Blocking endothelial apoptosis revascularises the retina in a model of ischemic retinopathy

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Abstract

Aberrant, neovascular retinal blood vessel growth is a vision-threatening complication in ischemic retinal diseases. It is driven by retinal hypoxia frequently caused by capillary non-perfusion and endothelial cell (EC) loss. We investigated the role of EC apoptosis in this process using a mouse model of ischemic retinopathy, in which vessel closure and EC apoptosis cause capillary regression and retinal ischemia followed by neovascularisation. Protecting ECs from apoptosis in this model did not prevent capillary closure or retinal ischemia. Nonetheless, it prevented the clearance of ECs from closed capillaries, delaying vessel regression and allowing ECs to persist in clusters throughout the ischemic zone. In response to hypoxia, these preserved ECs underwent a vessel sprouting response and rapidly reassembled into a functional vascular network. This alleviated retinal hypoxia, preventing subsequent pathogenic neovascularisation. Vessel reassembly was not limited by VEGFA neutralisation, suggesting it was not dependent on the excess VEGFA produced by the ischemic retina. Neutralisation of ANG2 did not prevent vessel reassembly, but did impair subsequent angiogenic expansion of the reassembled vessels. Blockade of EC apoptosis may promote ischemic tissue re-vascularisation by preserving ECs within ischemic tissue that retain the capacity to reassemble a functional network and rapidly restore blood supply.

Authors

Zoe L. Grant, Lachlan Whitehead, Vickie H. Y. Wong, Zheng He, Richard Y. Yan, Abigail R. Miles, Andrew V. Benest, David O. Bates, Claudia Prahst, Katie Bentley, Bang V. Bui, Robert C.A. Symons, Leigh Coultas

Chemotherapy-induced S100A10 recruits KDM6A to facilitate OCT4-mediated breast cancer stemness

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Abstract

Breast cancer stem cells (BCSCs) play a critical role in cancer recurrence and metastasis. Chemotherapy induces BCSC specification through increased expression of pluripotency factors, but how their expression is regulated is not fully understood. Here, we delineate a hypoxia-inducible factor 1 (HIF-1)-controlled pathway that epigenetically activates pluripotency factor gene transcription in response to chemotherapy. Paclitaxel induces HIF-1-dependent expression of S100A10, which forms a complex with ANXA2 that interacts with histone chaperone SPT6 and histone demethylase KDM6A. S100A10, ANXA2, SPT6, and KDM6A are recruited to OCT4 binding sites and KDM6A erases H3K27me3 chromatin marks, facilitating transcription of genes encoding the pluripotency factors NANOG, SOX2, and KLF4, which along with OCT4 are responsible for BCSC specification. Silencing of S100A10, ANXA2, SPT6, or KDM6A expression blocks chemotherapy-induced enrichment of BCSCs, impairs tumor initiation, and increases time to tumor recurrence after chemotherapy is discontinued. Pharmacological inhibition of KDM6A also impairs chemotherapy-induced BCSC enrichment. These results suggest that targeting HIF-1/S100A10-dependent and KDM6A-mediated epigenetic activation of pluripotency factor gene expression in combination with chemotherapy may block BCSC enrichment and improve clinical outcome.

Authors

Haiquan Lu, Yangyiran Xie, Linh Tran, Jie Lan, Yongkang Yang, Naveena L. Murugan, Ru Wang, Yueyang J. Wang, Gregg L. Semenza

Dynamic transcriptome analysis unveils key pro-resolving factors of chronic inflammatory arthritis

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Abstract

Despite recent advances in understanding chronic inflammation remission, global analyses have not been explored to systematically discover genes or pathways underlying the resolution dynamics of chronic inflammatory diseases. Here, we performed time-course gene expression profiling of mouse synovial tissues along progression and resolution of collagen-induced arthritis (CIA) and identified genes associated with inflammation resolution. Through network analysis of these genes, we predicted three key secretory factors responsible for the resolution of CIA: Itgb1, Rps3, and Ywhaz. These factors were predominantly expressed by regulatory T cells and anti-inflammatory M2 macrophages, suppressing production of pro-inflammatory cytokines. In particular, Ywhaz was elevated in the sera of mice with arthritis resolution and in the urine of rheumatoid arthritis (RA) patients with good therapeutic responses. Moreover, adenovirus-mediated transfer of the Ywhaz gene to the affected joints substantially inhibited arthritis progression in mice with CIA and suppressed expression of pro-inflammatory cytokines in joint tissues, lymph nodes, and spleens, suggesting Ywhaz as an excellent target for RA therapy. Therefore, our comprehensive analysis of dynamic synovial transcriptomes provides previously unidentified anti-arthritic genes, Itgb1, Rps3, and Ywhaz, which can serve as molecular markers to predict disease remission, as well as therapeutic targets for chronic inflammatory arthritis.

Authors

Jin-Sun Kong, Ji-Hwan Park, Seung-Ah Yoo, Ki-Myo Kim, Yeung-Jin Bae, Yune-Jung Park, Chul-Soo Cho, Daehee Hwang, Wan-Uk Kim

Maternal diesel particle exposure promotes offspring asthma through NK cell-derived granzyme B

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Abstract

Mothers living near high-traffic roads before or during pregnancy have increased odds of having children with asthma. Mechanisms are unknown. Using a mouse model, here we showed that maternal exposure to diesel exhaust particles (DEP) predisposed offspring to allergic airway disease/AAD (murine counterpart of human asthma) through programming of their NK cells; predisposition to AAD did not develop in ‘DEP’ pups that lacked NK cells and was induced in normal pups receiving NK cells from wild type ‘DEP’ pups. “DEP’ NK cells expressed GATA3 and co-secreted IL-13 and the ‘killer’ protease granzyme B in response to allergen challenge. Extracellular granzyme B did not kill but instead it stimulated protease-activated receptor 2 (PAR2) to cooperate with IL-13 in the induction of IL-25 in airway epithelial cells. Through loss-of-function and reconstitution experiments in pups, we showed that NK cells and granzyme B were required for IL-25 induction and activation of the type-2 immune response, and IL-25 mediated NK cell effects on type-2 response and AAD. Lastly, experiments using human cord blood and airway epithelial cells suggested that DEP might induce an identical pathway in humans. Collectively, we described an NK cell-dependent endotype of AAD that emerged in early life as a result of maternal exposure to DEP.

Authors

Qian Qian, Bidisha Paul Chowdhury, Zehua Sun, Jerica Lenberg, Rafeul Alam, Eric Vivier, Magdalena M. Gorska

MKRN3 inhibits the reproductive axis through actions in kisspeptin-expressing neurons

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Abstract

The identification of loss-of-function mutations in MKRN3 in patients with central precocious puberty (CPP) in association with the decrease in MKRN3 expression in the medial basal hypothalamus (MBH) of mice prior to the initiation of reproductive maturation suggest that MKRN3 is acting as a ‘brake’ on GnRH secretion during childhood. In the current study, we investigated the mechanism by which MKRN3 prevents premature manifestation of the pubertal process. We showed that, as in mice, MKRN3 expression is high in the hypothalamus of rats and nonhuman primates early in life, declining as puberty approaches, and is independent of sex steroid hormones. We demonstrated that Mkrn3 is expressed in Kiss1 neurons of the mouse hypothalamic arcuate nucleus (ARC) and that MKRN3 repressed promoter activity of human KISS1 and TAC3, two key stimulators of GnRH secretion. We further showed that MKRN3 has ubiquitinase activity, that this activity is reduced by MKRN3 mutations affecting the RING finger domain, and that these mutations compromised the ability of MKRN3 to repress KISS1 and TAC3 promoter activity. These results indicate that MKRN3 acts to prevent puberty initiation, at least in part, by repressing KISS1 and TAC3 transcription and that this action may involve a MKRN3-directed ubiquitination-mediated mechanism.

Authors

Ana Paula Abreu, Carlos A. Toro, Yong Bhum Song, Victor M Navarro, Martha A. Bosch, Aysegul Eren, Joy N. Liang, Rona S. Carroll, Ana Claudia Latronico, Oline K. Ronnekleiv, Carlos F Aylwin, Alejandro Lomniczi, Sergio R. Ojeda, Ursula B Kaiser

Elevated circulating amyloid concentrations in obesity and diabetes promote vascular dysfunction

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Abstract

Diabetes, obesity and Alzheimer’s disease (AD) are associated with vascular complications and impaired nitric oxide (NO) production. Furthermore, increased β-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1), APP and β-amyloid (Aβ) are linked with vascular disease development and raised BACE1 and Aβ accompany hyperglycemia and hyperlipidemia. However, the causal relationship between obesity and diabetes, raised Aβ and vascular dysfunction is unclear. We report that diet-induced obesity (DIO) in mice raised plasma and vascular Aβ42 that correlated with decreased NO bioavailability, endothelial dysfunction and raised blood pressure. Genetic or pharmacological reduction of BACE1 activity and Aβ42 prevented and reversed, respectively, these outcomes. In contrast, expression of human mutant APP in mice or Aβ42 infusion into control diet-fed mice to mimic obese levels impaired NO production, vascular relaxation and raised blood pressure. In humans, raised plasma Aβ42 correlated with diabetes and endothelial dysfunction. Mechanistically, higher Aβ42 reduced endothelial NO synthase (eNOS), cyclic GMP and protein kinase G (PKG) activity independently of diet whereas endothelin-1 was increased by diet and Aβ42. Lowering Aβ42 reversed the DIO deficit in the eNOS-cGMP-PKG pathway and decreased endothelin-1. Our findings suggest that BACE1 inhibitors may have therapeutic value in the treatment of vascular disease associated with diabetes.

Authors

Paul J. Meakin, Bethany M. Coull, Zofia Tuharska, Christopher McCaffery, Ioannis Akoumianakis, Charalambos Antoniades, Jane Brown, Kathryn J. Griffin, Fiona Platt, Claire H. Ozber, Nadira Y. Yuldasheva, Natallia Makava, Anna Skromna, Alan Russell Prescott, Alison D. McNeilly, Moneeza K. Siddiqui, Colin Neil Alexander Palmer, Faisel Khan, Michael LJ Ashford

Nonalcoholic fatty liver disease in CLOCK mutant mice

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Abstract

Nonalcoholic fatty liver disease (NAFLD) is becoming a major health issue as obesity increases around the world. We studied the effect of a circadian locomotor output cycles kaput (CLOCK) mutant (ClkΔ19/Δ19) protein on hepatic lipid metabolism in C57Bl6 Clkwt/wt and apolipoprotein E–deficient (Apoe−/−) mice. Both ClkΔ19/Δ19 and ClkΔ19/Δ19Apoe−/− mice developed a full spectrum of liver diseases (steatosis, steatohepatitis, cirrhosis, and hepatocellular carcinoma) recognized in human NAFLD when challenged with a Western diet, lipopolysaccharide, or CoCl2. We identified induction of cluster of differentiation 36 (CD36) and hypoxia-inducible factor 1α (HIF1α) proteins as contributing factors for NAFLD. Mechanistic studies showed that wild-type CLOCK protein interacted with the E-box enhancer elements in the promoters of the proline hydroxylase domain (PHD) proteins to increase expression. In ClkΔ19/Δ19 mice, PHD levels were low, and HIF1α protein levels were increased. When its levels were high, HIF1α interacted with the Cd36 promoter to augment expression and enhance fatty acid uptake. Thus, these studies establish a novel regulatory link among circadian rhythms, hypoxia response, fatty acid uptake, and NAFLD. The mouse models described here may be useful for further mechanistic studies in the progression of liver diseases and in the discovery of drugs for the treatment of these disorders.

Authors

Xiaoyue Pan, Joyce Queiroz, M. Mahmood Hussain

Ribosomal S6 protein kinase 4 promotes radioresistance in esophageal squamous cell carcinoma

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Abstract

Esophageal squamous cell carcinoma (ESCC) is one of the most aggressive cancers and is highly resistant to current treatments. ESCC harbors a subpopulation of cells exhibiting cancer stem-like cell (CSC) properties that contribute to therapeutic resistance including radioresistance, but the molecular mechanisms in ESCC CSCs are currently unknown. Here, we report that ribosomal S6 protein kinase 4 (RSK4) plays a pivotal role in promoting CSC properties and radioresistance in ESCC. RSK4 was highly expressed in ESCC CSCs and associated with radioresistance and poor survival in ESCC patients. RSK4 was found to be a direct downstream transcriptional target of ΔNp63α, the main p63 isoform, which is frequently amplified in ESCC. RSK4 activated the β-catenin signaling pathway through direct phosphorylation of GSK-3β Ser9. Pharmacologic inhibition of RSK4 effectively reduced CSC properties and improves radiosensitivity in both nude mice and patient-derived xenograft models. Collectively, our results strongly suggest that the ΔNp63α-RSK4-GSK-3β axis plays a key role in driving CSC properties and radioresistance in ESCC, indicating that RSK4 is a promising therapeutic target for ESCC treatment.

Authors

Mingyang Li, Linni Fan, Donghui Han, Zhou Yu, Jing Ma, Yixiong Liu, Peifeng Li, Danhui Zhao, Jia Chai, Lei Jiang, Shiliang Li, Juanjuan Xiao, Qiuhong Duan, Jing Ye, Mei Shi, Yongzhan Nie, Kai-Chun Wu, Dezhong Joshua Liao, Yu Shi, Yan Wang, Qingguo Yan, Shuangping Guo, Xiu-Wu Bian, Feng Zhu, Jian Zhang, Zhe Wang

Germline RBBP8 variants associated with early-onset breast cancer compromise replication fork stability

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Abstract

Haploinsufficiency of factors governing genome stability underlies hereditary breast and ovarian cancer. Homologous recombination (HR) repair is a major pathway disabled in these cancers. With the aim of identifying new candidate genes, we examined early onset breast cancer patients negative for BRCA1 and BRCA2 pathogenic variants. Here, we focused on CtIP (RBBP8 gene) that mediates HR repair through the end-resection of DNA double-strand breaks (DSB). Notably, the patients exhibited a number of rare germline RBBP8 variants, and functional analysis revealed that these variants did not affect DNA DSB end-resection efficiency. However, expression of a subset of variants led to deleterious nucleolytic degradation of stalled DNA replication forks in a manner similar to cells lacking BRCA1 or BRCA2. In contrast to BRCA1 and BRCA2, CtIP deficiency promoted the helicase-driven destabilization of RAD51 nucleofilaments at damaged DNA replication forks. Taken together, our work identifies CtIP as a critical regulator of DNA replication fork integrity, which when compromised, may predispose to the development of early onset breast cancer.

Authors

Reihaneh Zarrizi, Martin R. Higgs, Karolin Voßgröne, Maria Rossing, Birgitte Bertelsen, Muthiah Bose, Arne N. Kousholt, Heike I. Rösner, Bent Ejlertsen, Grant S. Stewart, Finn Cilius Nielsen, Claus Sørensen

Deficiency of MFSD7c results in microcephaly-associated vasculopathy in Fowler syndrome

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Abstract

Several missense mutations in the orphan transporter FLVCR2 have been reported in Fowler syndrome. Affected subjects exhibit signs of severe neurological defects. We identified the mouse ortholog Mfsd7c as a gene, which is expressed in the blood brain barrier. Here, we report the characterizations of Mfsd7c knockout (KO) mice and compare it to phenotypic findings in humans with bi-allelic FLVCR2 mutations. Global KO of Mfsd7c in mice resulted in late gestation lethality, likely due to central nervous system (CNS) phenotypes. We found that the angiogenic growth of CNS blood vessels in the brain of Mfsd7c KO embryos was inhibited in cortical ventricular zones and ganglionic eminences. Vascular tips were dilated and fused resulting in glomeruloid vessels. Nonetheless, CNS blood vessels were intact without haemorrhage. Both embryos and humans with bi-allelic FLVCR2 mutations exhibited reduced cerebral cortical layers, enlargement of the cerebral ventricles, and microcephaly. Transcriptomic analysis of Mfsd7c knockout (KO) embryonic brains revealed upregulation of genes involved in glycolysis and angiogenesis. The Mfsd7c KO brain exhibited hypoxia and neuronal cell death. Our results indicate MFSD7c is required for the normal growth of CNS blood vessels and ablation of this gene results in microcephaly-associated vasculopathy in mice and humans.

Authors

Pazhanichamy Kalailingam, Kai Qi Wang, Xiu Ru Toh, Toan Q. Nguyen, Madhuvanthi Chandrakanthan, Zafrul Hasan, Clair Habib, Aharon Schif, Francesca Clementina Radio, Bruno Dallapiccola, Karin Weiss, Long N. Nguyen