Sinoatrial node toxicity after stereotactic ablative radiation therapy to lung tumors.
Practical radiation oncology
Glucocorticoids enhance muscle endurance and ameliorate Duchenne muscular dystrophy through a defined metabolic program.
Proceedings of the National Academy of Sciences of the United States of America
2015; 112 (49): E6780–9
Stereotactic ablative radiation therapy (SABR) is an established treatment for selected lung tumors. Sinoatrial node (SAN) toxicity after thoracic SABR has not been reported in the literature. We sought to understand the risk of SAN toxicity owing to incidental dose to the SAN from SABR.We conducted a retrospective review of patients with early-stage lung cancer or limited pulmonary metastases who underwent thoracic SABR to a right-sided central lung tumor (within 2 cm of the mainstem bronchus or other mediastinal structures) between January 2008 and December 2014, analyzed a subset whose treatment imparted dose to the SAN exceeding 10% of the prescription dose, and examined patient and treatment dosimetric characteristics. Mean follow-up interval was 28 months. Time to toxicity was defined from start of SABR.Of 47 patients with central tumors in the right lung treated with SABR reviewed, 13 met our study criteria. A contouring atlas of regional cardiac anatomy was created. One patient treated with SABR for non-small cell lung cancer at the right hilum developed symptomatic sick sinus syndrome, requiring pacemaker placement 6 months after treatment. Her acute presentation and short interval between SABR and onset of symptoms suggest that SAN toxicity was likely due to radiation-induced injury. Both her age and mean dose to her SAN were the third highest in our cohort. She remained free from cancer progression at 24 months' follow-up. Twelve additional patients who received significant dose to the SAN from SABR did not develop toxicity.While uncommon, SAN toxicity from SABR to right-sided central thoracic tumors should be recognized and followed in future studies.
View details for PubMedID 28669706
miR-222 is necessary for exercise-induced cardiac growth and protects against pathological cardiac remodeling.
2015; 21 (4): 584–95
Classic physiology studies dating to the 1930s demonstrate that moderate or transient glucocorticoid (GC) exposure improves muscle performance. The ergogenic properties of GCs are further evidenced by their surreptitious use as doping agents by endurance athletes and poorly understood efficacy in Duchenne muscular dystrophy (DMD), a genetic muscle-wasting disease. A defined molecular basis underlying these performance-enhancing properties of GCs in skeletal muscle remains obscure. Here, we demonstrate that ergogenic effects of GCs are mediated by direct induction of the metabolic transcription factor KLF15, defining a downstream pathway distinct from that resulting in GC-related muscle atrophy. Furthermore, we establish that KLF15 deficiency exacerbates dystrophic severity and muscle GC-KLF15 signaling mediates salutary therapeutic effects in the mdx mouse model of DMD. Thus, although glucocorticoid receptor (GR)-mediated transactivation is often associated with muscle atrophy and other adverse effects of pharmacologic GC administration, our data define a distinct GR-induced gene regulatory pathway that contributes to therapeutic effects of GCs in DMD through proergogenic metabolic programming.
View details for DOI 10.1073/pnas.1512968112
View details for PubMedID 26598680
View details for PubMedCentralID PMC4679037
Kruppel-like factor 15 is a critical regulator of cardiac lipid metabolism.
The Journal of biological chemistry
2014; 289 (9): 5914–24
Exercise induces physiological cardiac growth and protects the heart against pathological remodeling. Recent work suggests exercise also enhances the heart's capacity for repair, which could be important for regenerative therapies. While microRNAs are important in certain cardiac pathologies, less is known about their functional roles in exercise-induced cardiac phenotypes. We profiled cardiac microRNA expression in two distinct models of exercise and found microRNA-222 (miR-222) was upregulated in both. Downstream miR-222 targets modulating cardiomyocyte phenotypes were identified, including HIPK1 and HMBOX1. Inhibition of miR-222 in vivo completely blocked cardiac and cardiomyocyte growth in response to exercise while reducing markers of cardiomyocyte proliferation. Importantly, mice with inducible cardiomyocyte miR-222 expression were resistant to adverse cardiac remodeling and dysfunction after ischemic injury. These studies implicate miR-222 as necessary for exercise-induced cardiomyocyte growth and proliferation in the adult mammalian heart and show that it is sufficient to protect the heart against adverse remodeling.
View details for DOI 10.1016/j.cmet.2015.02.014
View details for PubMedID 25863248
View details for PubMedCentralID PMC4393846
Kruppel-like factor 15 regulates skeletal muscle lipid flux and exercise adaptation.
Proceedings of the National Academy of Sciences of the United States of America
2012; 109 (17): 6739–44
The mammalian heart, the body's largest energy consumer, has evolved robust mechanisms to tightly couple fuel supply with energy demand across a wide range of physiologic and pathophysiologic states, yet, when compared with other organs, relatively little is known about the molecular machinery that directly governs metabolic plasticity in the heart. Although previous studies have defined Kruppel-like factor 15 (KLF15) as a transcriptional repressor of pathologic cardiac hypertrophy, a direct role for the KLF family in cardiac metabolism has not been previously established. We show in human heart samples that KLF15 is induced after birth and reduced in heart failure, a myocardial expression pattern that parallels reliance on lipid oxidation. Isolated working heart studies and unbiased transcriptomic profiling in Klf15-deficient hearts demonstrate that KLF15 is an essential regulator of lipid flux and metabolic homeostasis in the adult myocardium. An important mechanism by which KLF15 regulates its direct transcriptional targets is via interaction with p300 and recruitment of this critical co-activator to promoters. This study establishes KLF15 as a key regulator of myocardial lipid utilization and is the first to implicate the KLF transcription factor family in cardiac metabolism.
View details for DOI 10.1074/jbc.M113.531384
View details for PubMedID 24407292
View details for PubMedCentralID PMC3937660
Elevated fibroblast growth factor-2 increases tumor necrosis factor-alpha induced endothelial cell death in high glucose.
Journal of cellular physiology
2008; 217 (1): 86–92
The ability of skeletal muscle to enhance lipid utilization during exercise is a form of metabolic plasticity essential for survival. Conversely, metabolic inflexibility in muscle can cause organ dysfunction and disease. Although the transcription factor Kruppel-like factor 15 (KLF15) is an important regulator of glucose and amino acid metabolism, its endogenous role in lipid homeostasis and muscle physiology is unknown. Here we demonstrate that KLF15 is essential for skeletal muscle lipid utilization and physiologic performance. KLF15 directly regulates a broad transcriptional program spanning all major segments of the lipid-flux pathway in muscle. Consequently, Klf15-deficient mice have abnormal lipid and energy flux, excessive reliance on carbohydrate fuels, exaggerated muscle fatigue, and impaired endurance exercise capacity. Elucidation of this heretofore unrecognized role for KLF15 now implicates this factor as a central component of the transcriptional circuitry that coordinates physiologic flux of all three basic cellular nutrients: glucose, amino acids, and lipids.
View details for DOI 10.1073/pnas.1121060109
View details for PubMedID 22493257
View details for PubMedCentralID PMC3340075
A porous photocurable elastomer for cell encapsulation and culture.
2007; 28 (32): 4826–35
Glucose and tumor necrosis factor-alpha (TNFalpha) concentrations are elevated in diabetes. Both of these factors correlate with diabetic vasculopathy and endothelial cell apoptosis, yet their combined effects have not been measured. We have previously shown that the angiogenic growth factor fibroblast growth factor-2 (FGF-2), which is generally protective against endothelial cell death, is similarly elevated in high glucose conditions. We therefore investigated the effect of TNFalpha on endothelial cell death under normal and elevated glucose conditions, with a particular focus on FGF-2. Porcine aortic endothelial cells were cultured in 5 and 30 mM glucose and stimulated with TNFalpha, together with FGF-2 or a neutralizing FGF-2 antibody. Cell death was measured via cell counts or an annexin apoptotic assay, and cell cycle phase was determined by propidium iodide labeling. TNFalpha-induced endothelial cell death increased for cells in high glucose, and cell death was enhanced with increasing FGF-2 exposure and negated by a neutralizing FGF-2 antibody. Endothelial cells were most susceptible to TNFalpha-induced cell death when stimulated with FGF-2 18 h prior to TNFalpha, corresponding to cell entry into S phase of the proliferative cycle. The FGF-2 associated increase in TNFalpha-induced cell death was negated by blocking cell entry into S phase. Endothelial cell release of FGF-2 in high glucose leads to cell cycle progression, which makes cells more susceptible to TNFalpha-induced cell death. These data suggest that growth factor outcomes in high glucose depend on secondary mediators such as cytokines and stimulation cell cycle timing.
View details for DOI 10.1002/jcp.21476
View details for PubMedID 18446810
View details for PubMedCentralID PMC2838244
Encapsulating cells within a polymer matrix creates a three-dimensional (3D) scaffold that may more accurately represent the native microenvironment and cell organization. Here we report a porous scaffold prepared from a photocurable elastomer, poly(glycerolco-sebacate)-acrylate (PGSA). The scaffold porosity, swelling, mass loss, toxicity and mechanical properties, suggest that porous PGSA could be used to support the growth and differentiation of encapsulated cells. Neuroblastoma (NB) and human embryonic stem cells (hESCs) were encapsulated into the matrix and found to adhere to the material and interact with each other within 24h. After 7 days, encapsulated NB cells were found to grow, and form matrix fibrils and tissue. Undifferentiated hESCs proliferated and differentiated in the PGSA scaffold. In vivo experiments showed that both porous scaffolds have similar biocompatibility profiles as non-porous PGSA, but porous PGSA promotes tissue ingrowth, as compared to non-porous PGSA. We therefore propose that porous PGSA scaffolds can provide a logistical template for 3D growth of cells and tissue engineering.
View details for DOI 10.1016/j.biomaterials.2007.07.039
View details for PubMedID 17692371