The Probable Protective Effect of Photobiomodulation on the Immunologic Factor’s mRNA Expression Level in the Lung: An Extended COVID-19 Preclinical and Clinical Meta-analysis

Background: Different expression of cytokine genes in the body determines the type of immune response (Th1 or Th2), which can play an important role in the pathogenesis of the COVID-19 disease. Aims: This meta-analysis was conducted to evaluate the probable effect of photobiomodulation (PBMT) therapy on the cytokine’s mRNA expression in the lung. Methods: We systematically searched indexing databases, including PubMed/Medline, ISI web of science, Scopus, EMBASE, and Cochrane central, using standard terms without language, study region or type restrictions. Studies on using PBM in lung injury modeling with samples collected from lung tissue to observe IL-1β, TNF-α, IL-10, and IL-6 mRNA expression were included. RevMan 5.3 software was used for data analysis and standardized mean difference as effect size. Results: Of the 438 studies found through initial searches, 17 met the inclusion criteria. The main properties of 13 articles on 384 animals included in this meta-analysis with a wide range of species include rats (n = 10) and rabbits (n = 3). The analysis revealed that PBMT reduced the mRNA expression of TNFα (SMD: −3.70, 95% CI: −6.29, −1.11, P = .005, I 2 = 71%) and IL-1β (SMD: −5.85, 95% CI: −8.01, −3.69, P < .00001, I 2 = 37%) significantly, but no statistically significant reduction in IL-6 (SMD: −2.89, 95% CI: −5.79, 0.01, P = .05, I 2 = 88%) was observed compared with the model controls. Also, PBMT increased IL-10 mRNA expression significantly compared with the model controls (SMD: 1.04, 95% CI: 0.43, 1.64, P = .0008, I 2 = 17%). Conclusion: This meta-analysis revealed that the PBMT utilizes beneficial anti-inflammatory effects and modulation of the immune system on lung damage in animal models and clinical studies. However, animal models and clinical studies appear limited considering the evidence’s quality; therefore, large clinical trials are still required.