Identification of a risk dependent microRNA expression signature in myelodysplastic syndromes.

The myelodysplastic syndromes (MDS) display both haematological and biological heterogeneity with variable leukaemia potential. MicroRNAs play an important role in tumour suppression and the regulation of self-renewal and differentiation of haematopoietic progenitors. Using a microarray platform, we evaluated microRNA expression from 44 patients with MDS and 17 normal controls. We identified a thirteen microRNA signature with statistically significant differential expression between normal and MDS specimens (P < 0·01), including down-regulation of members of the leukaemia-associated MIRLET7 family. A unique signature consisting of 10 microRNAs was closely associated with International Prognostic Scoring System (IPSS) risk category permitting discrimination between lower (Low/Intermediate-1) and higher risk (Intermediate-2/High) disease (P < 0·01). Selective overexpression of MIR181 family members was detected in higher risk MDS, indicating pathogenetic overlap with acute myeloid leukaemia. Survival analysis of an independent cohort of 22 IPSS lower risk MDS patients revealed a median survival of 3·5 years in patients with high expression of MIR181 family compared to 9·3 years in patients with low MIR181 expression (P = 0·002). Our pilot study suggested that analysis of microRNA expression profile offers diagnostic utility, and provide pathogenetic and prognostic discrimination in MDS.

Protein kinase C-zeta is critical in pancreatitis-induced apoptosis of Kupffer cells.

Protein kinase C-zeta (PKC-zeta) regulates cell death via NF-kappaB; therefore, we tested the hypothesis that PKC-zeta plays a critical role in pancreatitis-induced Kupffer cell apoptosis. Acute pancreatitis was induced in rats by cerulein injection 24 h later, livers were assayed for PKC-zeta, IKKalpha, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, and apoptosis was assessed with Caspase-3 and DNA fragmentation. Kupffer cells from unoperated rats were infected with a PKC-zeta domain-negative adenovirus (AdPKCzeta-DN) to inhibit PKC-zeta, or transfected with pCMVPKC-zeta to overexpress PKC-zeta, and then stimulated with pancreatic elastase; cellular extracts were assayed for PKC-zeta, IKKalpha, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3, and DNA fragmentation. Cerulein-induced pancreatitis upregulated PKC-zeta protein and activity, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3 and increased DNA fragmentation in rat livers (all p < 0.001 vs control). AdPKCzeta-DN abolished elastase-induced upregulation of PKC-zeta activity, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3 and DNA fragmentation (all p < 0.001 vs infection control), whereas overexpression of PKC-zeta augmented elastase-induced upregulation of IKKbeta, IKKgamma, Fas/FasL, Caspase-3 and DNA fragmentation (p < 0.001 vs control). PKC-zeta plays a critical role in pancreatitis-induced Kupffer cell apoptosis via NF-kappaB and Fas/FasL. The ability of Kupffer cells to autoregulate their stress response by upregulating their death receptor/ligand and key proapoptotic cell signaling systems warrants further investigation.

Protein kinase C-zeta (PKC-zeta) regulates Kupffer cell apoptosis during experimental sepsis.

BACKGROUND: Kupffer cells play an important role in sepsis-mediated liver injury. We tested the hypothesis that PKC-zeta plays a critical role in Kupffer cell apoptosis during sepsis. METHODS: Sepsis was induced in rats by cecal ligation and puncture (CLP); 12 h later, livers were assayed for PKC-zeta, IKKalpha, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3, and DNA fragmentation. Kupffer cells from control rats were infected with AdPKC-zeta DN to inhibit PKC-zeta, or transfected with pCMVPKC-zeta to overexpress PKC-zeta, and then treated with lipopolysaccharide (LPS). Cellular extracts were assayed for PKC-zeta, IKKalpha, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3, and DNA fragmentation. RESULTS: During sepsis, PKC-zeta localized in cells positive for the macrophage marker (F4/80). CLP upregulated PKC-zeta protein and activity, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3, and increased DNA fragmentation in rat livers (all p<0.001). AdPKC-zeta DN attenuated the LPS-induced upregulation of PKC-zeta activity, IKKbeta, IKKgamma, NF-kappaB, Fas/FasL, Caspase-3, and DNA fragmentation in Kupffer cells (all p<0.001), whereas overexpression of PKC-zeta augmented LPS-induced upregulation of IKKbeta, IKKgamma, NF-kappaB, Caspase-3, and DNA fragmentation (p<0.001). CONCLUSION: PKC-zeta plays an important role in sepsis-induced apoptosis of Kupffer cells via activation of NF-kappaB and Fas/FasL. Manipulating the response of Kupffer cells to cellular stress may have important therapeutic implications.

Protein kinase C-zeta mediates apoptosis of mouse Kupffer cells via ERK-1/2: a novel mechanism.

BACKGROUND: We have demonstrated that activated Kupffer cells undergo accelerated apoptosis via Toll-like receptor (TLR)-4 and protein kinase C (PKC)-ζ-dependent nuclear factor (NF)-κB activation. Because PKC-ζ plays a pivotal role in cell signaling, we sought to determine the signaling pathway of PKC-ζ in Kupffer cell apoptosis. METHODS: Mouse Kupffer cell line (MKCL3-2) were transfected with PKC-ζ small interfering RNA (siRNA) and then treated with elastase alone or elastase along with the extracellular signal-regulated kinase (ERK) inhibitor U0126. Cell extracts were assayed for PKC-ζ (protein and activity), TLR-4, NF-κB nuclear translocation, phosphorylated ERK-1/2, activated caspase-3, and DNA fragmentation. All n ≥3; data are expressed as mean values ± standard deviations; means were compared using the t test; P < .05 was considered significant. RESULTS: Elastase upregulated TLR-4, PKC-ζ, NF-κB, ERK-1/2, caspase-3, and DNA fragmentation (all P < .01 versus control). Transfection with PKC-ζ siRNA attenuated the elastase-induced upregulation of PKC-ζ activity, NF-κB, ERK-1/2, caspase-3, and DNA fragmentation (all P < .01 versus control). The interaction of PKC-ζ with ERK-1/2 was increased by elastase and was attenuated by PKC-ζ siRNA as confirmed by co-immunoprecipitation and immunofluorescent staining. CONCLUSION: Activation of Kupffer cells upregulates PKC-ζ activity, increases apoptosis, and induces nuclear translocation of NF-κB via ERK-1/2-dependent pathways. Inhibiting the activity of PKC-ζ significantly attenuates Kupffer cell apoptosis, NF-κB, and ERK-1/2 activation. The interaction of PKC-ζ and ERK-1/2 warrants further investigation.

Deletion of toll-like receptor-4 downregulates protein kinase C-zeta and attenuates liver injury in experimental pancreatitis.

BACKGROUND: Toll-like receptor-4 (TLR4) and protein kinase C-zeta (PKC-zeta) play a role in macrophage activation. We hypothesized that deletion of TLR4 downregulates PKC-zeta and attenuates liver cell apoptosis in experimental pancreatitis. METHODS: Acute pancreatitis was induced by choline-deficient ethionine diet in C57/BL6 (TLR4+/+ and TLR4-/-) mice. RESULTS: During pancreatitis, staining for TLR4 and PKC-zeta, which colocalized in Kupffer cells but not in hepatocytes, increased in TLR4+/+ mice and decreased in TLR4-/- mice. In TLR4+/+ mice, pancreatitis increased TLR4 protein and mRNA and PKC-zeta protein and activity, nuclear factor (NF)-kappaB, ERK1/2, caspase-3 cleavage, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining; all P < .01 versus controls. In TLR4-/- mice with pancreatitis, PKC-zeta mRNA and activity were reduced, ERK1/2 and caspase-3 did not increase, and NF-kappaB and TUNEL (mostly in hepatocytes) increased mildly (all P < .01 vs control). PKC-zeta did not interact directly with NF-kappaB; however, during pancreatitis, coimmunoprecipitation of PKC-zeta with ERK1/2 was increased in TLR4+/+ mice and was attenuated in TLR4-/- mice (all P < .01 vs control), indicating that PKC-zeta interacts with ERK1/2. CONCLUSION: Acute pancreatitis upregulates TLR4, PKC-zeta, NF-kappaB, and ERK1/2, and increases apoptosis in mice livers. PKC-zeta induces nuclear translocation of NF-kappaB via ERK1/2-dependent mechanisms. Deletion of TLR4 downregulates PKC-zeta, NF-kappaB, and ERK1/2, and attenuates pancreatitis-induced liver cell apoptosis.