Well, it depends on the concentration of reactive oxygen species in your experimental set-up. If it is very high the antioxidant systems in the cell become overloaded so that the cell cannot cope with the stress level. Did you measure gene expression under different levels of oxidative stress?

Cheers, Christian

Yes, I have checked the gene expression level. In the early stages of treatment, I got a significant down-regulation. But, later there was a recovery phase. The level of expression was increasing with the time.

Dear Debaprasad Koner;

 Oxidative damage is an important consequence of oxidative stress, which is a state characterized by an imbalance between the generation of reactive oxygen species (ROS) and the antioxidant defense capacity. In general, antioxidant defense systems consist of low-molecular-weight antioxidants and antioxidant enzymes including SOD, CAT, GPx and GST. These antioxidant enzymes activities are closely related to their mRNA levels. Hence, there are 2 factors that can influence the expression pattern of antioxidant enzymes: Firstly, it depends on the concentration of ROS; Secondly, it depends on some signaling molecules syntheses including the target of rapamycin (TOR) and nuclear factor erythoid 2-related factor 2 (Nrf2), which play important roles in the regulation of antioxidant enzyme gene transcriptions.

For farther you may read our publication (related study):

Habte-Tsion, H.M., Ren, M.C., Liu, B., Ge, X.P., Xie, J. & Chen, R. (2015) Threonine modulates immune response, antioxidant status and gene expressions of antioxidant enzymes and antioxidant-immune-cytokine-related signaling molecules in juvenile blunt snout bream (Megalobrama amblycephala). Fish & Shellfish Immunology, in Press, doi: 10.1016/j.fsi.2015.11.033

Best regards

H. Michael

Dear Debaprasad;

The balance in the 'ROS-antioxidant enzymes' system changes dynamically and can have a regular cyclic (oscillatory) nature, as our computational experiments showed. For details, see our article "Active ribosomal genes, translational homeostasis and oxidative stress in the pathogenesis of schizophrenia and autism"

in PSYCHIATRIC GENETICS 25(2):79-87 (https://www.researchgate.net/profile/Lev_Porokhovnik2/publication/272842066_Active_ribosomal_genes_translational_homeostasis_and_oxidative_stress_in_the_pathogenesis_of_schizophrenia_and_autism/links/55ae422508aed614b099ca96.pdf?origin=publication_detail&ev=pub_int_prw_xdl&msrp=jVj3qZMG_qUw_RbF871KpqEiBvOfe_NqVeG55w9wrAl7WD2d69xabcCFIlmkGijrRMuxJXCYAqZdthTK6Fw1lg.jCcf5FzVmeuaefrMxPBAHPwcewcAirVXAMmd_r-avjs9Muo8urS4h3sOADIe4lkclYCotlPEPeuwZObzMgEuXw.e7eQXyo3Z3-iYX_8MIDlap7zGtH-YvMBMzYV3shIoan09EC2KS5kIFinI0N_xUwgtbUByNyGZF4LG2nOgDO-NQ)

So, you could miss the first increase of the cycle and register a secondary decrease, etc.

Article Active ribosomal genes, translational homeostasis and oxidat...

The expression of these antioxidant enzymes depends on the quantity and quality of generated free radicals into the biological system (biological membranes, cytosolic compartments, nucleus, tissues or artificial systems), as well as it depends on different cell types and diseases. Then, It is important not just quantify these enzymes but also antioxidant-response genes and other factors. 

It is really urgent that reviewers can perform systematic reviews searching for a pattern (if really exist) of oxidaitve/nitrosative stresses for some types of cells or diseases. However, it can not be possible to characterize those patterns, since during each clinical stage of the disease the production of free radicals and antioxidants substantially change.  

Thank you all very much for your answers. 

With regards,

Deb

In clinical studies, erythrocyte SOD activity with higher values means increased mild oxidative stress and this is an adaptation response .  In the precursors of the mature red blood cell, the radicals increase the expression of the gene for SOD.  

Erythrocyte SOD activity with lower values means increased (severe ) oxidative stress.

Thank you very much for answer. Prior to performing the experiment, there was a mind set-up that in up-regulation of antioxidant enzymes is the sign of oxidative stress. But, now after going through the valuable answers I am realizing the phenomenon.

Dear Debaprasad Koner;

Well, I can share with you my paper, and I hope it to help you 

Best regards; 

Thank you dear Soliman for your valuable paper.

for example , my paper: ABOUT TOTAL ANTIOXUDANT (TAC)

In the present study, total antioxidant level of serum in fish treated with diazinon compared with control group after two weeks. This decrease may be the result of continuous production of free radicals in diazinon metabolism. In other words, decrease of TAC level occurs after scavenging process and inhibiting free radicals through enzymatic and non-enzymatic factors of antioxidant defense system and using these factors.

the findings of this study showed that TAC level increased in the end of fourth week in comparison with second week, however the difference was not significant in comparison with control group. The reason for this compensation in TAC level could be attributed to the increase in catalase and superoxide dismutase levels in the fourth week, as subacute doses of diazinon has improved the chance for compensatory and adaptive responses for the cells to reach a kind of homeostasis. According to some studies, the increase of total antioxidant capacity (TAC) caused by oxidative stresses in biological systems could be due to the increase in antioxidant activities via cellular defense mechanism in order to reach homeostasis and somehow adaptation in dealing with antioxidative stresses

In Research what ever expression you get is the expression, it is only that you need to make sure that you have proper controls/criteria, then you need to explain your results, based on your findings to the best of your knowledge, without bias.