Calcium Ion Channels: Roles in Infection and Sepsis Mechanisms of Calcium Channel Blocker Benefits in Immunocompromised Patients at Risk for Infection.

Immunosuppression may occur for a number of reasons related to an individual's frailty, debility, disease or from therapeutic iatrogenic intervention or misadventure. A large percentage of morbidity and mortality in immunodeficient populations is related to an inadequate response to infectious agents with slow response to antibiotics, enhancements of antibiotic resistance in populations, and markedly increased prevalence of acute inflammatory response, septic and infection related death. Given known relationships between intracellular calcium ion concentrations and cytotoxicity and cellular death, we looked at currently available data linking blockade of calcium ion channels and potential decrease in expression of sepsis among immunosuppressed patients. Notable are relationships between calcium, calcium channel, vitamin D mechanisms associated with sepsis and demonstration of antibiotic-resistant pathogens that may utilize channels sensitive to calcium channel blocker. We note that sepsis shock syndrome represents loss of regulation of inflammatory response to infection and that vitamin D, parathyroid hormone, fibroblast growth factor, and klotho interact with sepsis defense mechanisms in which movement of calcium and phosphorus are part of the process. Given these observations we consider that further investigation of the effect of relatively inexpensive calcium channel blockade agents of infections in immunosuppressed populations might be worthwhile.

Dysfunction of neuronal calcium signalling in neuroinflammation and neurodegeneration.

Neurodegeneration has been increasingly recognised as the leading structural correlate of disability progression in autoimmune diseases such as multiple sclerosis. Since calcium signalling is known to regulate the development of degenerative processes in many cell types, it is believed to play significant roles in mediating neurodegeneration. Because of its function as a major juncture linking various insults and injuries associated with inflammatory attack on neuronal cell bodies and axons, it provides potential for the development of neuroprotective strategies. This is of great significance because of the lack of neuroprotective agents presently available to supplement the current array of immunomodulatory treatments. In this review, we summarise the role that various calcium channels and pumps have been shown to play in the development of neurodegeneration under inflammatory autoimmune conditions. The identification of suitable targets might also provide insights into applications in non-inflammatory neurodegenerative diseases.

Lambert-Eaton myasthenic syndrome following H1N1-influenza vaccination: a case report.

BACKGROUND: The outbreak of influenza A (H1N1) pandemic during the year 2009 led to the development of several vaccinations against H1N1 virus. In Finland, 2.6 million citizens were vaccinated during pandemic 2009 - 2010 with adjuvanted influenza vaccine, Pandemrix(®) . CLINICAL PRESENTATION: In this case report, we describe a patient with non-paraneoplastic Lambert-Eaton myasthenic syndrome following Pandemrix(®) vaccination. CONCLUSION: Development of various autoimmune diseases in genetically predisposed subjects following exposure to certain environmental factors, including vaccinations, is a well-known entity. Clinicians should be aware of the possibility of the induction of autoimmune diseases following vaccinations and actively ask the relevant clinical history in a newly diagnosed patient with an autoimmune disorder.

TRPV1-mediated itch in seasonal allergic rhinitis.

BACKGROUND: Patients with allergic rhinitis may be abnormally sensitive to stimulation of the ion channel transient receptor potential vanilloid-1 (TRPV1). AIM OF THE STUDY: To examine effects of various TRP ion channel activators on sensory symptoms in allergic rhinitis prior to and during seasonal allergen exposure. METHODS: Nasal challenges were carried out with the TRPV1-activators capsaicin, anandamide and olvanil. Moreover, challenges were performed with mustard oil (allylisothiocyanate) and cinnamaldehyde as well as menthol, activators of TRPA1 and TRPM8, respectively. Nasal symptoms were monitored after each challenge and compared with symptoms reported following corresponding sham challenges. Symptoms recorded after challenge prior to pollen season were also compared with challenge-induced symptoms during pollen season. RESULTS: The TRPV1, TRPA1 and TRPM8-activators produced sensory symptoms dominated by pain and smart. During seasonal allergen exposure, but not prior to season, TRPV1-activators also induced itch. Furthermore, the seasonal challenge to the TRPV1-activator olvanil was associated with rhinorrhoea. CONCLUSION: Patients with allergic rhinitis feature an increased itch response to TRPV1 stimulation at seasonal allergen exposure. We suggest that this reflects part of the hyperresponsiveness that characterizes on-going allergic rhinitis. Intervention with the TRPV1-signalling pathway may offer potential treatments of this condition.

K+ channels as targets for specific immunomodulation.

The voltage-gated Kv1.3 channel and the Ca(2+)-activated IKCa1 K(+) channel are expressed in T cells in a distinct pattern that depends on the state of lymphocyte activation and differentiation. The channel phenotype changes during the progression from the resting to the activated cell state and from naïve to effector memory cells, affording promise for specific immunomodulatory actions of K(+) channel blockers. In this article, we review the functional roles of these channels in both naïve cells and memory cells, describe the development of selective inhibitors of Kv1.3 and IKCa1 channels, and provide a rationale for the potential therapeutic use of these inhibitors in immunological disorders.

Lambert-eaton myasthenic syndrome: diagnosis and treatment.

A high index of suspicion is essential in arriving at the correct diagnosis of Lambert-Eaton myasthenic syndrome (LEMS). LEMS should be considered in the differential in any patient who has proximal weakness, reduced or absent muscle stretch reflexes, and dry mouth. Weakness predominates in hip and shoulder muscles, but may also affect ocular and oropharyngeal muscles to a lesser extent. The diagnosis is confirmed by demonstrating characteristic electromyographic findings-low-amplitude muscle responses that increase dramatically after activation. Most patients also have circulating antibodies to the voltage-gated calcium channel. Half the patients with LEMS have a malignancy, usually small-cell lung cancer. The diagnosis should trigger an intensive search for malignancy, especially in older patients with a history of smoking. Younger, nonsmoking patients are likely to have LEMS as part of a more general autoimmune state. Successful treatment of the underlying cancer leads to improvement in many patients. More than 85% of patients have clinically significant benefit from 3,4-diaminopyridine (DAP). In over half of these, the improvement is marked. If severe weakness persists despite DAP, immunotherapy should be considered. Plasma exchange and high-dose immunoglobulin induce transient improvement in many patients, but function rarely becomes normal. Combinations of prednisone, azathioprine, or cyclosporine have been used with variable success. Improvement, if any, occurs only after many months and requires chronic administration of immunosuppressive medications at significant doses. The long-term prognosis in LEMS is determined by the presence of cancer or other autoimmune disease.

The TRPV6 gene, cDNA and protein.

The mouse TRPV6 gene is localized on chromosome 6 and extends over 15.66kb. The encoded protein comprises 727 amino acid residues with a calculated relative molecular mass of 83,210Da. TRPV6 is glycosylated and both variants, the glycosylated and the de-glycosylated proteins, are recognized by various polyclonal and monoclonal antibodies, which were raised against TRPV6. Like human TRPV6, mouse TRPV6 binds calmodulin in the presence, but not in the absence of Ca2+. TRPV6 is abundantly expressed in mouse pancreas and placenta, and to a much lesser extend in mouse stomach and kidney. No transcript expression was detected in poly(A)+RNA isolated from heart, brain, intestine, esophagus or aortic endothelial cells.

Expression of the alpha1F calcium channel subunit by photoreceptors in the rat retina.

PURPOSE: The CACNA1F gene encodes a voltage-gated calcium channel alpha1 subunit, alpha1F, which is expressed in the human retina. Mutations in this gene cause incomplete X-linked congenital stationary night blindness (CSNB2). The aim of this study was to obtain the sequence of the rat alpha1F cDNA and localize the encoded polypeptide in the rat retina. METHODS: The full-length rat alpha1F sequence was compiled from sequencing of overlapping alpha1F PCR fragments amplified from rat retinal cDNA. Antiserum was raised against a human alpha1F peptide. It was found that the human alpha1F peptide used to generate the antiserum was conserved at only 11 out of 19 residues in the cloned rat sequence. Therefore, antibodies were affinity purified against either the human alpha1F peptide or the equivalent rat peptide and used for immunofluorescent staining of rat retina sections. RESULTS: The rat alpha1F amino acid sequence was found to be 91% and 95% identical to the human and mouse alpha1F sequences, respectively. Antibodies affinity purified against the human alpha1F peptide stained both the outer nuclear layer (ONL) and outer plexiform layer of rat retina sections. In contrast, staining with antibodies affinity purified against the corresponding rat alpha1F peptide was restricted to the ONL. CONCLUSIONS: The rat alpha1F amino acid sequence is highly homologous to the human and mouse sequences. The immunohistochemical results indicate the existence of distinct alpha1F isoforms or alpha1F-like channels, which are differentially distributed in the cell bodies and synaptic terminals of photoreceptors in the rat retina.

Dendritic localization of Ca(2+)-permeable AMPA/kainate channels in hippocampal pyramidal neurons.

Although it is well established that cortical and hippocampal gamma-aminobutyric acid (GABA)-ergic neurons generally have large numbers of Ca(2+)-permeable alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate channels (Ca-A/K channels), their presence on pyramidal neurons is controversial. Ca2+ permeability of AMPA channels is regulated by expression of a particular glutamate receptor subunit (GluR2), which confers Ca2+ impermeability to heteromeric channels. Most electrophysiology studies, as well as in situ hybridization and immunolabeling studies demonstrating expression of GluR2 mRNA or peptide in pyramidal neurons, have provided evidence against the presence of Ca-A/K channels on pyramidal neurons. However, observations that pyramidal neurons often appear to be labeled by kainate-stimulated Co2+ influx (Co2+(+) cells), a histochemical stain that identifies cells possessing Ca-A/K channels, suggests that they may have these channels. The present study futher examines cellular and subcellular distribution of Ca-A/K channels on hippocampal pyramidal neurons in slice as well as in culture. To this end, techniques of kainate-stimulated Co2+ influx labeling, supplemented by AMPA receptor subunit immunocytochemistry and fluorescent imaging of kainate-stimulated intracellular Ca2+ ([Ca2+]i) rises are employed. Co2+ labeling is often seen in pyramidal neuronal dendrites in both slice and in culture. In addition, although GluR1 and 4 staining in these neurons is often seen in the soma and dendrites, GluR2 label, when evident, is generally more restricted to the soma. Finally, measurement of kainate-stimulated [Ca2+]i rises in cultured neurons, assessed by using low affinity Ca2+ indicators in the presence of N-methyl-D-aspartate (NMDA) receptor and voltage-sensitive Ca2+ channel blockade, often shows dendritic rises to precede those in the somata. Thus, these data support the hypothesis that Ca-A/K channels are present in dendritic domains of many pyramidal neurons, and may help to provide resolution of the apparently conflicting data regarding their distribution.

Spatiotemporal dynamics of the [Ca2+]i rise induced by microinjection of sperm extract into mouse eggs: preferential induction of a Ca2+ wave from the cortex mediated by the inositol 1,4,5-trisphosphate receptor.

Hamster sperm extract (SE) possessing Ca2+ oscillation-inducing activity was microinjected into the peripheral or central region of mouse eggs, and the first increase in intracellular Ca2+ concentration ([Ca2+]i), together with the spread of fluorescence-labeled SE in the ooplasm, was investigated by imaging with confocal microscopy. Injection into the periphery always induced a Ca2+ wave that started from the injection site after a delay of 5 to 30 s depending on the concentration of SE. The diluted SE caused a wave of two-step [Ca2+]i rises, which was always observed at fertilization. Injection into the center could induce a radial Ca2+ wave with relatively high dose of SE, but lower dose of SE caused a [Ca2+]i rise after a longer delay which was initiated synchronously over the ooplasm or was preceded in a peripheral area. Injection of diluted SE remarkably prolonged the delay time and reduced the rate of [Ca2+]i rise. The critical concentration of SE needed to induce [Ca2+]i rise was significantly lower in the periphery. These results indicate that the sensitivity to SE is higher in the cortex. SE-induced [Ca2+]i rises were blocked by an antibody against the type 1 inositol 1,4,5-trisphosphate receptor (InsP3R). The cortex was substantially more sensitive to injected InsP3 induction of Ca2+ release than the center. It is suggested that the cortex of mouse eggs may involve a functionally specialized organization of InsP3Rs and Ca2+ pools in which a cytosolic sperm factor(s) could act upon sperm-egg fusion to cause Ca2+ release, leading to the Ca2+ wave at fertilization.

Serum from diabetic BB/W rats enhances calcium currents in primary sensory neurons.

We examined the hypothesis that exposure of nondiabetic rat dorsal root ganglion (DRG) neurons to sera from diabetic BB/W rats would produce an increase in calcium currents associated with impaired regulation of the inhibitory G protein-calcium channel complex. Acutely dissociated rat DRGs were incubated for 18-24 h in medium supplemented with sera (10% vol/vol) from either diabetic rats with neuropathy or age-matched, nondiabetic controls. Exposure of DRG neurons to sera from diabetic BB/W rats resulted in a surface membrane immunofluorescence pattern when treated with an anti-rat light-chain antibody that was not observed in neurons exposed to control sera. Calcium current density (IDCa) was assessed with the use of the whole cell variation of the patch-clamp technique. IDCa in neurons exposed to diabetic sera was significantly increased compared with neurons exposed to control sera. Guanine nucleotide-binding (G) protein regulation of calcium channel function was examined with the use of a two-pulse "facilitation" or IDCa enhancement protocol in the presence of activators [guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S)] or antagonists [guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) and pertussis toxin (PTX)] of G protein function. Facilitation was significantly decreased in neurons exposed to diabetic sera. Intracellular diffusion of neurons with GDP beta s blocked facilitation, whereas dialysis with GTP gamma s increased facilitation to a similar magnitude in neurons exposed to either diabetic or control sera. Treatment with PTX resulted in a significant increase in IDCa and approximately 50% decrease in facilitation in neurons treated with control sera but no significant changes in neurons exposed to diabetic sera. We conclude that serum from diabetic BB/W rats with neuropathy contains an autoimmune immunoglobulin that impairs regulation of the inhibitory G protein-calcium channel complex, resulting in enhanced calcium influx. Regulation of the inhibitory G protein-calcium channel complex involves PTX-sensitive and -insensitive G proteins.

Anti-Ig-induced calcium influx in rat B lymphocytes mediated by cGMP through a dihydropyridine-sensitive channel.

In contrast to excitable tissues where calcium channels are well characterized, the nature of the B lymphocyte calcium channel is unresolved. Here, we demonstrate by single cell analysis of freshly isolated rat B cells that the anti-immunoglobulin (Ig)-induced calcium influx takes place through a channel which shares pharmacologic and serologic properties with the L-type calcium channel found in excitable tissues. It is sensitive to the dihydropyridines nicardipine and Bay K 8644, to calciseptine, and to an anti-peptide antibody raised against the alpha1 subunit of the L-type calcium channel, but is voltage-insensitive. Anti-alpha1 and anti-alpha2 antibodies stain B but not T lymphocytes. Application of a cGMP agonist, measurement of cGMP levels in anti-Ig-stimulated B cells, and examining the effect of a guanylyl cyclase inhibitor on the anti-Ig response show that cGMP mediates the influx. This possibly involves a cGMP-dependent protein kinase. The anti-Ig-induced response is not abolished by prior treatment of B cells with a high dose of thapsigargin. These findings undermine the widely held belief of a categorical divide between excitable and non-excitable tissue calcium channels, demonstrate the limitations of the capacitative calcium influx theory, and point to a distinction between the calcium response mechanisms utilized by B and T lymphocytes.

Expression and antibody inhibition of P-type calcium channels in human small-cell lung carcinoma cells.

P-type channels, a recently described form of voltage-gated calcium channels, are found in many central and peripheral neurons. In the present study, a partial cDNA clone sharing extensive nucleotide identity with a putative P-type voltage-gated calcium channel alpha 1 subunit was isolated from a small-cell lung carcinoma (SCLC) cell line. Anti-peptide antibodies generated to a unique acidic stretch in the IVS5-S6 linker region of the putative SCLC P-type channel reacted specifically with a SCLC fusion protein produced in bacteria and with a cell surface molecule in SCLC cells. Calcium currents in SCLC cells, measured by whole-cell patch clamp, were inhibited by these antibodies and by the P-type channel-specific toxin omega-agatoxin IVA. The inhibitory effects of the antibody and the toxin were not additive, consistent with their proposed action on the same type of channel. These results provide evidence for the expression of P-type calcium channels by SCLC cells. The expression of neuron-related molecules by these cells is of particular interest because small-cell lung carcinoma is frequently associated with paraneoplastic disorders affecting the nervous system.