HMGB1 Enhances Drug Resistance and Promotes In Vivo Tumor Growth of Lung Cancer Cells.

Drug resistance is an obstacle in the chemotherapeutic treatment of lung cancers. In the present study, the effects of high-mobility group box 1 (HMGB1) protein in chemotherapeutic resistance and the relationships between HMGB1 and chemotherapy drug-induced cell apoptosis or necrosis were clarified. We used cisplatin-sensitive A549 cells and cisplatin-resistant A549/DDP cells as cell models with IC50 of 11.58 and 46.95 µM, respectively. A549/DDP had higher level of HMGB1 compared with A549 cells. Interestingly, with the increasing concentration of DDP, HMGB1 was gradually located into cytoplasm in cisplatin-sensitive A549 cells. Moreover, interference with endogenous HMGB1 sensitized the effects of chemotherapeutic drugs, including 5-Fu, DDP, and OXA. Furthermore, results from an in vivo tumorigenesis experiment demonstrated that serum concentration of HMGB1 was much lower in the group inoculated with HMGB1 shRNA-transfected A549 cells than in the N.C. shRNA-transfected A549 inoculated group, as well as the tumor volume, suggesting that serum HMGB1 contributed to tumor growth in a mouse model. In conclusion, higher levels of HMGB1 probably contributed to chemotherapy drug resistance, and higher serum concentration of HMGB1 promoted in vivo tumor growth. The study would provide new clues to overcome drug resistance in chemotherapy of human lung cancers.

Inflammation status of rabbit carotid artery model endothelium during intermittent hypoxia exposure and its relationship with leptin.

OBJECTIVES: To develop an intermittent hypoxia/reoxygenation (IH/ROX) rabbit carotid artery model and then investigate the inflammation status of rabbit carotid artery endothelium after IH exposure and its relationship with leptin. MATERIALS AND METHODS: After anesthetization, rabbit's right common carotid artery was cleared of surrounding tissue with anatomic microscope, cannulated to its distal part and the proximal part was ligated. Preparations were challenged by changing the PO(2) of the gas mixture equilibrating the perfusate. Alternate perfusing (2 mL/min) of equilibrated perfusate bubbled with normoxia or hypoxia gas mixtures formed IH/ROX cycles in the right carotid common artery, simulating the pattern of hypoxic episodes seen in obstructive sleep apnea (OSA), or continuous perfusing of hypoxia perfusate to form continuous hypoxia (CH) modes. Sixty adult male New Zealand White rabbits (2.5-3.0 kg) were separated into six groups, ten per group. Groups were: A, intermittent normoxia (IN) group, perfused with perfusion equilibrated with 21% O(2) [PO(2) about 141 +/- 2.87 mmHg] for 15 s and 21% O(2) for 1 min 45 s, 60 cycles; B, severe IH group, 5% O(2) [PO(2) about 35.2 +/- 1.27 mmHg] 15 s and 21% O(2) 1 min 45 s, 60 cycles; C, mild IH group, 10% O(2) [PO(2) about 54.3 +/- 3.31 mmHg] 15 s and 21% O(2) 1 min 45 s, 60 cycles; D, severe IH+Lep group, protocol was the same with severe IH group; E, CH group, IN for 1 h 45 min and then 5% O(2) for 15 min; and F, Lep group, the same with IN group. Right common carotid artery parts distal to the cannula were harvested after exposure, and endothelial cell layers were gotten from longitudinal outspread vessels. Nuclear factor kappaB (NFkappaB) DNA binding activities of partial cell layers were measured with electrophoretic mobility shift assay in the IN group, severe IH group, mild IH group, and CH group nuclear extracts. The other part of the cell layers in the IN group, severe IH group, severe IH+Lep group, and Lep group were cultured for 2 h, and during the culture procedure, recombinated human leptin solutions were added to culture dishes of severe IH+Lep group and Lep group (resulted concentration, 10 ng/mL). Enzyme-linked immunosorbent assay was used to analyze medium interleukin-6 (IL-6) concentrations, reverse transcription polymerase chain reaction was used to analyze endothelial cell Ras homology A (RhoA) mRNA expression levels. Statistical analysis was done with SPSS 11.5 software package. RESULTS: NFkappaB DNA binding activities were significantly different between groups (F = 112.428, P < 0.001). This activity in the severe IH group (4.27 +/- 0.64) was higher than that in the mild IH group (2.33 +/- 0.45, P < 0.001), IN group (1.00 +/- 0.26, P < 0.001), and CH group (1.15 +/- 0.36, P < 0.001). RhoA mRNA expression levels were different in groups (F = 26.634, P < 0.001).This level in the severe IH+Lep group (2.54 +/- 0.53) was higher than that in the severe IH group (1.57 +/- 0.44, P = 0.002), IN group (1.00 +/- 0.31, P < 0.001), and Lep group (1.31 +/- 0.30, P < 0.001). IL-6 concentrations were different in groups (F = 79.922, P < 0.001). IL-6 concentration in the severe IH+Lep group (1591.50 +/- 179.57 pg/mL) was higher than that in the severe IH group (1217.20 +/- 320.62 pg/mL, P = 0.036), IN group (325.40 +/- 85.26 pg/mL, P < 0.001), and Lep group (517.40 +/- 183.09 pg/mL, P < 0.001). CONCLUSIONS: IH/ROX activated the inflammation pathway significantly in the endothelium, which was more intensive than CH and intensity-dependent. When exposed to both IH/ROX and leptin, inflammation occurs more dramatically. It means that synergic activating roles were performed by IH/ROX and leptin. This study may have a clinical implication that IH can cause endothelial damage through activated inflammation in OSA patients, and if the OSA patients have obesity at the same time, the endothelial damage or the inflammation would be more significant because of elevated leptin level as a synergic factor.

[Carotid body inflammation and carotid sinus nerve afferent activity after intermittent hypoxia exposure of various frequencies in rabbits].

OBJECTIVE: To explore the inflammatory reactions, endothelin level and carotid sinus nerve (CSN) afferent activity of carotid body (CB) after intermittent hypoxia/reoxygenation (IH/ROX) exposure of various frequencies in rabbits. METHODS: Forty-nine male adult New Zealand white rabbits (2.5-3.0 kg) were separated into 7 groups (n = 7 each). After anesthetization, the right carotid artery and CSN were cleared of surrounding tissues without touching the right CB and the left carotid region. The CSN was unenveloped to partially expose the myelin sheath, and electrodes were placed to the "single" chemoreceptor bundle of the CSN, with CSN afferent activity carefully monitored and recorded. Then the right common carotid artery was exposed, cannulated to distal part and its proximal part was ligated. Preparations were challenged by changing the PO2 of the gas mixture equilibrating the perfusate. Alternatively perfusion (2 ml/min) of equilibrated perfusate bubbled with normoxia or hypoxia gas mixtures formed IH/ROX cycles in right carotid common artery, simulating the pattern of hypoxic episodes seen in obstructive sleep apnea, or with continuously perfusing hypoxia perfusate to form continuous hypoxia (CH) modes. Groups were defined with different frequencies, and groups were: intermittent normoxia group (IN group) (21% O2, 15 s; 21% O2, 1 min 45 s), 10/hr group (5% O2, 15 s; 21% O2, 5 min 45 s), 30/hr group (5% O2, 15 s; 21% O2, 1 min 45 s), 50/hr group (5% O2, 15 s; 21% O2, 57 s), 60/hr group (5% O2, 15 s; 21% O2, 45 s) and 90/hr group (5% O2, 15 s; 21% O2, 25 s). All the above groups were exposed to 60 treatment cycles; continuous hypoxia group (CH group), IN for 1 h 45 min and then 5% O2 for 15 min. After exposure and 30 min of static placing, CSN afferent frequencies (Charge F) were recorded from chemoreceptor bundles, and the right CB was cleared of surrounding tissues and harvested. Interleukin-6 (IL-6), endothelin-1 (ET-1), hypoxia-inducible factor-1 (HIF-1), and vascular endothelial growth factor (VEGF) concentrations of the CB lysate were measured with enzyme linked immuno sorbent assay (ELISA) kits and standardized. Data were analyzed with SPSS 12.0 software package; and after one way analysis of variance (ANOVA) for whole difference, Tamhane's T2 was used for post hoc analysis. RESULTS: IL-6, ET-1 and Charge F increased but then decreased with increasing IH frequencies (F = 25,601.39, 2390.48, 6945.84, all P values < 0.01). IL-6, ET-1 and Charge F levels in 50/hr group were the highest among groups. Charge F levels correlated significantly with IL-6 or ET-1 (with IL-6: r = 0.736, P < 0.01; with ET-1: r = 0.757, P < 0.01, respectively). IL-6, ET-1 and Charge F levels between IN group and CH group were not statistically different (all P values > 0.05). HIF-1 levels elevated gradually (F = 5241.10, P < 0.01) with increasing exposure frequencies, and the CH group had the highest value (all P values < 0.01). VEGF level in CH group was the highest in all groups (all P values < 0.01). CONCLUSIONS: After IH/ROX exposure, afferent activity of CB CSN increases, which significantly correlates with inflammation and vasomotor mechanism of CB. CB inflammation comes not from IH phases but from ROX phases. Increased CB CSN activity results in elevated SNA tension, which plays a key role in the pathogenesis of systemic hypertension. This procedure influenced by IH/ROX frequencies. CH for 15 min causes no definitely damages. However, HIF-1 and VEGF can be considered as members of adaptive pathway during IH/ROX exposure.