply a refractory clinical course in patients with chronic rhinosinusitis (CRS). Previously, we showed that hypoxia-inducible factor (HIF) 1 could mediate nasal polypogenesis through epithelial-to-mesenchymal transition (EMT). Sirtuin 1 (SIRT1), a histone deacetylase, reportedly suppresses the transcriptional activity of HIF-1. Thus we hypothesized that SIRT1 attenuates nasal polyposis by inhibiting HIF-1-induced EMT. OBJECTIVE We sought to determine the role of SIRT1 in patients with nasal polyposis. METHODS The effects of SIRT1 on nasal polypogenesis were investigated in previously developed murine models. Immunohistochemistry, immunoblotting, and immunoprecipitation were done to evaluate SIRT1, EMT, and hypoxic markers in human nasal epithelial cells or sinonasal tissues from the mice and the patients with CRS with or without NPs. RESULTS SIRT1 transgenic mice had significantly fewer mucosal lesions with epithelial disruption and fewer NPs than wild-type (WT) mice. In addition, resveratrol (a SIRT1 activator) treatment suppressed nasal polypogenesis in WT mice; however, sirtinol (a SIRT1 inhibitor) administration increased the polyp burden in SIRT1 transgenic mice. In sinonasal specimens from patients with CRS, SIRT1 was downregulated in the mucosa from patients with polyps compared with levels seen in patients without polyps. SIRT1 overexpression or activation reversed hypoxia-induced EMT in human nasal epithelial cells. The intranasal transfection of a small hairpin SIRT1 lentiviral vector induced more nasal polypoid lesions in SIRT1 transgenic mice. Finally, mucosal extracts from patients with CRS without NPs increased SIRT1 expression in nasal epithelial cells, whereas those from patients with CRS with NPs did not. CONCLUSION SIRT1 suppressed NP formation, possibly because of inhibition of HIF-1-induced EMT. Thus nasal epithelium SIRT1 might be a therapeutic target for NPs.

HIF-1α Upregulation due to Depletion of the Free Ubiquitin Pool

Hypoxia-inducible factor 1alpha (HIF-1α), which transactivates a variety of hypoxia-induced genes, is rapidly degraded under nomoxia through the hydroxylation-ubiquitination-proteasome pathway. In this study, we addressed how HIF-1α is stabilized by proteasome inhibitors. The ubiquitin pool was rapidly reduced after proteasome inhibition, followed by the accumulation of non-ubiquitinated HIF-1α. The poly-ubiquitination of HIF-1α was resumed by restoration of free ubiquitin, which suggests that the HIF-1α stabilization under proteasome inhibition is attributed to depletion of the free ubiquitin pool. Ni2+ and Zn2+ also stabilized HIF-1α with depletion of the free ubiquitin pool and these effects of metal ions were attenuated by restoration of free ubiquitin. Ni2+ and Zn2+ may disturb the recycling of free ubiquitin, as MG132 does. Based on these results, the state of the ubiquitin pool seems to be another critical factor determining the cellular level of HIF-1α. Graphical Abstract

Cervical cancer is addicted to SIRT1 disarming the AIM2 antiviral defense

Mammalian cells are equipped with antiviral innate immunity. To survive and grow, human papilloma virus (HPV)-infected cervical cancer cells must overcome this host defense system. However, the precise mechanism whereby cervical cancer cells evade the immunity is not fully understood. We noted that Sirtuin 1 (SIRT1) is overexpressed in HPV-infected cervical cancer cells and hypothesized that SIRT1 counteracts antiviral immunity. Here, we found that cervical cancer cells undergo massive death by SIRT1 knockdown, but this effect is reversed by SIRT1 restoration. SIRT1-knocked-down cells showed representative features of pyroptosis, as well as highly expressed absent in melanoma 2 (AIM2) and its downstream genes related to the inflammasome response. Mechanistically, SIRT1 repressed the NF-κB-driven transcription of the AIM2 gene by destabilizing the RELB mRNA. Interestingly, pyroptotic death signaling in SIRT1-knocked-down cells was transmitted to naïve cervical cancer cells, which was mediated by extracellular vesicles carrying AIM2 inflammasome proteins. Furthermore, the growth of cervical cancer xenografts was significantly inhibited by either SIRT1-targeting siRNAs or SIRT1-knockdown-derived extracellular vesicles. Immunohistochemical analyses showed that SIRT1 expression correlated with poor clinical outcomes in cervical cancer. In conclusion, SIRT1 enabled HPV-infected cervical cancer cells to continue growing by nullifying AIM2 inflammasome-mediated immunity. Without SIRT1, cervical cancer cells could no longer survive because of the derepression of the AIM2 inflammasome. SIRT1 could therefore be a target for the effective treatment of cervical cancer.

Urinary Metabolomic Signatures in Obstructive Sleep Apnea through Targeted Metabolomic Analysis: A Pilot Study

IntroductionObstructive sleep apnea (OSA) is very common sleep problem, and it is associated with serious morbidities such as cardiovascular diseases and metabolic diseases. Overnight polysomnography (PSG) is the gold standard test for OSA, but it is expensive and requires specific facilities and equipment. Thus, novel screening methods are needed for effective diagnosis and follow-up in OSA.ObjectivesThe aims of the study were to investigate the urinary metabolic signatures and identify potential urine markers for OSA using a mass spectrometry (MS)-based assay for targeted metabolomics.MethodsUrine samples were collected from 48 male subjects who visited a sleep clinic for suspicious OSA. All underwent overnight in-laboratory polysomnography. The Biocrates AbsoluteIDQ p180 kit was used for targeted metabolomics.ResultsAmong the 86 metabolites quantified, three acylcarnitines, one biogenic amine, two glycerophospholipids, and two sphingomyelins were differently expressed in OSA patients [apnea-hypopnea index (AHI) ≥5] compared with control groups (AHI <5 and/or simple snoring with no other sleep disorders). Additional partial correlation and multivariate logistic regression analysis revealed that long-chain acylcarnitine C14:1, symmetric dimethylarginine, and sphingomyelin C18:1 might be potential biomarkers for OSA. Receiver operating characteristic analysis showed favorable predictive properties of these metabolites. Furthermore, a combination of the metabolites exceeding cutoff values yielded further improved sensitivity or specificity.ConclusionsMS-based targeted metabolomics identified specific classes of urinary metabolites that were up-regulated in OSA patients. Further assessments in large populations are required to clarify the screening values of these metabolite markers.