ABSTRACT
A potential link between obesity, circulating leptin levels and autoimmune disease symptoms suggests that targeting the leptin receptor (ObR) might be a viable novel strategy to combat rheumatoid arthritis (RA). However, studies in animal models and evaluation of clinical cases did not provide clear view on leptin's involvement in RA. To validate ObR as RA target, we used our peptide-based ObR agonists and antagonist in different in vitro and in vivo models of the disease. In human peripheral blood mononuclear cells, leptin and its agonist fragment, desI(2)-E1/Aca, moderately induced constitutive activation of a major proinflammatory transcription factor, NF-κB, while the ObR antagonist peptide Allo-aca inhibited the process. Leptin administration itself did not induce arthritis in rats, but worsened the clinical condition of mice given K/BxN serum transfer arthritis. Simultaneous administration of Allo-aca reduced leptin-dependent increase in disease severity by more than 50%, but the antagonist was ineffective when injected with a 3-day delay. In rats inflicted with mild adjuvant-induced arthritis, both leptin and Allo-aca reduced the extent of joint swelling and the number of arthritic joints. In a more aggressive disease stage, Allo-aca decreased the number of arthritic joints in a dose-dependent manner but did not affect other arthritis markers. In summary, leptin exerts diverse effects on RA depending on the experimental model. This might reflect the heterogeneous character of RA, which is differently impacted by leptin and is unmasked by ObR antagonism. Nevertheless, the results suggest that ObR antagonists might become useful therapeutics in leptin-sensitive early stages of RA.
Subject(s)
Arthritis, Rheumatoid/metabolism , Leptin/metabolism , Receptors, Leptin/antagonists & inhibitors , Animals , Arthritis, Experimental/metabolism , Disease Models, Animal , Female , Humans , Leukocytes, Mononuclear/metabolism , Mice , Mice, Transgenic , Oligopeptides/pharmacology , Rats , Receptors, Leptin/metabolismABSTRACT
Although the designer proline-rich antimicrobial peptide A3-APO has only modest activity against Escherichia coli and Acinetobacter baumannii in vitro, in mouse models of systemic and wound infections it shows superior efficacy compared with conventional antibiotics. In this study, the efficacy of A3-APO in several additional mouse models was investigated, including Staphylococcus aureus wound infection, mixed Klebsiella pneumoniae-A. baumannii-Proteus mirabilis wound infection and K. pneumoniae lung infection, mimicking blast wound infections, foot ulcers and ventilator-induced nosocomial infections, respectively. Whilst the peptide practically did not kill the strains in vitro, when administered intramuscularly or as an aerosol it significantly improved mouse survival and reduced bacterial counts at the infection site and in blood. In the lung infection study, the blood bacterial counts following A3-APO treatment were as low as after treatment with colistin and were lower than after treatment with imipenem or amikacin. The wounds of treated animals, unlike their untreated counterparts, lacked pus and signs of inflammation. In human peripheral blood mononuclear cells, A3-APO upregulated the expression of the anti-inflammatory cytokines interleukin-4 and interleukin-10 by four- to six-fold. One of the mechanisms mediating the in vivo protective effects might be the prevention of inflammation around bacterial infiltration.
Subject(s)
Anti-Bacterial Agents/administration & dosage , Bacteria/drug effects , Bacterial Infections/drug therapy , Drug Resistance, Multiple, Bacterial , Peptides/administration & dosage , Pneumonia, Bacterial/drug therapy , Wound Infection/drug therapy , Animals , Anti-Bacterial Agents/pharmacology , Bacterial Infections/microbiology , Bacterial Load , Cells, Cultured , Cytokines/biosynthesis , Disease Models, Animal , Escherichia coli/drug effects , Humans , Klebsiella pneumoniae/drug effects , Leukocytes, Mononuclear/immunology , Leukocytes, Mononuclear/microbiology , Mice , Microbial Sensitivity Tests , Peptides/pharmacology , Pneumonia, Bacterial/microbiology , Proteus mirabilis/drug effects , Staphylococcus aureus/drug effects , Survival Analysis , Up-Regulation , Wound Infection/microbiologyABSTRACT
Interleukin-6 (IL-6) binds to a receptor complex consisting of an 80 kDa binding unit (IL-6R) and gp130 responsible for signal transduction. Due to alternative splicing and/or proteolytic digestion IL-6R occurs in soluble form (sIL-6R), as well. Soluble IL-6R is able to bind to gp130 expressing on nucleated cells, thus sIL-6R makes most cells responsive to IL-6. In this study we found that oncostatin M (OSM), an other gp130 dependent cytokine with proliferation inhibitory potential, increases the expression of both membrane-bound IL-6R and sIL-6R generated by alternative splicing in hepatic and mammary carcinoma cell lines. Furthermore, we studied the functional relevance of the presence and binding of soluble IL-6R to HepG2 cells. Using a cDNA expression array, mRNA levels of about 580 human genes were tested by differential display analysis. Our findings suggest, that elevation of surface density of IL-6R by attachment of sIL-6R induces major modulation in gene expression profile of the hepatoma cells. Soluble IL-6R alone has minor effect, it rather decreases expression of some genes, while incubation with IL-6 and sIL-6R together induces major changes in the mRNA pattern of HepG2 cells. These data strongly suggest that presence and binding of soluble cytokine receptors are important elements of inter-cytokine cross talk and affects actual gene expression profile of responding cells.