Astrid Hjelde

Monitoring of hexyl 5-aminolevulinate-induced photodynamic therapy in rat bladder cancer by optical spectroscopy

Monitoring of the tissue response to photodynamic therapy (PDT) can provide important information to help optimize treatment variables such as drug and light dose, and possibly predict treatment outcome. A urinary bladder cancer cell line (AY-27) was used to induce orthotopic transitional cell carcinomas (TCC) in female Fischer rats, and hexyl 5-aminolevulinate (HAL, 8 mM, 1 h)-induced PDT was performed on day 14 after instillation of the cancer cells (20 J/cm(2) fluence at 635 nm). In vivo optical reflectance and fluorescence spectra were recorded from bladders before and after laser treatment with a fiberoptic probe. Calculated fluorescence bleaching and oxygen saturation in the bladder wall were examined and correlated to histology results. Reflectance spectra were analyzed using a three-layer optical photon transport model. Animals with TCC treated with PDT showed a clear treatment response; decreased tissue oxygenation and protoporphyrin IX (PpIX) fluorescence photobleaching were observed. Histology demonstrated that 3 of 6 animals with treatment had no sign of the tumor 7 days after PDT treatment. The other 3 animals had significantly reduced the tumor size. The most treatment-responsive animals had the highest PpIX fluorescence prior to light irradiation. Thus, optical spectroscopy can provide useful information for PDT. The model has proved to be very suitable for bladder cancer studies.

Venous gas embolism as a predictive tool for improving CNS decompression safety

A key process in the pathophysiological steps leading to decompression sickness (DCS) is the formation of inert gas bubbles. The adverse effects of decompression are still not fully understood, but it seems reasonable to suggest that the formation of venous gas emboli (VGE) and their effects on the endothelium may be the central mechanism leading to central nervous system (CNS) damage. Hence, VGE might also have impact on the long-term health effects of diving. In the present review, we highlight the findings from our laboratory related to the hypothesis that VGE formation is the main mechanism behind serious decompression injuries. In recent studies, we have determined the impact of VGE on endothelial function in both laboratory animals and in humans. We observed that the damage to the endothelium due to VGE was dose dependent, and that the amount of VGE can be affected both by aerobic exercise and exogenous nitric oxide (NO) intervention prior to a dive. We observed that NO reduced VGE during decompression, and pharmacological blocking of NO production increased VGE formation following a dive. The importance of micro-nuclei for the formation of VGE and how it can be possible to manipulate the formation of VGE are discussed together with the effects of VGE on the organism. In the last part of the review we introduce our thoughts for the future, and how the enigma of DCS should be approached.

Tissue responses to hexyl 5-aminolevulinate-induced photodynamic treatment in syngeneic orthotopic rat bladder cancer model: possible pathways of action.

Orthotopic bladder cancer model in rats mimics human bladder cancer with respect to urothelial tumorigenesis and progression. Utilizing this model at pT1 (superficial stage), we analyze the tissue responses to hexyl 5-aminolevulinate-induced photodynamic therapy (HAL-PDT). In comparison to untreated rats, HAL-PDT causes little change in tumor-free rat bladder but induces inflammatory changes with increased lymphocytes and mononuclear cell infiltration in rat bladders with tumor. Immunohistochemistry reveals that HAL-PDT is without effect on proliferating cell nuclear antigen expression within the tumor and increases caspase-3 expression in both normal urothelium and the tumor. Transmission electron microscopy reveals severe mitochondrial damage, formations of apoptotic bodies, vacuoles, and lipofuscin bodies, but no microvillus-formed niches in HAL-PDT-treated bladder cancer rats. Bioinformatics analysis of the gene expression profile indicates an activation of T-cell receptor signaling pathway in bladder cancer rats without PDT. HAL-PDT increases the expression of CD3 and CD45RA in the tumor (determined by immunohistochemistry). We suggest that pathways of action of HAL-PDT may include, at least, activations of mitochondrial apoptosis and autophagy, breakdown of cancer stem cell niches, and importantly, enhancement of T-cell activation.

Aortic Function in Rats After Decompression Without Ultrasonically Detectable Bubble Formation

BACKGROUND Several studies have demonstrated an adverse effect of bubbles on endothelial function. The degree of dysfunction appears to be related to the number of bubbles present. The aim of the study was to determine whether decompression without bubble formation visible by ultrasound had any effect on arterial endothelial function. METHODS We decompressed 21 Sprague-Dawley rats weighing 215-260 g from 700 kPa (approximately 6.9 ATA) in a dry hyperbaric chamber followed by a 1-h observation period and measured aortic endothelial-dependent relaxation to acetylcholine. Later, we determined the specific weight of the brain as a measure of edema formation and vascular bubbles in the arterial circulation. RESULTS No bubbles were seen in the pulmonary arteries of seven rats. We found a significant lower vasodilatory response to acetylcholine in the decompressed rats (44% +/- 14%) compared to the control rats (58% +/- 12%) as a sign of endothelial dysfunction. There was no significant difference between the two groups in the specific gravity of the brain. CONCLUSION We conclude that measurable arterial dysfunction in the aorta can occur even if no visible venous bubble formation is seen. There are no results in this study suggesting that these rats had damaged blood-brain barriers or brain edema.

Evaluation of cerebral gas retention and oedema formation in decompressed rats by using a simple gravimetric method.

Objective: The objective of the study is twofold: first, to develop a specific gravity method for distinguishing between bubbles and oedema following decompression, and, second, to evaluate the extent to which the change in specific gravity is due to retained gas in cerebral tissue. Methods: A brombenzene/kerosene gradient column was used to measure changes in brain specific gravity at 100 and 300 kPa, respectively. This study was performed on 23 rats. Non-exposed rats constituted the control group A (n = 6). The exposed animals were divided into two groups according to the number of bubbles they developed upon decompression; group B (bubble grade 0-2, n = 9) and group C (bubble grade 3-5, n = 8). Results: Cerebral gas retention was determined by increasing the pressure on the gradient column from 100 to 300 kPa. Median specific gravity of the brain at 300 kPa bar was significantly higher compared to 100 kPa for the decompressed groups B (p = 0.018) and C (p = 0.012), thus implying gas retention. The cerebral gas volume was significantly higher for rats with a high bubble score compared to rats with a low bubble score (p = 0.043). However, the major contribution to the change in specific gravity was due to oedema formation. Conclusion: The brombenzene/kerosene gradient column was found to be a sensitive method for distinguishing between gas retention and oedema formation in decompressed animals. There was a higher gas retention in rats with a high bubble score compared to rats with a low bubble score. The major contribution to the change in specific gravity in decompressed animals is due to oedema formation.

Blood gene expression and vascular function biomarkers in professional saturation diving

Saturation diving is an established way to conduct subsea operations with human intervention. While working, the divers must acclimatize to the hyperbaric environments. In this study, genome-wide gene expression and selected plasma biomarkers for vascular function were investigated. We also examined whether antioxidant vitamin supplements affected the outcome. The study included 20 male professional divers, 13 of whom took vitamin C and E supplements in doses of 1,000 and 30 mg daily during saturation periods that lasted 7–14 days. The dives were done in a heliox atmosphere with 40 kPa oxygen partial pressure (ppO2) to a depth of 100–115 m of sea-water (msw), from which the divers performed in-water work excursions to a maximum depth of 125 msw with 60 kPa ppO2. Venous blood was collected immediately before and after saturation. Following gene expression profiling, post-saturation gene activity changes were analyzed. Protein biomarkers for inflammation, endothelial function, and fibrinolysis: Il-6, CRP, ICAM-1, fibrinogen, and PAI-1, were measured in plasma. Post-saturation gene expression changes indicated acclimatization to elevated ppO2 by extensive downregulation of factors involved in oxygen transport, including heme, hemoglobin, and erythrocytes. Primary endogenous antioxidants; superoxide dismutase 1, catalase, and glutathione synthetase, were upregulated, and there was increased expression of genes involved in immune activity and inflammatory signaling pathways. The antioxidant vitamin supplements had no effect on post-saturation gene expression profiles or vascular function biomarkers, implying that the divers preserved their homeostasis through endogenous antioxidant defenses.

Evaluating PAI-1 as a biomarker for stress in diving: human serum total PAI-1 is unaltered after 2 h dry exposures to 280 kPa hyperbaric air

Plasminogen activator inhibitor (PAI‐1) is induced in the vasculature and secreted into the vascular lumen in response to inflammation and oxidative stress. We have previously reported a fivefold increase in plasma PAI‐1 from rats exposed to 708 kPa hyperbaric air. In the current study we assess the potential of human serum total PAI‐1 as a biomarker for stress in compressed air diving. Eleven recreational divers, nine males and two females, completed four 2 h hyperbaric air exposures to 280 kPa in a pressure chamber over a period of 2 weeks. The air pressure corresponds to a diving depth of 18 m in water. Serum was collected before the study and again 3 h 30 min after completion of each hyperbaric exposure. All samples were taken in the afternoon to minimize the contribution of circadian variation. The analysis revealed no change in serum total PAI‐1 after hyperbaric exposures within the group of divers (P = 0.064), but significant interindividual differences persisted throughout the study (P < 0.0005). A case of decompression sickness after the third round of hyperbaric exposure did not affect PAI‐1. In conclusion, compressed air exposure to 280 kPa does not affect serum total PAI‐1, and significant interindividual variation in PAI‐1 levels may limit its usefulness as a biomarker. This does, however, not give a complete answer regarding PAI‐1 in physiologically stressful dives. Further studies with different exposures and timing are needed for that.

Erratum to: Venous gas embolism as a predictive tool for improving CNS decompression safety

Erratum to: Eur J Appl PhysiolDOI 10.1007/s00421-011-1998-9An incorrect citation was included in the originalpublication:Vince RV, Chrismas B, Midgley AW, McNaughton LR,Madden LA (2009) Hypoxia mediated release of endo-thelial microparticles and increased association ofS100A12 with circulating neutrophils. Oxid Med CellLongev 2:2–6The correct reference should be:Vince RV, McNaughton LR, Taylor L, Midgley AW,Laden G, Madden LA (2009) Release of VCAM-1 asso-ciated endothelial microparticles following simulatedSCUBA dives. Eur J Appl Physiol 105:507–513