Platelets store laminins 411/421 and 511/521 in compartments distinct from α- or dense granules and secrete these proteins via microvesicles.

BACKGROUND: Blood platelets secrete upon activation of laminins 411/421 and 511/521, large adhesive proteins mainly found in the basement membranes of blood vessels and other tissues. At present, the subcellular localization and secretion mechanisms of platelet laminins are largely unknown. OBJECTIVES: Our aim was to compare the subcellular localization of laminins 411/421 and 511/521 and specific granule markers in platelets. We also elucidated the role of microvesicles and exosomes in laminin release in platelet activation. METHODS: We studied laminin and granule marker protein localization in platelets by using immunofluorescence confocal microscopy and immunoelectron microscopy. Microvesicles and exosomes were separated from material released from platelets on activation by thrombin. The expression of laminins in microvesicles and exosomes was studied by using SDS-PAGE and Western blotting as well as by flow cytometric analysis. The exosomes were immunoprecipitated with magnetic microbeads coated with anti-CD63 antibodies. RESULTS AND CONCLUSIONS: We demonstrate that laminins 411/421 and 511/521 are present in compartments of platelets that do not express α-granule, dense granule, or lysosome marker proteins. Moreover, laminins secreted by activated platelets are mostly found in microvesicles shed from the plasma membrane, while their presence in simultaneously released exosomes is minimum.

Modifying effect of the AR gene trinucleotide repeats and SNPs in the AHR and AHRR genes on the association between persistent organohalogen pollutant exposure and human sperm Y:X ratio.

Persistent organohalogen pollutants (POPs) have been suggested to be involved in changing the proportion of ejaculated Y-bearing sperm. The androgen receptor (AR), aryl hydrocarbon receptor (AHR) and aryl hydrocarbon receptor repressor (AHRR) may modulate the effect of POPs with regard to previously observed sperm Y:X ratio changes. The objective of this study was to investigate whether sperm Y:X ratio changes in subjects exposed to 2,2'4,4'5,5'-hexachlorobiphenyl (CB-153) and dichlorodiphenyl dichloroethene (p,p'-DDE) were modified by polymorphisms in the AR, AHR and AHRR genes. Semen for analysis of Y- and X-bearing sperm by two-colour fluorescence in situ hybridization and blood for leukocyte DNA genotyping and analysis of CB-153 and p,p'-DDE concentrations were obtained from 195 Swedish fishermen. The polymorphic CAG and GGN repeats in the AR and the R554K and P185A single-nucleotide polymorphisms in the AHR and AHRR genes, respectively, were determined by direct sequencing and allele-specific PCR. The effect of p,p'-DDE was modified by CAG or GGN repeat category in relation to the proportion of Y-bearing sperm (P = 0.005 and 0.02 for CAG and GGN, respectively). Moreover, p,p'-DDE, but not CB-153, levels were associated with Y-sperm proportion in men with CAG < 22 (P < 0.001), but not in those carrying CAG > or = 22 (P = 0.73). This association was even more pronounced in subjects carrying a short CAG repeat in combination with an AHRR G-allele. The association in regard to p,p'-DDE was found for GGN = 23 but not for the GGN < 23 or GGN > 23 subgroups (P = 0.01, 0.44 and 0.99, respectively). In conclusion The endocrine-disrupting action of POPs, in relation to the observed changes in sperm Y:X ratio, may be modulated by the genes involved in sex steroid and dioxin-mediated pathways.