Cyclosporine and tacrolimus have inhibitory effects on toll-like receptor signaling after liver transplantation

Abstract

Toll‐like receptors (TLRs) play a key role in transplantation biology. The effect of immunosuppression on TLR function after liver transplantation is unknown. Peripheral blood mononuclear cells (PBMCs) from 113 post–liver transplant patients and 13 healthy controls were stimulated with TLR‐specific ligands [lipopolysaccharide (TLR4), pan‐3‐cys (P3C) (TLR2), Poly (I:C) (PIC) (TLR3), R848 (TLR7/8), and CpG (TLR9)] for 24 hours. PBMCs from 5 healthy controls were also cultured with therapeutic concentrations of cyclosporine A (CYA) and tacrolimus (TAC). Cytokine production was measured with enzyme‐linked immunosorbent assays and flow cytometry. PBMCs from patients on calcineurin inhibitors after liver transplantation produced less interleukin‐6 (IL‐6) and tumor necrosis factor α (TNFα) in response to TLR2 stimulation (IL‐6: P=0.02; TNFα: P=0.01), TLR4 stimulation (IL‐6: P=0.02; TNFα: P=0.01), and TLR7/8 stimulation (IL‐6: P=0.02; TNFα: P=0.02), compared with healthy controls. Both CD56bright and CD56dim natural killer (NK) cells from patients on calcineurin inhibitors also produced less interferon‐γ (IFNγ) with TLR7/8 stimulation compared with healthy controls (CD56bright: P=0.002; CD56dim: P=0.004). Similar findings were demonstrated in healthy PBMCs cultured with CYA (PBMCs: TLR2, IL‐6: P=0.005; TLR4, IL‐6: P=0.03, TNFα: P=0.03; TLR7/8, IL‐6: P=0.02, TNFα: P=0.01; CD56dim NK cells: TLR7/8, IFNγ: P=0.03). TAC impaired TLR4‐mediated IL‐6 and TNFα production by PBMCs (IL‐6; P = 0.02; TNFα P = 0.009). In conclusion, patients on calcineurin inhibitors had impaired inflammatory cytokine production in response to TLR2, TLR4, and TLR7/8 stimulation compared comparison with healthy controls. Importantly, TAC and CYA appear to have different effects on TLR signaling. Impaired TLR function has important repercussions for risk of infection, graft rejection, and disease recurrence after transplantation, and the different immunosuppressive profiles of CYA and TAC may guide the choice of therapy to improve disease outcomes. Liver Transpl 19:1099‐1107, 2013. © 2013 AASLD.

Impairment of early fracture healing by skeletal muscle trauma is restored by FK506

“…The restorative effects of FK506 on fracture healing may also occur through modulation of multiple types of immune cells. Several reports suggest FK506 modulates innate immune cells to generate reduced responses to innate stimuli [38–40]. For example, dendritic cells and macrophages pretreated with FK506 were shown to produce lower amounts of pro-inflammatory cytokines after exposure to lipopolysaccharide, a pathogen associated molecular pattern (PAMP) [38, 39].…”

“…For example, dendritic cells and macrophages pretreated with FK506 were shown to produce lower amounts of pro-inflammatory cytokines after exposure to lipopolysaccharide, a pathogen associated molecular pattern (PAMP) [38, 39]. PAMPs and damage-associated molecular patterns (DAMPs) both signal through Toll-like receptor (TLR) pathways that are damped in TLR-ligand stimulated peripheral blood mononuclear cells isolated from patients who received FK506 [40]. FK506 also affects the regulatory T (Treg) cell population, which is known to dampen pro-inflammatory immune responses [41].…”

Role of toll-like receptors in liver transplantation

“…Natural killer CD56 dim cells from post–liver transplant patients on calcineurin inhibitors also produced less IFN‐γ with TLR7/8 stimulation in comparison with those from healthy controls. Furthermore, these findings were confirmed in healthy human peripheral blood mononuclear cells cocultured with therapeutic concentrations of cyclosporine and stimulated with TLR2, TLR4, and TLR7/8 ligands . These findings are important because they suggest that calcineurin inhibition may further reduce cellular rejection through inhibition of innate immune signaling as well as adaptive immunity.…”

“…Our group recently showed that peripheral blood mononuclear cells from patients on calcineurin inhibitors after liver transplantation had impaired IL‐6 and TNF‐α secretion after ex vivo TLR2, TLR4, and TLR7/8 stimulation in comparison with healthy controls . Natural killer CD56 dim cells from post–liver transplant patients on calcineurin inhibitors also produced less IFN‐γ with TLR7/8 stimulation in comparison with those from healthy controls.…”

“…Both IFN‐α signaling and IFN‐γ signaling are crucial in defenses against viral infection, and these findings demonstrate an important role for TLR7/8 signaling in HCV recurrence after transplantation. This is particularly interesting when it is considered in the context of recent evidence showing that calcineurin inhibitors impair TLR7/8‐mediated IFN‐γ secretion by human natural killer CD56 dim cells after liver transplantation . As our understanding of the effects of immunosuppressive drugs on innate immunity expands, tailoring immunosuppression regimens after liver transplantation to reduce adverse outcomes in the graft will become increasingly important.…”