| 1. |
- Grenegård, Magnus, et al.
(författare)
-
The ATP-gated P2X1 receptor plays a pivotal role in activation of aspirin-treated platelets by thrombin and epinephrine
- 2008
-
Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 283:27, s. 18493-18504
-
Tidskriftsartikel (refereegranskat)abstract
- Human platelets express protease-activated receptor 1 (PAR1) and PAR4 but limited data indicate for differences in signal transduction. We studied the involvement of PAR1 and PAR4 in the cross-talk between thrombin and epinephrine. The results show that epinephrine acted via alpha(2A)-adrenergic receptors to provoke aggregation, secretion, and Ca(2+) mobilization in aspirin-treated platelets pre-stimulated with subthreshold concentrations of thrombin. Incubating platelets with antibodies against PAR4 or the PAR4-specific inhibitor pepducin P4pal-i1 abolished the aggregation. Furthermore, platelets pre-exposed to the PAR4-activating peptide AYPGKF, but not to the PAR1-activating peptide SFLLRN, were aggregated by epinephrine, whereas both AYPGKF and SFLLRN synergized with epinephrine in the absence of aspirin. The roles of released ATP and ADP were elucidated by using antagonists of the purinergic receptors P2X(1), P2Y(1), and P2Y(12) (i.e. NF449, MRS2159, MRS2179, and cangrelor). Intriguingly, ATP, but not ADP, was required for the epinephrine/thrombin-induced aggregation. In Western blot analysis, a low concentration of AYPGKF, but not SFLLRN, stimulated phosphorylation of Akt on serine 473. Moreover, the phosphatidyl inositide 3-kinase inhibitor LY294002 antagonized the effect of epinephrine combined with thrombin or AYPGKF. Thus, in aspirin-treated platelets, PAR4, but not PAR1, interacts synergistically with alpha(2A)-adrenergic receptors, and the PI3-kinase/Akt pathway is involved in this cross-talk. Furthermore, in PAR4-pretreated platelets, epinephrine caused dense granule secretion, and subsequent signaling from the ATP-gated P2X(1)-receptor and the alpha(2A)-adrenergic receptor induced aggregation. These results suggest a new mechanism that has ATP as a key element and circumvents the action of aspirin on epinephrine-facilitated PAR4-mediated platelet activation.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Svensson Holm, Ann-Charlotte B., et al.
(författare)
-
Platelets bind to hyaluronic acid through CD44 and induce a focal adhesion kinase dependent airway smooth muscle cell proliferation
- 2008
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Platelets have been implicated as important players in the remodeling process, e.g. due to their ability to induce airway smooth muscle cell (ASMC) proliferation. The aim of the present study was to investigate the role of the extracellular matrix component hyaluronic acid (HA), the HA-binding surface receptor CD44 and focal adhesion kinase (FAK) in platelet-induced ASMC proliferation. The ability of ASMC to synthesize HA was investigated by fluorescent staining using biotinylated HA-binding protein and streptavidin conjugate. In addition, the interaction between ASMC and platelets was studied by fluorescent staining of the F-actin. We found that ASMC produced HA and that a CD44 blocking antibody and the hyaluronic acid synthase inhibitor 4-Methylumbelliferone (4-MU) inhibited platelet binding to the area surrounding the ASMC. Proliferation of ASMC was measured using the MTS-assay, and we found that the CD44 blocking antibody and 4-MU inhibited platelet-induced ASMC proliferation. We also found that co-culture of ASMC and platelets resulted in increased phosphorylation of FAK as detected by Western blot analysis. Furthermore, the FAKinhibitor PF 573228 inhibited platelet-induced ASMC proliferation. In conclusion, our findings demonstrate that HA, CD44 and FAK contribute to the increased ASMC proliferation caused by platelets. This event is initiated by an interaction between platelets CD44 and HA produced by the ASMC. These new findings may be important in understanding the interplay between ECM, platelets and ASMC in the remodeling process. In conclusion, our results demonstrate that FAK is phosphorylated and on that account activated during the CD44-dependent platelet/ASMC interaction and this contributes to proliferation of the ASMC. These new findings may be important in understanding the interplay between ECM, platelets and ASMC in the remodeling process.
|
|
| 6. |
- Svensson Holm, Ann-Charlotte B., et al.
(författare)
-
Platelets stimulate airway smooth muscle cell proliferation through mechanisms involving 5-lipoxygenase and reactive oxygen species
- 2008
-
Ingår i: Platelets. - : Informa UK Limited. - 0953-7104 .- 1369-1635. ; 19:7, s. 528-536
-
Tidskriftsartikel (refereegranskat)abstract
- Continuous recruitment and inappropriate activity of platelets in the airways may contribute to airway remodeling, a characteristic feature of inflammatory airway diseases that includes increased proliferation of the smooth muscle. The aim of the present investigation was to examine the effect of platelets on proliferation of airway smooth muscle cells (ASMC) in culture and to determine the possible role of 5-lipoxygenase (5-LOX) and reactive oxygen species (ROS) in this context. ASMC obtained from guinea pigs were cultured and co-incubated with washed platelets for 24 hours. Thereafter, the proliferation was measured with the MTS-assay; the results were also verified by using thymidine incorporation, DNA measurements and manual counting. The interaction between platelets and ASMC was visualized with fluorescence microscopy. We found that platelets bind to the ASMC and the presence of platelets caused a significant dose-dependent increase in ASMC proliferation. Co-incubation of ASMC with platelets also increased ROS-production, detected by the fluorescent probe DCFDA. Furthermore, the platelet-induced proliferation was reduced in the presence of the NADPH-oxidase inhibitors DPI and apocynin. A possible role of 5-LOX in platelet-induced proliferation and ROS-generation was evaluated by using the 5-LOX inhibitor AA-861 and the PLA2-inhibitor ATK. The results showed that inhibition of these enzymes significantly reduced the platelet-induced proliferation. Moreover, Western blot analysis revealed that the ASMC but not the platelets express 5-LOX. In addition, our experiments revealed that the presence of AA-861 and ATK significantly inhibited the ROS-production generated upon co-incubation of platelets and ASMC. In conclusion, we show that platelets have a marked capacity to induce ASMC proliferation. Furthermore, our study indicates that the interaction between platelets and ASMC leads to activation of 5-LOX in the ASMC followed by an increased ROS-production, events resulting in enhanced ASMC proliferation. The new findings are of importance in understanding possible mechanisms contributing to airway remodeling. © 2008 Informa UK Ltd.
|
|
