Apoptosis and Bcl-2 Expression in Irradiated Lungs and the Effect of Pentoxifylline

Targeting Tumor Necrosis Factor Alpha to Mitigate Lung Injury Induced by Mustard Vesicants and Radiation

Pulmonary injury induced by mustard vesicants and radiation is characterized by DNA damage, oxidative stress, and inflammation. This is associated with increases in levels of inflammatory mediators, including tumor necrosis factor (TNF)α in the lung and upregulation of its receptor TNFR1. Dysregulated production of TNFα and TNFα signaling has been implicated in lung injury, oxidative and nitrosative stress, apoptosis, and necrosis, which contribute to tissue damage, chronic inflammation, airway hyperresponsiveness, and tissue remodeling. These findings suggest that targeting production of TNFα or TNFα activity may represent an efficacious approach to mitigating lung toxicity induced by both mustards and radiation. This review summarizes current knowledge on the role of TNFα in pathologies associated with exposure to mustard vesicants and radiation, with a focus on the therapeutic potential of TNFα-targeting agents in reducing acute injury and chronic disease pathogenesis.

Vascular endothelium derived endothelin-1 is required for normal heart function after chronic pressure overload in mice

Background

Endothelin-1 participates in the pathophysiology of heart failure. The reasons for the lack of beneficial effect of endothelin antagonists in heart failure patients remain however speculative. The anti-apoptotic properties of ET-1 on cardiomyocytes could be a reasonable explanation. We therefore hypothesized that blocking the pro-apoptotic TNF-α pathway using pentoxifylline could prevent the deleterious effect of the lack of ET-1 in a model for heart failure.

Methods

We performed transaortic constriction (TAC) in vascular endothelial cells specific ET-1 deficient (VEETKO) and wild type (WT) mice (n = 5–9) and treated them with pentoxifylline for twelve weeks.

Results

TAC induced a cardiac hypertrophy in VEETKO and WT mice but a reduction of fractional shortening could be detected by echocardiography in VEETKO mice only. Cardiomyocyte diameter was significantly increased by TAC in VEETKO mice only. Pentoxifylline treatment prevented cardiac hypertrophy and reduction of fractional shortening in VEETKO mice but decreased fractional shortening in WT mice. Collagen deposition and number of apoptotic cells remained stable between the groups as did TNF-α, caspase-3 and caspase-8 messenger RNA expression levels. TAC surgery enhanced ANP, BNP and bcl2 expression. Pentoxifylline treatment reduced expression levels of BNP, bcl2 and bax.

Conclusions

Lack of endothelial ET-1 worsened the impact of TAC-induced pressure overload on cardiac function, indicating the crucial role of ET-1 for normal cardiac function under stress. Moreover, we put in light a TNF-α-independent beneficial effect of pentoxifylline in the VEETKO mice suggesting a therapeutic potential for pentoxifylline in a subpopulation of heart failure patients at higher risk.

Apoptosis-Related Gene Bcl-2 in Lung Tissue After Experimental Traumatic Brain Injury in Rats

BACKGROUND

We have recently shown that experimental traumatic brain injury resulted in ultra structural damage in lung tissue. The main objective of the current study was to investigate in a rat model of brain injury whether expression of Bcl-2 gene and lipid peroxidation levels in the lung tissue after traumatic brain injury were affected by methylprednisolone sodium succinate (MPSS) treatment.

METHODS

Fifty-six Wistar-Albino female rats weighing 180-220 g were used, which were allocated into seven groups. A weight-drop method was used to achieve head trauma. Real time quantitative PCR analyses for Bcl-2 gene expression and measurement of the levels of lipid peroxidation were carried out. All the data was analyzed by using SPSS 11.5 for Windows.

RESULTS

Mean Bcl-2 expression in the methylprednisolone group was considerably higher compared to that of all the other groups (p<.05). Mean lipid peroxidation levels were significantly higher in the trauma group and notably lower in the methylprednisolone group (p<.01).

CONCLUSIONS

The oxidative stress imposed on lung tissue, as seen by high levels of lipid peroxidation, after brain injury was significantly attenuated by MPSS treatment. MPSS treatment following brain injury also augmented putative anti-apoptotic Bcl-2 gene expression in lung tissue. Further studies are required to determine the full range and lower limits of effective MPSS dose. More importantly the optimal efficacy according to the timing of MPSS treatment after brain injury needs to be determined for impact on more diverse markers of cell inflammation, apoptosis and injury.

Pulmonary complications of radiation therapy

There have been important developments in understanding the difference in pathogenesis and clinical significance between acute or sporadic pneumonitis and late radiation fibrosis. Corticosteroid therapy and other forms of therapy are useful in the treatment of acute pneumonitis. Late radiation fibrosis is refractory to treatment; therefore, minimizing the likelihood of developing it is particularly important. Baseline lung assessments are appropriate in patients who are clinically at risk. A new development is the use of the DVH to compare radiation treatment plans to minimize the volume of normal lung irradiated in patients who are at risk. It is hoped that the study of mechanisms that lead to the development of radiation fibrosis will point the way to possible future therapies. Patients who are included in studies of novel irradiation treatments for lung cancer need, in particular, to be monitored for late radiation lung toxicity.