TLR4 and major depressive disorder: Although this ability to suppress PCSK9 by alirocumab was positively correlated to its ability to decrease the HMGB1/RAGE/TLR4 axis and NLP3 inflammasome, however, further studies are required to explore more and confirm the effect of alirocumab on different neurotransmitters involved in depression as serotonin and other downstream mediators of those pathological pathways and correlate the antidepressant effect to the right specific mediators.