Biology Reference
In-Depth Information
to extracellular stress remains poorly understood. However, it is well known that
senescence, injury and inflammation can cause intercellular gaps in the corneal
endothelial monolayer, which not only affect barrier integrity, but could also ham-
per GJIC. In such situations, functional capacity and restoration of integrity of the
corneal monolayer could depend to a large extent on PIC. Therefore, our aim was
to investigate the contribution, role and mechanism of PIC and GJIC in corneal
endothelial cells. In this chapter we describe some of our experimental data about
IC in corneal endothelial cells, with emphasis on the mechanism, regulation and
possible role of hemichannel-mediated purinergic PIC.
10.3 PIC in BCEC
10.3.1 IC in BCEC Consists of GJIC and PIC
BCEC subjected to mechanical stimulation of a single cell in a confluent monolayer
show a transient [Ca
2+
]
i
rise. This Ca
2+
transient propagates as a decremental inter-
cellular Ca
2+
wave, which activates cells up to a distance of four to six neighboring
cells away from the mechanically stimulated cell (Fig. 10.2). The amplitude of the
Ca
2+
rise and percentage of responsive cells decrease with increasing distance from
the mechanically stimulated cell [44]. We investigated the mechanism of the Ca
2+
wave propagation in BCEC to identify whether the propagation is mediated by GJIC
and/or PIC.
In scrape-loading experiments with the membrane-impermeable dye lucifer yel-
low, and in fluorescence recovery after photobleaching (FRAP) experiments using
carboxyfluorescein, significant transfer of the hydrophilic dyes between different
cells was observed. These results provide evidence for the presence of functional
GJIC in BCEC. However, Ca
2+
wave propagation was also found to activate cells
without cell-cell contacts in non-confluent monolayers obtained by sparse seeding of
cells. Furthermore, the Ca
2+
wave was also able to cross cell-free lanes obtained by
deliberate scratching of confluent monolayers [43, 44]. These experiments clearly
demonstrate the contribution of an extracellular messenger to the intercellular Ca
2+
wave propagation. Together these experiments provided evidence that both GJIC
and PIC contribute to IC in BCEC.
10.3.2 Mechanism of PIC in BCEC
10.3.2.1 PIC is Mediated Via Purinergic Signaling
ATP is a prime candidate for eliciting PIC-induced Ca
2+
wave propagation through
its action on the P2 family of purinergic receptors, which can either cause Ca
2+
influx via P2X receptors or evoke IP
3
-induced Ca
2+
release from intracellular stores
by activating PLC via P2Y receptors.
Search WWH ::
Custom Search