TLR4 and serum lipopolysaccharide activity: During endotoxemia, LPS-induced toll-like receptor-4 (TLR-4) activation promotes expressions of inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukins (IL-1β and IL-6) through transcription of nuclear factor-κB (NF-κB), which is a crucial regulator of immune system [10].