Exclusion criteria
The exclusion criteria of the PICOS strategy were also applied, following the recommended sequence of PICOS. These criteria were selected based on the main guidelines for cell culture (American Type Culture Collection - ATCC, 2018).  In the first phase of eligibility, the title and abstract were read and the following exclusion criteria applied: 1) Not RAW 264.7 macrophages; 2) Not LPS induced RAW 264.7 macrophages; 3) Not reporting “nitric oxide or nitrites” AND “TNF-alpha or IL-1 beta or IL-6”; 4) Study design: experimental studies using exclusively animal models, clinical trials or other studies involving humans, reviews, Guidelines, Letters, Editorials, Comments, News, conference abstracts, thesis, and dissertations; Not written in the English language; full texts unavailable. In the second phase, the full text was read and some further exclusion criteria were added: 5) LPS concentration different from 1 µg/mL; LPS-exposure time different from 12, 24 or/and 48 hours; 6)  “nitric oxide or nitrites” AND TNF-alpha and/or IL-1 beta and/or IL-6 measurements presented as gene or ratio of expression OR other measurements (%, IC50); 7) Nitric oxide or nitrite production equal or less than 20 µM in the LPS control group; 8) Studies that did not use a basal control group (comparator: RAW 264.7 macrophages not induced by LPS and another substance); 9) DMEM not used as a cell culture medium; 10) Full texts unavailable; 11) NO not measured by the Griess method; 12) atmospheric condition other than 5% CO25 mL; 15) NO and cytokines not measured in the same experimental condition; 16) NO levels >300 µM (the reactivity threshold); 17) Duplicate studies.