Emerging role of Lipopolysaccharide binding protein in sepsis-induced acute kidney injury.

Sepsis remains a serious cause of morbidity and mortality in critically ill patients, with limited therapeutic options available. Of the several disorders connected with sepsis, acute kidney injury (AKI) is one of the major complications. The pathophysiology of sepsis-induced AKI is characterized by severe inflammation in renal parenchyma with endothelial dysfunction, intra-glomerular thrombosis and tubular injury. Endothelial dysfunction is regulated by several mechanisms implicated in cellular de-differentiation, such as endothelial-to-mesenchymal transition (EndMT). Gram-negative bacteria and their cell wall component lipopolysaccharides (LPSs) are frequently involved in the pathogenesis of AKI. The host recognition of LPS requires a specific receptor, which belongs to the Toll-like receptor (TLR) family of proteins, called TLR4, and two carrier proteins, namely the LPS-binding protein (LBP) and cluster of differentiation 14 (CD14). In particular, LBP is released as a consequence of Gram-negative infection and maximizes the activation of TLR4 signalling. Recent findings regarding the emerging role of LBP in mediating sepsis-induced AKI, and the possible beneficial effects resulting from the removal of this endogenous adaptor protein, will be discussed in this review.

Endothelial dysfunction and renal fibrosis in endotoxemia-induced oliguric kidney injury: possible role of LPS-binding protein.

INTRODUCTION: The pathophysiology of endotoxemia-induced acute kidney injury (AKI) is characterized by an intense activation of the host immune system and renal resident cells by lipopolysaccharide (LPS) and derived proinflammatory products. However, the occurrence of renal fibrosis in this setting has been poorly investigated. The aim of the present study was to investigate the possible association between endothelial dysfunction and acute development of tissue fibrosis in a swine model of LPS-induced AKI. Moreover, we studied the possible effects of coupled plasma filtration adsorption (CPFA) in this setting. METHODS: After 9 hours from LPS infusion and 6 hours of CPFA treatment, histologic and biochemical changes were analyzed in pigs. Apoptosis and endothelial dysfunction were assessed on renal biopsies. The levels of LPS-binding protein (LBP) were quantified with enzyme-linked immunosorbent assay (ELISA). Endothelial cells (ECs) were stimulated in vitro with LPS and cultured in the presence of swine sera and were analyzed with FACS and real-time RT-PCR. RESULTS: In a swine model of LPS-induced AKI, we observed that acute tubulointerstitial fibrosis occurred within 9 hours from LPS injection. Acute fibrosis was associated with dysfunctional alpha-smooth muscle actin (α-SMA)+ ECs characterized by active proliferation (Ki-67+) without apoptosis (caspase-3-). LPS led to EC dysfunction in vitro with significant vimentin and N-cadherin expression and increased collagen I mRNA synthesis. Therapeutic intervention by citrate-based CPFA significantly prevented acute fibrosis in endotoxemic animals, by preserving the EC phenotype in both peritubular capillaries and renal arteries. We found that the removal of LBP from plasma was crucial to eliminate the effects of LPS on EC dysfunction, by blocking LPS-induced collagen I production. CONCLUSIONS: Our data indicate that EC dysfunction might be pivotal in the acute development of tubulointerstitial fibrosis in LPS-induced AKI. Selective removal of the LPS adaptor protein LBP might represent a future therapeutic option to prevent EC dysfunction and tissue fibrosis in endotoxemia-induced AKI.

CAFs and TGF-ß Signaling Activation by Mast Cells Contribute to Resistance to Gemcitabine/Nabpaclitaxel in Pancreatic Cancer.

Tumor⁻stroma interactions are of key importance for pancreatic ductal adenocarcinoma (PDAC) progression. Our aim was to investigate whether cancer associated fibroblasts (CAFs) and mast cells (MC) affected the sensitivity of PDAC cells to gemcitabine/nabpaclitaxel (GEM/NAB). For this purpose, the combination cytotoxicity and the effect on tumor invasion and angiogenesis were evaluated with or without a conditioned medium from the mast cell line HMC-1 (human mast cell line-1 cells) and CAFs. Beside the clinical outcome of a homogenous population of PDAC patients, receiving GEM/NAB, was correlated to the circulating levels of mast cell tryptase and to a panel of inflammatory and immunosuppressive cytokines. CAFs neither affected drugs' cytotoxicity nor the inhibition of angiogenesis, but promoted tumor cell invasion. The MC instead, caused resistance to drugs by reducing apoptosis, by activating the TGF-ß signalling and by promoting tumor invasion. Indeed, the inhibition of TßRI serine/threonine kinase activity by galunisertib restored drugs cytotoxicity. Moreover, MC induced the release of TGF-ß1, and increased expression of PAR-2, ERK1/2 and Akt activation. Accordingly, TGF-ß1, tryptase and other pro-inflammatory and immunosuppressive cytokines increased in the unresponsive patients. In conclusion, MC play a pivotal role in the resistance to GEM/NAB. A correlation between high level of circulating pro-inflammatory/ immunosuppressive cytokines and unresponsiveness was found in PDAC patients.

Activation of the kynurenine pathway predicts poor outcome in patients with clear cell renal cell carcinoma.

OBJECTIVE: To investigate the expression of the kynurenine (KYN) pathway components and the prognostic role of the KYN-to-tryptophan ratio (KTR) in a cohort of patients with clear cell renal cell carcinoma (ccRCC). MATERIALS AND METHODS: The expression of KYN pathway components was investigated by tissue microarray-based immunohistochemistry, indirect immunofluorescence, and confocal microscopy analysis in 100 ccRCC cases and 30 normal renal samples. The role of this pathway in sustaining cancer cell proliferation, migration, and chemoresistance was evaluated. In addition, tryptophan and KYN concentrations and their ratio were measured in serum of 195 patients with ccRCC using a sandwich enzyme-linked immunosorbent assay. The role of KTR as a prognostic factor for ccRCC cancer-specific survival (CSS) and progression-free survival (PFS) was assessed. RESULTS: Tissue microarray-based immunohistochemistry and indirect immunofluorescence staining showed an increased signal for KYN pathway components in ccRCC. Kaplan-Meier curves showed significant differences in CSS and PFS among groups of patients with high vs. low KTR. In particular, patients with high KTR values had a 5-year survival rate of 76.9% as compared with 92.3% for subjects with low levels (P  < 0.0001). Similar findings were observed for PFS (72.8% vs. 96.8% at 5y). At multivariate analysis, KTR was an independent adverse prognostic factor for CSS (hazard ratio  = 1.24, P  =  0.001), and PFS (hazard ratio  =  1.14, P  =  0.001). CONCLUSIONS: The involvement of the KYN pathway enzymes and catabolites in ccRCC occurs via both immune and nonimmune mechanisms. Our data suggest that KTR could serve as a marker of ccRCC aggressiveness and as a prognostic factor for CSS and PFS.