Extremely high Tp53 mutation load in esophageal squamous cell carcinoma in Golestan Province, Iran

Background

Golestan Province in northeastern Iran has one of the highest incidences of esophageal squamous cell carcinoma (ESCC) in the world with rates over 50 per 100,000 person-years in both sexes. We have analyzed TP53 mutation patterns in tumors from this high-risk geographic area in search of clues to the mutagenic processes involved in causing ESCC.

Methodology/Principal Findings

Biopsies of 119 confirmed ESCC tumor tissue from subjects enrolled in a case-control study conducted in Golestan Province were analyzed by direct sequencing of TP53 exons 2 through 11. Immunohistochemical staining for p53 was carried out using two monoclonal antibodies, DO7 and 1801. A total of 120 TP53 mutations were detected in 107/119 cases (89.9%), including 11 patients with double or triple mutations. The mutation pattern was heterogeneous with infrequent mutations at common TP53 “hotspots” but frequent transversions potentially attributable to environmental carcinogens forming bulky DNA adducts, including 40% at bases known as site of mutagenesis by polycyclic aromatic hydrocarbons (PAHs). Mutations showed different patterns according to the reported temperature of tea consumption, but no variation was observed in relation to ethnicity, tobacco or opium use, and alcoholic beverage consumption or urban versus rural residence.

Conclusion/Significance

ESCC tumors in people from Golestan Province show the highest rate of TP53 mutations ever reported in any cancer anywhere. The heterogeneous mutation pattern is highly suggestive of a causative role for multiple environmental carcinogens, including PAHs. The temperature and composition of tea may also influence mutagenesis.     

HMGB1 contributes to the development of acute lung injury after hemorrhage

High mobility group box 1 (HMGB1) is a novel late mediator of inflammatory responses that contributes to endotoxin-induced acute lung injury and sepsis-associated lethality. Although acute lung injury is a frequent complication of severe blood loss, the contribution of HMGB1 to organ system dysfunction in this setting has not been investigated. In this study, HMGB1 was detected in pulmonary endothelial cells and macrophages under baseline conditions. After hemorrhage, in addition to positively staining endothelial cells and macrophages, neutrophils expressing HMGB1 were present in the lungs. HMGB1 expression in the lung was found to be increased within 4 h of hemorrhage and then remained elevated for more than 72 h after blood loss. Neutrophils appeared to contribute to the increase in posthemorrhage pulmonary HMGB1 expression since no change in lung HMGB1 levels was found after hemorrhage in mice made neutropenic with cyclophosphamide. Plasma concentrations of HMGB1 also increased after hemorrhage. Blockade of HMGB1 by administration of anti-HMGB1 antibodies prevented hemorrhage-induced increases in nuclear translocation of NF-kappa B in the lungs and pulmonary levels of proinflammatory cytokines, including keratinocyte-derived chemokine, IL-6, and IL-1 beta. Similarly, both the accumulation of neutrophils in the lung as well as enhanced lung permeability were reduced when anti-HMGB1 antibodies were injected after hemorrhage. These results demonstrate that hemorrhage results in increased HMGB1 expression in the lungs, primarily through neutrophil sources, and that HMGB1 participates in hemorrhage-induced acute lung injury.     

IL-13 may mediate allergen-induced hyperresponsiveness independently of IL-5 or eotaxin by effects on airway smooth muscle

IL-13 is a mediator of allergen-induced airway hyperresponsiveness (AHR). The aim of this study was to evaluate whether eotaxin and IL-5 were implicated in the effects of IL-13 on allergen-induced AHR or whether IL-13 may exert its effects through direct actions on airway smooth muscle (ASM). To study this question airway inflammation and AHR were induced in mice by sensitization and subsequent challenge on three successive days with ovalbumin. A monoclonal anti-IL-13 antibody administered before each challenge significantly reduced AHR without affecting airway eosinophilia. No changes of mRNA in BAL and lung tissues or protein levels in BAL of IL-5 or eotaxin were found following anti-IL-13 treatment. Combined injection of monoclonal anti-IL-5 and antieotaxin antibodies before each antigen challenge blocked airway eosinophilia but failed to reduce AHR. IL-13 induced calcium transients in cultured murine ASM cells and augmented the calcium and contractile responses of these cells to leukotriene D4. These results suggest that IL-13 plays an important role in allergen-induced AHR and is important in the early phases of the inflammatory process. Its effects on AHR are mediated independently of IL-5 and eotaxin and may involve a direct effect on ASM to augment its responsiveness.     

Abnormalities in cartilage and bone development in the Apert syndrome FGFR2(+/S252W) mouse

Apert syndrome is an autosomal dominant disorder characterized by malformations of the skull, limbs and viscera. Two-thirds of affected individuals have a S252W mutation in fibroblast growth factor receptor 2 (FGFR2). To study the pathogenesis of this condition, we generated a knock-in mouse model with this mutation. The Fgfr2(+/S252W) mutant mice have abnormalities of the skeleton, as well as of other organs including the brain, thymus, lungs, heart and intestines. In the mutant neurocranium, we found a midline sutural defect and craniosynostosis with abnormal osteoblastic proliferation and differentiation. We noted ectopic cartilage at the midline sagittal suture, and cartilage abnormalities in the basicranium, nasal turbinates and trachea. In addition, from the mutant long bones, in vitro cell cultures grown in osteogenic medium revealed chondrocytes, which were absent in the controls. Our results suggest that altered cartilage and bone development play a significant role in the pathogenesis of the Apert syndrome phenotype.     

Kinetic measurement by LC/MS of gamma-glutamylcysteine ligase activity

gamma-Glutamylcysteine ligase (GCL) combines cysteine and glutamate through its gamma carboxyl moiety as the first step for glutathione (GSH) synthesis and is considered to be the rate-limiting enzyme in this pathway. The enzyme is a heterodimer, with a heavy catalytic and a light regulatory subunit, which plays a critical role in the anti-oxidant response. Besides the original method of Seelig designed for the measurement of a purified enzyme, few endpoint methods, often unrefined, are available for measuring it in complex biological samples. We describe a new, fast and reliable kinetic LC/MS method which enabled us to optimize its detection. l-2-Aminobutyrate is used instead of cysteine (to avoid glutathione synthetase interference) as triggering substrate with saturating concentrations of glutamate and ATP; the gamma glutamylaminobutyrate formed is measured at m/z=233 at regular time intervals. Reaction rate is maximum because ATP is held constant by enzymatic recycling of ADP by pyruvate kinase and phosphoenolpyruvate. The repeatability of the method is good, with CV% of 6.5 and 4% for catalytic activities at, respectively 0.9 and 34 U/l. The affinities of rat and human enzymes for glutamate and aminobutyrate are in good agreement with previous published data. However, unlike the rat enzyme, human GCL is not sensitive to reduced glutathione and displays a more basic optimum pH.     

Neurogenesis and neuronal communication on micropatterned neurochips

Neural networks are formed by accurate connectivity of neurons and glial cells in the brain. These networks employ a three-dimensional bio-surface that both assigns precise coordinates to cells during development and facilitates their connectivity and functionality throughout life. Using specific topographic and chemical features, we have taken steps towards the development of poly(dimethylsiloxane; PDMS) neurochips that can be used to generate and study synthetic neural networks. These neurochips have micropatterned structures that permit adequate cell positioning and support cell survival. Within days of plating, cells differentiate into neurons displaying excitability and communication, as evidenced by intracellular calcium oscillations and action potentials. The structural and functional capacities of such simple neural networks open up new opportunities to study synaptic communication and plasticity.     

Stochastic boundary molecular dynamics simulation of L-ribose in the active site of Actinoplanes missouriensis xylose isomerase and its Val135Asn mutant with improved reaction rate

We used molecular dynamics simulations to study how a non-natural substrate, L-ribose, interacts with the active site of Actinoplanes missouriensis xylose isomerase. The simulations showed that L-ribose does not stay liganded in the active site in the same way as D-xylose, in which the oxygens O2 and O4 are liganded to the metal M1. The oxygen O4 of L-ribose moved away from the metal M1 to an upside down position. Furthermore, the distances of the carbons C1 and C2 of L-ribose to the catalytic metal M2 were higher than in the case of D-xylose. These findings explain the extremely low reaction rate of xylose isomerase with L-ribose. The mutation V135N close to the C5-OH of the substrate increased the reaction efficiency 2- to 4-fold with L-ribose. V135N did not affect the reaction with D-xylose and L-arabinose, whereas the reaction with D-glucose was impaired, probably due to a hydrogen bond between Asn-135 and the substrate. When L-ribose was the substrate, Asn-135 formed a hydrogen bond to Glu-181. As a consequence, O4 of L-ribose stayed liganded to the metal M1 in the V135N mutant in molecular dynamics simulations. This explains the decreased K(m) of the V135N mutant with L-ribose.     

Global natural regulatory T cell depletion in active systemic lupus erythematosus

The immune defect that could account for the multisystemic involvement that characterizes systemic lupus erythematosus (SLE) remains unknown. We hypothesized that iterative disease flares correspond to a recurrent defect in the peripheral immune suppression exerted by naturally occurring T regulatory cells (Tregs). Surprisingly, Tregs isolated from lupus patients show the same phenotypic and functional characteristics as corresponding cells found in healthy controls. A decrease in the proportion of circulating Tregs among other CD4+ T cells is nevertheless evidenced in active patients when this group is compared with healthy controls (0.57 +/- 0.24%, n = 45 vs 1.29 +/- 0.38%, n = 82, p < 0.0001) or with inactive patients (1.22 +/- 0.67%, n = 62, p < 0.0001). In contrast, the proportion of Tregs in other systemic autoimmune diseases such as primary Sj?gren syndrome and inflammatory myopathy does not significantly differ from controls' values (1.15 +/- 0.46%, n = 21, p = 0.09 and 1.16 +/- 0.44%, n = 16, p = 0.43, respectively). Lupus Tregs do not accumulate in either the lymph nodes or the diseased kidneys and are not killed by a circulating soluble factor, but demonstrate in vitro a heightened sensitivity to Fas-induced apoptosis. Finally, we show that the extent of Treg depletion correlates with the clinical severity of the flare. SLE flares are therefore associated with a global Treg depletion and not with a phenomenon of tissue redistribution. In summary, we suggest that the physiopathology of SLE could be tied to a defect in the homeostatic control of the Treg subpopulation.     

Long-term effects of the PPAR gamma activator pioglitazone on cardiac inflammation in stroke-prone spontaneously hypertensive rats

We investigated the long-term effects of the thiazolidinedione PPARgamma activator pioglitazone on cardiac inflammation in stroke-prone spontaneously hypertensive rats (SHRSP), a model of malignant of hypertension. Six-week-old SHRSP were treated with pioglitazone (10 mg/kg per day p.o.) for 20 weeks. The rise in systolic blood pressure (SBP) in SHRSP was only transiently and slightly attenuated by pioglitazone (P < 0.05). On one hand, cardiac hypertrophy was little affected by the pioglitazone treatment, and there was only a reduction of subepicardial interstitial fibrosis. On the other hand, left ventricular NFkappaB and AP-1 binding activities, the expression of TNFalpha, and the adhesion of molecule PECAM were significantly decreased by pioglitazone treatment. Expression of the pro-apoptotic proteins p53 and bax was significantly increased by pioglitazone. Thus, pioglitazone-attenuated cardiac inflammation in SHRSP had little effect on BP or cardiac hypertrophy. PPARgamma activation may play a preventive cardiovascular role by offsetting the cardiac inflammatory response as demonstrated in this genetic model of malignant hypertension.