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Original

Modulation of SERCA in the chronic phase of adjuvant arthritis as a possible adaptation mechanism of redox imbalance

, , , , , , & show all
Pages 852-864 | Received 11 Feb 2009, Published online: 01 Sep 2009
 

Abstract

Adjuvant arthritis (AA) is a condition that involves systemic oxidative stress. Unexpectedly, it was found that sarcoplasmic reticulum Ca2 +-ATPase (SERCA) activity was elevated in muscles of rats with AA compared to controls, suggesting possible conformational changes in the enzyme. There was no alteration in the nucleotide binding site but rather in the transmembrane domain according to the tryptophan polar/non-polar fluorescence ratio. Higher relative expression of SERCA, higher content of nitrotyrosine but no increase in phospholipid oxidation in AA SR was found. In vitro treatments of SR with HOCl showed that in AA animals SERCA activity was more susceptible to oxidative stress, but SR phospholipids were more resistant and SERCA could also be activated by phosphatidic acid. It was concluded that increased SERCA activity in AA was due to increased levels of SERCA protein and structural changes to the protein, probably induced by direct and specific oxidation involving reactive nitrogen species.

Abbreviations
AA=

adjuvant arthritis

a.u.=

arbitrary units

BSA=

bovine serum albumin

Cai=

intracellular calcium

=

free calcium ions

Co=

control

DNPH=

dinitrophenylehydrazine

FITC=

fluorescein-5-isothiocyanate

GSH=

reduced glutathione

I=

fluorescence intensity

IC50=

half maximal inhibitory concentration

LC-MS=

liquid chromatography-mass spectrometry

NO=

nitric oxide

pATP=

negative logarithm of the concentration of ATP

PA=

phosphatidic acid

PCs=

phosphatidylcholines

PEs=

phosphatidylethanolamines

PLs=

phospholipids

pCafree=

negative logarithm of the concentration of free Ca2 + ions

RA=

rheumatoid arthritis

RFUs=

relative fluorescence units

RNS=

reactive nitrogen species

ROS=

reactive oxygen species

SERCA=

sarcoplasmic/endoplasmic reticulum Ca2 +-ATPase

SR=

sarcoplasmic reticulum

TBARS=

thiobarbituric acid reactive substances

Abbreviations
AA=

adjuvant arthritis

a.u.=

arbitrary units

BSA=

bovine serum albumin

Cai=

intracellular calcium

=

free calcium ions

Co=

control

DNPH=

dinitrophenylehydrazine

FITC=

fluorescein-5-isothiocyanate

GSH=

reduced glutathione

I=

fluorescence intensity

IC50=

half maximal inhibitory concentration

LC-MS=

liquid chromatography-mass spectrometry

NO=

nitric oxide

pATP=

negative logarithm of the concentration of ATP

PA=

phosphatidic acid

PCs=

phosphatidylcholines

PEs=

phosphatidylethanolamines

PLs=

phospholipids

pCafree=

negative logarithm of the concentration of free Ca2 + ions

RA=

rheumatoid arthritis

RFUs=

relative fluorescence units

RNS=

reactive nitrogen species

ROS=

reactive oxygen species

SERCA=

sarcoplasmic/endoplasmic reticulum Ca2 +-ATPase

SR=

sarcoplasmic reticulum

TBARS=

thiobarbituric acid reactive substances

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