Sepsis-induced organ failure is mediated by different pathways in the kidney and liver: acute renal failure is dependent on MyD88 but not renal cell apoptosis

Abstract

Toll-like receptors (TLRs) are important in sepsis. Myeloid differentiation factor 88 (MyD88) is a key molecule involved in signal transduction by multiple TLRs. The objective of this study was to investigate the contribution of TLR4 and MyD88 to acute renal failure (ARF) induced by polymicrobial sepsis. Liver dysfunction and apoptosis in the spleen contribute to sepsis severity after cecal ligation and puncture (CLP). Therefore, we also investigated liver injury and splenic apoptosis. We used a mouse model of sepsis-induced ARF using CLP to generate polymicrobial sepsis. Despite fluid and antibiotic resuscitation the mice developed multi-organ failure, including ARF, which resembles human sepsis. We investigated the role of the TLR4 receptor by comparing C3H/HeJ mice (which lack TLR4) with C3H/He0UJ normal controls. The role of MyD88 was investigated by comparing MyD88 knockout mice (MyD88(-/-)) with wild-type controls. Following CLP, mice lacking TLR4 and wild-type mice both developed comparable ARF. However, MyD88(-/-) mice did not develop ARF compared to wild-type controls. In contrast, MyD88(-/-) mice developed liver injury comparable to wild type. After CLP, MyD88(-/-) mice had significantly reduced apoptosis in the spleen compared with wild type. Apoptosis was not detected in the kidney of wild-type or MyD88(-/-) mice after CLP. In summary, ARF induced by polymicrobial sepsis is dependent on MyD88, but not TLR4. The absence of MyD88 dissociates ARF from liver injury; liver injury is MyD88-independent. There was MyD88-dependent apoptosis in the spleen, but no apoptosis in the kidney. MyD88 may be a good drug target for some, but not all, organ dysfunctions following sepsis.

Figure 1

Effect of CLP on mice lacking TLR4 (C3H/HeJ) and MyD88 (MyD88^-/-) compared with controls (C3H/He0uJ and C57BL/6, respectively). A) serum creatinine values 24 hours after sham surgery or CLP. B) Blood Urea nitrogen values 24 hours after sham surgery or CLP. C) Serum TNFα levels 24 hours after CLP. Sham represents values from C3H/HeJ and C3H/He0uJ mice or MyD88^-/- and C57BL/6 mice. * p<0.05 vs sham, # p<0.05 vs C57BL/6. PAS stained kidney sections × 40 from sham operated MyD88^-/-mice (D), CLP –operated C57BL/6 (E) and CLP-operated MyD88^-/- mice (F) 24 hours after surgery.

Figure 2

Effect of CLP on liver function in mice lacking TLR4 (C3H/HeJ) and MyD88 (MyD88^-/-) compared with controls (C3H/He0uJ and C57BL/6, respectively). A) Serum aspartate transaminase levels 24 hours after sham or CLP surgery. B) Serum alanine transaminase levels 24 hours after sham or CLP surgery. Sham represents values from C3H/HeJ and C3H/He0uJ mice or MyD88^-/- and C57BL/6 mice. Typical liver histology stained with PAS. 24 hours after sham surgery in MyD88^-/- (C). 24 hours after CLP surgery in C57BL/6 (D). 24 hours after CLP surgery in MyD88^-/- (E). * p<0.05 vs sham. NS=not significant.

Figure 3

Splenic apoptosis 24 hours after sham and CLP surgery in MyD88^-/- mice (compared with C57BL/6 controls). A) Number of splenic activated caspase 3 positive cells or TUNEL positive nuclei per ×40 field. * p<0.05 vs sham, # p<0.05 vs C57BL/6, n=3 per group. B) Typical spleen sections 24 hours after CLP from C57BL/6 mice and MyD88^-/- mice. The sections are stained with anti-activated caspase 3 antibody or TUNEL.