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Intracellular spermine prevents acid-induced uncoupling of Cx43 gap junction channels.

Skatchkov SN, Bukauskas FF, Benedikt J, Inyushin M, Kucheryavykh YV - Neuroreport (2015)

Bottom Line: Our results showed (i) a higher increase in gap junctional communication at higher concentrations of cytoplasmic spermine, and (ii) that spermine prevented uncoupling of gap junctions at low intracellular pH.Taken together, we conclude that spermine enhances Cx43-mediated gap junctional communication and may preserve neuronal excitability during ischemia and trauma when pH in the brain acidifies.We, therefore, suggest a new role of spermine in the regulation of a Cx43-based network under (patho)physiological conditions.

View Article: PubMed Central - PubMed

Affiliation: Departments of aPhysiology bBiochemistry, Universidad Central del Caribe, School of Medicine, Bayamón, Puerto Rico cDominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Yeshiva University, New York, New York, USA.

ABSTRACT
Polyamines (PAs), such as spermine and spermidine, modulate the activity of numerous receptors and channels in the central nervous system (CNS) and are stored in glial cells; however, little attention has been paid to their role in the regulation of connexin (Cx)-based gap junction channels. We have previously shown that PAs facilitate diffusion of Lucifer Yellow through astrocytic gap junctions in acute brain slices; therefore, we hypothesized that spermine can regulate Cx43-mediated (as the most abundant Cx in astrocytes) gap junctional communication. We used electrophysiological patch-clamp recording from paired Novikoff cells endogenously expressing Cx43 and HeLaCx43-EGFP transfectants to study pH-dependent modulation of cell-cell coupling in the presence or absence of PAs. Our results showed (i) a higher increase in gap junctional communication at higher concentrations of cytoplasmic spermine, and (ii) that spermine prevented uncoupling of gap junctions at low intracellular pH. Taken together, we conclude that spermine enhances Cx43-mediated gap junctional communication and may preserve neuronal excitability during ischemia and trauma when pH in the brain acidifies. We, therefore, suggest a new role of spermine in the regulation of a Cx43-based network under (patho)physiological conditions.

No MeSH data available.


Related in: MedlinePlus

Spermine (SPM) rescues uncoupling of Cx43 gap junctions induced by intracellular acidification (pHi6) of Novikoff cells. (a) Averaged and normalized junctional conductance (gj) measured in Novikoff cells. Intracellular acidification (pHi=6) significantly enhanced gj decay compared with gj changes at pHi=7.2. SPM added in the patch pipette solution transformed gj decay into gj increase even at pHi=6. (b) Summarized data from (a) at 10 min of the recordings. Error bars represent SEM. *Significant difference (P<0.05, n=4 in each group).
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Figure 2: Spermine (SPM) rescues uncoupling of Cx43 gap junctions induced by intracellular acidification (pHi6) of Novikoff cells. (a) Averaged and normalized junctional conductance (gj) measured in Novikoff cells. Intracellular acidification (pHi=6) significantly enhanced gj decay compared with gj changes at pHi=7.2. SPM added in the patch pipette solution transformed gj decay into gj increase even at pHi=6. (b) Summarized data from (a) at 10 min of the recordings. Error bars represent SEM. *Significant difference (P<0.05, n=4 in each group).

Mentions: Hydrogen cations (H+) are known blockers of Cxs, including Cx43 23,24. We found that PAs not only increase Cx43-mediated gap junctional communication (Fig. 1), but also protect Cx43 gap junctions from acidification-induced uncoupling (Fig. 2). For this, we recorded Ij from Novikoff cells, in which internal acidification was induced by reducing the pHi of the pipette solution to 6 (Fig. 2). Within a few minutes after patch opening, Ij declined on average to 35±10% (P<0.05, n=4; Fig. 2a and b). This gj reduction was rescued by PAs added to the pipette (Fig. 2a and b). At a concentration of spermine greater than 1 mM, the blocking effect at pHi=6 was fully removed (Fig. 2a and b).


Intracellular spermine prevents acid-induced uncoupling of Cx43 gap junction channels.

Skatchkov SN, Bukauskas FF, Benedikt J, Inyushin M, Kucheryavykh YV - Neuroreport (2015)

Spermine (SPM) rescues uncoupling of Cx43 gap junctions induced by intracellular acidification (pHi6) of Novikoff cells. (a) Averaged and normalized junctional conductance (gj) measured in Novikoff cells. Intracellular acidification (pHi=6) significantly enhanced gj decay compared with gj changes at pHi=7.2. SPM added in the patch pipette solution transformed gj decay into gj increase even at pHi=6. (b) Summarized data from (a) at 10 min of the recordings. Error bars represent SEM. *Significant difference (P<0.05, n=4 in each group).
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4493885&req=5

Figure 2: Spermine (SPM) rescues uncoupling of Cx43 gap junctions induced by intracellular acidification (pHi6) of Novikoff cells. (a) Averaged and normalized junctional conductance (gj) measured in Novikoff cells. Intracellular acidification (pHi=6) significantly enhanced gj decay compared with gj changes at pHi=7.2. SPM added in the patch pipette solution transformed gj decay into gj increase even at pHi=6. (b) Summarized data from (a) at 10 min of the recordings. Error bars represent SEM. *Significant difference (P<0.05, n=4 in each group).
Mentions: Hydrogen cations (H+) are known blockers of Cxs, including Cx43 23,24. We found that PAs not only increase Cx43-mediated gap junctional communication (Fig. 1), but also protect Cx43 gap junctions from acidification-induced uncoupling (Fig. 2). For this, we recorded Ij from Novikoff cells, in which internal acidification was induced by reducing the pHi of the pipette solution to 6 (Fig. 2). Within a few minutes after patch opening, Ij declined on average to 35±10% (P<0.05, n=4; Fig. 2a and b). This gj reduction was rescued by PAs added to the pipette (Fig. 2a and b). At a concentration of spermine greater than 1 mM, the blocking effect at pHi=6 was fully removed (Fig. 2a and b).

Bottom Line: Our results showed (i) a higher increase in gap junctional communication at higher concentrations of cytoplasmic spermine, and (ii) that spermine prevented uncoupling of gap junctions at low intracellular pH.Taken together, we conclude that spermine enhances Cx43-mediated gap junctional communication and may preserve neuronal excitability during ischemia and trauma when pH in the brain acidifies.We, therefore, suggest a new role of spermine in the regulation of a Cx43-based network under (patho)physiological conditions.

View Article: PubMed Central - PubMed

Affiliation: Departments of aPhysiology bBiochemistry, Universidad Central del Caribe, School of Medicine, Bayamón, Puerto Rico cDominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Yeshiva University, New York, New York, USA.

ABSTRACT
Polyamines (PAs), such as spermine and spermidine, modulate the activity of numerous receptors and channels in the central nervous system (CNS) and are stored in glial cells; however, little attention has been paid to their role in the regulation of connexin (Cx)-based gap junction channels. We have previously shown that PAs facilitate diffusion of Lucifer Yellow through astrocytic gap junctions in acute brain slices; therefore, we hypothesized that spermine can regulate Cx43-mediated (as the most abundant Cx in astrocytes) gap junctional communication. We used electrophysiological patch-clamp recording from paired Novikoff cells endogenously expressing Cx43 and HeLaCx43-EGFP transfectants to study pH-dependent modulation of cell-cell coupling in the presence or absence of PAs. Our results showed (i) a higher increase in gap junctional communication at higher concentrations of cytoplasmic spermine, and (ii) that spermine prevented uncoupling of gap junctions at low intracellular pH. Taken together, we conclude that spermine enhances Cx43-mediated gap junctional communication and may preserve neuronal excitability during ischemia and trauma when pH in the brain acidifies. We, therefore, suggest a new role of spermine in the regulation of a Cx43-based network under (patho)physiological conditions.

No MeSH data available.


Related in: MedlinePlus