Fluid Shear Stress-induced Cytosolic Calcium And Degranulation Dynamics In Mast Cell

To achieve the "needle grasp (deqi)", the needle manipulation is necessary, which is composed of pulling, inserting and rotating the needle. Essentially, the manipulation is the shear stress exerted on the tissue and cells in the acupoint. And in Chinese medicine, the definition of needle manipulation is blurry, which needs scientifically quantitive definition to promote next research. Among the researches relative to the mechanism, the mast cell gets much attention. The past researches, e.g., mast cell and calcium accumulating in acupoints, and degranulation of mast cell increasing with the acupuncture needle stimulated in the acupoint, and the analgesic effect of acupuncture decreasing when the degranulation of mast cell inhibited by sodium cromoglicate, showed that mast cell and calcium were related to the effect of acupuncture. It indicates that mast cell, calcium are related to acupuncture. So we focus on the effect of shear stress on calcium and degranulation dynamics in mast cells.So, in this paper, with the scanning confocal microscopy, the effects and mechanism of shear stress on the intracellular calcium ([Ca2+];) in RBL-2H3mast cell were studied. We use fluo-3/AM to mark the cytosolic calcium concentration, fluorescence intensity increase with cytosolic calcium concentration. The cytosolic calcium concentration in mast cell is larger than extracellular calcium, but the Ca2+pumps on cell membrane prevent the infiltration of Ca2+from entering the cells. Former studies[1] indicate shear stress can open channels on cell membrane on mast cells, then extracellular Ca2+can enter cytosol and increase the cytosolic concentration of Ca2+in mast cell. The increase of calcimu promote degranulation, and the main ingredients of granules emitted from the cells are histamine and interleukin. And some experiments prove that degranulation has relation with threshold of pain, and has similar effectiveness of acupuncture. At the same time, we observe distinct calcium oscillation in mast cell, and shear stress increase the frequence of calcium oscillation.In our experiments, we discover that under the fluid shear stress triggered by stepping motor, calcium fluorescence intensity present calcium oscillations and steady states according to shear stress. And the frequence of calcium oscillation under shear stress is larger than without shear stress, which indicate that shear stress can promote calcium oscillation.At the same time, we establish a mathematical model of cytosolic calcium and degranulation dynamics response to fluid shear stress in mast cells. cytosolic calcium depends on four flux:calcium influx into cytosol as ion channel open on internal Ca2+stores, extracellular calcium influx into cytosol as ion channel open on cell membrane, cytosolic calcium pump out of cell by internal store and membrane exchangers. Shear stress transfer into strain energy density on cell membrane to increase the probability of opening channels. By mathematical calculation, we can conclude that shear stress can result in calcium oscillation or steady state. Increase of shear stress could increase frequence of calcium oscillation under oscillation state. Farther increase of shear stress could promote calcium concentration achive a relaive highly steay state, which increase with the shear stress. And calcium dynamics promote mast cell to degranulation, which have similar phenomenon to calcium dynamics.