The Impact of Phorbol Ester on the Regulation of Amiloride-Sensitive Epithelial Sodium Channel in Alveolar Type Ii Epithelial Cells

Yamagata, Toshiyuki; Yamagata, Yuko; Nishimoto, Tetsuya; Nakanishi, Masayoshi; Nakanishi, Hiroyuki; Minakata, Yoshiaki; Mune, Masatoshi; Yukawa, Susumu

doi:10.1080/01902140290103062

Cited by 8 publications

(8 citation statements)

References 43 publications

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“…These data indicate that PKC activation rather than depletion is involved in this process. Our results are similar to what has been noted in other epithelial cells (Zentner et al 1998;Stockand et al 2000;Yamagata et al 2002;Booth and Stockand 2003), in which the expression of either α, β, or γENaC is modulated by PMA.…”

Section: Discussionsupporting

confidence: 94%

“…Recently, Yamagata et al (2002) reported that 24-h treatment of alveolar epithelial cells decreases ENaC expression and function. Their study focused only on the impact of 24-h treatment with PMA.…”

Section: Discussionmentioning

confidence: 99%

“…Although PKC influences Na + transport (Hays et al 1987;Ling et al 1990;Duchatelle et al 1992) and ENaC (Awayda et al 1996;Yue et al 2000;Booth and Stockand 2003) or Na + -K + -ATPase activity (Liang and Knox 1999;Bertuccio et al 2003) in kidney epithelial cells, its importance in the modulation of Na + transport in alveolar epithelial cells has not been studied much. Recently, it was reported that PKC activation can downregulate ENaC expression in alveolar type II cells (Yamagata et al 2002). However, the mechanism involved and the physiological impact of this response are not well known.…”

Section: Introductionmentioning

confidence: 99%

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Modulation of Na⁺transport and epithelial sodium channel expression by protein kinase C in rat alveolar epithelial cells

Yamagata¹,

Yamagata²,

Massé³

et al. 2005

Can. J. Physiol. Pharmacol.

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Although the amiloride-sensitive epithelial sodium channel (ENaC) plays an important role in the modulation of alveolar liquid clearance, the precise mechanism of its regulation in alveolar epithelial cells is still under investigation. Protein kinase C (PKC) has been shown to alter ENaC expression and activity in renal epithelial cells, but much less is known about its role in alveolar epithelial cells. The objective of this study was to determine whether PKC activation modulates ENaC expression and transepithelial Na+ transport in cultured rat alveolar epithelial cells. Alveolar type II cells were isolated and cultured for 3 to 4 d before they were stimulated with phorbol 12-myristate 13-acetate (PMA 100 nmol/L) for 4 to 24 h. PMA treatment significantly decreased alpha, beta, and gammaENaC expression in a time-dependent manner, whereas an inactive form of phorbol ester had no apparent effect. This inhibitory action was seen with only 5-min exposure to PMA, which suggested that PKC activation was very important for the reduction of alphaENaC expression. The PKC inhibitors bisindolylmaleimide at 2 micromol/L and Gö6976 at 2 micromol/L diminished the PMA-induced suppression of alphaENaC expression, while rottlerin at 1 micromol/L had no effect. PMA elicited a decrease in total and amiloride-sensitive current across alveolar epithelial cell monolayers. This decline in amiloride-sensitive current was not blocked by PKC inhibitors except for a partial inhibition with bisindolylmaleimide. PMA induced a decrease in rubidium uptake, indicating potential Na+-K+-ATPase inhibition. However, since ouabain-sensitive current in apically permeabilized epithelial cells was similar in PMA-treated and control cells, the inhibition was most probably related to reduced Na+ entry at the apical surface of the cells. We conclude that PKC activation modulates ENaC expression and probably ENaC activity in alveolar epithelial cells. Ca2+-dependent PKC is potentially involved in this response.

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Section: Discussionsupporting

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modulation of Na⁺transport and epithelial sodium channel expression by protein kinase C in rat alveolar epithelial cells

Yamagata¹,

Yamagata²,

Massé³

et al. 2005

Can. J. Physiol. Pharmacol.

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“…After 5 days, untreated epithelia showed a resistance of 1276 Ϯ 46 ⍀.cm 2 (p Ͻ0.01 compared with phorbol 12-myristate 13-acetate). However, phorbol 12-myristate 13-acetate has been shown to decrease amiloride-sensitive sodium currents, and thus we cannot conclude that the increase in Rt is solely due to an effect on the paracellular pathway (18).…”

Section: Unphosphorylated Pp2a Is Associated With Tight Junction Protmentioning

confidence: 76%

erbB1 Functions as a Sensor of Airway Epithelial Integrity by Regulation of Protein Phosphatase 2A Activity

Vermeer

Panko

Welsh

et al. 2006

Journal of Biological Chemistry

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Two enzymes, protein phosphatase 2A and atypical protein kinase C, are associated with the tight junction and regulate its function. For example, phosphorylation of the tight junction protein occludin is required for its incorporation into the junction. The association of a kinase and phosphatase with the tight junction suggests that a balance between their activities exists and is required for normal tight junction function. This hypothesis predicts that loss of epithelial integrity may disrupt this balance in such a way as to facilitate restoration of epithelial integrity. Our previous data have shown that apically localized growth factors segregate from their basolaterally localized erbB receptors. Loss of epithelial integrity allows ligand access to the basolateral membrane where it immediately binds to and activates erbB receptors. We found that activation of erbB1 leads to phosphorylation of protein phosphatase 2A, inhibiting its activity. Importantly, this phosphorylation event was dependent on factors in the overlying airway surface liquid; washing away this liquid prevented phosphorylation. erbB1-mediated inhibition of phosphatase activity would shift the balance in favor of the kinase such that tight junction proteins would regain their phosphorylation, allowing for their incorporation into the junction complex. This mechanism provides a rapid means of sensing the loss of epithelial integrity and subsequently restoring barrier function.Polarized epithelia line the cavities of the body, forming a physical barrier between the external environment and the body compartments. Essential to the function of an epithelium is its polarity. Cellular polarity is established and maintained by cell-cell adhesion junctions, including the tight junction and the adherens junction. We have previously demonstrated that maintenance of barrier function is required for silencing signaling cascades in differentiated primary cultures of human airway epithelia (1). Airway epithelia secrete growth factors into the airway surface liquid (ASL).2 Among these is heregulin-␣, a ligand for the family of erbB tyrosine kinase receptors that localize to the basolateral membrane in airway epithelia. This arrangement allows for receptor activation the instant epithelial integrity is compromised. In the presence of intact tight junctions, erbB receptors are silent (not phosphorylated). Disruption of cell-cell junctions allows ASL factors immediate access to the basolateral membrane, resulting in erbB receptor activation. Receptor activation triggers signaling cascades involved in injury repair. Following restoration of epithelial integrity, heregulin-␣ regains its restriction to the ASL, and erbB receptors are once again silenced. These data emphasize the importance of epithelial polarity and the cellcell adhesion junctions that maintain it. In the absence of tight junctions, polarity ceases to exist and erbB signaling cascades become activated. Such aberrant signaling can lead to many downstream effects, including cellular proliferation, ...

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“…We postulated that ENaC may be the ultimate downstream target of (c)PKC. This view is based on several studies that showed a reduction in ENaC expression following exposure to PMA (1,7,37). Our model is somewhat different: we are looking at the acute functional effect of PKC activation, while most previous studies focused on longer-term downregulation of ENaC mRNA.…”

Section: Discussionmentioning

confidence: 99%

Physiological effect of protein kinase C on ENaC-mediated lung liquid regulation in the adult rat lung

Soukup

Benjamin

Orogo-Wenn

et al. 2012

American Journal of Physiology-Lung Cellular and Molecular Phys

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The aim of this work was to determine whether PKC activation is involved in the physiological regulation of LL volume in a whole lung preparation. Rat lungs were perfused with a modified Ringer solution, and the lumen was filled with the same solution without glucose. LL volume was measured during a control period and after modulating drugs were administered, and net LL transepithelial movement (Jv) was calculated. When the PKC activator PMA (10 Ϫ5 M) and the Ca 2ϩ ionophore ionomycin (10 Ϫ6 M) were instilled into the lung together, Jv was significantly reduced (P ϭ 0.03). This reduction was blocked by the PKC inhibitor chelerythrine chloride (10 Ϫ6 M; P ϭ 0.56) and by a second PKC inhibitor GF109203X (10 Ϫ5 M; P ϭ 0.98). When PMA and ionomycin were added with the ␤-adrenergic agonist terbutaline, the terbutaline-induced increase in Jv was abolished. Addition of PMA and ionomycin with the epithelial Na ϩ channel (ENaC) blocker amiloride had no additional inhibitory effect. Together, these results suggest that PKC is likely to be involved in LL absorption, and the ability of PMA/ionomycin to block the terbutaline-induced increase in Jv suggests that the downstream target of PKC is ENaC.calcium-dependent protein kinase C; ionomycin; phorbol 12-myristate 13-acetate TIGHT CONTROL OF LUMINAL lung liquid (LL) volume is essential for normal pulmonary function. An excess or deficiency of LL in the airway and the alveoli leads to pathology, so mechanisms to control LL volume are critical. In the airway, there is a dynamic balance between secretion and absorption of liquid (30), and some of the cellular mechanisms involved have been shown to be present in alveolar cells (13). Cl Ϫ transport seems to underlie liquid secretion into the lumen, while Na ϩ transport has been shown to be essential for liquid absorption. The Na ϩ absorptive mechanisms have received more attention than the Cl Ϫ secretory mechanisms, and the airway epithelium has been better studied than the alveolar barrier, although the latter contributes by far more surface area (by a ratio of Ն500:1, if not 850:1) (18).The principal channel responsible for Na ϩ absorption is the epithelial Na ϩ channel (ENaC), which has been the focus of much research. In the perinatal period, activation of lung ENaC is very sensitive to epinephrine, which causes a dramatic reversal of net transepithelial liquid flow (J v ), thereby facilitating the change at birth from a prenatal secreting phenotype to an absorption phenotype (9, 17). Hummler et al. (15) demonstrated that ␣-ENaC-deficient (Ϫ/Ϫ) mice were unable to survive beyond 40 h after birth. These animals died from acute respiratory failure with liquid-filled lungs, providing conclusive evidence that ENaC is vital for the liquid absorption at birth. During postnatal life, there is a dynamic balance between the secretory and absorptive processes. Although liquid absorption predominates in the liquid-filled lung, a secretory mechanism persists and can be demonstrated to be present under certain circumstances (25). The me...

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The Impact of Phorbol Ester on the Regulation of Amiloride-Sensitive Epithelial Sodium Channel in Alveolar Type Ii Epithelial Cells

Cited by 8 publications

References 43 publications

Modulation of Na⁺transport and epithelial sodium channel expression by protein kinase C in rat alveolar epithelial cells

Modulation of Na⁺transport and epithelial sodium channel expression by protein kinase C in rat alveolar epithelial cells

erbB1 Functions as a Sensor of Airway Epithelial Integrity by Regulation of Protein Phosphatase 2A Activity

Physiological effect of protein kinase C on ENaC-mediated lung liquid regulation in the adult rat lung

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The Impact of Phorbol Ester on the Regulation of Amiloride-Sensitive Epithelial Sodium Channel in Alveolar Type Ii Epithelial Cells

Cited by 8 publications

References 43 publications

Modulation of Na+transport and epithelial sodium channel expression by protein kinase C in rat alveolar epithelial cells

Modulation of Na+transport and epithelial sodium channel expression by protein kinase C in rat alveolar epithelial cells

erbB1 Functions as a Sensor of Airway Epithelial Integrity by Regulation of Protein Phosphatase 2A Activity

Physiological effect of protein kinase C on ENaC-mediated lung liquid regulation in the adult rat lung

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Modulation of Na⁺transport and epithelial sodium channel expression by protein kinase C in rat alveolar epithelial cells

Modulation of Na⁺transport and epithelial sodium channel expression by protein kinase C in rat alveolar epithelial cells