Effects Of Methylene Blue On The Nitric Oxide-Soluble Guanylate Cyclase-Cyclic Guanylyl Monophosphate Pathway And Cytokine Levels In Rats With Sepsis

Background: Methylene blue (MB) inhibits the production of nitric oxide (NO) and cyclic guanylyl monophosphate (cGMP) and thus reverses septic hypotension, but the specific effects of MB on the NO-soluble guanylate cyclase (sGC)-cGMP pathway in different organs of septic rats are unclear. The present study aimed to elucidate the effects of MB on the NO-sGC-cGMP pathway and inflammatory reactions in rats with sepsis. Methods: A Wistar rat model of sepsis was established by cecal ligation and puncture (CLP). The rats were given an injection of 15 mg/kg of MB via the caudal vein at 6, 12, or 18 h after CLP. The rats were sacrificed at 6 h after the injection. Then, mRNA and protein expressions of sGC alpha 1 (sGC alpha 1) in lung, liver, and kidney tissues were measured by real-time polymerase chain reaction and western blotting, respectively. Levels of cGMP in the lung, liver, and kidney tissues were assessed by enzyme-linked immunosorbent assays (ELISAs). Levels of serum lactic acid, procalcitonin (PCT), interleukin-6 (IL-6), IL-10, and tumor necrosis factor alpha (TNF-alpha) were also detected by ELISAs. A NO reduction method was used to detect the level of serum NO. Results: The levels of sGC alpha 1 and cGMP in lung, liver, and kidney tissues were upregulated in the septic rats and were downregulated after MB administration (P < 0.01 or P < 0.05). Additionally, the levels of serum NO were increased in septic rats and were decreased after MB administration (P < 0.01 or P < 0.05). In a separate set of experiments, the levels of PCT, IL-6, IL-10, and TNF-alpha were increased (P < 0.01) in septic rats but were unchanged after MB administration. Conclusion: The NO-sGC-cGMP pathway is activated in different organs of septic rats. Moreover, MB inhibits the NO-sGC-cGMP pathway, but does not affect systemic inflammation.