Immunomanipulation of appetite and body temperature through the functional mimicry of leptin.

Objective: Although current obesity therapies produce some benefits, there is a need for new strategies to treat obesity. A novel proposal is the use of anti-idiotypic antibodies as surrogate ligands or hormones. These anti-idiotypic antibodies carry an internal motif that imitates or mimics an epitope in the antigen (i.e., hormone or ligand). Thus, anti-idiotypic antibodies to several ligands may mimic them in transducing signals when binding to their receptors. Research Methods and Procedures: We developed an anti-idiotypic polyclonal antibody against the region of a leptin monoclonal antibody that competitively binds leptin, mimicking the active site structure of leptin. To test whether our anti-idiotype could also reproduce leptin functions, we examined food intake, body weight, and colonic temperature in male Wistar rats (n = 9) in response to intracerebroventricular administration of the leptin anti-idiotype. Results: Our leptin anti-idiotype induced a significant reduction in food intake coupled with an increase in body temperature comparable to that of leptin. That is, the intracerebroventricular administration of 8.0 microg of leptin anti-idiotype or 5.0 microg leptin significantly increased colonic temperature (Delta 1.9 plusminus 0.11 °C and Delta1.7 plusminus 0.12 °C, respectively). In addition, both decreased 24-hour food intake (-26.4 plusminus 2.4% and -21.9 plusminus 2.2%) compared with the control. The gain in body weight was also decreased by acute administration of the anti-idiotype (-1.4 plusminus 0.28%) and leptin (-1.1 plusminus 0.17%) vs. the phosphate-buffered saline control (1.3 plusminus 0.15%). Discussion: These studies revealed that the leptin anti-idiotype inhibited food intake and enhanced heat production, mimicking leptin's central actions

Immunoneutralization and anti-idiotype production: two-sided applications of leptin

The neuroendocrine and immune systems are linked through a complex bi-directional network, in which hormones modify immune function, and the immune system, through the action of cytokines, affects neuroendocrine responses involved in the maintenance of body homeostasis. The adipocyte-derived, peptide hormone leptin is a pleiotropic molecule belonging to the helical cytokine family. On pp. 182-187, Matarese et al. suggest the possibility of new leptin-based therapeutic strategies for the treatment of both infection and autoimmune disease

Cardiotrophin-1 defends the liver against ischemia-reperfusion injury and mediates the protective effect of ischemic preconditioning

Ischemia-reperfusion (I/R) liver injury occurs when blood flow is restored after prolonged ischemia. A short interruption of blood flow (ischemic preconditioning [IP]) induces tolerance to subsequent prolonged ischemia through ill-defined mechanisms. Cardiotrophin (CT)-1, a cytokine of the interleukin-6 family, exerts hepatoprotective effects and activates key survival pathways like JAK/STAT3. Here we show that administration of CT-1 to rats or mice protects against I/R liver injury and that CT-1-deficient mice are exceedingly sensitive to this type of damage. IP markedly reduced transaminase levels and abrogated caspase-3 and c-Jun-NH2-terminal kinase activation after I/R in normal mice but not in CT-1-null mice. Moreover, the protective effect afforded by IP was reduced by previous administration of neutralizing anti-CT-1 antibody. Prominent STAT3 phosphorylation in liver tissue was observed after IP plus I/R in normal mice but not in CT-1-null mice. Oxidative stress, a process involved in IP-induced hepatoprotection, was found to stimulate CT-1 release from isolated hepatocytes. Interestingly, brief ischemia followed by short reperfusion caused mild serum transaminase elevation and strong STAT3 activation in normal and IL-6-deficient mice, but failed to activate STAT3 and provoked marked hypertransaminasemia in CT-1-null animals. In conclusion, CT-1 is an essential endogenous defense of the liver against I/R and is a key mediator of the protective effect induced by IP

Decreased cardiotrophin-1 levels are associated with a lower risk of developing the metabolic syndrome in overweight/obese children after a weight loss program

Objective: Cardiotrophin-1 (CT-1) shares some similarities with other cytokines, and participates in the control of energy metabolism. Higher circulating levels are observed in obese humans, but little information is gathered in weight loss (WL) programs. Therefore, we aimed to investigate the association of serum CT-1 levels with metabolic variables and the risk of developing metabolic syndrome (MetS) after a WL program in overweight/obese children. Subjects and Methods: Forty-four overweight/obese children (mean age 11.5 yr; 50% males) undergoing a 10-week WL program were enrolled. Subjects were dichotomized at the median of Body Mass Index-Standard Deviation Score (BMI-SDS) change, as high and low responders after intervention. Results: CT-1 levels were significantly reduced (-48 fmol/mL, p=0.043) in the high responder group after the WL program. They had significantly lower body weight (-3.7 kg, p<0.001), body fat mass (-8%, p<0.001), BMI-SDS (-0.78, p<0.001) and waist circumference (-5.4 cm, p<0.001), and a significant improvement in lipid and glucose profiles (p<0.05). Interestingly, decreased CT-1 levels significantly predicted changes in total cholesterol (41%) and LDL-cholesterol (28%). Moreover, in our participants the lower the CT-1 levels, the higher the reduction in MetS risk components, after the 10- week intervention, (p-ANCOVA=0.040, p-trend=0.024). Conclusion: We showed, for the first time, a reduction in serum CT-1 levels after a WL program and this decrease in CT-1 was strongly associated with a reduction in cholesterol levels and in MetS risk factors in overweight/obese children. Our findings may suggest that CT-1 could be an indirect marker for the diagnosis of MetS in this population

Induction of hypothermia, hypoglycemia and hyperinsulinemia after acute leptin immunoneutralization in overnight fasted mice

Acute immunoneutralization of circulating leptin, with an anti-leptin antibody, significantly reduced rectal temperature at 30 min and 75 min post-injection in overnight fasted and at 30 min in overnight fed mice, while no effects in metabolic and ponderal indicators were observed after antibody administration for 22 days. Furthermore, hyperinsulinemia and hypoglycemia were induced by passive immunization against leptin, being both influenced by the post-prandrial status. These experiments confirm through an indirect approach that leptin is involved in energy, but also in glucose homeostasis

Recurrent exposure to nicotine differentiates human bronchial epithelial cells via epidermal growth factor receptor activation

Cigarette smoking is the major preventable cause of lung cancer in developed countries. Nicotine (3-(1-methyl-2-pyrrolidinyl)-pyridine) is one of the major alkaloids present in tobacco. Besides its addictive properties, its effects have been described in panoply of cell types. In fact, recent studies have shown that nicotine behaves as a tumor promoter in transformed epithelial cells. This research focuses on the effects of acute repetitive nicotine exposure on normal human bronchial epithelial cells (NHBE cells). Here we show that treatment of NHBE cells with recurrent doses of nicotine up to 500 muM triggered cell differentiation towards a neuronal-like phenotype: cells emitted filopodia and expressed neuronal markers such as neuronal cell adhesion molecule, neurofilament-M and the transcription factors neuronal N and Pax-3. We also demonstrate that nicotine treatment induced NF-kB translocation to the nucleus, phosphorylation of the epidermal growth factor receptor (EGFR), and accumulation of heparin binding-EGF in the extracellular medium. Moreover, addition of AG1478, an inhibitor of EGFR tyrosine phosphorylation, or cetuximab, a monoclonal antibody that precludes ligand binding to the same receptor, prevented cell differentiation by nicotine. Lastly, we show that differentiated cells increased their adhesion to the extracellular matrix and their protease activity. Given that several lung pathologies are strongly related to tobacco consumption, these results may help to better understand the damaging consequences of nicotine exposure

Immunohistochemical detection of chloride/bicarbonate anion exchangers in human liver

Sodium-independent Cl-/HCO3- exchange activity has been observed in isolated rat hepatocytes and intrahepatic bile duct epithelial cells, where it is involved in intracellular pH regulation and, possibly, biliary bicarbonate secretion. Monoclonal antibodies to the membrane domain of human chloride/bicarbonate anion exchanger proteins, AE1 and AE2, were prepared so that we might determine by immunohistochemical methods the presence and location of these antiporters in the human liver. To obtain the antibody against AE1, we immunized mice with injections of washed human erythrocytes. The selected monoclonal antibody was found to be specific for the 17-kD proteolytic membrane fragment of AE1 protein. The antibody to AE2 was produced with a 14-mer synthetic peptide, whose sequence corresponds specifically to amino acid residues 871 to 884 in the deduced primary structure of human kidney AE2 protein. When the monoclonal antibody to AE2 peptide was employed for the immunohistochemical study of liver specimens (by both immunofluorescence and immunoperoxidase), a clearly defined staining was present at the canalicular membrane of hepatocytes, as well as the luminal side of the membrane of bile duct epithelial cells from small and medium-sized bile ducts. No staining was observed in the liver parenchyma with the monoclonal antibody to AE1, which instead strongly decorated the erythrocytes in liver blood vessels. We conclude that AE2 immunoreactivity is present in human liver, where it localizes very specifically to the membrane regions, which appear most probably involved in the transport of bicarbonate to bile (i.e., the canalicular membrane of hepatocytes and the apical side of epithelial cells of small and medium bile ducts)

Selective excision of chain-terminating nucleotides by HIV-1 reverse transcriptase with phosphonoformate as substrate

A major mechanism for human immunodeficiency virus 1 (HIV-1) reverse transcriptase (RT) resistance to nucleoside analogs involves the phosphorolytical removal of the chain-terminating nucleotide from the 3'-end of the primer. In this work, we analyzed the effect of phosphonoformate (PFA) and other pyrophosphate (PP(i)) analogs on PP(i)- and ATP-dependent phosphorolysis catalyzed by HIV-1 RT. Our experimental data demonstrated that PFA did not behave as a linear inhibitor but as an alternative substrate, allowing RT to remove AZT from a terminated primer through a PFA-dependent mechanism. Interestingly, in non-terminated primers, PFA was not a substrate for this reaction and competitively inhibited PP(i)- and ATP-dependent phosphorolysis. In fact, binding of PFA to the RT.template/primer complex was hindered by the presence of a chain terminator at the 3'-end of the primer. Other pyrophosphate analogs, such as phosphonoacetate, were substrates for the excision reaction with both terminated and nonterminated primers, whereas pamidronate, a bisphosphonate that prevents bone resorption, was not a substrate for these reactions and competitively inhibited the phosphorolytic activity of RT. As expected from their mechanisms of action, pamidronate (but not PFA) synergistically inhibits HIV-1 RT in combination with AZT-triphosphate in the presence of PP(i) or ATP. These results provide new clues about the mechanism of action of PFA and demonstrate that only certain pyrophosphate analogs can enhance the effect of nucleosidic inhibitors by blocking the excision of chain-terminating nucleotides catalyzed by HIV-1 RT. The relevance of these findings in combined chemotherapy is discussed