ROLE OF LYSOPHOSPHATIDIC ACID IN REGULATION OF CANCER CELL METABOLISM

The simplest phospholipid, lysophosphatidic acid (LPA), is a heat stable component of serum known for its proliferative and migratory activities in cancer cells. Strong evidence suggests that LPA production and expression of its receptors are dysregulated in multiple human malignancies. The mechanism behind LPA-mediated tumor cell growth and oncogenesis remains poorly understood. In this thesis project I used ovarian and other cancer cells as a model system to examine the hypothesis that LPA present in the tumor microenvironment is a pathophysiological determinant of hyperactive de novo lipogenesis and aerobic glycolysis, two hallmarks of cancer cells. We demonstrated that LPA induced proteolytic activation of sterol regulatory element binding proteins (SREBPs) in a cancer specific manner, leading to activation of the SREBP-FAS (fatty acid synthase) lipogenic pathway. Treatment of cancer cell lines with LPA also led to dephosphorylation and inhibition of AMP-activated kinase (AMPK), thereby activating acetyl CoA carboxylase (ACC). Moreover, these effects of LPA were mediated by LPA2, a receptor subtype overexpressed in multiple cancers, providing an explanation for the cancer specific regulation of FAS and ACC by LPA. Downstream of the LPA2 receptor, we identified the Gα12-Rho-Rock pathway to activate SREBPs and the Gαq-PLC (phospholipase C) pathway to inactivate AMPK. Consistent with LPA mediated activation of the key lipogenic enzymes FAS and ACC, LPA stimulated de novo lipid synthesis via LPA2, leading to accumulation of intracellular triacylglycerol and phospholipids. Pharmacological and molecular inhibition of LPA2, FAS or ACC attenuated LPA-dependent cell proliferation, indicating that upregulation of lipid synthesis is an integral component of the proliferative response to LPA. In further support of this, downregulation of LPA2 expression led to dramatic inhibition of anchorage-dependent and –independent growth of ovarian cancer cells. To support increased biomass generation, rapidly proliferating cancer cells enhance carbon influx by activating glycolysis. In the next part of the study, we investigated if LPA signaling was also involved in activating aerobic glycolysis in cancer cells. LPA indeed activated glycolysis in ovarian and other cancer cells but failed to elicit this response in non-transformed cells, suggesting a cancer specific role of LPA in regulation of glucose metabolism. While LPA had no effect on glucose uptake, we found that LPA altered expression of multiple genes involved in glucose metabolism. The most significant observation was that LPA treatment dramatically upregulated expression of HK-2, one of the rate-limiting glycolytic enzymes. We explored the underlying mechanism and found that LPA activates HK-2 transcription through LPA2-mediated activation of SREBP-1. Two sterol regulator elements (SREs) on the human HK-2 promoter were identified to be responsible for LPA activation of the promoter. DNA pulldown and chromatin immunoprecipitation assays confirmed that SREBP-1 bound to these SREs in LPA-treated cells. Although in ovarian cancer cells, LPA treatment also stabilized Hif-1α protein, an established activator of HK-2 and glycolysis, LPA-regulated HK-2 expression and glycolysis was largely independent of Hif-1α. These results established that LPA stimulates glycolysis via the LPA2-SREBP-HK-2 cascade in neoplastic cells. Taken together, this dissertation provides the first evidence for regulation of cancer cell metabolism by LPA. The results indicate that LPA signaling is causally linked to lipogenic and glycolytic phenotypes of cancer cells. Therefore, targeting the key LPA2 receptor could offer a novel and innovative approach to blocking tumor-specific metabolism

Visual Attention-based Small Screen Adaptation for H.264 Videos

We develop a framework that uses visual attention analysis combined with temporal coherence to detect the attended region from a H.264 video bitstream, and display it on a small screen. A visual attention module based upon Walther and Koch's model gives us the attended region in I-frames. We propose a temporal coherence matching framework that uses the motion information in P-frames to extend the attended region over the H.264 video sequence. Evaluations show encouraging results with over 80% successful detection rate for objects of interest, and 85% respondents claiming satisfactory output

Progressive Multifocal Leukoencephalopathy Presenting as Transverse Myelitis

Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating disease caused by reactivation of JC virus affecting typically subcortical and periventricular white matter of immunocompromised hosts (HIV infection, hematologic malignancies). We present an unusual case of PML predominantly affecting cervical spinal cord and brainstem in an immunocompetent host. A 65-year-old female presented with vertigo, hemiparesis and right sided weakness. MRI of the brain without contrast showed T2 signal abnormality involving the medulla extending into the upper cervical cord to C2-C3 level. Further work up showed positive ANA, elevated SS-A/Ro and SS-B/La antibodies consistent with Sjögren Syndrome. The patient deteriorated rapidly, expiring eight days after onset of acute respiratory failure. Autopsy showed multifocal white matter lesions with perivascular lymphocytic cuffing, microglial nodules, influx of activated microglial and numerous oligodendroglial nuclei with ground glass inclusions in the spinal cord, brain stem, cerebellum and cerebral hemisphere. The inclusions were immunoreactive with Simian virus-40 (SV-40), P53 and MIB-1 immunostains. The distributions of the lesions were predominantly in the medulla and upper cervical cord, correlating with pre-mortem MRI. A rare subset of PML cases can occur in association with connective tissue disorders (Sjögren in this case), Systemic Lupus Erythematosus (SLE) being the most common. Predominantly spinal involvement by PML is also rare. PML should be considered in the differential diagnosis of spinal cord/brainstem lesions, particularly in the patients with connective tissue disorders. This highlights the importance of post-mortem examination in selected cases without definite clinical diagnosis.https://scholarlycommons.henryford.com/merf2019caserpt/1068/thumbnail.jp

The Hospital Frailty Risk Score (HFRS) applied to primary data: protocol for a systematic review

Introduction Frailty is characterised by vulnerability to adverse health outcomes and increases with age. Many frailty risk scores have been developed. One important example is the Hospital Frailty Risk Score (HFRS) which has the potential to be widely used and automatically calculated which will provide accurate assessment of frailty in a time/cost-effective manner. This systematic review, therefore, seeks to describe the HFRS use since its publication in 2018. Methods and analysis The proposed systematic review will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We will include published original peer-reviewed articles, preprints, conference proceedings and letters to the editor reporting primary data where there is an English language abstract available from 1 January 2018 to 30 June 2022. Databases to be searched are MEDLINE, EMBASE and Web of Science. Additional studies from, for example, the reference of the included studies will be identified and assessed for potential inclusion. Two independent reviewers will perform and assess the following: (1) eligibility of the included studies, (2) critical appraisal using the Cochrane Risk of Bias in Non-randomized Studies of Interventions tool, and (3) data extraction using a predefined form. Disagreements will be resolved through discussions or by involvement of a third reviewer. It may be possible to undertake a meta-analysis if there are sufficient studies reporting effect measures in homogenous populations and/or settings. Effect sizes will be calculated using meta-analysis methods and expressed as risk ratios or ORs with 95% CIs. Ethics and dissemination No ethical approval is required for this systematic review as it will use secondary data only. The results of the systematic review will be submitted for publication in recognised peer-reviewed journals related to frailty and geriatric care and will be widely disseminated through conferences, congresses, seminars, symposia and scientific meetings

Follistatin-like 3 (FSTL3) mediated silencing of transforming growth factor (TGF ) signaling is essential for testicular aging and regulating testis size

Follistatin-like 3 (FSTL3) is a glycoprotein that binds and inhibits the action of TGFβ ligands such as activin. The roles played by FSTL3 and activin signaling in organ development and homeostasis are not fully understood. The authors show mice deficient in FSTL3 develop markedly enlarged testes that are also delayed in their age-related regression. These FSTL3 knockout mice exhibit increased Sertoli cell numbers, allowing for increased spermatogenesis but otherwise showing normal testicular function. The data show that FSTL3 deletion leads to increased AKT signaling and SIRT1 expression in the testis. This demonstrates a cross-talk between TGFβ ligand and AKT signaling and leads to a potential mechanism for increased cellular survival and antiaging. The findings identify crucial roles for FSTL3 in limiting testis organ size and promoting age-related testicular regression

Inhibition of Activin/Myostatin signalling impairs mouse testis Inhibition of Activin/Myostatin signalling induces skeletal muscle hypertrophy but impairs mouse testicular development

Numerous approaches are being developed to promote post-natal muscle growth based on attenuating Myostatin/Activin signalling for clinical uses such as the treatment neuromuscular diseases, cancer cachexia and sarcopenia. However there have been concerns about the effects of inhibiting Activin on tissues other than skeletal muscle. We intraperitoneally injected mice with the Activin ligand trap, sActRIIB, in young, adult and a progeric mouse model. Treatment at any stage in the life of the mouse rapidly increased muscle mass. However at all stages of life the treatment decreased the weights of the testis. Not only were the testis smaller, but they contained fewer sperm compared to untreated mice. We found that the hypertrophic muscle phenotype was lost after the cessation of sActRIIB treatment but abnormal testis phenotype persisted. In summary, attenuation of Myostatin/Activin signalling inhibited testis development. Future use of molecules based on a similar mode of action to promote muscle growth should be carefully profiled for adverse side-effects on the testis. However the effectiveness of sActRIIB as a modulator of Activin function provides a possible therapeutic strategy to alleviate testicular seminoma development

Inhibition of Activin/Myostatin signalling induces skeletal muscle hypertrophy but impairs mouse testicular development

Numerous approaches are being developed to promote post-natal muscle growth based on attenuating Myostatin/Activin signalling for clinical uses such as the treatment neuromuscular diseases, cancer cachexia and sarcopenia. However there have been concerns about the effects of inhibiting Activin on tissues other than skeletal muscle. We intraperitoneally injected mice with the Activin ligand trap, sActRIIB, in young, adult and a progeric mouse model. Treatment at any stage in the life of the mouse rapidly increased muscle mass. However at all stages of life the treatment decreased the weights of the testis. Not only were the testis smaller, but they contained fewer sperm compared to untreated mice. We found that the hypertrophic muscle phenotype was lost after the cessation of sActRIIB treatment but abnormal testis phenotype persisted. In summary, attenuation of Myostatin/Activin signalling inhibited testis development. Future use of molecules based on a similar mode of action to promote muscle growth should be carefully profiled for adverse side-effects on the testis. However the effectiveness of sActRIIB as a modulator of Activin function provides a possible therapeutic strategy to alleviate testicular seminoma development.Peer reviewe

Homologous and heterologous desensitization of guanylyl cyclase-B signaling in GH3 somatolactotropes

The guanylyl cyclases, GC-A and GC-B, are selective receptors for atrial and C-type natriuretic peptides (ANP and CNP, respectively). In the anterior pituitary, CNP and GC-B are major regulators of cGMP production in gonadotropes and yet mouse models of disrupted CNP and GC-B indicate a potential role in growth hormone secretion. In the current study, we investigate the molecular and pharmacological properties of the CNP/GC-B system in somatotrope lineage cells. Primary rat pituitary and GH3 somatolactotropes expressed functional GC-A and GC-B receptors that had similar EC50 properties in terms of cGMP production. Interestingly, GC-B signaling underwent rapid homologous desensitization in a protein phosphatase 2A (PP2A)-dependent manner. Chronic exposure to either CNP or ANP caused a significant down-regulation of both GC-A- and GC-B-dependent cGMP accumulation in a ligand-specific manner. However, this down-regulation was not accompanied by alterations in the sub-cellular localization of these receptors. Heterologous desensitization of GC-B signaling occurred in GH3 cells following exposure to either sphingosine-1-phosphate or thyrotrophin-releasing hormone (TRH). This heterologous desensitization was protein kinase C (PKC)-dependent, as pre-treatment with GF109203X prevented the effect of TRH on CNP/GC-B signaling. Collectively, these data indicate common and distinct properties of particulate guanylyl cyclase receptors in somatotropes and reveal that independent mechanisms of homologous and heterologous desensitization occur involving either PP2A or PKC. Guanylyl cyclase receptors thus represent potential novel therapeutic targets for treating growth-hormone-associated disorders