Photobiomodulation Inhibits Long-term Structural and Functional Lesions of Diabetic Retinopathy.

Previous studies demonstrated that brief (3 to 4 min) daily application of light at 670 nm to diabetic rodents inhibited molecular and pathophysiologic processes implicated in the pathogenesis of diabetic retinopathy (DR) and reversed diabetic macular edema in small numbers of patients studied. Whether or not this therapy would inhibit the neural and vascular lesions that characterize the early stages of the retinopathy was unknown. We administered photobiomodulation (PBM) therapy daily for 8 months to streptozotocin-diabetic mice and assessed effects of PBM on visual function, retinal capillary permeability, and capillary degeneration using published methods. Vitamin D receptor and Cyp24a1 transcripts were quantified by quantitative real-time PCR, and the abundance of c-Kit+ stem cells in blood and retina were assessed. Long-term daily administration of PBM significantly inhibited the diabetes-induced leakage and degeneration of retinal capillaries and also significantly inhibited the diabetes-induced reduction in visual function. PBM also inhibited diabetes-induced reductions in retinal Cyp24a1 mRNA levels and numbers of circulating stem cells (CD45-/c-Kit+), but these effects may not account for the beneficial effects of PBM on the retinopathy. PBM significantly inhibits the functional and histopathologic features of early DR, and these effects likely are mediated via multiple mechanisms.

Efeito da irradiação LED sobre a microinfiltração auricular em camundongo / Effect of LED irradiation on microcirculation of auricular mouse

A microcirculação pode ser considerada uma unidade funcional do sistema circulatório, sendo constituída pelos menores vasos distais. A radiação eletromagnética pode influenciar essa unidade agindo sobre esfíncteres pré-capilares. Essa influência pode gerar alterações na pressão hidrostática capilar, contribuindo na reabsorção de exsudato inflamatório e eliminando acúmulos de catabólitos intermediários. O efeito da radiação eletromagnética coerente na região do visível (vermelho) tem sido estudado principalmente no processo inflamatório, tendo sido encontrado aumento da permeabilidade capilar e vasodilatação. Contudo, poucos trabalhos foram realizados com o emprego de radiação eletromagnética não-coerente (LED) na região do visível. Dessa forma, o objetivo deste estudo foi observar o efeito do LED (640 :!: 20 nm, 100 m W, 1,77 cm2) sobre a microcirculação auricular em camundongos. Para tal, foram utilizados oito animais divididos em dois grupos (grupo placebo e grupo 3 J/cm2). A superfície auricular externa dos animais foi monitorada (durante 15 minutos) sob microscopia óptica (100x) e analisada com o auxílio do programa ImageJ. Observou-se uma diferença significativa no diâmetro dos vasos nos primeiros minutos após a irradiação, comprovando a existência de um efeito vasodilatador da radiação eletromagnética não-coerente, na região do vermelho, com os parâmetros testados. Esse resultado pode ser otimizado empregando-se maior fluência.

Microcirculation, considered a functional unit of the circulatory system, is composed of many smaller distal vessels. The electromagnetic radiation can influence this unit acting on the precapillary sphincters. This influence might generate alterations on the capillary hydrostatic pressure, contributing to the reabsortion of the inflammatory exudation and eliminating intermediate catabolite accumulation. The effect of coherent electromagnetic radiation on the visible region (red) has been studied mainly in the inflammatory process, and an increase in the capillary permeability and vasodilation was found. However few studies have been conducted on the use of noncoherent electromagnetic radiation (LED) in the visible region. Therefore, the aim of this study was to observe the effect of the LED (640:!: 20 nm, 100 mW, 1.77 cm2) on the auricular circulation of mice. To this end 8 animals were separated into 2 groups (placebo group and 3 J/cm2 group). The external auricular surface was monitored (15 minutes) under light microscopy (100X) and analysed with the help of IMAGEJ program. A significant difference was observed in the vessel diameter in the first minutes after the irradiation, proving the existence of a vasodilator effect of non coherent electromagnetic radiation in the red region of the tested parameters. This result can be optimized with the use of greater fluence.

Low level laser therapy (LLLT) decreases pulmonary microvascular leakage, neutrophil influx and IL-1beta levels in airway and lung from rat subjected to LPS-induced inflammation.

BACKGROUND AND OBJECTIVE: Low level laser therapy (LLLT) is a known anti-inflammatory therapy. Herein we studied the effect of LLLT on lung permeability and the IL-1beta level in LPS-induced pulmonary inflammation. STUDY DESIGN/METHODOLOGY: Rats were divided into 12 groups (n = 7 for each group). Lung permeability was measured by quantifying extravasated albumin concentration in lung homogenate, inflammatory cells influx was determined by myeloperoxidase activity, IL-1beta in BAL was determined by ELISA and IL-1beta mRNA expression in trachea was evaluated by RT-PCR. The rats were irradiated on the skin over the upper bronchus at the site of tracheotomy after LPS. RESULTS: LLLT attenuated lung permeability. In addition, there was reduced neutrophil influx, myeloperoxidase activity and both IL-1beta in BAL and IL-1beta mRNA expression in trachea obtained from animals subjected to LPS-induced inflammation. CONCLUSION: LLLT reduced the lung permeability by a mechanism in which the IL-1beta seems to have an important role.

Tumor vascular permeabilization by vascular-targeting photosensitization: effects, mechanism, and therapeutic implications.

PURPOSE: Loss of vascular barrier function has been observed shortly following vascular-targeting photodynamic therapy. However, the mechanism involved in this event is still not clear, and the therapeutic implications associated with this pathophysiologic change have not been fully explored. EXPERIMENTAL DESIGN: The effect of vascular-targeting photodynamic therapy on vascular barrier function was examined in both s.c. and orthotopic MatLyLu rat prostate tumor models and endothelial cells in vitro, using photosensitizer verteporfin. Vascular permeability to macromolecules (Evans blue-albumin and high molecular weight dextran) was assessed with dye extraction (ex vivo) and intravital microscopy (in vivo) methods. Intravital microscopy was also used to monitor tumor vascular functional changes after vascular-targeting photodynamic therapy. The effects of photosensitization on monolayer endothelial cell morphology and cytoskeleton structures were studied with immunofluorescence staining. RESULTS: Vascular-targeting photodynamic therapy induced vascular barrier dysfunction in the MatLyLu tumors. Thus, tumor uptake of macromolecules was significantly increased following photodynamic therapy treatments. In addition to vascular permeability increase, blood cell adherence to vessel wall was observed shortly after treatment, further suggesting the loss of endothelial integrity. Blood cell adhesion led to the formation of thrombi that can occlude blood vessels, causing vascular shutdown. However, viable tumor cells were often detected at tumor periphery after vascular-targeting photodynamic therapy. Endothelial cell barrier dysfunction following photodynamic therapy treatment was also observed in vitro by culturing monolayer endothelial cells on Transwell inserts. Immunofluorescence study revealed microtubule depolymerization shortly after photosensitization treatment and stress actin fiber formation thereafter. Consequently, endothelial cells were found to retract, and this endothelial morphologic change led to the formation of intercellular gaps. CONCLUSIONS: Vascular-targeting photodynamic therapy permeabilizes blood vessels through the formation of endothelial intercellular gaps, which are likely induced via endothelial cell microtubule depolymerization following vascular photosensitization. Loss of endothelial barrier function can ultimately lead to tumor vascular shutdown and has significant implications in drug transport and tumor cell metastasis.

[Change of 5-fluorouracil penetration in blood-pancreatic barrier of rats after high-dose radiotherapy].

OBJECTIVE: The high-dose intraoperative radiotherapy has become an important therapy to control local recur of pancreatic carcinoma. But the relevant effect of high-dose radiotherapy on chemotherapy is not clear now. METHODS: We studied the effect of high-dose radiotherapy to the penetration of 5-FU (5-Fluorouracil) in blood-pancreatic barrier of rats after the pancreatic region of the rats had treated with 10(Gy) external beam radiotherapy, the penetration ratio (PR) of 5-FU in the pancreatic tissue was investigated with HPLC assay. RESULTS: We found the PR increased with the time processing. And reached the peak on the 6th day, (PR = 0.8300 +/- 0.1662, P < 0.05). Then, the PR began to descend and was 0.7028 on the 10th day. But it was still significantly higher than control group (P < 0.05). CONCLUSION: After the treatment of high-dose radiotherapy, in addition to chemotherapy on the 4th day, and finished the course on the 10th day, the effect of radiotherapy may improve chemotherapy significantly.

Comparative studies on the tolerance to photoinduced cutaneous inflammatory reactions by psoralen and rose bengal.

The photochemotherapeutic value of topical 8-methoxypsoralen (8-MOP) plus UVA irradiation has been well recognized. The phototoxicity associated with psoralen plus UVA (PUVA) therapy is hallmarked by an increase in vascular permeability (iVP), the accumulation of polymorphonuclear leukocytes (aPMN) and erythema formation in situ. Rose bengal (RB) plus UVA-VIS light (320-700 nm) produces a similar acute inflammatory response, but without immediate or delayed erythema and perceptible edema. This study describes some of the parameters involved in inflammatory reactions evoked by PUVA and the results are compared with RB-induced phototoxic reactions. The rates of iVP and aPMN with a 3 h pulse were quantified using 125I-albumin and 51Cr-labelled PMNs respectively. The erythemal response was graded visually. 8-MOP cream was applied topically, while RB was injected intradermally in rabbit skin before UVA-VIS (9.4 J cm-2) irradiation. The data show that there is no significant difference in the rates of iVP, aPMN and erythema formation between normal skin sites and mast cell-depleted skin sites when challenged with 8-MOP plus light. These results suggest that in situ mast cells do not play a significant role in 8-MOP-photoinduced acute cutaneous inflammatory reactions, in contrast with RB-photoinduced reactions. The iVP and aPMN responses are minimal or absent in sites subjected to repeated exposure to 8-MOP plus light for three or more consecutive days, suggesting the establishment of a desensitized/unresponsive state. Moreover, 8-MOP-photo-desensitized sites do not produce iVP and aPMN of the same magnitude as the normal (naive) skin sites when challenged with RB plus light. Similarly, RB-photo-desensitized sites do not produce iVP and aPMN of the same magnitude as the native skin sites when challenged with 8-MOP plus light. The desensitization and cross-desensitization of skin sites to 8-MOP- or RB-photoinduced reactions suggest that there is either direct attack on the target cell(s), thereby removing the ability to express adhesion molecules, such as endothelial leukocyte adhesion molecule 1 (ELAM-1) or intercellular adhesion molecule 1 (ICAM-1), involved in the accumulation of inflammatory cells, or downregulation of the secretion/release of putative agent(s), such as interleukin 1 (IL-1) and tumor necrosis factor alpha (TNF-alpha), responsible for the initiation and progression of cutaneous inflammations.

MR assessment of radiation-induced blood-brain barrier permeability changes in rat glioma model.

PURPOSE: To assess the potential of a T1-weighted, gadolinium-enhanced MR technique for quantifying radiation-induced changes of blood-brain barrier permeability in a model of stereotactically implanted intracerebral gliomas in rats. METHODS: We calculated the gadolinium blood-to-tissue transport coefficient for gadopentetate dimeglumine from signal intensities in sequential MR images in nine control animals that were not irradiated and in five and three animals that had received 2500 cGy and 1500 cGy whole-brain irradiation, respectively, at 2 days before imaging. RESULTS: The average blood-to-tissue transport coefficient values were 9.76 mL.kg-1.min-1 in the control group, 23.41 mL.kg-1.min-1 in the 2500 cGy group, and 25.63 mL.kg-1.min-1 in the 1500-cGy group. Blood-to-tissue transport coefficients were significantly higher after irradiation, indicating increased radiation-induced blood-brain barrier permeability. Similar increased blood-brain barrier leakiness in brain tumors after high-dose irradiation has been shown by previous nuclear medicine studies using quantitative autoradiography. CONCLUSION: Contrast-enhanced dynamic MR of brain gliomas is a sensitive method to document radiation-induced blood-brain barrier breakdown. Quantitative gadolinium-enhanced MR may become a useful tool for the management of patients with brain tumors undergoing radiation therapy.

Pathophysiological aspects of malignant brain tumors studied with positron emission tomography.

To further understand the control of brain tumor fluid balance and pH, the following studies were undertaken. The transport of a water soluble molecule across the brain and tumor capillary endothelium was studied during glucocorticoid and radiation treatment. The brain and brain-tumor acidity (pH) was evaluated as a single measurement in patients receiving a low maintenance dose of glucocorticoid. Transport changes and pH were measured in 61 patients with cerebral tumors using 82Rubidium (82Rb) and 11C-Dimethyloxa-zolidindione (11C-DMO), respectively, and Positron Emission Tomography (PET). Supplementary studies of tumor and contralateral brain blood flow and blood volume using the C15O2/PET and C15O/PET technique, respectively, were included to validate the 82Rb/PET model and obtain further information. A total of 125 PET scans were performed. Supplementary studies were undertaken to estimate delay of blood registration and form distribution of arterial blood isotope activity curves. Blood-to-tumor barrier transport was outlined at baseline and at 6 and 24 hours after the start of glucocorticoid treatment, finding a significant decrease in the transport. Radiation treatment (2-6 gray) did not alter the blood-to-tumor barrier transport when restudied within one hour in patients receiving glucocorticoid. In accordance with others, we observed pH values in gray and white matter in the range of 6.74-7.09 and 6.77-7.03 respectively. The pH in brain tumors was as high as 6.88-7.26, suggesting that tumors are more alkalotic than the normal brain. The permeability surface area product and the permeability coefficient were determined from the 82Rb/PET transport and C15O2/PET flow studies. Baseline permeability values were comparable to the literature values both for 82Rb and potassium. No difference in tissue blood volume was seen between 82Rb/PET and C15O/PET models and was of the same magnitude in the tumor and the contralateral tissue. The pH and fluid control in human brain tumors are perceived as metabolically controlled rather than, as previously believed, a result of simple passive exchange of alkalotic or osmotic active molecules between plasma and tumor interstitial space. Aspects of tumor alkalosis, tumor edema production, glucocorticoid edema clearance, and relationship between the anti-edema effect of glucocorticoid and the shown transport changes to 82Rb will be reviewed in the light of metabolic control mechanisms.

Effects of hyperthermia, radiotherapy and thermoradiotherapy on tumor microvascular permeability.

Morphological changes in rabbit VX-2 tumor and its vascular permeability to ferritin following hyperthermia, radiotherapy and thermoradiotherapy were investigated by light and electron microscopy. Tumors treated by thermoradiotherapy successively showed a decrease in volume compared with those treated by hyperthermia or radiotherapy. Light microscopically, degenerative or necrotic changes progressed more widely in tumors treated by thermoradiotherapy than in those treated by hyperthermia or radiotherapy alone. When vascular permeability to ferritin was examined, an increase in tumor vascular permeability occurred at 1 day after hyperthermia or thermoradiotherapy, and at 3 days after radiotherapy. These results suggest that the early reaction of tumor microvasculature is a factor contributing to delayed cell death in tumors after thermoradiotherapy or hyperthermia.

Transport of molecules across tumor vasculature.

The vascular-extravascular exchange of fluid and solute molecules in a tissue is determined by three transport parameters (vascular permeability, P, hydraulic conductivity, Lp, and reflection coefficient, sigma); the surface area for exchange, A; and the transluminal concentration and pressure gradients. The transport parameters and the exchange area for a given molecule are governed by the structure of the vessel wall. In general, tumor vessels have wide interendothelial junctions; large number of fenestrae and transendothelial channels formed by vesicles; and discontinuous or absent basement membrane. While these factors favor movement of molecules across tumor vessels, high interstitial pressure and low microvascular pressure may retard extravasation of molecules and cells, especially in large tumors. These characteristics of the transvascular transport have significant implications in tumor growth, metastasis, detection and treatment.

Microvascular leakage of plasma proteins after PUVA and UVA.

The transcapillary escape rate of albumin (TERalb), i.e., the fraction of intravascular albumin mass passing to the extravascular space per unit time, is a parameter of the leakage of macromolecules from the total microvasculature. In patients with psoriasis short-term PUVA treatment induces an increase in TERalb. In this study TERalb was measured in 3 groups of normal humans treated with PUVA, UVA and 8-methoxypsoralen. Treatment with PUVA and UVA caused a statistically significant increase in TERalb, whereas treatment with 8-methoxypsoralen did not induce any measurable changes. It is concluded that the UVA irradiation causes the abnormal leakage of macromolecules, whereas psoralen is not the responsible component. Furthermore the phenomenon can be elicited in normals and is not based on a preexisting psoriasis.