Ken-ichi Takano

Silencing of Fas-associated Death Domain Protects Mice from Septic Lung Inflammation and Apoptosis

RATIONALE A better understanding of the molecular mechanisms involved in the pathogenesis of sepsis and its resultant organ failure and new therapeutic approaches and targets are urgently needed. Accumulating evidence suggests that apoptosis plays an important role in the pathophysiology of sepsis and that apoptosis may be detrimental in septic acute lung injury (ALI). OBJECTIVES We tested the hypothesis that systemic administration of small interfering RNA (siRNA) targeting Fas-associated death domain (FADD), which recruits procaspase-8 into the death-inducing signaling complex, may be protective in septic ALI and mortality. METHODS Polymicrobial sepsis was induced by cecal ligation and puncture (CLP) in BALB/c mice. In vivo delivery of siRNA was performed by using a transfection reagent at 10 hours after CLP. As a negative control, animals received nonsense (scrambled) siRNA. MEASUREMENTS AND MAIN RESULTS In CLP-induced septic mice, surface expression of death receptors was up-regulated, and FADD was highly expressed. DNA fragmentation ladder and transferase-mediated dUTP nick end labeling assays showed that treatment with FADD siRNA suppressed apoptosis induction in septic lungs. This siRNA treatment prevented the ALI development in CLP mice, as indicated by the findings that blood-gas derangements, histologic lung damage, and increased pulmonary inflammatory cells were greatly improved. Finally, FADD siRNA administration dramatically improved the survival of CLP mice. CONCLUSIONS These results indicate the pathophysiologic significance of the death receptor apoptotic pathway, including FADD, in septic ALI and the potential usefulness of FADD siRNA for gene therapy of the septic syndrome.

Modulation of glucocorticoid receptor expression, inflammation, and cell apoptosis in septic guinea-pig lungs using methylprednisolone

The use of glucocorticoids for treatment of sepsis has waxed and waned during the past several decades, and recent randomized controlled trials have evoked a reassessment of this therapy. Most glucocorticoid actions are mediated by its specific intracellular receptors (GRs). Thus we initially evaluated whether sepsis and high-dose corticosteroid therapy can regulate guinea pig pulmonary expression of GRs: active receptor, GRalpha, and dominant negative receptor, GRbeta. Sepsis induction by LPS injection (300 mug/kg ip) decreased mRNA and protein levels of GRalpha and increased protein expression of GRbeta in lungs. High-dose methylprednisolone (40 mg/kg ip), administered simultaneously with LPS, markedly potentiated the decrease in GRalpha expression but slightly affected the increase in GRbeta expression. Consequently, this led to a significant reduction in GRalpha nuclear translocation. Nevertheless, methylprednisolone treatment strongly eliminated LPS induction of NF-kappaB activity, as determined by NF-kappaB nuclear translocation and by gel mobility shift assays. Furthermore, the LPS-induced increase in inflammatory cells in bronchoalveolar lavage fluid was blunted by administration of the corticosteroid. On the other hand, immunofluorescent staining for cleaved caspase-3 showed a marked increase in this proapoptotic marker in lung sections, and terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling (TUNEL) represented an enhanced appearance of cell apoptosis in lungs and spleen when methylprednisolone was given together with LPS. Cell apoptosis is now considered to play a role in the pathogenesis of septic syndrome. We thus suggest that the action of glucocorticoids at high doses to accelerate sepsis-induced cell apoptosis may overwhelm their therapeutic advantages in septic shock.

Successful Treatment of Acute Lung Injury with Pitavastatin in Septic Mice: Potential Role of Glucocorticoid Receptor Expression in Alveolar Macrophages

There is growing evidence that the HMG-CoA reductase inhibitors (statins) provide some of the beneficial effects that are independent of their lipid-lowering effects. Recent animal experiments and clinical trials suggest that statin use may limit the development of sepsis and associated systemic inflammation. The aim of this study was to explore the potential role of statins in the prevention treatment of sepsis-induced acute lung injury (ALI). Mice were rendered septic by cecal ligation and puncture (CLP). An intraperitoneal injection of 3 mg/kg per day of pitavastatin was initiated 4 days before surgery and was maintained for life support afterward, which significantly improved the survival of CLP mice. Treatment with pitavastatin prevented the ALI development in CLP mice, as indicated by the findings that severe hypoxemia, increased pulmonary vascular permeability, and histological lung damage, including inflammatory cell infiltrate, were greatly remedied. This was associated with down-regulation of increased activity of nuclear factor-κB (NF-κB) in septic lungs. Although plasma cortisol showed a sharp rise, glucocorticoid receptor (GCR) expression in the lungs was strikingly reduced after the onset of CLP-induced sepsis. It is noteworthy that pitavastatin increased GCR expression with an increase in alveolar macrophages in which GCRs are localized, without modifying the sepsis-associated rise in plasma cortisol. These results confirm significant protection by pitavastatin on septic ALI and demonstrate that down-regulated NF-κB activation associated with the GCR expression increase consequent to the increased number of alveolar macrophages may explain, in part, the mechanisms responsible for favorable effects of statins on the ALI management.

Olprinone and colforsin daropate alleviate septic lung inflammation and apoptosis through CREB-independent activation of the Akt pathway

Olprinone, a specific phosphodiesterase III inhibitor, and corforsin daropate, a direct adenylate cyclase activator, are now being used in critical conditions. We investigated whether their therapeutic use provides protection against septic acute lung injury (ALI) and mortality. Polymicrobial sepsis was induced by cecal ligation and puncture (CLP) in BALB/c mice. Olprinone or colforsin daropate was continuously given through an osmotic pump that was implanted into the peritoneal cavity immediately following CLP. These treatments prevented the ALI development in CLP mice, as indicated by the findings that severe hypoxemia, increased pulmonary vascular permeability, and histological lung damage were strikingly remedied. Furthermore, continued administration of olprinone or colforsin daropate suppressed apoptosis induction in septic lungs and improved the survival of CLP mice. Olprinone and corforsin daropate enhanced Akt phosphorylation in septic lungs. Wortmannin, which inhibits the Akt upstream regulator phosphatidylinositol 3-kinase, abrogated the protective effects of olprinone and corforsin daropate on sepsis-associated lung inflammation and apoptosis. In vivo transfection of cyclic AMP response element binding protein (CREB) decoy oligodeoxynucleotide failed to negate the abilities of these agents to increase Akt phosphorylation and to inhibit IκBα degradation in septic lungs. These results demonstrate for the first time that CREB-independent Akt-mediated signaling is a critical mechanism contributing to the therapeutic effects of olprinone and corforsin daropate on septic ALI. Moreover, our data also suggest that these cyclic AMP-related agents, by blocking both nuclear factor-κB activation and apoptosis induction, may represent an effective therapeutic approach to the treatment of the septic syndrome.

Increased death receptor pathway of apoptotic signaling in septic mouse aorta: effect of systemic delivery of FADD siRNA

Recent evidence suggests that apoptotic cell death plays an important role in the pathophysiology of sepsis. Because there is extensive apoptosis of vascular endothelial cells in sepsis, we examined whether the death receptor pathway of apoptotic signaling is altered in thoracic aortas from mice with polymicrobial sepsis, as produced by cecal ligation and puncture (CLP). In septic aorta, total and surface expression levels of the two death receptors tumor necrosis factor receptor 1 and Fas were highly upregulated. Furthermore, marked increases in the mRNA and protein levels of Fas-associated death domain (FADD), an adaptor molecule to recruit procaspase-8 into the death-inducing signal complex, were observed in septic aorta, which were strongly suppressed by systemic delivery of small interfering RNA (siRNA) against FADD. No increase in expression of death receptors and FADD was observed in endothelium-denuded aortic tissues from septic animals. Systemic administration of FADD siRNA also resulted in great attenuation of sepsis-induced increases in expression and activation of caspase-3, an effector protease in the apoptosis cascade. Terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling (TUNEL) revealed that the significant appearance of cell apoptosis in aortic endothelium after CLP-induced sepsis was eliminated when FADD siRNA was systemically applied. Light and electron microscopic examinations of septic aorta showed cell swelling, nuclear fragmentation, and partial detachment of endothelial cells from the basal membrane, which were prevented by systemic treatment with FADD siRNA. Finally, FADD siRNA administration dramatically improved survival of CLP mice, supporting the feasibility of this gene-based approach for treating septic shock.

Up-Regulation of Histamine H4 Receptors Contributes to Splenic Apoptosis in Septic Mice: Counteraction of the Anti-Apoptotic Action of Nuclear Factor-κB

The histamine H4 receptor is the most recently identified receptor and is considered to play a role in a variety of inflammatory diseases. Histamine levels in the plasma are known to be elevated in animal models of sepsis and in septic patients. The aim of this study was to test the hypothesis that the H4 receptor may play a significant role in the pathophysiology of sepsis. Polymicrobial sepsis was induced by cecal ligation and puncture in BALB/c mice. Although the H4 receptor gene was undetectable in normal peripheral key organs, with the exception of the spleen, the expression levels of this gene were highly up-regulated in all those organs of septic mice. In vivo transfection of nuclear factor-κB (NF-κB) decoy oligodeoxynucleotide, but not of its scrambled form, resulted in a great inhibition of sepsis-induced overexpression of the H4 receptor gene. In septic mice, marked increases in caspase-3 activation and follicular lymphocyte apoptosis in spleens were strongly suppressed by systemic treatment with synthetic small interfering RNA (siRNA) targeted to the H4 receptor. This was associated with the up-regulation of a number of antiapoptotic proteins. These antiapoptotic effects of H4 receptor siRNA treatment were all inhibited by further application of NF-κB decoy oligonucleotide. Our results suggest that superinduction of the histamine H4 receptor gene in peripheral key organs, including the spleen, that is promoted by sepsis is transcriptionally controlled by NF-κB, whereas stimulation of this receptor is involved in the development of sepsis-induced splenic apoptosis through counteraction of the antiapoptotic action of NF-κB.