ABSTRACT
Objective To investigate the mechanism of mechano-chemical coregulation in chemokine-induced calcium response of Jurkat T cells under fluid shear stress (FSS). Methods By using parallel-plate flow chamber combined with fluorescence microscope, the calcium response of Jurkat T cells on CXCL12 was observed to extract the corresponding characteristic parameters under static or flow state, with or without extracellular Ca2+, respectively. Results Immobilized CXCL12 could induce firm adhesion of the circulating Jurkat T cells, and the arrested cells increased with the increase of CXCL12 concentration. Force could trigger the calcium response of Jurkat T cells and sharply raised the activation ratio from 4% up to 75% when the FSS increased from 0 to 20 mPa. Under 20 mPa FSS, extracellular Ca2+ could stimulate quickly the calcium response by shortening the delay time (about 23 s), and enhance calcium intensity by prolonging the climbing time (about 7 s) and half time (about 20 s). Conclusions The cooperation between FSS and extracellular Ca2+ would accelerate and enhance CXCL12-mediated-calcium response of Jurkat T cells, which indicated a fast mechanosensitive pathway through ‘extracellular calcium influx-intracellular calcium store release’. The research results would contribute to understanding the process of T cells activation and providing the clue for relevant pathological and drug research.
ABSTRACT
Objective To investigate the shear rate and VWF-A1-mediated platelets calcium response. Methods Flou-4 AM was used as the fluorescent indicator of intracellular calcium, and the intracellular calcium concentrations of adherent platelets on VWF-A1 with different concentrations at different shear rates were detected by parallel plate flow chamber system combined with fluorescence microscope. The effect of shear stress and chemical signaling on intensity and speed of calcium response was also analyzed. Results VWF-A1 specifically mediated platelet adhesion and calcium response under flow. The shear rate and molecular concentrations had positive regulation of platelets activation ratio and negative regulation of delay time of calcium response. Compared with static conditions, the activation ratio was increased by 37 times at shear rate of 500 s-1. When the concentration of VWF-A1 was increased from 60 mg/L to 240 mg/L, the delay time of calcium response was shortened by 10 s. Conclusions The shear rate could modulate the calcium response of platelets in cooperation with VWF-A1. The result of this study will be helpful to deepen the understanding about the process of hemostatic reaction of platelet coagulation in bloodstream.
ABSTRACT
Objective To investigate the E-selectin mediated-calcium response of neutrophils under flow fields. Methods A parallel-plate flow chamber combined with a fluorescence microscope was used to observe the adhesion and subsequent calcium response of neutrophils on E-selectin at different concentrations under fluid shear stress (FSS) of 0-600 mPa. Results E-selectin could capture neutrophils from the flow to the chamber substrate and induce further intracellular calcium flux of firmly adhered cells. The arrested cell and activation ratio increased gradually as the concentration of E-selectin increased. Only immobilized E-selectin could conduct the external force-signal to trigger the calcium response of neutrophils effectively. By increasing FSS, not only was the activation ratio increased from 23% to 70%, but the calcium response intensity also increased from 0.92 to 1.45, while the delay time from cell adhesion to calcium response was greatly reduced from 70 s to 27 s. Conclusions FSS can modulate the calcium response of neutrophils in cooperation with E-selectin, and it positively regulates the activation rate and level of calcium response. This study may deepen the understanding of the immune response of leukocytes under a hemodynamic environment.
ABSTRACT
Calcium is not only the important signaling molecule within and between bone cells, but also the primary component of extracellular matrix in bone. It has been demonstrated during the past over 100 years that mechanical stimulations can regulate the molecular signal transduction and intercellular communication in bone cells as well as the bone mineralization and resorption at tissue level, but further more researches are still needed to give insight into the mechanism of mechanical stimulation-induced bone remodeling. This paper will summarize the related works on the following aspects: (1) the primary experimental approaches for studying mechanical stimulation induced calcium response and transfer in osteoblasts, (2) the calcium sources and mechanism of calcium response in osteoblasts, (3) the intercellular calcium transfer pathways and (4) characteristic parameters of calcium response and transfer in osteoblasts. Finally, several potential research directions in this field are presented in the paper.
ABSTRACT
Objective To investigate the specific roles of gap junction and ATP in mechanical stimulation induced calcium transfer in osteoblasts. Methods The isolated osteoblastic pattern without gap junctions was established by using the micropatterning method. Then fluid shear stress was applied on cells using the flow chamber to observe and analyze the characteristic parameters of calcium response. Results Multiple calcium response still occurred in osteoblastic pattern without gap junction, but the response time to the first responsive peak was much longer than that with gap junction. When the intracellular and extracellular calcium ions were removed, only 40% cells responded to the mechanical stimulation, with single peak and multiple peaks accounting for 50%, respectively. If ATP pathway was blocked, only 20% cells responded, most of which showed single peak. Conclusions ATP was the major pathway mediating intercellular calcium transfer, while the gap junction was not the necessary one.