Lipopolysaccharide-Induced Ionized Hypocalcemia and Acute Kidney Injury in Carotid Chemo/Baro-Denervated Rats.

The acute kidney injury (AKI) observed during sepsis is due to an uncontrolled release of inflammatory mediators. Septic patients develop electrolytic disturbances and one of the most important is ionized hypocalcemia. AKI adversely affects the function of other organs and hypocalcemia is associated with cardiovascular and respiratory dysfunctions. Since carotid body chemoreceptors modulate the systemic inflammatory response during sepsis syndromes, we used pentobarbitone-anesthetized male Sprague-Dawley rats in control condition (SHAM surgery) and after bilateral carotid neurotomy (carotid chemo/baro-denervated, BCN). We evaluate serum creatinine (CRE), serum neutrophil gelatinase-associated lipocaline (NGAL), ionized calcium (iCa) and cardiac Troponin I (cTnI) 90 min after the IP administration of 15 mg/kg lipopolysaccharide (LPS) or saline. In the SHAM group, LPS failed to induce significant changes CRE, NGAL, or iCa, and increased cTnI. Conversely, in the BCN group LPS increased CRE and NGAL, decreased iCa, and enhanced the increase of cTnI. Our results suggest that carotid chemo/baro-receptors might contribute to the regulation of both renal function and calcemia during sepsis. In addition, results imply that the carotid chemo-baroreceptors serve as an immunosensory organ.

T-kininogen can either induce or inhibit proliferation in Balb/c 3T3 fibroblasts, depending on the route of administration.

T-kininogen (T-KG) is a precursor of T-kinin, the most abundant kinin in rat serum, and also acts as a strong and specific cysteine proteinase inhibitor. Its expression is strongly induced during aging in rats, and expression of T-KG in Balb/c 3T3 fibroblasts results in inhibition of cell proliferation. However, T-KG is a serum protein produced primarily in the liver, and thus, most cells are only exposed to the protein from the outside. To test the effect of T-KG on fibroblasts exposed to exogenous T-KG, we purified the protein from the serum of K-kininogen-deficient Katholiek rats. In contrast to the results obtained by transfection, exposure of Balb/c 3T3 fibroblasts to exogenously added T-KG leads to a dose-dependent increase in [3H]-thymidine incorporation. This response does not require kinin receptors, but it is clearly mediated by activation of the ERK pathway. As a control, we repeated the transfection experiments, using a different promoter. The results are consistent with our published data showing that, under these circumstances, T-KG inhibits cell proliferation. We conclude that T-KG exerts opposite effects on fibroblast proliferation, depending exclusively on the way that it is administered to the cells (transfection versus exogenous addition).

ALEPH-2, a suspected anxiolytic and putative hallucinogenic phenylisopropylamine derivative, is a 5-HT2a and 5-HT2c receptor agonist.

To assess the pharmacodynamic profile of ALEPH-2, a phenylisopropylamine derivative with alleged anxiolytic and hallucinogenic properties, Xenopus laevis oocytes were microinjected with either of the rat cRNA for the 5-HT2A or the 5-HT2C receptor. Concentration-response curves were obtained following the exposure of the oocytes to varying concentrations of either ALEPH-2 or 5-hydroxytryptamine (5-HT) for 10 s. ALEPH-2 is a partial agonist on the 5-HT2A receptor with a similar potency to 5-HT. In contrast, ALEPH-2 is a full 5-HT2C receptor agonist and is about 15-fold less potent than 5-HT. Pre-application of 1 microM ritanserin antagonized the responses induced by 5-HT and ALEPH-2 to the same extent; however, the 5-HT2A receptor is more sensitive to ritanserin blockade than the 5-HT2C receptor.

Zinc and copper modulate differentially the P2X4 receptor.

The rat ATP P2X4 receptor was expressed in Xenopus laevis oocytes to assess the effect of zinc and copper as possible regulators of purinergic mechanisms. ATP applied for 20 s evoked an inward cationic current with a median effective concentration (EC50) of 21.4+/-2.8 microM and a Hill coefficient (nH) of 1.5+/-0.1. Coapplication of ATP plus 10 microM zinc displaced leftward, in a parallel fashion, the ATP concentration-response curve, reducing the EC50 to 8.4+/-1.8 microM (p < 0.01) without altering the receptor nH. The zinc potentiation was fast in onset, easily reversible, and voltage-independent and did not require metal preexposure. The zinc EC50 was 2-5 microM, with a bell-shaped curve. At concentrations of 100-300 microM, zinc produced less potentiation, and at 1 mM, it inhibited 50% the ATP current. The effect of zinc was mimicked by cadmium. In contrast, copper inhibited the ATP-evoked currents in a time- and concentration-dependent fashion, reducing the maximal current (Imax) without altering the EC50. The copper-induced inhibition was slow in onset, slowly reversible, and voltage-independent. Whereas coapplication of 300 microM copper plus ATP reduced Imax to 36.2+/-5%, the coapplication of, or 60-s preexposure by, 10 microM copper reduced Imax to 79+/-9.2% (p < 0.05) and 39.6+/-8.7% (p < 0.01), respectively. The inhibition was noncompetitive in nature and mimicked by mercury. Cobalt, barium, and manganese did not modify significantly the ATP-evoked current, demonstrating metal specificity. The simultaneous 1-min preapplication of both metals revealed that the 10 microM zinc-induced potentiation was obliterated by 10 microM copper, whereas 30 microM copper not only reduced the potentiation, but inhibited the ATP response. Following coapplication of both metals for 20 s with ATP, at least 100 microM copper was required to counteract the 10 microM zinc-induced potentiation. The simultaneous preincubation with both metals provided evidence for a noncompetitive interaction. We hypothesize the existence of metal binding site(s), which are most likely localized in the extracellular domain of the P2X4 receptor structure. These sites are selective and accessible to extracellular metal applications and bind micromolar concentrations of metals. The present results are compatible with the working hypothesis that trace metals, such as copper and zinc, are physiological modulators of the P2X4 receptor. The modulation of brain purinergic transmission by physiologically and toxicologically relevant trace metal cations is highlighted.

Expression of intercellular adhesion molecule 1 (ICAM-1) on the human oviductal epithelium and mediation of lymphoid cell adherence.

The epithelium of the human oviduct expresses the major histocompatibility complex (MHC) class II and shows endocytic properties towards luminal antigens. Therefore, the epithelial cells might behave as antigen-presenting cells, inducing a local immune response. The activation of antigen-specific T cells not only requires presentation of the peptide antigen by MHC class II, but also the presence of co-stimulatory molecules in the antigen-presenting cells. Therefore, the expression of the intercellular adhesion molecule 1 (ICAM-1) was examined in the epithelium of the human oviduct. Most oviducts showed epithelial ICAM-1 expression, as assessed by immunocytochemistry, western blot analysis and RT-PCR assay, and the expression was restricted to the luminal border of ciliated and secretory cells. Interferon gamma, interleukin 1 and lipopolysaccharide treatments increased the percentage of ICAM-1-positive cells in primary cultures, indicating that the expression of ICAM-1 in the oviduct might be upregulated in vivo by inflammatory cytokines or bacterial infections. Binding assays between allogenic phytohaemagglutinin-activated lymphocytes and epithelial monolayers expressing ICAM-1 demonstrated that this molecule stimulated lymphocyte adherence. The presence of ICAM-1, in addition to MHC class II, supports the putative role of the oviductal epithelium in antigen presentation. The exclusive apical distribution of ICAM-1 indicates that T-cell activation would occur in a polarized manner. Binding of lymphoid cells to the surface of the oviductal epithelium may help to retain these immune cells that are required for the clearance of pathogens.