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.