*2.5. Oxidized Protein Pattern in the Studied Groups*

Protein oxidation was evaluated by serum levels of 3-nitrotyrosine (µmol/L), carbonylated proteins (PCO-µmol/L), native thiols (NT-µmol/L), total thiols (TT-µmol/L), disulphides (DS-µmol/L) and DS/NT, DS/TT and NT/TT ratios. Nitrotyrosine increased 2.23-fold in non-LN group (*p* < 0.001), and 3-fold in LN group (*p* < 0.001) when compared with control group. Nitrotyrosine varied statistically significantly between LN and non-LN group (*p* < 0.001). PCO increased 1.54-fold in non-LN group (*p* < 0.01), and 1.67-fold in LN group (*p* < 0.01) when compared with control group. PCO also varied statistically significantly between LN and non-LN group (*p* < 0.01). NT decreased by 1.12-fold in non-LN group (*p* < 0.001), and 1.23-fold in LN group (*p* < 0.001) when compared with the control group. NT varied statistically significantly between LN and non-LN group (*p* < 0.001). TT decreased 1-fold in non-LN group (*p* < 0.001), and 1.13-fold in LN group (*p* < 0.001) when compared with the control group. TT varied statistically significantly between LN and non-LN group (*p* < 0.001). DS increased 1.31-fold in non-LN group (*p* < 0.001), and 1.63-fold in LN group (*p* < 0.001) when compared with control group. DS varied statistically significantly between LN and non-LN group (*p* < 0.001). DS/NT increased 1.48-fold in non-LN group (*p* < 0.001), and 2.02-fold in LN group (*p* < 0.001) when compared with control group. DS/NT varied statistically significantly between LN and non-LN group (*p* < 0.001). DS/TT increased 1.58-fold in non-LN group (*p* < 0.001), and 2.06-fold in LN group (*p* < 0.001) when compared with the control group. DS/TT varied statistically significantly between LN and non-LN group (*p* < 0.001). NT/TT decreased 1.04-fold in non-LN group (*p* < 0.001), and 1.09-fold in LN group (*p* < 0.001) when compared with the control group. NT/TT varied statistically significantly between LN and non-LN group (*p* < 0.001). 3-NT, PCO, NT, TT, DS and DS/NT, DS/TT and NT/TT ratios had similar statistical variations when compared type IV lupus nephritis with SLE and controls and no statistical variations when compared with SLE–LN. All results are presented in Table 6.


**Table 6.** Oxidized protein pattern in the studied groups.

PCO—Carbonylated proteins, NT—Native thiol, TT—Total thiol, DS—Disulphide, SLE—Systemic lupus erythematosus, LN—Lupus nephritis, *p*—Statistical significance, *p*1—Triple comparison of the groups, *p*2—Pairwise comparison of the groups, A—SLE non-LN, B—LN, C—type IV lupus nephritis, D—Control.
