Inhibition of mammalian target of rapamycin aggravates the respiratory burst defect of neutrophils from decompensated patients with cirrhosis.
Cirrhosis is commonly accompanied by impaired defense functions of polymorphonuclear leucocytes (PMNs), increased patient susceptibility to infections, and hepatocellular carcinoma (HCC). PMN antimicrobial activity is dependent on a massive production of reactive oxygen species (ROS) by nicotinamide adenine dinucleotide phosphate (NADPH) 2 (NADPH oxidase 2; NOX2), termed respiratory burst (RB). Rapamycin, an antagonist of mammalian target of rapamycin (mTOR), may be used in the treatment of HCC and in transplanted patients. However, the effect of mTOR inhibition on the PMN RB of patients with cirrhosis remains unexplored and was studied here using the bacterial peptide, formyl-Met-Leu-Phe (fMLP), as an RB inducer. fMLP-induced RB of PMN from patients with decompensated alcoholic cirrhosis was strongly impaired (30%-35% of control) as a result of intracellular signaling alterations. Blocking mTOR activation (phospho-S2448-mTOR) with rapamycin further aggravated the RB defect. Rapamycin also inhibited the RB of healthy PMNs, which was associated with impaired phosphorylation of the NOX2 component, p47phox (phox: phagocyte oxidase), on its mitogen-activated protein kinase (MAPK) site (S345) as well as a preferential inhibition of p38-MAPK relative to p44/42-MAPK. However, rapamycin did not alter the fMLP-induced membrane association of p47phox and p38-MAPK in patients' PMNs, but did prevent their phosphorylation at the membranes. The mTOR contribution to fMLP-induced RB, phosphorylation of p47phox and p38-MAPK was further confirmed by mTOR knockdown in HL-60 cells. Finally, rapamycin impaired PMN bactericidal activity, but not bacterial uptake.


CONCLUSIONS
mTOR significantly up-regulates the PMN RB of patients with cirrhosis by p38-MAPK activation. Consequently, mTOR inhibition by rapamycin dramatically aggravates their PMN RB defect, which may increase patients' susceptibility to infection. Thus, concerns should be raised about the use of rapamycin in immuno-depressed patients.
INSERM U773, CRB3, Faculté de Médécine X. Bichat, Paris, France.
Loïc
L
Rolas
Nesrine
N
Makhezer
Soumeya
S
Hadjoudj
Jamel
J
El-Benna
Bahia
B
Djerdjouri
Laure
L
Elkrief
Richard
R
Moreau
Axel
A
Périanin
D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D004347:Drug Interactions; D004927:Escherichia coli Infections / Q000276:immunology / Q000378:metabolism; D005260:Female; D018922:HL-60 Cells; D006801:Humans; D008104:Liver Cirrhosis, Alcoholic / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000276:immunology; D008297:Male; D008875:Middle Aged; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000031:analogs & derivatives / Q000494:pharmacology; D019255:NADPH Oxidases / Q000378:metabolism; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology; D010587:Phagocytosis / Q000276:immunology; D010766:Phosphorylation / Q000187:drug effects / Q000276:immunology; D016897:Respiratory Burst / Q000187:drug effects / Q000276:immunology*; D020123:Sirolimus / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D000903:Antibiotics, Antineoplastic; D009240:N-Formylmethionine Leucyl-Phenylalanine; C042932:formylmethionyl-leucyl-phenylalanine methyl ester; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020123:Sirolimus