Synchronous transporting activity in epithelial cells in relation to intracellular calcium concentration

Autoantibodies to sweat glands detected by different methods in serum and in tissue from patients affected by a new variant of endemic pemphigus foliaceus

Examining the patients with a new variant of endemic pemphigus foliaceus (EPF) in El Bagre, Colombia, (El Bagre-EPF), we noted several polymorphic clinical lesions around their axillary areas. Based on our clinical findings and on previous histopathological studies on the skin of these patients that showed abnormalities in their sweat glands, and the presence of mercuric selenides and iodines by autometallography assay, we decided to investigate immunoreactivity to the sweat glands in these patients. We tested for autoreactivity utilizing direct and indirect immunofluorescence (DIF, IIF). To be able to distinguish between non-specific immune deposits and real autoimmune response, and knowing that sweat glands have some intrinsic autofluorescence for the presence of lipofuscin granules (that naturally fluoresce under the UV light microscope), as well as by the presence of secretory IgA, we used simultaneously immunohistochemistry (IHC). We tested ten El Bagre-EPF patients, ten healthy controls from the endemic area and ten healthy controls from the United States. We were able to visualize a specific autoreactivity to sweat glands in 8/10 cases of El Bagre-EPF by DIF, IIF and by IHC. In addition when using anti-human monoclonal antibodies to CD3, CD68, and CD20, we confirmed the presence of several specific immune responses in situ, an around the sweat glands. No healthy control cases yielded positive findings. In some chronic cases, decrease and sometimes a complete absence of sweat glands and other skin appendices was found. In addition to this, sclerodermoid changes or early sclerodermatous changes sometimes extending into the adipose tissue as a membranous lipodystrophy were observed. Autoreactivity to the neurovascular components around the sweat glands were also observed. Our data demonstrate for the first time that there is immunoreactivity toward sweat glands in El Bagre-EPF patients that seems to destroy some of these structures.

Ruled by waves? Intracellular and intercellular calcium signalling

The field of calcium signalling has evolved rapidly the last 20 years. Physiologists had worked with cytosolic Ca2+ as the coupler of excitation and contraction of muscles and as a secretory signal in exocrine glands and in the synapses of the brain for several decades before the discovery of cellular calcium as a second messenger. Development of powerful techniques for measuring the concentration of cytosolic free calcium ions in cell suspensions and later in single cells and even in different cellular compartments, has resulted in an upsurge in the knowledge of the cellular machinery involved in intracellular calcium signalling. However, the focus on intracellular mechanisms might have led this field of study away from physiology. During the last few years there is an increasing evidence for an important role of calcium also as an intercellular signal. Via gap junctions calcium is able to co-ordinate cell populations and even organs like the liver. Here we will give an overview of the general mechanisms of intracellular calcium signalling, and then review the recent data on intercellular calcium signals. A functional coupling of cells in different tissues and organs by the way of calcium might be an important mechanism for controlling and synchronizing physiological responses

Evidence for voltage-sensitive, calcium-conducting channels in airway epithelial cells

In airways epithelial cultures, mechanical stimulation induces intracellular Ca2+ concentration ([Ca2+]i) changes by causing Ca2+ entry and intracellular Ca2+ release. Mechanically induced Ca2+ fluxes across the plasma membrane are blocked by Ni2+ (Boitano, S., M. J. Sanderson, and E. R. Dirksen. J. Cell. Sci. 107: 3037-3044, 1994). In this report we use fluorescence imaging microscopy with fura 2 and intracellular recording of the transmembrane potential to further characterize Ca2+ flux in the plasma membrane of these cells. Mechanically induced Ca2+ influx is blocked by nifedipine. Addition of the dihydropyridine agonist BAY K8644 (2 microM) leads to a delayed increase of [Ca2+]i that is dependent on extracellular Ca2+. Switching to high extracellular K+ concentration ([K+]o) causes depolarization of the plasma membrane and a transient increase in [Ca2+]i. The number of cells that respond to high [K+]o is significantly decreased by Ni2+ (1 mM) or nifedipine (10 microM). Mechanical stimulation causes a rapid depolarization of the stimulated cell that can be suppressed by the K+ ionophore valinomycin. Valinomycin treatment also blocks mechanically induced Ca2+ dux. These results suggest that voltage-sensitive Ca(2+)-conducting channels exist in airway epithelial cells, and these channels contribute to the [Ca2+]i changes observed after mechanical stimulation or depolarization of the plasma membrane.

Binding of human factor VIIa to tissue factor induces cytosolic Ca2+ signals in J82 cells, transfected COS-1 cells, Madin-Darby canine kidney cells and in human endothelial cells induced to synthesize tissue factor

Tissue factor (TF) is the most potent trigger of blood clotting known. It activates factor VII (FVII) thereby initiating a cascade of proteolytic reactions resulting in thrombin production. The cloning of TF revealed its structural characteristics to be those of a receptor related to the class 2 cytokine receptor superfamily, but until now no intracellular signal has been discovered related to binding of the ligand (FVIIa) to the putative receptor. We have studied possible intracellular signaling effects of the FVIIa-TF interaction by measuring cytosolic free Ca2+ in single fura-2-loaded cells and found that 200 nM FVIIa caused Ca2+ transients in about 30% of human umbilical vein endothelial cells treated with interleukin-1 beta to express TF, compared to below 5% in uninduced cells. A gradual increase of the basal Ca2+ level was also caused by binding of FVIIa. In the human bladder carcinoma cell line J82, which has a high constitutive TF activity, similar results were found. An antibody neutralizing TF activity decreased the response rate to control levels. COS-1 cells which do not make TF did not respond to FVIIa as opposed to COS-1 cells expressing TF after transfection with a human TF cDNA construct. The canine kidney cell line MDCK, a constitutive TF producer, responded especially well; up to 100% of the cells examined showed Ca2+ oscillations which were dose dependent with regard to frequency, latency, maximal amplitude, and recruitment of responding cells. The frequency was reduced by inhibition of Ca2+ influx with 100 microM LaCl3. In confluent MDCK cells the Ca2+ oscillations were synchronous, constituting the first evidence of a synchronous cytosolic Ca2+ oscillator generated by global application of agonist. Thus, TF mediates a cytosolic Ca2+ signal upon interaction with its ligand FVIIa, thereby suggesting a more complex biological role for TF.

Cyclic AMP and Ca2+ interactions affecting epithelial chloride secretion in human cultured colonic epithelia

1. Chloride secretion in three types of cultured epithelial monolayers derived from a single human colonic adenocarcinoma was measured in terms of short circuit current. The three cell types were designated HCA-7, Colony 3 and Colony 29. 2. Responses of HCA-7 monolayers to basolaterally applied lysylbradykinin (LBK) (10-1000 nM) or carbachol (1-100 microM) were potentiated by pre-exposure to forskolin (10 microM) for 5 min. Forskolin itself increased short circuit current (SCC), so that the total response to forskolin and LBK or carbachol were non-additive. 3. Colony 3 cells did not respond to LBK on either face but did to carbachol on the basolateral side, while Colony 29 epithelia responded to LBK on both sides and to carbachol and histamine basolaterally. Unlike HCA-7 epithelia, responses in Colony 3 and Colony 29 epithelia were not potentiated by forskolin, but were attenuated by piroxicam. 4. In the presence of piroxicam, both forskolin and prostaglandin E2 were able to potentiate the action of both LBK and carbachol in Colony 29 epithelia. 5. LBK receptor activation in Colony 29 epithelia is transduced into an increase in intracellular Ca2+ and cyclic AMP, while in HCA-7 epithelia there is only an increase in intracellular Ca2+ (Cai). These conclusions are considered to apply to both apical and basolateral kinin receptors. 6. It is shown that forskolin has no effect on the elevation of Ca2+ by LBK in either HCA-7 or Colony 29 cells. 7. It is concluded that potentiation of agonist responses occurs when cyclic AMP is raised at the time that intracellular Ca2+ increases. No potentiation of LBK or carbachol by forskolin occurs in Colony 29 monolayers as these agonists increase cyclic AMP via eicosanoid production.

Antagonism of kinin effects on epithelial by Hoe 140: apparently competitive and non-competitive interactions

1. Hoe-140, a potent kinin receptor antagonist, was investigated for its ability to inhibit the effects of lysylbradykinin (kallidin) on a cultured colonic epithelium, HCA-7 Colony 29, derived from a human adenocarcinoma. 2. Measurements of electrogenic chloride secretion (as short circuit current), and of intracellular Ca2+ (from Fura-2 fluorescence) were used to assess the action of lysylbradykinin in the absence and presence of Hoe 140. 3. From short circuit current data, Hoe 140 appeared to be a competitive antagonist with a Ki value of 5 nM. However, with measurements of intracellular Ca2+ Hoe 140 was apparently a non-competitive antagonist with a Ki of between 4-6 nM. 4. Because of the unexpected finding of non-competitive antagonism, measurements were made with a second antagonist pair, histamine and mepyramine. Mepyramine behaved as a competitive antagonist against responses to histamine with a Ki value of approximately 5 nM when short circuit current measurements were evaluated. However, when intracellular Ca2+ concentration was used as a measure mepyramine, 30 nM, produced a near parallel shift in the response curve, but at 100 nM the maximal response was depressed. 5. The reasons why the apparent type of antagonism depends upon the method of measurement is discussed, bearing in mind that the increase in intracellular Ca2+ is a signal which precedes the increase in short circuit current.