Procalcitonin Impairs Endothelial Cell Function and Viability.

BACKGROUND: Procalcitonin is used as a diagnostic tool for the identification and risk stratification of septic patients. Procalcitonin plasma concentrations tightly correlate with the severity of the ongoing inflammatory reaction and can rise up to 10,000-fold. Impairment of endothelial cell function plays an important role in the pathogenesis of hypotension and disturbed organ perfusion during sepsis. We investigated the possible effects of procalcitonin itself on endothelial cell function and viability. METHODS: Human endothelial cells were exposed to 0.01 to 100 ng/mL procalcitonin and investigated for endothelial permeability using transwells, migration in a scratch wound assay and new capillary formation on extracellular matrix in vitro. Tumor necrosis factor-α and vascular endothelial growth factor served as positive controls. Procalcitonin's impact on the response of endothelial cells toward ischemia was investigated in vivo in the murine model of unilateral femoral artery ligation. Procalcitonin-exposed endothelial cells were subjected to immunoblot for the investigation of vascular endothelial-cadherin expression and angiogenic signaling pathways. Flow cytometry was used for the detection of inflammatory activation and viability, and genomic analysis was performed. Data are presented as difference in means and 95% confidence intervals; statistical analyses were performed using analysis of variance/Bonferroni, and P values are reported as adjusted for multiple comparisons (Padjust). RESULTS: Tumor necrosis factor-α and 0.1 ng/mL procalcitonin induced endothelial barrier disruption after incubation of endothelial monolayers for 6 hours (-2.53 [-4.16 to -0.89], P = .0008 and -2.09 [-3.73 to -0.45], Padjust = .0064 compared with vehicle-treated control, respectively). Procalcitonin beginning at concentrations of 0.02 ng/mL reduced endothelial cell migration (0.26 [0.06 to 0.47], Padjust = .0069) and new capillary formation in vitro (0.47 [0.28 to 0.66], Padjust < .0001) contrasting the proangiogenic action of vascular endothelial growth factor. Left ventricular injection of procalcitonin in mice on postoperative day 1, 3, and 5 after induction of ischemia impaired new capillary formation and recovery of hindlimb perfusion in vivo (number of capillaries/mm in the ischemic leg of vehicle-treated versus procalcitonin-treated mice, 852.6 [383.4-1322], Padjust = .0002). Twenty-four-hour incubation with procalcitonin reduced the expression of vascular endothelial-cadherin at 100 ng/mL (0.39 [0.06-0.71], Padjust = .0167) and induced endothelial cell death (apoptosis, -5.4 [-10.67 to -0.13], Padjust = .0431). No alteration in the expression of intercellular adhesion molecule-1, vascular cell adhesion molecule-1 or extracellular signal-regulated kinase 1/2, and AKT signaling pathways was observed. Genomic analysis revealed regulation of a variety of genes involved in inflammation, angiogenesis, and cell growth. CONCLUSIONS: This study found that procalcitonin itself impaired several aspects of endothelial cell function. Procalcitonin-induced loss of endothelial barrier function may contribute to capillary leakage and therapy-refractory hypotension during sepsis. Anti-angiogenic properties of procalcitonin at low concentrations could also identify procalcitonin as a mediator of vascular disease associated with the metabolic syndrome. Future studies are needed to further test procalcitonin as a potential therapeutic target for preserving vascular dysfunction during acute and chronic inflammatory disorders.

New TiAg composite coating for bone prosthesis engineering shows promising microvascular compatibility in the murine dorsal skinfold chamber model.

The incorporation of antimicrobial substances like silver into implant surface coatings is one promising concept against primary infections of endoprosthesis, especially for immunocompromised patients as well as against reinfection after revision operations. However, besides good antimicrobial and mechanical properties it is equally important that the implant material does not disturb the local microvascular perfusion of muscle tissue to enable microbial host defense and tissue repair processes. In this study the biocompatibility of a newly developed TiAg-composite coating applied on conventional titanium via physical vapor deposition was analysed. To evaluate the local microvascular and inflammatory response of striated muscle tissue upon implantation of TiAg-coated plates the murine dorsal skinfold chamber model was used. We repetitively examined local capillary and venular perfusion, endothelial integrity as well as leucocyte activation by intravital fluorescence microscopy at 1 h, 24 h as well as 3 and 7 days after implantation. TiAg-implants were well tolerated by the vascular system as indicated by intact functional capillary density and endothelial integrity compared to pure titanium plates and controls without a metal implant. Furthermore, quantification of rolling and adherent leucocytes did not reveal signs of inflammation upon TiAg-implantation.

Protein z exerts pro-angiogenic effects and upregulates CXCR4.

OBJECTIVE: Protein Z (PZ) is a vitamin K-dependent coagulation factor without catalytic activity. Evidence points towards PZ as an independent risk factor for the occurrence of human peripheral arterial disease. However, the role of PZ in ischemia-driven angiogenesis and vascular healing processes has not been elucidated so far. APPROACH: Angiogenic potency of PZ was assessed in established in vitro assays using endothelial cells. PZ-deficient (PZ(-/-)) mice and their wild-type littermates (PZ(+/+)) were subjected to hindlimb ischemia. Furthermore, PZ(-/-) mice were exposed to PZ expressing adenovirus (AdV-PZ) or control adenovirus (AdV-GFP). In an additional set of animals, PZ(-/-) mice were exposed to AdV-PZ and AdV-GFP, each in combination with the CXCR4 antagonist AMD3100. RESULTS: In vitro, PZ stimulated migratory activity and capillary-like tube formation of endothelial cells comparable to SDF-1. PZ(-/-) mice exhibited diminished hypoxia-driven neovascularization and reperfusion in post-ischemic hindlimbs, which was restored by adenoviral gene transfer up to levels seen in PZ(+/+) mice. The stimulatory impact of PZ on endothelial cells in vitro was abolished by siRNA targeting against PZ and PZ was not able to restore reduced migration after knock-down of CXCR4. The increased surface expression of CXCR4 on PZ-stimulated endothelial cells and the abrogated restoration of PZ(-/-) mice via AdV-PZ after concomitant treatment with the CXCR4 antagonist AMD3100 supports the idea that PZ mediates angiogenesis via a G-protein coupled pathway and involves the SDF-1/CXCR4 axis. This is underlined by the fact that addition of the G-protein inhibitor PTX to PZ-stimulated endothelial cells abolished the effect of PZ on capillary-like tube formation. CONCLUSIONS: The results of the current study reveal a role of PZ in ischemia-induced angiogenesis, which involves a G-protein coupled pathway and a raised surface expression of CXCR4. Our findings thereby extend the involvement of PZ from the coagulation cascade to a beneficial modulation of vascular homeostasis.

Protein Z-deficiency is associated with enhanced neointima formation and inflammatory response after vascular injury in mice.

BACKGROUND: Protein Z (PZ) is a vitamin K-dependent coagulation factor without catalytic activity. Evidence points towards PZ as an independent risk factor for the occurrence of human atherosclerotic vascular diseases. The aim of this study was to investigate the role of PZ in vascular arterial disease. MATERIAL AND METHODS: PZ-deficient (PZ(-/-)) mice and their wild-type littermates (PZ(+/+)) were subjected to unilateral carotid artery injury by using ferric chloride and dissected 21 days thereafter for histological analysis. Human aortic smooth muscle cells (SMC) were used for in vitro wound healing assay to assess the influence of PZ on SMC migration and for cell proliferation studies. RESULTS: Morphometric analysis of neointima formation revealed a significantly increased area and thickness of the neointima and subsequently increased luminal stenosis in carotid arteries of PZ(-/-) mice compared to PZ(+/+) mice (p < 0.05, n = 9). Immunohistochemical analysis of neointima lesion composition revealed significantly higher numbers of PCNA-positive and α-SMA-positive cells in the neointima of PZ(-/-) mice. Furthermore, PZ showed an anti-migratory potency in in vitro wound healing assay with SMCs, while no effect of PZ on SMC proliferation was detectable. Conclusion: PZ contributes to a reduced neointima formation after vascular injury, underlining the modulatory role of the coagulation cascade in vascular homeostasis.

Lifelong caloric restriction reprograms hepatic fat metabolism in mice.

Calorie lowering slows the aging process and extends life span in diverse species by so far unknown mechanisms. The inverse linear relationship between calorie intake and life span suggests that regulators of energy metabolism are of importance in aging. The present study shows that lifelong caloric restriction in mice induces a metabolic adaptation with reduced lipogenesis and enhanced lipolysis and ketogenesis. This process, that is, the reprogramming of hepatic fat metabolism, is associated with a marked rise of fibroblastic growth factor 21 as a putative starvation master regulator. Due to the life span-extending properties of fibroblastic growth factor 21, the rise in fibroblastic growth factor 21 might contribute to the markedly better health status found in mice upon lifelong caloric restriction feeding. In addition, adropin, known as a peptide that controls lipid homeostasis, is significantly upregulated, underlining the diminution of lipogenesis that was further substantiated by decreased expression of liver-X-receptor α and its target genes sterol regulatory element-binding protein-1c, fatty acid synthase, and member 1 of human transporter subfamily ABCA upon lifelong caloric restriction feeding.

TLR2-deficiency of cKit+ bone marrow cells is associated with augmented potency to stimulate angiogenic processes.

OBJECTIVE: Toll-like receptor 2 (TLR2)-deficiency is associated with the preservation of vascular function and TLR2-deficient (TLR2(-/-)) mice exhibit increased neovascularization following induction of hindlimb ischemia. Hematopoietic stem cells play an important role in ischemia-induced angiogenesis and we now investigated whether the effects observed in TLR2(-/-) mice may be attributed to TLR2 deficiency on bone marrow-derived stem cells. APPROACH AND RESULTS: cKit-positive (cKit(+)) bone marrow cells (BMC) were isolated from wild type (WT) and TLR2(-/-) mice employing MACS-bead technology. Co-incubation of TLR2(-/-)cKit(+) BMC with mature endothelial cells (ECs) resulted in increased tube formation of ECs on matrigel, augmented sprouting in a 3D-collagen matrix and increased migratory capacity compared to co-incubation with WT cKit(+) BMC. In an in vivo matrigel plug assay, TLR2(-/-)cKit(+) BMC exhibited enhanced formation of capillary-like networks. In a murine model of hindlimb ischemia, administration of TLR2(-/-) cKit(+) BMC to WT mice augmented capillary density and reperfusion of ischemic M. gastrocnemius muscle tissue to the level of TLR2(-/-) mice. Western Blot analysis revealed comparable expression of CXCR4 on TLR2(-/-)cKit(+) BMC but increased activation of the PI3K downstream signaling molecule protein kinase B (PKB/AKT) compared to WT cKit(+) cells. CONCLUSIONS: The absence of TLR2 on cKit(+) BMC is associated with augmented potency to support angiogenic processes in vitro and in vivo. Functional inhibition of TLR2 may therefore provide a novel tool to enhance stem cell function for the treatment of vascular diseases.

Impact of hyperglycemia and acute pancreatitis on the receptor for advanced glycation endproducts.

Since hyperglycemia aggravates acute pancreatitis and also activates the receptor for advanced glycation endproducts (RAGE) in other organs, we explored if RAGE is expressed in the pancreas and if its expression is regulated during acute pancreatitis and hyperglycemia. Acute pancreatitis was induced by cerulein in untreated and streptozotocin treated diabetic mice. Expression of RAGE was analyzed by Western blot and immunohistochemistry. To evaluate signal transduction the phosphorylation of ERK1/ERK2 was assessed by Western blot and the progression of acute pancreatitis was monitored by evaluation of lipase activity and the pancreas wet to dry weight ratio. RAGE is mainly expressed by acinar as well as interstitial cells in the pancreas. During acute pancreatitis infiltrating inflammatory cells also express RAGE. Using two distinct anti-RAGE antibodies six RAGE proteins with diverse molecular weight are detected in the pancreas, whereas just three distinct RAGE proteins are detected in the lung. Hyperglycemia, which aggravates acute pancreatitis, significantly reduces the production of two RAGE proteins in the inflamed pancreas.

Hydrocortisone reduces the beneficial effects of toll-like receptor 2 deficiency on survival in a mouse model of polymicrobial sepsis.

INTRODUCTION: Toll-like receptors (TLRs) play a crucial role in early host defense against microorganisms. Toll-like receptor 2 (TLR2) polymorphisms have a prevalence of 10%; functional defects of TLR2 are associated with higher susceptibility toward gram-positive bacteria, and TLR2 deficiency has been associated with an impaired adrenal stress response. In the present study, we compared endogenous corticosterone production of wild-type (WT) and TLR2-deficient (TLR2) mice and analyzed survival after hydrocortisone therapy during sepsis induced by cecal ligation and puncture (CLP). METHODS: Male C57BL/6J (WT); and B6.129-Tlr2tm1Kir/J (TLR2) mice were subjected to CLP or sham operation and randomly assigned to postoperative treatment with either hydrocortisone (5 mg/kg) or vehicle (n = 10 mice/group). Survival was documented for an observation period of 48 h. Endogenous corticosterone production following hydrocortisone treatment and lipoteichoic acid (LTA) exposure, interleukin 6 (IL-6) and IL-1ß plasma levels, and blood counts were determined following sham operation or CLP using another n = 5 mice/group. Statistical analysis was performed using analysis of variance/Bonferroni. RESULTS: TLR2 mice exhibited a lack of suppression and an attenuated increase in endogenous corticosterone production following hydrocortisone or LTA treatment, respectively. After CLP, TLR2 mice exhibited an uncompromised adrenal stress response, higher IL-6 levels, and increased survival compared with WT controls (75 vs. 35%; P < 0.05). Hydrocortisone therapy of TLR2 mice completely abolished this advantage (decrease in survival to 45%, P < 0.05 vs. vehicle-treated TLR2 mice) and was associated with decreased IL-1ß plasma concentrations. CONCLUSIONS: Toll-like receptor 2 deficiency is associated with an uncompromised adrenal stress response and increased survival rates during polymicrobial sepsis. Hydrocortisone treatment increases mortality of septic TLR2 mice, suggesting that hydrocortisone therapy might be harmful for individuals with functional TLR2 polymorphisms.

Contribution of protein Z and protein Z-dependent protease inhibitor in generalized Shwartzman reaction.

OBJECTIVE: Sepsis, a leading cause of mortality in critically ill patients, is closely linked to the excessive activation of coagulation and inflammation. Protein Z, a cofactor for the protein Z-dependent protease inhibitor, enhances the inhibition of coagulation factor Xa, and protein Z-dependent protease inhibitor inhibits factor XIa in a protein Z-independent fashion. The functions of protein Z and protein Z-dependent protease inhibitor in the inflammatory and coagulant responses to septic illness have not been evaluated. DESIGN: For induction of generalized Shwartzman reaction, dorsal skinfold chamber-equipped mice were challenged twice with lipopolysaccharide (0.05 mg/kg on day -1 and 5 mg/kg body weight 24 hr later). Time-matched control animals received equal volumes of saline. SETTING: University research laboratory. SUBJECTS, INTERVENTIONS, AND MEASUREMENTS: Using intravital fluorescence microscopy in protein Z-dependent protease inhibitor deficient (ZPI) and protein Z deficient (PZ) mice, as well as their wild-type littermates (ZPI, PZ), kinetics of light/dye-induced thrombus formation and microhemodynamics were assessed in randomly chosen venules. Plasma concentrations of chemokine (C-X-C motif) ligand 1, interleukin-6, and interleukin-10 were measured. Liver and lung were harvested for quantitative analysis of leukocytic tissue infiltration and thrombus formation. MAIN RESULTS: After induction of generalized Shwartzman reaction, all mice showed significant impairment of microhemodynamics, including blood flow velocity, volumetric blood flow, and functional capillary density, as well as leukocytopenia and thrombocytopenia. Thrombus formation time was markedly prolonged after induction of generalized Shwartzman reaction in all mice, except of ZPI mice, which also had a significantly higher fraction of occluded vessels in liver sections. PZ mice developed the highest concentrations of interleukin-6 and interleukin-10 in response to generalized Shwartzman reaction and showed greater leukocytic tissue infiltration than their wild-type littermates. CONCLUSIONS: In this murine model of generalized Shwartzman reaction, protein Z-dependent protease inhibitor deficiency enhanced the thrombotic response to vascular injury, whereas protein Z deficiency increased inflammatory response.

Effects of systemic pretreatment with CpG oligodeoxynucleotides on skin wound healing in mice.

Unmethylated CpG oligodeoxynucleotides (ODN) bind to the Toll-like receptor 9, thus stimulating the immune system. To study the effects of systemic pretreatment with CpG ODN on dermal regeneration, C57BL6/J Tyr mice were treated with CpG or control ODN 6 days prior to implantation of a dorsal skinfold chamber and skin wounding. Wound epithelialization was analyzed by planimetric microscopy. On day 18, wound tissues were taken for (immuno)histochemical staining. CpG ODN increased epithelialization compared with control ODN treatment. Histological analysis revealed reduced capillary density, reduced wound cellularity, and reduced numbers of infiltrating leukocytes, as well as reduced F4/80-positive macrophages, but increased numbers of RELM-α-positive M2 macrophages after CpG ODN treatment, reflecting a better quality of wound healing on day 18 compared with control ODN treatment. Reverse transcription-polymerase chain reaction analysis of Toll-like receptor 9 showed the receptor expression on both fibroblasts and keratinocytes. Fibroblasts showed an increase of migration upon increasing dosages of CpG and not control ODN, reaching ∼50% of the response of basic fibroblast growth factor-exposed cells. Keratinocytes dose-dependently responded to both CpG and control ODN up to values found in keratinocyte growth factor-exposed cells. In summary, CpG ODN support late tissue-remodeling processes that contribute to resolution of inflammation and solid wounds during skin regeneration.