Abscopal effect of low-LET γ-radiation mediated through Rel protein signal transduction in a mouse model of nontargeted radiation response.

Ascertaining the ionizing radiation (IR)-induced bystander response and its preceding molecular regulation would increase our understanding of the mechanism of acute and delayed radiobiological effects. Recent evidence clearly prompted that radiation-induced nuclear factor kappa B (NF-κB) would play a key role in bystander responses in nontargeted cells. Accordingly, we investigated the orchestration of NF-κB signaling after IR in a nontargeted distant organ. Heart tissues from C57/BL6 mice either mock irradiated or exposed (limited to lower abdomen 1 cm diameter) to single-dose IR (SDR: 2 or 10 Gy) or fractionated IR (FIR, 2 Gy per day for 5 days) were examined for onset of abscopal NF-κB signal transduction, translated activity, downstream functional signaling and associated DNA damage. Radiation significantly induced NF-κB DNA binding activity in nontargeted heart. Transcriptional profiling showed that 51, 46 and 26 of 88 genes were significantly upregulated after 2 Gy, 10 Gy and FIR. Of these genes, 22 showed dose- and fractionation-independent upregulation. Immunohistochemistry revealed a robust increase in p65 and cMyc expression in distant heart after SDR and FIR. Immunoblotting revealed increased phosphorylation of p38 after 2 Gy and extracellular signal-regulated kinases 1/2 after 10 Gy in nontargeted heart. In addition, IR exposure significantly enhanced DNA fragmentation in nontargeted heart. Together, these data clearly indicated an induced abscopal response in distant organ after clinically relevant IR doses. More importantly, the results imply that orchestration of NF-κB signal transduction in nontargeted tissues may serve as an effector and could play a key role in induced abscopal responses.

Adhesion molecule expression and ventricular remodeling in chronic rheumatic heart disease: a cause or effect in the disease progression--a pilot study.

BACKGROUND: Rheumatic fever and chronic rheumatic heart disease (RHD) remains one of the most important causes of cardiovascular morbidity leading to a major public health problem, especially in developing countries. This was a pilot study to assess the presence of inflammation and expression of adhesion molecules by immunohistochemistry (IHC) in endomyocardial biopsy specimens of patients with chronic RHD. METHODS: Endomyocardial biopsy was obtained from 14 patients of chronic RHD with no features of activity clinically. Biopsies were processed for histology and IHC. IHC was carried using monoclonal antibodies against CD3, CD4, CD8, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1. RESULTS: Histomorphologically, varying degree of interstitial and perivascular fibrosis was seen in all the 13 patients (100%). Mild fibrosis (1+) was seen in five patients (38.5%); moderate interstitial fibrosis (2+) was present in four patients (30.8%).There was no Aschoff nodule or evidence of active myocarditis in any of the biopsy specimens. IMMUNOHISTOCHEMISTRY: Moderate positivity of (2+) and intense positivity of (3+) for intercellular adhesion molecule-1 was seen in 11 and 2 patients, respectively. With vascular cell adhesion molecule-1, four showed mild positivity (1+), and three showed intense positivity (3+). The phenotypic analysis of the inflammatory cells in our study revealed CD8(+) cells in 77%, CD4(+) in 23.1%, and CD3(+) in 38.5% of total patients, which suggests chronicity. CONCLUSION: The nonspecific histomorphological changes and increased adhesion molecules expression could be a part of the ventricular remodeling due to the hemodynamic stress by the stenotic or regurgitant lesions of RHD itself.