Phosphodiesterase 4 inhibition but not beta-adrenergic stimulation suppresses tumor necrosis factor-alpha release in peripheral blood mononuclear cells in septic shock.
BACKGROUND
Stimulation of beta2-adrenergic receptors (beta2-ARs) inhibits tumor necrosis factor-alpha (TNF-alpha) release in monocytes. In septic shock, endogenous catecholamines induce beta2-AR downregulation, leading to an increased TNF-alpha release. The aims of this study were to analyze the molecular mechanisms of beta-adrenergic downregulation and to explore therapeutic interventions with maintained anti-inflammatory efficacy in septic shock using the inhibition of phosphodiesterase 4 (PDE4).


METHODS
We conducted in vitro stimulation of peripheral blood mononuclear cells of healthy volunteers (n = 20) and patients with septic shock (n = 20) with lipopolysaccharide (LPS) or Staphylococcus aureus enterotoxin B (SEB) without or with isoprenaline, forskolin (an activator of adenylate cyclase), or ropipram (an inhibitor of PDE4). We also conducted flow cytometric analysis of Toll-like receptor (TLR) 4 and TLR2 surface expression and intracellular TNF-alpha production of untreated and stimulated CD14+ monocytes. Protein expression of beta-ARs, of G proteins, of adenylate cyclase, and of TLRs was measured by Western blotting.


RESULTS
Investigations were done by LPS (100 ng/mL) or SEB (10 ng/mL) when TLR4 and TLR2 were maximally expressed. LPS- or SEB-treated CD14+ monocytes of healthy volunteers were able to produce TNF-alpha. This effect was attenuated by isoprenaline, forskolin, or rolipram in a concentration-dependent manner. In CD14+ monocytes of patients with septic shock, the anti-inflammatory effect of isoprenaline was completely blunted whereas efficacy of forskolin and rolipram was maintained. CD14+ monocytes of healthy volunteers were compared with patients with septic shock: protein expression of beta2-ARs was reduced and inhibitory G protein was increased, whereas no changes in adenylate cyclase and stimulatory G protein were found.


CONCLUSIONS
In septic shock, the anti-inflammatory effects of catecholamines are blunted by downregulation of beta2-ARs and upregulation of the inhibitory G protein in CD14+ monocytes. Beta-adrenergic downregulation is overcome by inhibitors of PDE4. These results provide a mechanistic rationale for the therapeutic use of selective PDE4 inhibitors in the treatment of septic shock.
Link
Andreas
A
Klinik für Innere Medizin III, Universität des Saarlandes, 66421 Homburg/Saar, Germany. link@med-in.uni-saarland.de
Selejan
Simina
S
Maack
Christoph
C
Lenz
Monika
M
Böhm
Michael
M
D058666:Adrenergic beta-2 Receptor Agonists; D016022:Case-Control Studies; D005576:Colforsin / Q000494:pharmacology; D005434:Flow Cytometry; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D007963:Leukocytes, Mononuclear / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D058988:Phosphodiesterase 4 Inhibitors; D010726:Phosphodiesterase Inhibitors / Q000378:metabolism* / Q000494:pharmacology; D020889:Rolipram / Q000494:pharmacology; D012772:Shock, Septic / Q000201:enzymology / Q000378:metabolism* / Q000503:physiopathology; D051195:Toll-Like Receptor 2 / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D058666:Adrenergic beta-2 Receptor Agonists; D058988:Phosphodiesterase 4 Inhibitors; D010726:Phosphodiesterase Inhibitors; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D005576:Colforsin; D019204:GTP-Binding Proteins; D020889:Rolipram; D007545:Isoproterenol