Po-Shun Lee

Plasma gelsolin is a marker and therapeutic agent in animal sepsis

Objective:Plasma gelsolin is a circulating actin-binding protein that serves a protective role against tissue injuries. Depletion of plasma gelsolin in systemic inflammation may contribute to adverse outcomes. We examined the role of plasma gelsolin in animal models of sepsis. Design:Animal and laboratory experiments. Setting:Academic research laboratory. Subjects:Adult male mice. Interventions:Mice subjected to endotoxin or cecal ligation and puncture (CLP) were treated with exogenous plasma gelsolin or placebo. Measurements and Main Results:We document the depletion of plasma gelsolin (25–50% of normal) in murine models of sepsis associated with the presence of circulating actin within 6 hrs of septic challenge. Repletion of plasma gelsolin leads to solubilization of circulating actin aggregates and significantly reduces mortality in endotoxemic mice (survival rates were 88% in the gelsolin group vs. 0% in the saline group, p < .001) and in CLP-challenged mice (survival rates were 30% in the gelsolin group vs. 0% in the saline group, p = .001). Plasma gelsolin repletion also shifted the cytokine profile of endotoxemic mice toward anti-inflammatory (plasma interleukin-10 levels were 205 ± 108 pg/mL in the gelsolin group vs. 39 ± 29 pg/mL in the saline group, p = .02). Conclusions:We propose that circulation of particulate actin is a marker for sepsis-induced cell injury, that plasma gelsolin has a crucial protective role in sepsis, and that gelsolin replacement represents a potential therapy for this common lethal condition.

Plasma Gelsolin Depletion and Circulating Actin in Sepsis—A Pilot Study

Background Depletion of the circulating actin-binding protein, plasma gelsolin (pGSN) has been described in septic patients and animals. We hypothesized that the extent of pGSN reduction correlates with outcomes of septic patients and that circulating actin is a manifestation of sepsis. Methodology/Principal Findings We assayed pGSN in plasma samples from non-surgical septic patients identified from a pre-existing database which prospectively enrolled patients admitted to adult intensive care units at an academic hospital. We identified 21 non-surgical septic patients for the study. Actinemia was detected in 17 of the 21 patients, suggesting actin released into circulation from injured tissues is a manifestation of sepsis. Furthermore, we documented the depletion of pGSN in human clinical sepsis, and that the survivors had significantly higher pGSN levels than the non-survivors (163±47 mg/L vs. 89±48 mg/L, p = 0.01). pGSN levels were more strongly predictive of 28-day mortality than APACHE III scores. For every quartile reduction in pGSN, the odds of death increased 3.4-fold. Conclusion We conclude that circulating actin and pGSN deficiency are associated with early sepsis. The degree of pGSN deficiency correlates with sepsis mortality. Reversing pGSN deficiency may be an effective treatment for sepsis.

Rapamycin-Insensitive Up-Regulation of MMP2 and Other Genes in Tuberous Sclerosis Complex 2–Deficient Lymphangioleiomyomatosis-Like Cells

Increased matrix metalloproteinase (MMP) activity has been implicated in the pathogenesis of lymphangioleiomyomatosis (LAM). The objective of this study was to investigate how tuberous sclerosis complex (TSC) 1 or TSC2 deficiency alters MMP expression and regulation. We studied immortalized cells that lack TSC2 derived from an angiomyolipoma of a patient with LAM, a TSC2 addback derivative, and murine embryonic fibroblast cells that lack Tsc1 or -2 and respective controls. Global gene expression analysis was performed in the angiomyolipoma and derivative cell lines. MMP levels in the conditioned media from these cells were analyzed by zymography and ELISA. We found increased MMP-2 expression in cells lacking TSC1/TSC2 compared with their respective controls by zymography. MMP-2 overproduction by these cells was not affected by rapamycin treatment. Gene expression analysis confirmed increased MMP-2 gene expression that was not affected by rapamycin. Furthermore, multiple other genes were found to be overexpressed in rapamycin-treated TSC2-deficient cells compared with TSC2(+) cells. We conclude that TSC1/TSC2 deficiency leads to MMP-2 overproduction that is rapamycin-insensitive, and that several genes exhibit similar patterns, suggesting that TSC1/TSC2-dependent, but mammalian target of rapamycin-independent, pathways may be involved in the pathogenesis of LAM.

Estradiol and mTORC2 cooperate to enhance prostaglandin biosynthesis and tumorigenesis in TSC2-deficient LAM cells

Estradiol enhances COX-2 expression and prostaglandin biosynthesis in TSC2-deficient cells via a rapamycin-insensitive, mTORC2-dependent mechanism.

mTORC1-S6K Activation by Endotoxin Contributes to Cytokine Up-Regulation and Early Lethality in Animals

Background mTORC1 (mammalian target of rapamycin complex 1) activation has been demonstrated in response to endotoxin challenge, but the mechanism and significance are unclear. We investigated the effect of mTORC1 suppression in an animal model of endotoxemia and in a cellular model of endotoxin signaling. Methodology/Principal Findings Mice were treated with the mTORC1 inhibitor rapamycin or vehicle prior to lethal endotoxin challenge. Mortality and cytokine levels were assessed. Cultured macrophage-like cells were challenged with endotoxin with or without inhibitors of various pathways known to be upstream of mTORC1. Activated pathways, including downstream S6K pathway, were assessed by immunoblots. We found that mTORC1-S6K suppression by rapamycin delayed mortality of mice challenged with lethal endotoxin, and was associated with dampened circulating levels of VEGF, IL-1β, IFN-γ and IL-5. Furthermore, in vitro cellular studies demonstrated that LPS (lipopolysaccharide) activation of mTORC1-S6K still occurs in the presence of PI3K-Akt inhibition alone, but can be suppressed by concurrent inhibition of PI3K-Akt and MEK-ERK pathways. Conclusions/Significance We conclude that cellular activation of mTORC1-S6K contributes to cytokine up-regulation and mortality in response to endotoxin, and may occur via multiple pathways.

Gelsolin decreases actin toxicity and inflammation in murine multiple sclerosis

Gelsolin is the fourth most abundant protein in the body and its depletion in the blood has been found in multiple sclerosis (MS) patients. How gelsolin affects the MS brain has not been studied. We found that while the secreted form of gelsolin (pGSN) decreased in the blood of experimental autoimmune encephalomyelitis (EAE) mice, pGSN concentration increased in the EAE brain. Recombinant human pGSN (rhp-GSN) decreased extracellular actin and myeloperoxidase activity in the brain, resulting in reduced disease activity and less severe clinical disease, suggesting that gelsolin could be a potential therapeutic target for MS.

Rapamycin-Insensitive Up-Regulation of Adipocyte Phospholipase A2 in Tuberous Sclerosis and Lymphangioleiomyomatosis

Tuberous sclerosis syndrome (TSC) is an autosomal dominant tumor suppressor gene syndrome affecting multiple organs, including renal angiomyolipomas and pulmonary lymphangioleiomyomatosis (LAM). LAM is a female-predominant interstitial lung disease characterized by the progressive cyst formation and respiratory failure, which is also seen in sporadic patients without TSC. Mutations in TSC1 or TSC2 cause TSC, result in hyperactivation of mammalian target of rapamycin (mTOR), and are also seen in LAM cells in sporadic LAM. We recently reported that prostaglandin biosynthesis and cyclooxygenase-2 were deregulated in TSC and LAM. Phospholipase A2 (PLA2) is the rate-limiting enzyme that catalyzes the conversion of plasma membrane phospholipids into prostaglandins. In this study, we identified upregulation of adipocyte AdPLA2 (PLA2G16) in LAM nodule cells using publicly available expression data. We showed that the levels of AdPLA2 transcript and protein were higher in LAM lungs compared with control lungs. We then showed that TSC2 negatively regulates the expression of AdPLA2, and loss of TSC2 is associated with elevated production of prostaglandin E2 (PGE2) and prostacyclin (PGI2) in cell culture models. Mouse model studies also showed increased expression of AdPLA2 in xenograft tumors, estrogen-induced lung metastatic lesions of Tsc2 null leiomyoma-derived cells, and spontaneous renal cystadenomas from Tsc2+/− mice. Importantly, rapamycin treatment did not affect the expression of AdPLA2 and the production of PGE2 by TSC2-deficient mouse embryonic fibroblast (Tsc2 −/−MEFs), rat uterine leiomyoma-derived ELT3 cells, and LAM patient-associated renal angiomyolipoma-derived “mesenchymal” cells. Furthermore, methyl arachidonyl fluorophosphate (MAFP), a potent irreversible PLA2 inhibitor, selectively suppressed the growth and induced apoptosis of TSC2-deficient LAM patient-derived cells relative to TSC2-addback cells. Our findings suggest that AdPLA2 plays an important role in promoting tumorigenesis and disease progression by modulating the production of prostaglandins and may serve as a potential therapeutic target in TSC and LAM.

Rapamycin-Resistant Poly (ADP-Ribose) Polymerase-1 Overexpression Is a Potential Therapeutic Target in Lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a female-predominant cystic lung disease that can lead to respiratory failure. LAM cells typically have inactivating tuberous sclerosis complex 2 (TSC2) mutations and mammalian target of rapamycin (mTOR) complex (mTORC) 1 activation. Clinical response to the mTORC1 inhibitors has been limited, prompting a search for additional therapy for LAM. In this study, we investigated the impact of TSC2 on the expression of poly (ADP-ribose) polymerase (PARP)-1 that initiates the DNA repair pathway, and tested the efficacy of PARP1 inhibitors in the survival of TSC2-deficient (TSC2(-)) cells. We analyzed publicly available expression arrays of TSC2(-) cells and validated the findings using real-time RT-PCR, immunoblotting, and immunohistochemistry. We examined the impact of rapamycin and Torin 1 on PARP1 expression. We also tested the effect of PARP1 inhibitors, 8-hydroxy-2-methylquinazoline-4-one and 3,4-dihydro-5[4-(1-piperindinyl)butoxy]-1(2H)-isoquinoline, on the survival of TSC2(-) cells. We identified the up-regulation of PARP1 in TSC2(-) cells relative to cells in which wild-type TSC2 has been reintroduced (TSC2-addback [TSC2(+)] cells). The transcript levels of PARP1 in TSC2(-) cells were not affected by rapamycin. PARP1 levels were increased in TSC2(-) cells, xenograft tumors of rat-derived TSC2(-) cells, renal cystadenomas from Tsc2(+/-) mice, and human LAM nodules. RNA interference of mTOR failed to reduce PARP1 levels. Proliferation and survival of TSC2(-) cells was reduced in response to PARP1 inhibitor treatment, more so than TSC2(+) cells. TSC2(-) cells exhibit higher levels of PARP1 relative to TSC2(+) cells in an mTOR-insensitive manner. PARP1 inhibitors selectively suppress the growth and induce apoptosis of TSC2(-) cells from patients with LAM. Targeting PARP1 may be beneficial in the treatment of LAM and other neoplasm with mTORC1 activation.

Abstract B10: Estradiol and mTORC2 cooperate to enhance prostaglandin biosynthesis and tumorigenesis in tuberous sclerosis complex

Lymphangioleiomyomatosis LAM is a female predominant and devastating pulmonary disease, characterized by diffusely infiltrated smooth muscle like cells that carry mutations in the tuberous sclerosis complex (TSC) genes. TSC1, TSC2 and TBC1D7 interact and inhibit the mammalian target of rapamycin complex 1 (mTORC1). The reasons that LAM exclusively affects women and how TSC1 or TSC2 deficiency contributes to the pathogenesis of LAM are not yet fully understood. We previously discovered that estrogen promotes the survival and lung metastases of tuberin-deficient rat uterine leiomyoma-derived ELT3 cells in a xenograft tumor model (PNAS 2009). Recently, we reported that estrogen and mTORC2 coordinate to enhance prostaglandin biosynthesis and tumorigenesis in LAM (J. Expt. Med. 2013). Prostaglandins are lipid mediators that participate in tumor survival, growth, invasion, and inflammation. Phospholipase A2 (PLA2), Cyclooxygenase-2 (COX-2) and prostacyclin synthase (PTGIS) are critical enzymes responsible for the production of prostaglandins. Prostaglandin receptors (EPs) mediate the biological function of prostaglandins. This study is to determine whether suppression of prostaglandin biosynthesis pathway potentially leads to tumor regression LAM in both cell culture and preclinical models of LAM. To identify additional pathways activated by TSC loss, we performed bioinformatics analysis of public expression arrays and found a rapamycin-insensitive upregulation of prostaglandin biosynthesis genes including (PLA2), cyclooxygenase-2 (COX-2), prostacyclin synthase (PTGIS), and prostaglandin E2 (PGE2) receptor 3 (EP3), in TSC2-deficient LAM patient-derived cells compared to TSC2-addback cells. Real-time RT-PCR assays validated the enhanced expression of PLA2, COX-2, PTGIS and EP3 in TSC2-deficient cells. Immunoblotting analysis showed the increased levels of PLA2, COX-2, PTGIS and EP3 in TSC2-deficient cells compared to TSC2-addback cells. Immunohistochemistry demonstrated abundant accumulation of PLA2, COX-2 and EP3 in LAM lung lesions compared to adjacent normal tissues. Interestingly, PGE2 specifically stimulated the growth of TSC2-deficient LAM patient-derived cells compared to TSC2-addback cells. Importantly, treatment of TSC2-deficient LAM patient-derived cells with PLA2 inhibitor or EP3 inhibitor more potently reduced cell proliferation in dose-dependent manner compared to TSC2-addback cells. Our data documents that loss of TSC2 leads to the aberrant expression and accumulation of prostaglandin biosynthesis regulators PLA2, COX-2, PTGIS and EP3, thereby enhancing prostaglandin production and promoting TSC-related cell growth and tumor development. Our data supports the potential application of prostaglandin metabolites as biomarkers of disease severity and the development of prostaglandin biosynthesis inhibitors as alternative therapeutic options for lesions occurring in LAM patients and in other gender-specific neoplasm. Citation Format: Chenggang Li, Po-Shun Lee, Yang Sun, Erik Zhang, Xiaoxiao Gu, Jing Li, Kai-Feng Xu, Alfredo Csibi, John Blenis, Elizabeth Petri Henske, Bruce Levy, David Kwiatkowski, Jane J. Yu. Estradiol and mTORC2 cooperate to enhance prostaglandin biosynthesis and tumorigenesis in tuberous sclerosis complex. [abstract]. In: Proceedings of the AACR Special Conference: Targeting the PI3K-mTOR Network in Cancer; Sep 14-17, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(7 Suppl):Abstract nr B10.

Abstract C59: Estradiol and mTORC2 orchestrate to enhance prostaglandin biosynthesis andtumorigenesis in tuberous sclerosis complex

Lymphangioleiomyomatosis (LAM) is a female predominant progressive and neoplastic disorder that leads to lung destruction and respiratory failure primarily in women. LAM is typically due to TSC2 mutations resulting in mTORC1 activation in proliferative smooth muscle-like cells in the lung. The female predominance of LAM suggests that estradiol contributes to disease development. Metabolomic profiling identified estradiol-enhanced prostaglandin biosynthesis signature in Tsc2-deficient cells, both in vitro and in vivo. Estradiol increased the expression of cyclooxygenase-2 (COX-2), a rate-limiting enzyme in prostaglandin biosynthesis, which was increased at baseline in TSC2-deficient cells, and was not affected by rapamycin treatment, but decreased by Torin 1 treatment and Rictor knockdown, associated with reduction of levels phospho-Akt (S473). Prostaglandin production was also increased in TSC2-deficient cells. In preclinical models, Celecoxib or aspirin treatment suppressed tumor progression. LAM patients had significantly higher serum prostaglandin levels than healthy women. 15-epi-lipoxin-A4 was identified in exhaled breath condensate from LAM subjects and was increased by aspirin treatment, indicative of functional COX-2 expression in the LAM airway. Targeting COX-2 and prostaglandin pathways may have therapeutic value in LAM and TSC-related diseases, and possibly in other conditions associated with mTOR-hyperactivation. Citation Format: Chenggang Li, Po-Shun Lee, Xiaoxiao Gu, Yang Sun, Erik Zhang, Alfredo Csibi, Jing Li, Carmen Priolo, Yanan Guo, Chin-Lee Wu, John Blenis, Kai-Feng Xu, Elizabeth Petri Henske, Bruce Levy, David Kwiatkowski, Jane J. Yu. Estradiol and mTORC2 orchestrate to enhance prostaglandin biosynthesis andtumorigenesis in tuberous sclerosis complex. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr C59.