Novel Correlation between TGF-ß1/-ß3 and Hormone Receptors in the Human Corneal Stroma.

This study investigated the interplay between transforming growth factor beta (TGF-ß1/T1 and TGF-ß3/T3), and sex hormone receptors using our 3D in vitro cornea stroma model. Primary human corneal fibroblasts (HCFs) from healthy donors were plated in transwells at 106 cells/well and cultured for four weeks. HCFs were supplemented with stable vitamin C (VitC) and stimulated with T1 or T3. 3D construct proteins were analyzed for the androgen receptor (AR), progesterone receptor (PR), estrogen receptor alpha (ERα) and beta (ERß), luteinizing hormone receptor (LHR), follicle-stimulating hormone receptor (FSHR), gonadotropin-releasing hormone receptor (GnRHR), KiSS1-derived peptide receptor (KiSS1R/GPR54), and follicle-stimulating hormone subunit beta (FSH-B). In female constructs, T1 significantly upregulated AR, PR, ERα, FSHR, GnRHR, and KiSS1R. In male constructs, T1 significantly downregulated FSHR and FSH-B and significantly upregulated ERα, ERß, and GnRHR. T3 caused significant upregulation in expressions PR, ERα, ERß, LHR, FSHR, and GNRHR in female constructs, and significant downregulation of AR, ERα, and FSHR in male constructs. Semi-quantitative Western blot findings present the interplay between sex hormone receptors and TGF-ß isoforms in the corneal stroma, which is influenced by sex as a biological variable (SABV). Additional studies are warranted to fully delineate their interactions and signaling mechanisms.

Potentiation of Sphingolipids and TGF-ß in the human corneal stroma reveals intricate signaling pathway crosstalks.

Corneal haze brought on by fibrosis due to insult can lead to partial or complete vision loss. Currently, corneal transplantation is the gold standard for treating severe corneal fibrosis, which comes with the risk of rejection and the issue of donor tissue shortages. Sphingolipids (SPLs) are known to be associated with fibrosis in various tissues and organs, including the cornea. We previously reported that SPLs are tightly related to Transforming Growth Factor ß (TGF-ß) signaling and corneal fibrogenesis. This study aimed to elucidate the interplay of SPLs, specifically sphingosine-1-phosphate (S1P) signaling, and its' interactions with TGF-ß signaling through detailed analyses of the corresponding downstream signaling targets in the context of corneal fibrosis, in vitro. Healthy human corneal fibroblasts (HCFs) were isolated, plated on polycarbonate membranes, and stimulated with a stable Vitamin C derivative. The 3D constructs were treated with either 5 µM sphingosine-1-phosphate (S1P), 5 µM SPHK I2 (I2; inhibitor of sphingosine kinase 1, one of the two enzymes responsible for generating S1P in mammalian cells), 0.1 ng/mL TGF-ß1, or 0.1 ng/mL TGF-ß3. Cultures with control medium-only served as controls. All 3D constructs were examined for protein expression of fibrotic markers, SPLs, TGF-ßs, and relevant downstream signaling pathways. This data revealed no significant changes in any LTBP (latent TGF-ß binding proteins) expression when stimulated with S1P or I2. However, LTBP1 was significantly upregulated via stimulation of TGF-ß1 and TGF-ß3, whereas LTBP2 was significantly upregulated only with TGF-ß3 stimulation. Significant downregulation of TGF-ß receptor II (TGF-ßRII) following S1P stimulation but significant upregulation following I2 stimulation was observed. Following TGF-ß1, S1P, and I2 stimulation, phospho-SMAD2 (pSMAD2) was significantly downregulated. Furthermore, I2 stimulation led to significant downregulation of SMAD4. Adhesion/proliferation/transcription regulation targets, SRC, FAK, and pERK 1/2 were all significantly downregulated by exogenous S1P, whereas I2 only significantly downregulated FAK. Exogenous TGF-ß3 caused significant upregulation of AKT. Interestingly, both I2 and TGF-ß3 caused significant downregulation of JNK expression. Lastly, TGF-ß1 led to significant upregulation of sphingosine kinase 1 (SphK1) and sphingosine-1-phosphate receptor 3 (S1PR3), whereas TGF-ß3 caused significant upregulation of only SphK1. Together with previously published work from our group and others, S1P inhibition exhibits great potential as an efficacious anti-fibrotic modality in human corneal stromal ECM. The current findings shed further light on a very complex and rather incompletely investigated mechanism, and cement the intricate crosstalk between SPLs and TGF-ß in corneal fibrogenesis. Future studies will dictate the potential of utilizing SPLs/TGF-ß signaling modulators as novel therapeutics in corneal fibrosis.

Increased platelet activation in sleep apnea subjects with intermittent hypoxemia.

PURPOSE: Obstructive sleep apnea (OSA) is independently associated with increased risk for stroke and other cardiovascular diseases. Since activated platelets play an important role in cardiovascular disease, the objective of this study was to determine whether platelet reactivity was altered in OSA subjects with intermittent nocturnal hypoxemia. METHODS: Thirty-one subjects, without hypertension or cardiovascular disease and not taking medication, participated in the study. Subjects were stratified based on OSA-related oxygen desaturation index (ODI) recorded during overnight polysomnography. Platelet reactivity to a broad panel of agonists (collagen, thrombin, protease-activated receptor1 hexapeptide, epinephrine, ADP) was measured by monitoring platelet aggregation and ATP secretion. Expression of platelet activation markers CD154 (CD40L) and CD62P (P-selectin) and platelet-monocyte aggregates (PMA) was quantified by flow cytometry. RESULTS: Epinephrine-induced platelet aggregation was substantially decreased in OSA subjects with significant intermittent hypoxemia (ODI ≥ 15) compared with subjects with milder hypoxemia levels (ODI < 15) (area under curve, p = 0.01). In addition, OSA subjects with ODI ≥ 15 exhibited decreased thrombin-induced platelet aggregation (p = 0.02) and CD40L platelet surface expression (p = 0.05). Platelet responses to the other agonists, CD62P platelet surface expression, and PMA levels were not significantly different between groups. Reduction in platelet responses to epinephrine and thrombin, and decreased CD40L surface marker expression in significant hypoxemic OSA individuals, is consistent with their platelets being in an activated state. CONCLUSIONS: Increased platelet activation was present in otherwise healthy subjects with intermittent nocturnal hypoxemia due to underlying OSA. This prothrombotic milieu in the vasculature is likely a key contributing factor toward development of thrombosis and cardiovascular disease. TRIAL REGISTRATION: NCT00859950.

Inflammasomes: molecular regulation and implications for metabolic and cognitive diseases.

Inflammasomes are specialized signaling platforms critical for the regulation of innate immune and inflammatory responses. Various NLR family members (i.e., NLRP1, NLRP3, and IPAF) as well as the PYHIN family member AIM2 can form inflammasome complexes. These multi-protein complexes activate inflammatory caspases (i.e., caspase-1) which in turn catalyze the maturation of select pro-inflammatory cytokines, including interleukin (IL)-1ß and IL-18. Activation of the NLRP3 inflammasome typically requires two initiating signals. Toll-like receptor (TLR) and NOD-like receptor (NLR) agonists activate the transcription of pro-inflammatory cytokine genes through an NF-κB-dependent priming signal. Following exposure to extracellular ATP, stimulation of the P2X purinoreceptor-7 (P2X7R), which results in K(+) efflux, is required as a second signal for NLRP3 inflammasome formation. Alternative models for NLRP3 activation involve lysosomal destabilization and phagocytic NADPH oxidase and/or mitochondria-dependent reactive oxygen species (ROS) production. In this review we examine regulatory mechanisms that activate the NLRP3 inflammasome pathway. Furthermore, we discuss the potential roles of NLRP3 in metabolic and cognitive diseases, including obesity, type 2 diabetes mellitus, Alzheimer's disease, and major depressive disorder. Novel therapeutics involving inflammasome activation may result in possible clinical applications in the near future.

Therapeutic potential of heme oxygenase-1/carbon monoxide in lung disease.

Heme oxygenase (HO), a catabolic enzyme, provides the rate-limiting step in the oxidative breakdown of heme, to generate carbon monoxide (CO), iron, and biliverdin-IXα. Induction of the inducible form, HO-1, in tissues is generally regarded as a protective mechanism. Over the last decade, considerable progress has been made in defining the therapeutic potential of HO-1 in a number of preclinical models of lung tissue injury and disease. Likewise, tissue-protective effects of CO, when applied at low concentration, have been observed in many of these models. Recent studies have expanded this concept to include chemical CO-releasing molecules (CORMs). Collectively, salutary effects of the HO-1/CO system have been demonstrated in lung inflammation/acute lung injury, lung and vascular transplantation, sepsis, and pulmonary hypertension models. The beneficial effects of HO-1/CO are conveyed in part through the inhibition or modulation of inflammatory, apoptotic, and proliferative processes. Recent advances, however, suggest that the regulation of autophagy and the preservation of mitochondrial homeostasis may serve as additional candidate mechanisms. Further preclinical and clinical trials are needed to ascertain the therapeutic potential of HO-1/CO in human clinical disease.

Genetically manipulated mouse models of lung disease: potential and pitfalls.

Gene targeting in mice (transgenic and knockout) has provided investigators with an unparalleled armamentarium in recent decades to dissect the cellular and molecular basis of critical pathophysiological states. Fruitful information has been derived from studies using these genetically engineered mice with significant impact on our understanding, not only of specific biological processes spanning cell proliferation to cell death, but also of critical molecular events involved in the pathogenesis of human disease. This review will focus on the use of gene-targeted mice to study various models of lung disease including airways diseases such as asthma and chronic obstructive pulmonary disease, and parenchymal lung diseases including idiopathic pulmonary fibrosis, pulmonary hypertension, pneumonia, and acute lung injury. We will attempt to review the current technological approaches of generating gene-targeted mice and the enormous dataset derived from these studies, providing a template for lung investigators.

Autophagy in inflammatory diseases.

Autophagy provides a mechanism for the turnover of cellular organelles and proteins through a lysosome-dependent degradation pathway. During starvation, autophagy exerts a homeostatic function that promotes cell survival by recycling metabolic precursors. Additionally, autophagy can interact with other vital processes such as programmed cell death, inflammation, and adaptive immune mechanisms, and thereby potentially influence disease pathogenesis. Macrophages deficient in autophagic proteins display enhanced caspase-1-dependent proinflammatory cytokine production and the activation of the inflammasome. Autophagy provides a functional role in infectious diseases and sepsis by promoting intracellular bacterial clearance. Mutations in autophagy-related genes, leading to loss of autophagic function, have been implicated in the pathogenesis of Crohn's disease. Furthermore, autophagy-dependent mechanisms have been proposed in the pathogenesis of several pulmonary diseases that involve inflammation, including cystic fibrosis and pulmonary hypertension. Strategies aimed at modulating autophagy may lead to therapeutic interventions for diseases associated with inflammation.