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The Importance of Differentiating Gelsolin Isoforms

We agree with Drs. Lee and Waxman that it is important to discriminate between plasma and cytoplasmic gelsolins, thus between secretion and leak from damaged cells. Indeed, in our paper (1) we have carefully eliminated from the proteomic and subsequent analysis the fluid obtained from epithelia where we suspected cell damage. We have followed three criteria. First, the transepithelial resistance, which was measured before the beginning of the washing sequence, had to remain high after the last fluid was recovered. Second, albumin must be absent from the fluid. In fact, bovine albumin is part of the serum contained in the medium bathing the basolateral side of the epithelia. Therefore, the absence of albumin as well as a high transepithelial resistance indicated that the integrity of the epithelium was maintained throughout the whole washing process. Moreover, gelsolin identified in the fluid was human and not bovine, excluding even the possibility of transport of serum gelsolin from the serosal to the mucosal side. Finally, actin should not be increased in the fluid. Actually, the amount of actin was always equal in the presence and absence of IL-4 (see Figure 1 of Reference 1).

If, as proposed by Lee and Waxman, gelsolin measured in the airway fluid was a result from cell damage, we would have found not only an increase of gelsolin but also of many other intracellular proteins, and in particular, of actin. That was not the case. Taking into account these considerations, we believe that the gelsolin present in the apical surface of cultured bronchial epithelia may arise by secretion. However, we agree with the comments by Lee and Waxman that this is an important issue that warrants further study with different techniques and tools.

Olga Zegarra-Moran and Luis J. V. Galietta

Istituto Giannina Gaslini, Genoa, Italy

FOOTNOTES

Conflict of Interest Statement: Neither author has a financial relationship with a commercial entity that has an interest in the subject of this manuscript.

REFERENCES

1. Candiano G, Bruschi M, Pedemonte N, Caci E, Liberatori S, Bini L, Pellegrini C, Vigano M, O'Connor BJ, Lee TH, Zegarra-Moran O. Gelsolin secretion in interleukin-4–treated bronchial epithelia and in asthmatic airways. Am J Respir Crit Care Med 2005;172:1090–1096.[Abstract/Free Full Text]

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