Quantitative image analysis of laminin immunoreactivity in skin basement membrane irradiated with 1 GeV/nucleon iron particles

We previously reported that laminin immunoreactivity in mouse mammary epith elium is altered shortly after whole-body irradiation with 0.8 Gy from 600 MeV/nucleon iron ions but is unaffected after exposure to sparsely ionizing radiation. This observation led us to propose that the effect could be due to protein damage from the high ionization density of the ion tracks. If s o, we predicted that it would be evident soon after radiation exposure in b asement membranes of other tissues and would depend on ion fluence. To test this hypothesis, we used immunofluorescence, confocal laser scanning micro scopy, and image segmentation techniques to quantify changes in the basemen t membrane of mouse skin epidermis. At 1 h after exposure to 1 GeV/nucleon iron ions with doses from 0.03 to 1.6 Gy, neither the visual appearance nor the mean pixel intensity of laminin in the basement membrane of mouse dors al skin epidermis was altered compared to sham-irradiated tissue. This resu lt does not support the hypothesis that particle traversal directly affects laminin protein integrity. However, the mean pixel intensity of laminin im munoreactivity was significantly decreased in epidermal basement membrane a t 48 and 96 h after exposure to 0.8 Gy 1 GeV/nucleon iron ions. We confirme d this effect with two additional antibodies raised against affinity-purifi ed laminin 1 and the E3 fragment of the long-arm of laminin 1. In contrast, collagen type IV, another component of the basement membrane, was unaffect ed. Our studies demonstrate quantitatively that densely ionizing radiation elicits changes in skin microenvironments distinct from those induced by sp arsely ionizing radiation. Such effects may might contribute to the carcino genic potential of densely ionizing radiation by altering cellular signalin g cascades mediated by cell-extracellular matrix interactions. (C) 2000 by Radiation Research Society.