UV-C irradiation disrupts platelet surface disulfide bonds and activates the platelet integrin αIIbβ3

Abstract

UV-C irradiation has been shown to be effective for pathogen reduction in platelet concentrates, but preliminary work indicated that UV-C irradiation of platelets can induce platelet aggregation. In this study, the mechanism underlying this phenomenon was investigated. Irradiation of platelets with UV-C light (1500 J/m 2 ) caused platelet aggregation, which was dependent on integrin ␣IIb␤3 activation (GPIIb/IIIa). This activation occurred despite treatment with several signal transduction inhibitors known to block platelet activation. UV-C also induced activation of recombinant ␣IIb␤3 in Chinese hamster ovary (CHO) cells, an environment in which physiologic agonists fail to activate. Activation of ␣IIb␤3 requires talin binding to the ␤3 tail, yet ␣IIb␤3-⌬724 (lacking the talin binding site) was activated by UV-C irradiation, excluding a requirement for talin binding. The UV-C effect appears to be general in that ␤ 1 and ␤ 2 integrins are also activated by UV-C. To explain these findings, we investigated the possibility of UV-C-induced photolysis of disulfide bonds, in analogy with the activating effect of reducing agents on integrins. Indeed, UV-C induced a marked increase in free thiol groups in platelet surface proteins including ␣IIb␤3. Thus, UV-C appears to activate ␣IIb␤3 not by affecting intracellular signal transduction, but by reduction of disulfide bonds regulating integrin conformation. (Blood. 2008;112:4935-4939) IntroductionViral and, especially, bacterial contamination of platelet concentrates remains an issue for platelet transfusions. 1 To minimize contamination of blood platelets, several pathogen reduction approaches have been developed that rely on irradiation with ultraviolet light (UV) in combination with a photosensitizer. [2][3][4] Recently, the possibility of using UV-C light without the addition of an exogenous sensitizer has been explored. 5,6 This approach uses UV-C at a wavelength of 254 nm, which is highly absorbed by nucleic acids, resulting in cyclobutane pyrimidine dimer formation and DNA degradation. 7,8 Since no photosensitizer needs to be added to the platelet concentrate, UV-C-based pathogen inactivation should be easier to implement in existing blood bank procedures.UV-based pathogen reduction in blood platelets has a few drawbacks, as some properties of platelets are affected by UV irradiation. Van Marwijk and colleagues observed that UV-B irradiation resulted in increased fibrinogen binding to platelets. 9 Furthermore, the UV-B-induced aggregation appeared to be dependent on PKC activation, signifying an important role for platelet signaling in UV-B-mediated activation of integrin ␣IIb␤3, the receptor binding fibrinogen.As a member of the integrin family, ␣IIb␤3 consists of a large type I transmembrane ␣/␤ heterodimer, which is capable of bidirectional signaling through the plasma membrane. On unstimulated platelets, ␣IIb␤3 resides in an inactive conformation on the plasma membrane, but it is rapidly switched to an "on" state when the platelet becomes activated after stimula...

LAD-1/variant syndrome is caused by mutations in FERMT3

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UVC Irradiation for Pathogen Reduction of Platelet Concentrates and Plasma

“…Indeed, disruption of disulfide bonds of αIIbβ3 by UVC may be responsible for the increased aggregability and PAC-1 binding detectable in UVC-treated platelets. However, the conditions in the study by Verhaar et al [40], including plasma content, platelet concentration, intensity and time for UVC delivery, type of irradiation vessel and agitation, were completely different from those used in the THERAFLEX UV-Platelets irradiation procedure (table 3). As already mentioned above, the treatment conditions have significant influence on the biological effects of UVC and, thus, on the quality of the product.…”

“…In a recent biochemical study by Verhaar et al [40], it was reported that UVC irradiation exerts a direct effect on αIIbβ3 (and other integrins) by modifying extracellular disulfide bonds regulating integrin conformation. This direct activation of platelet αIIbβ3, the fibrinogen receptor, may result in aggregation of stored platelets and influence the hemostatic function of the platelets.…”

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“…Thus, UV activate gene expression of a2, a1 and a5 in skin mice (Kligman et al, 1999), as well as they stimulate the activity of b1 subunit in fibroblasts and of a2b3 dimer in platelets (Verhaar et al, 2008).…”