IgG4-Related Disease: A Clinical Case Series From a Tertiary Care Center in India

AIM

Immunoglobulin G4-related disease (IgG4-RD) is often an unrecognized, rare fibroinflammatory condition that can involve various organ systems. This study aimed to identify the different clinical patterns of this disease in a single center in North India.

METHODS

Patients were diagnosed on the basis of published diagnostic criteria for IgG4-RD. Patients' presenting complaints; epidemiologic profiles; and laboratory, radiologic, and histologic findings along with the treatment and outcomes were collected and analyzed.

RESULTS

In total, 70 patients were diagnosed with the disease. The female-to-male ratio was 0.94:1, and it increased with multiorgan involvement. The mean age of patients was 41.4 years, and the majority of the patients (65.7%) were younger than 50 years. Patients were diagnosed as possible (38.57%), probable (32.85%), and definite (28.57%) IgG4-RD. The incidence of the involvement of orbital and periorbital tissues was the highest (52.9%); however, 13% of the patients had multiple organ involvement. Patients with involvement of the retroperitoneal tissues and the lymph nodes were 8.5% and 5.7%, respectively. Increased serum IgG4 levels were found in 74.3% of the patients with single-organ involvement, whereas all patients with multiorgan involvement had increased IgG4 levels. The majority of patients (94.3%) required immunosuppressive medications along with corticosteroids. Azathioprine was the most commonly used (72.8%) immunosuppressive medication. Rituximab was used in 17.1% of the patients, of whom only one had multisystem involvement.

CONCLUSIONS

This study depicts the most common patterns of organ involvement, along with the epidemiologic, laboratory, histologic, and radiologic data and response to treatment, in IgG4-RD, with a definite ophthalmology referral bias.

Epidemiology, clinical profile, management, and outcome of COVID-19-associated rhino-orbital-cerebral mucormycosis in 2826 patients in India - Collaborative OPAI-IJO Study on Mucormycosis in COVID-19 (COSMIC), Report 1

Purpose

COVID-19-associated rhino-orbital-cerebral mucormycosis (ROCM) has reached epidemic proportion during India's second wave of COVID-19 pandemic, with several risk factors being implicated in its pathogenesis. This study aimed to determine the patient demographics, risk factors including comorbidities, and medications used to treat COVID-19, presenting symptoms and signs, and the outcome of management.

Methods

This was a retrospective, observational study of patients with COVID-19-associated ROCM managed or co-managed by ophthalmologists in India from January 1, 2020 to May 26, 2021.

Results

Of the 2826 patients, the states of Gujarat (22%) and Maharashtra (21%) reported the highest number of ROCM. The mean age of patients was 51.9 years with a male preponderance (71%). While 57% of the patients needed oxygen support for COVID-19 infection, 87% of the patients were treated with corticosteroids, (21% for > 10 days). Diabetes mellitus (DM) was present in 78% of all patients. Most of the cases showed onset of symptoms of ROCM between day 10 and day 15 from the diagnosis of COVID-19, 56% developed within 14 days after COVID-19 diagnosis, while 44% had delayed onset beyond 14 days. Orbit was involved in 72% of patients, with stage 3c forming the bulk (27%). Overall treatment included intravenous amphotericin B in 73%, functional endoscopic sinus surgery (FESS)/paranasal sinus (PNS) debridement in 56%, orbital exenteration in 15%, and both FESS/PNS debridement and orbital exenteration in 17%. Intraorbital injection of amphotericin B was administered in 22%. At final follow-up, mortality was 14%. Disease stage >3b had poorer prognosis. Paranasal sinus debridement and orbital exenteration reduced the mortality rate from 52% to 39% in patients with stage 4 disease with intracranial extension (p < 0.05).

Conclusion

: Corticosteroids and DM are the most important predisposing factors in the development of COVID-19-associated ROCM. COVID-19 patients must be followed up beyond recovery. Awareness of red flag symptoms and signs, high index of clinical suspicion, prompt diagnosis, and early initiation of treatment with amphotericin B, aggressive surgical debridement of the PNS, and orbital exenteration, where indicated, are essential for successful outcome.

Correction of preexisting astigmatism by penetrating arcuate keratotomy in femtosecond laser-assisted cataract surgery

Purpose:

To evaluate the astigmatism correcting effect of penetrating arcuate keratotomy (AK) done during femtosecond laser-assisted cataract surgery (FLACS).

Methods:

In this nonrandomized prospective study, 80 eyes of 70 patients were studied. The study included patients who underwent combined FLACS and AK, with corneal astigmatism ranging from 0.4 to 1.5 diopters (D). Femtosecond laser-assisted penetrating arcuate keratotomies were created at 8 mm optical zone at 80% depth and were centered at the limbus. Keratometric astigmatism was measured prior to and 3 months post-surgery. Vector analysis was performed using Power vector analysis method.

Results:

The mean preoperative keratometric astigmatism without accounting for axis was 0.85 ± 0.27 D, which reduced significantly to 0.47 ± 0.27 D at 3-month follow-up. The mean astigmatism correction attained without accounting for axis was 0.38 ± 0.32 D. The vector corrected mean preoperative astigmatism was 0.85 ± 0.27 D which reduced significantly to 0.50 ± 0.31 D postoperatively (P < 0.001, 95% CI). Vector corrected mean astigmatism correction attained was 0.35 ± 0.38 D. There were no significant intraoperative or postoperative complications.

Conclusion:

Preexisting astigmatism can be tackled effectively with penetrating AK during FLACS although under correction is observed with present nomograms. Further refinements may achieve better correction.

All India Ophthalmological Society - Oculoplastics Association of India consensus statement on preferred practices in oculoplasty and lacrimal surgery during the COVID-19 pandemic

Oculoplastic surgeries encompass both emergency surgeries for traumatic conditions and infectious disorders as well as elective aesthetic procedures. The COVID-19 pandemic has brought about a drastic change in this practice. Given the highly infectious nature of the disease as well as the global scarcity of medical resources; it is only prudent to treat only emergent conditions during the pandemic as we incorporate evidence-based screening and protective measures into our practices. This manuscript is a compilation of evidence-based guidelines for surgical procedures that oculoplastic surgeons can employ during the COVID-19 pandemic. These guidelines also serve as the basic framework upon which further recommendations may be based on in the future, as elective surgeries start being performed on a regular basis.

Negative velocity fluctuations and non-equilibrium fluctuation relation for a driven high critical current vortex state

Under the influence of a constant drive the moving vortex state in 2H-NbS₂ superconductor exhibits a negative differential resistance (NDR) transition from a steady flow to an immobile state. This state possesses a high depinning current threshold (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\boldsymbol{I}}}_{{\boldsymbol{c}}}^{{\boldsymbol{h}}}$$\end{document}Ich) with unconventional depinning characteristics. At currents well above \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\boldsymbol{I}}}_{{\boldsymbol{c}}}^{{\boldsymbol{h}}}$$\end{document}Ich, the moving vortex state exhibits a multimodal velocity distribution which is characteristic of vortex flow instabilities in the NDR regime. However at lower currents which are just above \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\boldsymbol{I}}}_{{\boldsymbol{c}}}^{{\boldsymbol{h}}}$$\end{document}Ich, the velocity distribution is non-Gaussian with a tail extending to significant negative velocity values. These unusual negative velocity events correspond to vortices drifting opposite to the driving force direction. We show that this distribution obeys the Gallavotti-Cohen Non-Equilibrium Fluctuation Relation (GC-NEFR). Just above \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\boldsymbol{I}}}_{{\boldsymbol{c}}}^{{\boldsymbol{h}}}$$\end{document}Ich, we also find a high vortex density fluctuating driven state not obeying the conventional GC-NEFR. The GC-NEFR analysis provides a measure of an effective energy scale (E_eff) associated with the driven vortex state. The E_eff corresponds to the average energy dissipated by the fluctuating vortex state above \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\boldsymbol{I}}}_{{\boldsymbol{c}}}^{{\boldsymbol{h}}}$$\end{document}Ich. We propose the high E_eff value corresponds to the onset of high energy dynamic instabilities in this driven vortex state just above \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\boldsymbol{I}}}_{{\boldsymbol{c}}}^{{\boldsymbol{h}}}$$\end{document}Ich.

Study of the sign change of exchange bias across the spin reorientation transition in Co(Cr1-x Fe x )2O4 (x = 0.00-0.125)

We present the evolution of novel phenomena of magnetic compensation effect, exchange bias (EB) effect and the field induced anomalies in '[Formula: see text]' substituted multiferroic compound [Formula: see text]. A few percent of '[Formula: see text]' substitution for '[Formula: see text]' in [Formula: see text] results in the reversal of field cooled magnetization under low applied fields below compensation temperature T _comp. Further, increase in the field leads to the spin reorientation transition (T _SR). Signature of EB in a narrow temperature window in the vicinity of T _SR and its sign change across T _SR is observed. Magnitude of EB depends on the amount of compensation and rigidity of the spin reorientation. We also notice the appearance of positive EB below the lock-in transition (T _L). Presence of unidirectional anisotropy developed in the commensurate spin-spiral below T _L could be responsible for the appearance of EB below T _L.

Sodium-Calcium Exchanger in Pig Coronary Artery

This review focuses on the sodium-calcium exchangers (NCX) in the left anterior descending coronary artery smooth muscle. Bathing tissues in Na⁺-substituted solutions caused them to contract. In cultured smooth muscle cells, it increased the cytosolic Ca²⁺ concentration and extracellular entry of ⁴⁵Ca²⁺. All three activities were attributed to NCX since they were inhibited by NCX inhibitors. The tissues also expressed the sarco/endoplasmic reticulum (SER) Ca²⁺ pump SERCA2b whose activity was much greater than that of NCX. Inhibiting SERCA2b with thapsigargin decreased the NCX-mediated ⁴⁵Ca²⁺ accumulation by the cells. The decrease was not observed in cells loaded with the Ca²⁺-chelator BAPTA. The results are consistent with a limited diffusional space model with a proximity between NCX and SERCA2b. NCX molecules appear to be colocalized with the subsarcolemmal SERCA2b based on studies on membrane flotation experiments and microscopic fluorescence imaging of antibody-labeled cells. Thapsigargin inhibition of SERCA2b moved NCX even closer to SER. This provides a model for the NCX-mediated Ca²⁺ refilling of SER in the arterial smooth muscle. The model for the NCX-mediated refilling of the depleted SER proposed for smooth muscle did not apply to endothelium in which NCX levels were greater and SERCA levels were lower than in smooth muscle. The effect of thapsigargin on the NCX-mediated Ca²⁺ accumulation which was observed in smooth muscle was absent in the endothelium. We propose that the coupling between NCX and smooth muscle may be tissue dependent.

Paramagnetic magnetization signals and curious metastable behaviour in field-cooled magnetization of a single crystal of superconductor 2H-NbSe2

We present here some newer characteristics pertaining to paramagnetic Meissner effect like response in a single crystal of the low [Formula: see text] superconducting compound 2H-[Formula: see text] via a detailed study of effects of perturbation on the field-cooled magnetization response. In the temperature range, where an anomalous paramagnetic magnetization occurs, the field-cooled magnetization response is found to be highly metastable: it displays a curious tendency to switch randomly from a given paramagnetic value to a diamagnetic or to a different paramagnetic value, when the system is perturbed by an impulse of an externally applied ac magnetic field. The new facets revealed in a single crystal of 2H-[Formula: see text] surprisingly bear a marked resemblance with the characteristics of magnetization behaviour anticipated for the giant vortex states with multiple flux quanta ([Formula: see text], [Formula: see text], [Formula: see text]) predicted to occur in mesoscopic-sized superconducting specimen and possible transitions amongst such states.

Antioxidants and vision health: facts and fiction

A number of nutritional supplements containing antioxidants are advertised for better vision health. Do they benefit the average consumer? The literature was examined for the effectiveness of antioxidants for human eye health, and for the intricacies in collection of such evidence. The following diseases were considered: cataract, glaucoma, age-related macular degeneration (AMD), retinopathy, retinitis pigmentosa, eye infections, and uveitis. The literature indicates that antioxidant supplements plus lutein have a reasonable probability of retarding AMD. For glaucoma, such supplements were ineffectual in some studies but useful in others. In some studies, antioxidant rich fruits and vegetables were also useful for protection against glaucoma. For diabetic retinopathy, antioxidant supplements may have a small benefit, if any, but only as an adjunct to glycemic control. In very high-risk premature retinopathy and retinitis pigmentosa, antioxidant supplements may be beneficial but those with excess Vitamin E should be avoided. For cataract, there is no evidence for an advantage of such nutritional supplements. However, lubricant drops containing N-acetylcarnosine may be helpful in initial stages of the disease. For eye infections and other causes of uveitis, antioxidants have not been found useful. We recommend that a diet high in antioxidant rich foods should be developed as a habit from an early age. However, when initial signs of vision health deterioration are observed, the appropriate nutritional supplement products may be recommended but only to augment the primary medical treatments.

Store operated Ca2+ entry dependent contraction of coronary artery smooth muscle: inhibition by peroxide pretreatment

The sarco/endoplasmic reticulum (SER) Ca(2+) pool is refilled by the SER Ca(2+) pump (SERCA) using cytosolic Ca(2+) and/or extracellular Ca(2+) entering the cell. The effects of the SERCA pump inhibitor cyclopiazonic acid (CPA) were studied in pig coronary artery smooth muscle using two protocols. In protocol A, the SERCA pump was inhibited by adding CPA to cells/tissues in Ca(2+)-containing solution, whereas in protocol B, CPA was added to cells/tissues in Ca(2+)-free solution, followed by reintroduction of extracellular Ca(2+). Addition of CPA increased cytosolic Ca(2+) in cultured smooth muscle cells and elicited contraction in de-endothelialized coronary arteries in both protocols. Based on pharmacological experiments, the CPA-induced contraction of de-endothelialized arteries in protocol B resulted from store operated Ca(2+) entry (SOCE). Reactive oxygen species such as peroxides are known to damage the SERCA pump in this tissue. Consistently, CPA-induced contractions were decreased in arteries pre-treated with hydrogen peroxide in protocol A. However, this pretreatment also decreased the force of contraction due to SOCE in protocol B, suggesting that it closed SOCE. We propose that the closure of SOCE triggered by exposure to reactive oxygen species may be a protective mechanism, so that Ca(2+) entry by this pathway is disallowed when SERCA is damaged in pathologies such as ischemia-reperfusion.

Allosteric inhibitors of plasma membrane Ca2+ pumps: Invention and applications of caloxins

Plasma membrane Ca²⁺ pumps (PMCA) play a major role in Ca²⁺ homeostasis and signaling by extruding cellular Ca²⁺ with high affinity. PMCA isoforms are encoded by four genes which are expressed differentially in various cell types in normal and disease states. Therefore, PMCA isoform selective inhibitors would aid in delineating their role in physiology and pathophysiology. We are testing the hypothesis that extracellular domains of PMCA can be used as allosteric targets to obtain a novel class of PMCA-specific inhibitors termed caloxins. This review presents the concepts behind the invention of caloxins and our progress in this area. A section is also devoted to the applications of caloxins in literature. We anticipate that isoform-selective caloxins will aid in understanding PMCA physiology in health and disease. With strategies to develop therapeutics from bioactive peptides, caloxins may become clinically useful in cardiovascular diseases, neurological disorders, retinopathy, cancer and contraception.

Magnetic response in the vicinity of magnetic compensation: a case study in spin ferromagnetic Sm1 - xGdxAl2 intermetallic alloys

A compensated magnetic state in an ideally homogeneous system with long range magnetic order is characterized by a net zero magnetization (M) throughout the sample (macroscopic). In the pristine state of the sample (i.e. with no external field, H = 0), this implies that at the magnetic compensation temperature (Tcomp) we must have M = 0 at H = 0 irrespective of any thermal and magnetic history of the sample and any underlying physics. This simple fact voids the usual identification (and interpretation) of M-H loop parameters at and in the vicinity of magnetic compensation temperature, specifically the coercivity, the remanence, and the exchange bias characteristics. The physics of coercivity and exchange bias continues to be fully relevant, but its manifestation in an M-H loop would get camouflaged at (and near) a magnetic compensation because [Formula: see text] at H = 0. We present an experimental elucidation of the above premise through a case study in the spin ferromagnetic Sm1 - xGdxAl2 alloys [x = 0.01-0.06], where the specimens with x ≤ 0.03 show compensation below the Curie temperature Tc, while those with x ≥ 0.03 have rather small magnetization due to near cancellation of opposing contributions, but are otherwise devoid of compensation. The experiments comprised low field (near zero) as well as high field (70 kOe) magnetization measurements from the paramagnetic state down to 5 K in the ordered regime (Tc ∼ 125 K) and isothermal M-H loop studies on the remnant magnetic state of polycrystalline samples.

Sodium-calcium exchanger and lipid rafts in pig coronary artery smooth muscle

Pig coronary artery smooth muscle expresses, among many other proteins, Na+-Ca²+-exchanger NCX1 and sarcoplasmic reticulum Ca²+ pump SERCA2. NCX1 has been proposed to play a role in refilling the sarcoplasmic reticulum Ca²+ pool suggesting a functional linkage between the two proteins. We hypothesized that this functional linkage may require close apposition of SERCA2 and NCX1 involving regions of plasma membrane like lipid rafts. Lipid rafts are specialized membrane microdomains that appear as platforms to co-localize proteins. To determine the distribution of NCX1, SERCA2 and lipid rafts, we isolated microsomes from the smooth muscle tissue, treated them with non-ionic detergent and obtained fractions of different densities by sucrose density gradient centrifugal flotation. We examined the distribution of NCX1; SERCA2; non-lipid raft plasma membrane marker transferrin receptor protein; lipid raft markers caveolin-1, flotillin-2, prion protein, GM1-gangliosides and cholesterol; and cytoskeletal markers clathrin, actin and myosin. Distribution of markers identified two subsets of lipid rafts that differ in their components. One subset is rich in caveolin-1 and flotillin-2 and the other in GM1-gangliosides, prion protein and cholesterol. NCX1 distribution correlated strongly with SERCA2, caveolin-1 and flotillin-2, less strongly with the other membrane markers and negatively with the cytoskeletal markers. These experiments were repeated with a non-detergent method of treating microsomes with sonication at high pH and similar results were obtained. These observations are consistent with the observed functional linkage between NCX1 and SERCA2 and suggest a role for NCX1 in supplying Ca²+ for refilling the sarcoplasmic reticulum.

Caloxin 1b3: a novel plasma membrane Ca(2+)-pump isoform 1 selective inhibitor that increases cytosolic Ca(2+) in endothelial cells

The purpose of this study was to invent an extracellular inhibitor selective for the plasma membrane Ca(2+) pump(s) (PMCA) isoform 1. PMCA extrude Ca(2+) from cells during signalling and homeostasis. PMCA isoforms are encoded by 4 genes (PMCA1-4). Pig coronary artery endothelium and smooth muscle express the genes PMCA1 and 4. We showed that the endothelial cells contained mostly PMCA1 protein while smooth muscle cells had mostly PMCA4. A random peptide phage display library was screened for binding to synthetic extracellular domain 1 of PMCA1. The selected phage population was screened further by affinity chromatography using PMCA from rabbit duodenal mucosa which expressed mostly PMCA1. The peptide displayed by the selected phage was termed caloxin 1b3. Caloxin 1b3 inhibited PMCA Ca(2+)-Mg(2+)-ATPase in the rabbit duodenal mucosa (PMCA1) with a greater affinity (inhibition constant=17±2 μM) than the PMCA in the human erythrocyte ghosts (PMCA4, inhibition constant=45±4 μM). The affinity of caloxin 1b3 was also higher for PMCA1 than for PMCA2 and 3 indicating its selectivity for PMCA1. Consistent with an inhibition of PMCA1, caloxin 1b3 addition to the medium increased cytosolic Ca(2+) concentration in endothelial cells. Caloxin 1b3 is the first known PMCA1 selective inhibitor. We anticipate caloxin 1b3 to aid in understanding PMCA physiology in endothelium and other tissues.

Phage display: concept, innovations, applications and future

Phage display is the technology that allows expression of exogenous (poly)peptides on the surface of phage particles. The concept is simple in principle: a library of phage particles expressing a wide diversity of peptides is used to select those that bind the desired target. The filamentous phage M13 is the most commonly used vector to create random peptide display libraries. Several methods including recombinant techniques have been developed to increase the diversity of the library. On the other extreme, libraries with various biases can be created for specific purposes. For instance, when the sequence of the peptide that binds the target is known, its affinity and selectivity can be increased by screening libraries created with limited mutagenesis of the peptide. Phage libraries are screened for binding to synthetic or native targets. The initial screening of library by basic biopanning has been extended to column chromatography including negative screening and competition between selected phage clones to identify high affinity ligands with greater target specificity. The rapid isolation of specific ligands by phage display is advantageous in many applications including selection of inhibitors for the active and allosteric sites of the enzymes, receptor agonists and antagonists, and G-protein binding modulatory peptides. Phage display has been used in epitope mapping and analysis of protein-protein interactions. The specific ligands isolated from phage libraries can be used in therapeutic target validation, drug design and vaccine development. Phage display can also be used in conjunction with other methods. The past innovations and those to come promise a bright future for this field.

Functional linkage as a direction for studies in oxidative stress: α-adrenergic receptorsThis review is one of a selection of papers published in a Special Issue on Oxidative Stress in Health and Disease

The α-adrenergic receptors (adrenoceptors) are activated by the endogenous agonists epinephrine and norepinephrine. They are G protein-coupled receptors that may be broadly classified into α1 (subclasses α1A, α1B, α1D) and α2 (subclasses α2A, α2B, α2C). The α1-adrenoceptors act by binding to Gαq subunits of the G proteins, causing activation of phospholipase C (PLC). PLC converts phosphatidylinositol 4,5-bisphosphate into inositol trisphosphate (IP3) and diacylglycerol (DAG), which have downstream effects on cytosolic Ca2+ concentration. The α2-adrenoceptors bind to Gαi thus inhibiting adenylyl cyclase and decreasing cAMP levels. DAG alters protein kinase C activity and cAMP activates protein kinase A. The downstream pathways of the two receptors may also interact. Activation of α1- and α2-adrenoceptors in vascular smooth muscle results in vasoconstriction. However, the densities of individual receptor subclasses vary between vessel beds or between vessels of various sizes within the same bed. In vasculature, the densities of adrenoceptor subclasses differ between conduit arteries and arterioles. These differences, along with differences in coupling mechanisms, allow for fine regulation of arterial blood flow. This diversity is enhanced by interactions resulting from homo- and heterodimer formation of the receptors, metabolic pathways, and kinases. Reactive oxygen species generated in pathologies may alter α1- and α2-adrenoceptor cascades, change vascular contractility, or cause remodeling of blood vessels. This review emphasizes the need for understanding the functional linkage between α-adrenoceptor subtypes, coupling, cross talk, and oxidative stress in cardiovascular pathologies.

Large low-frequency fluctuations in the velocity of a driven vortex lattice in a single crystal of 2H-NbSe2 superconductor

The driven state of a well-ordered flux line lattice in a single crystal of 2H-NbSe2 in the time domain has revealed the presence of substantial fluctuations in velocity, with large and distinct time periods ( approximately seconds). A superposition of a periodic drive in the driven vortex lattice causes distinct changes in these fluctuations. We propose that prior to the onset of the peak effect there exists a heretofore unexplored regime of coherent dynamics, with unexpected behavior in velocity fluctuations.

Sodium-calcium exchange mediated contraction in left anterior descending and left ventricular branch arteries

We tested the hypothesis that the de-endothelialized artery rings from the left anterior descending (LAD) coronary artery and its left ventricular branch (LVB) differ in their contractile responses to Na⁺–Ca²⁺-exchanger (NCX) mediated Ca²⁺-entry, muscarinic receptor activation with carbachol, and sarco/endoplasmic reticulum Ca²⁺ pump (SERCA) inhibition with thapsigargin. In LVB, the force of contraction (in N/g tissue) produced by the NCX mediated Ca²⁺-entry (17.5 ± 1.4) and carbachol (18 ± 1.5) was only slightly smaller than that due to membrane depolarization with KCl (24.0 ± 1.0). In contrast, in LAD the force of contraction produced with NCX (8.7 ± 0.7) and carbachol (6.1 ± 1.1) was much smaller than with KCl (15.7 ± 0.7). Thapsigargin also contracted LVB with greater force than LAD. When isolated microsomes were used, the binding to the muscarinic receptor antagonist quinuclidinyl benzilate was greater in LVB than in LAD. Microsomes were also used for Western blots. The intensities of signals for both SERCA and NCX were greater in LVB than in LAD. These biochemical observations were consistent with the contractile experiments. Thus, it appears that the differences between LAD and the resistance arteries may begin as early as LVB.

Functional effects of caloxin 1c2, a novel engineered selective inhibitor of plasma membrane Ca(2+)-pump isoform 4, on coronary artery

Coronary artery smooth muscle expresses the plasma membrane Ca²⁺ pump (PMCA) isoforms PMCA4 and PMCA1. We previously reported the peptide inhibitor caloxin 1b1 that was obtained by using extracellular domain 1 of PMCA4 as the target (Am J Physiol Cell.290 [2006] C1341). To engineer inhibitors with greater affinity and isoform selectivity, we have now created a phage display library of caloxin 1b1-like peptides. We screened this library by affinity chromatography with PMCA from erythrocyte ghosts that contain mainly PMCA4 to obtain caloxin 1c2. Key properties of caloxin 1c2 are (a) Ki = 2.3 ± 0.3 μM which corresponds to a 20× higher affinity for PMCA4 than that of caloxin 1b1 and (b) it is selective for PMCA4 since it has greater than 10-fold affinity for PMCA4 than for PMCA1, 2 or 3. It had the following functional effects on coronary artery smooth muscle: (a) it increased basal tone of the de-endothelialized arteries; the increase being similar at 10, 20 or 50 μM, and (b) it enhanced the increase in the force of contraction at 0.05 but not at 1.6 mM extracellular Ca²⁺ when Ca²⁺ extrusion via the Na⁺–Ca²⁺ exchanger and the sarco/endoplasmic reticulum Ca²⁺ pump were inhibited. We conclude that PMCA4 is pivotal to Ca²⁺ extrusion in coronary artery smooth muscle. We anticipate caloxin 1c2 to aid in understanding the role of PMCA4 in signal transduction and home-ostasis due to its isoform selectivity and ability to act when added extracellularly.

Functional linkage of Na+-Ca2+-exchanger to sarco/endoplasmic reticulum Ca2+ pump in coronary artery: comparison of smooth muscle and endothelial cells

An increase in cytosolic Ca(2+) concentration in coronary artery smooth muscle causes a contraction but in endothelium it causes relaxation. Na(+)-Ca(2+)-exchanger (NCX) may play a role in Ca(2+) dynamics in both the cell types. Here, the NCX-mediated (45)Ca(2+) uptake was compared in Na(+)-loaded pig coronary artery smooth muscle and endothelial cells. In both the cell types, this uptake was inhibited by KB-R7943, SEA 0400 and by monensin, but not by cariporide. Prior loading of the cells with the Ca(2+) chelator BAPTA increased the NCX-mediated (45)Ca(2+) uptake in smooth muscle but not in endothelial cells. In the presence or absence of BAPTA loading, the Na(+)-mediated (45)Ca(2+) uptake was greater in endothelial than in smooth muscle cells. In smooth muscle cells without BAPTA loading, thapsigargin diminished the NCX-mediated (45)Ca(2+) entry. This effect was not observed in endothelial cells or in either cell type after BAPTA loading. The results in the smooth muscle cells are consistent with a limited diffusional space model in which the NCX-mediated (45)Ca(2+) uptake was enhanced by chelation of cytosolic Ca(2+) or by its sequestration by the sarco/endoplasmic reticulum Ca(2+) pump (SERCA). They suggest a functional linkage between NCX and SERCA in the smooth muscle but not in the endothelial cells. The concept of a linkage between NCX and SERCA in smooth muscle was also confirmed by similar distribution of NCX and SERCA2 proteins when detergent-treated microsomes were fractionated by flotation on sucrose density gradients. Thus, the coronary artery smooth muscle and endothelial cells differ not only in the relative activities of NCX but also in its functional linkage to SERCA.

Caloxins: a novel class of selective plasma membrane Ca2+ pump inhibitors obtained using biotechnology

Plasma membrane Ca2+ pumps (PMCA) extrude cellular Ca2+ with a high affinity and hence play a major role in Ca2+ homeostasis and signaling. Caloxins (selective extracellular PMCA inhibitors) would aid in elucidating the physiology of PMCA. PMCA proteins have five extracellular domains (exdoms). Our hypotheses are: 1) peptides that bind selectively to each exdom can be invented by screening a random peptide library, and 2) a peptide can modulate PMCA activity by binding to one of the exdoms. The first caloxin 2a1, selected for binding exdom 2 was selective for PMCA (Ki=529 microM). It has been used to examine the physiological role of PMCA. PMCA isoforms are encoded by four genes. PMCA isoform expression differs in various cell types, with PMCA1 and 4 being the most widely distributed. There are differences between PMCA1-4 exdom 1 sequences, which may be exploited for inventing isoform selective caloxins. Using exdom 1 of PMCA4 as a target, modified screening procedures and mutagenesis led to the high-affinity caloxin 1c2 (Ki=2.3 microM for PMCA4). It is selective for PMCA4 over PMCA1, 2, or 3. We hope that caloxins can be used to discern the roles of individual PMCA isoforms in Ca2+ homeostasis and signaling. Caloxins may also become clinically useful in cardiovascular diseases, neurological disorders, retinopathy, cancer, and contraception.

Ca2+-pumps and Na2+-Ca2+-exchangers in coronary artery endothelium versus smooth muscle

Vascular endothelial cells (EC) and smooth muscle cells (SMC) require a decrease in cytoplasmic Ca²⁺ concentration after activation. This can be achieved by Ca²⁺ sequestration by the sarco-/endoplasmic reticulum Ca²⁺ pumps (SERCA) and Ca²⁺ extrusion by plasma membrane Ca²⁺ pumps (PMCA) and Na⁺–Ca²⁺-exchangers (NCX). Since the two cell types differ in their structure and function, we compared the activities of PMCA, NCX and SERCA in pig coronary artery EC and SMC, the types of isoforms expressed using RT-PCR, and their protein abundance using Western blots. The activity of NCX is higher in EC than in SMC but those of PMCA and SERCA is lower. Consistently, the protein abundance for NCX protein is higher in EC than in SMC and those of PMCA and SERCA is lower. Based on RT-PCR experiments, the types of RNA present are as follows: EC for PMCA1 while SMC for PMCA4 and PMCA1; EC for SERCA2 and SERCA3 and SMC for SERCA2. Both EC and SMC express NCX1 (mainly NCX1.3). PMCA, SERCA and NCX differ in their affinities for Ca²⁺ and regulation. Based on these observations and the literature, we conclude that the tightly regulated Ca²⁺ removal systems in SMC are consistent with the cyclical control of contractility of the filaments and those in EC are consistent with Ca²⁺ regulation of the endothelial nitric oxide synthase near the cell surface. The differences between EC and SMC should be considered in therapeutic interventions of cardiovascular diseases.

Morning glory anomaly with bilateral choroidal colobomas in a patient with Goldenhar's syndrome

A child with Goldenhar's syndrome, bilateral choroidal colobomas, and a morning glory anomaly of the optic disk in one eye is described. Bilateral posterior segment anomalies associated with Goldenhar's syndrome are rare. An association between the morning glory anomaly and Goldenhar's syndrome has not been previously reported.

Ca2+-mediated ascorbate release from coronary artery endothelial cells

1.--The addition of Ca(2+) ionophore A23187 or ATP to freshly isolated or cultured pig coronary artery endothelial cells (PCEC) potentiated the release of ascorbate (Asc). Cultured PCEC were used to characterize the Ca(2+)-mediated release. An increase in Ca(2+)-mediated Asc release was observed from PCEC preincubated with Asc, Asc-2-phosphate or dehydroascorbic acid (DHAA). 2.--The effects of various ATP analogs and inhibition by suramin were consistent with the ATP-induced release being mediated by P2Y2-like receptors. 3.--ATP-stimulated Asc release was Ca(2+)-mediated because (a) ATP analogs that increased Asc release also elevated cytosolic [Ca(2+)], (b) Ca(2+) ionophore A23187 and cyclopiazonic acid stimulated the Asc release, (c) removing extracellular Ca(2+) and chelating intracellular Ca(2+)inhibited the ATP-induced release, and (d) inositol-selective phospholipase C inhibitor U73122 also inhibited this release. 4.--Accumulation of Asc by PCEC was examined at Asc concentrations of 10 microM (Na(+)-Asc symporter not saturated) and 5 mM (Na(+)-Asc symporter saturated). At 10 microM Asc, A23187 and ATP caused an inhibition of Asc accumulation but at 5 mM Asc, both the agents caused a stimulation. Substituting gluconate for chloride did not affect the basal Asc uptake but it abolished the effects of A23187. 5.--PCEC but not pig coronary artery smooth muscle cells show a Ca(2+)- mediated Asc release pathway that may be activated by agents such as ATP.

Characterization of SERCA2b Ca2+-Mg2+ ATPase mRNA decay by nuclear proteins

Gene expression is controlled at several levels including mRNA decay. Sarco/endoplasmic reticulum Ca2+-Mg2+-ATPase isoform 2b (SERCA2b) is central to Ca2+ signalling and homeostasis in several tissues. SERCA2b mRNA decay involves interactions between cis-acting elements in its 3'-region and trans-acting nuclear protein factors. In the presence of the protein factors, the synthetic capped and polyadenylated RNA fragment 2b1 (3444-3753) decays faster than other SERCA2b 3'-region fragments. Here we determined the minimum cis-acting destabilizing element in the decay and its interactions with the nuclear protein factors. The in vitro decay required ATP hydrolysis and Mg2+ but not Ca2+. The decay was directional from 3' to 5', and involved a novel 35b GC rich domain designated 2b1-4 corresponding to 3521-3555. The decay of 2b1 RNA was decreased by (a) competition with 2b1-4, (b) mutation of 2b1 to delete 2b1-4, and (c) depleting the extracts of destabilizing trans-acting factors using immobilized 2b1-4. To determine the minimal destabilizing elements 2b1-4 was divided into 7b domains A-E. Deleting AB, BC, CD or DE inactivated the destabilizing cis-acting element but deleting A, B, C, D or E had no effect. In electrophoresis mobility shift assays the nuclear protein extracts retarded the mobility of labeled uncapped 2b1 RNA without a poly A+ tail. A positive co-operativity in the interactions was shown in protein concentration dependence of the shift and in the competition of 2b1-4 in inhibiting the mobility of 2b1 RNA. Based on further experiments, the domain CDE (3535-3555) was sufficient to compete with 2b1 RNA for the protein binding. Consistent with this competition, excess CDE RNA retarded the in vitro decay of 2b1 RNA. Thus the RNA decay required ATP hydrolysis and Mg2+ but not Ca2+, the minimum binding domain was in the sequence 3535-3555, and the decay may involve a multimeric protein complex.

Hypotonic shock stimulates ascorbate release from coronary artery endothelial cells by a Ca2+ -independent pathway

In endothelial cells, anion channels open upon osmotic swelling during shear stress and hypotonic shock. Therefore, we examined the effects of hypotonic shock on release of the antioxidant anion ascorbate from pig coronary artery endothelial cells. Hypotonic shock potentiated ascorbate release from freshly isolated or cultured pig coronary artery endothelial cells; subsequently cultured endothelial cells were used. The hypotonic shock-induced increase in Asc release was rapid, depended on the degree of hypotonic shock, and not due to membrane leakiness. Stimulating P2Y2 like receptors in endothelial cells with ATP causes ascorbate release via a Ca2+ -mediated pathway. Hypotonic shock-induced release differed from the Ca2+-mediated Asc release because: (a) the increase in release with hypotonic shock was additive to that with ATP or A23187 (Ca2+ -ionophore), (b) apyrase, suramin or removing extracellular Ca2+ did not affect the hypotonic shock-stimulated release, (c) anion channel blockers inhibited the release by the two pathways differently, and (d) hypotonic shock increased the ascorbate release from endothelial cells and cultured smooth muscle cells whereas the Ca2+ -mediated ascorbate release occurred only in endothelial cells. Accumulation of ascorbate by endothelial cells was examined at extracellular ascorbate concentrations of 10 (Na+ -ascorbate symporter not saturated) and 5000 microM (Na+ -ascorbate symporter saturated). Hypotonic shock and A23187 decreased ascorbate accumulation at 10 microM ascorbate but increased it at 5000 microM. The effects of the two treatments were additive and also differed from each other with substitution of gluconate for extracellular chloride. Thus, ascorbate release from endothelial cells can be potentiated by two distinct pathways - hypotonic shock mediated and ATP/Ca2+ stimulated.

Control of protein expression through mRNA stability in calcium signalling

Specific sequences (cis-acting elements) in the 3'-untranslated region (UTR) of RNA, together with stabilizing and destabilizing proteins (trans-acting factors), determine the mRNA stability, and consequently, the level of expression of several proteins. Such interactions were discovered initially for short-lived mRNAs encoding cytokines and early genes like c-jun and c-myc. However, they may also determine the fate of more stable mRNAs in a tissue and disease-dependent manner. The interactions between the cis-acting elements and the trans-acting factors may also be modulated by Ca(2+) either directly or via a control of the phosphorylation status of the trans-acting factors. We focus initially on the basic concepts in mRNA stability with the trans-acting factors AUF1 (destabilizing) and HuR (stabilizing). Sarco/endoplasmic reticulum Ca(2+) pumps, SERCA2a (cardiac and slow twitch muscles) and SERCA2b (most cells including smooth muscle cells), are pivotal in Ca(2+) mobilization during signal transduction. SERCA2a and SERCA2b proteins are encoded by relatively stable mRNAs that contain cis-acting stability determinants in their 3'-regions. We present several pathways where 3'-UTR mediated mRNA decay is key to Ca(2+) signalling: SERCA2a and beta-adrenergic receptors in heart failure, renin-angiotensin system, and parathyroid hormones. Other examples discussed include cytokines vascular endothelial growth factor, endothelin and endothelial nitric oxide synthase. Roles of Ca(2+) and Ca(2+)-binding proteins in mRNA stability are also discussed. We anticipate that these novel modes of control of protein expression will form an emerging area of research that may explore the central role of Ca(2+) in cell function during development and in disease.

Aortic smooth muscle and endothelial plasma membrane Ca2+pump isoforms are inhibited differently by the extracellular inhibitor caloxin 1b1

Plasma membrane Ca2+pumps (PMCA) that expel Ca2+from cells are encoded by four genes (PMCA1–4). In this study, we show that aortic endothelium and smooth muscle differ in their PMCA isoform mRNA expression: endothelium expressed predominantly PMCA1, and smooth muscle expressed PMCA4 and a lower level of PMCA1. In this study, we report a novel peptide (caloxin 1b1, obtained by screening for binding to extracellular domain 1 of PMCA4), which inhibited PMCA extracellularly, selectively, and had a higher affinity for PMCA4 than PMCA1. It inhibited the PMCA Ca2+-Mg2+-ATPase activity in leaky erythrocyte ghosts (mainly PMCA4) with a Kivalue of 46 ± 5 μM, making it 10× more potent than the previously reported caloxin 2a1. It was isoform selective because it inhibited the PMCA1 Ca2+-Mg2+-ATPase in human embryonic kidney-293 cells with a higher Kivalue (105 ± 11 μM) than for PMCA4. Caloxin 1b1 was selective in that it did not inhibit other ATPases. Because caloxin 1b1 had been selected to bind to an extracellular domain of PMCA, it could be added directly to cells and tissues to examine its effects on smooth muscle and endothelium. In deendothelialized aortic rings, caloxin 1b1 (200 μM) produced a contraction. It also increased the force of contraction produced by a submaximum concentration of phenylephrine. In aortic rings with endothelium intact, precontracted with phenylephrine and relaxed partially with a submaximum concentration of carbachol, caloxin 1b1 increased the force of contraction rather than potentiating the endothelium-dependent relaxation. In cultured cells, caloxin 1b1 increased the cytosolic [Ca2+] more in arterial smooth muscle cells than in endothelial cells. Thus caloxin 1b1 is the first highly selective extracellular PMCA inhibitor that works better on vascular smooth muscle than on endothelium.

Plasma Membrane Calcium Pump Activity in Rat Pancreatic Islets: An Accurate Method to Measure its Calcium-Dependent Modulation

The aim of this study was to quantify the glucose modulation of the plasma membrane calcium pump (PMCA) function in rat pancreatic islets. Ca2+-ATPase activity and levels of phosphorylated PMCA intermediates both transiently declined to a minimum in response to stimulation by glucose. Strictly dependent on Ca2+ concentration, this inhibitory effect was fully expressed at physiological concentrations of the cation (less than 0.5 muM), then progressively diminished at higher concentrations. These results, together with those previously reported on the effects of insulin secretagogues and blockers on the activity, expression and cellular distribution of the PMCA, support the concept that the PMCA plays a key role in the regulation of Ca2+ signaling and insulin secretion in pancreatic islets.

Plasma membrane calcium pumps in smooth muscle: from fictional molecules to novel inhibitors

Plasma membrane Ca2+pumps (PMCA pumps) are Ca2+-Mg2+ATPases that expel Ca2+from the cytosol to extracellular space and are pivotal to cell survival and function. PMCA pumps are encoded by the genes PMCA1, -2, -3, and -4. Alternative splicing results in a large number of isoforms that differ in their kinetics and activation by calmodulin and protein kinases A and C. Expression by 4 genes and a multifactorial regulation provide redundancy to allow for animal survival despite genetic defects. Heterozygous mice with ablation of any of the PMCA genes survive and only the homozygous mice with PMCA1 ablation are embryolethal. Some PMCA isoforms may also be involved in other cell functions. Biochemical and biophysical studies of PMCA pumps have been limited by their low levels of expression. Delineation of the exact physiological roles of PMCA pumps has been difficult since most cells also express sarco/endoplasmic reticulum Ca2+pumps and a Na+-Ca2+-exchanger, both of which can lower cytosolic Ca2+. A major limitation in the field has been the lack of specific inhibitors of PMCA pumps. More recently, a class of inhibitors named caloxins have emerged, and these may aid in delineating the roles of PMCA pumps.Key words: ATPases, hypertension, caloxin, protein kinase A, protein kinase C, calmodulin.

Role of third extracellular domain of plasma membrane Ca2+-Mg2+-ATPase based on the novel inhibitor caloxin 3A1

The plasma membrane Ca2+ pump (PMCA) is a Ca2+-Mg2+-ATPase that expels Ca2+ from cells to help them maintain low concentrations of cytosolic Ca2+ ([Ca2+]i). It contains five putative extracellular domains (PEDs). Earlier we had reported that binding to PED2 leads to PMCA inhibition. Mutagenesis of residues in transmembrane domain 6 leads to loss of PMCA activity. PED3 connects transmembrane domains 5 and 6. PED3 is only five amino acid residues long. By screening a phage display library, we obtained a peptide sequence that binds this target. After examining a number of peptides related to this original sequence, we selected one that inhibits the PMCA pump (caloxin 3A1). Caloxin 3A1 inhibits PMCA but not the sarcoplasmic reticulum Ca2+-pump. Caloxin 3A1 did not inhibit formation of the 140 kDa acylphosphate intermediate from ATP or its degradation. Thus, PEDs play a role in the reaction cycle of PMCA even though sites for binding to the substrates Ca2+ and Mg-ATP2-, and the activator calmodulin are all in the cytosolic domains of PMCA. In endothelial cells exposed to low concentration of a Ca2+-ionophore, caloxin 3A1 caused a further increase in [Ca2+]i proving its ability to inhibit PMCA pump extracellularly. Thus, even though PED3 is the shortest PED, it plays key role in the PMCA function.

Ascorbate uptake in pig coronary artery endothelial cells

Although smooth muscle and endothelial cells in pig coronary artery are morphologically and functionally distinct, ascorbate uptake has been characterized only in smooth muscle cells. Ascorbate transporters in kidney and intestinal epithelial cells differ from those in smooth muscle. We examined ascorbate transport and mRNA expression of sodium-dependent vitamin C transporters (SVCT) by RT-PCR in the pig coronary artery endothelial cell cultures. When 14C-ascorbate uptake in endothelial cells was examined as 14C or by HPLC, the two values did not differ from each other. 14C-ascorbate uptake was Na(+)-dependent, stereoselective for L-ascorbate and inhibited by sulfinpyrazone. The kinetic characteristics of the uptake were: Km = 27 +/- 3 microM (Hill coefficient = 1) for ascorbate and Km = 73 +/- 14 mM (Hill coefficient = 2) for Na+. Surprisingly, endothelial cells had similar kinetic parameters as smooth muscle cells, except for a slightly lower uptake velocity in endothelial cells. Comparison with the smooth muscle showed that both tissue types expressed mRNA for SVCT2. Endothelial cells differ from epithelial cells which express mainly SVCT1 but resemble smooth muscle cells in this respect.

A novel plasma membrane Ca2+-pump inhibitor: caloxin 1A1

The plasma membrane Ca(2+)-Mg(2+)-ATPase is a Ca(2+)-pump that expels Ca2+ from cells. Here we report caloxin 1A1-a novel peptide inhibitor (Ki=100 microM) of plasma membrane Ca(2+)-pump-obtained by screening a cysteine bridge-constrained random peptide library for binding to the first extracellular domain of plasma membrane Ca(2+)-pump. Dithiothreitol removed the inhibition indicating that the constraint imposed by the cysteine bridge is required for the inhibition. Caloxin 1A1 also inhibited the fast twitch sarcoplasmic reticulum Ca(2+)-Mg(2+)-ATPase although weakly. Glutathione dimers (containing a cysteine bridge) inhibited the Ca(2+)-Mg(2+)-ATPase activity of sarcoplasmic reticulum Ca(2+)-Mg(2+)-ATPase, but not that of plasma membrane Ca(2+)-pump. Caloxin 1A1 stabilised Ca(2+)-dependent formation of the acid stable 140-kDa acylphosphate which is a partial reaction of this enzyme. Thus caloxin 1A1 inhibits the plasma membrane Ca(2+)-pump by perturbing the first extracellular domain indicating that the transmembrane domains 1 and 2 play a role in its reaction cycle. This finding is consistent with rearrangements that occur in transmembrane helices 1 and 2 during reaction cycle of sarcoplasmic reticulum Ca(2+)-pump. Caloxin 1A1 caused an increase in cytosolic Ca2+ concentration in endothelial cells.

Control of SERCA2a Ca2+ pump mRNA stability by nuclear proteins: role of domains in the 3′-untranslated region

Alternative splicing of the sarco/endoplasmic reticulum (SERCA2) Ca2+ pump transcript generates the two isoforms: SERCA2a in left ventricular myocytes (LVM) and SERCA2b in most tissues. Nuclear protein extracts from left ventricular myocytes can cause a decay of the 3'-region of the SERCA2a. To determine if all the domains in the 800 b SERCA2a 3'-end region (3344-4243) are equally stable, we examined in vitro decay of synthetically capped, polyadenylated overlapping RNA fragments 2A1-2A6 from the 3'-end region of SERCA2a. Whereas 2A1-2A5 RNAs were stable, the distal fragment 2A6 (4135-4243 b) decayed rapidly. Deleting the 2A6 sequence from the 800-b 3'-end region increased its stability. In mobility shift assays, 2A6 bound to protein(s) in the LVM nuclear extracts in a specific manner: unlabelled 2A6 or the 800 b 3'-region RNA competed for binding but poly A, poly U, and poly C RNA did not. Secondary structure analysis revealed three hairpin loops in 2A6. Experiments using small synthetic RNA fragments for competition with 2A6 binding to nuclear proteins were consistent with a model involving the three hairpin loops. Thus, the secondary structure of the distal domain of SERCA2a RNA may be important in regulating its stability.

Leber′s hereditary optic neuropathy with molecular characterization in two Indian families

PURPOSE

Leber's hereditary optic neuropathy (LHON) presents in early adulthood with painless progressive blindness of one or both eyes. Usually there is a positive family history of similar disease on the maternal side. Definitive diagnosis can be established by finding the change in the mitochondrial gene. No molecular studies have been reported from India.

MATERIAL AND METHODS

Clinical, ophthalmologic and molecular studies were carried out in two patients from different families and available first degree relatives. The subjects were tested for the three common mutations seen in LHON by molecular techniques of polymerase chain reaction using mutation specific primers.

RESULTS

The mutations G3460A and G11778A in the mitochondrial genes MTND1 and MTND4, known to be causative for LHON, were found in one family each.

CONCLUSION

Diagnosis of LHON should be considered in familial cases and in young adults with optic atrophy. Confirmation of diagnosis should be sought by molecular gene analysis. Genetic counselling should be offered to all 'at risk' relatives of a patient harbouring the mutation.

Peroxynitrite resistance of sarco/endoplasmic reticulum Ca2+ pump in pig coronary artery endothelium and smooth muscle

We examined the effects of peroxynitrite pre-treatment on sarco/endoplasmic reticulum Ca(2+) (SERCA) pump in pig coronary artery smooth muscle and endothelium. In saponin-permeabilized cells, smooth muscle showed much greater rates of the SERCA Ca(2+) pump-dependent (45)Ca(2+) uptake/mg protein than did the endothelial cells. Peroxynitrite treatment of cells inhibited the SERCA pump more severely in smooth muscle cells than in endothelial cells. To determine implications of this observation, we next examined the effect of the SERCA pump inhibitor cyclopiazonic acid (CPA) on intracellular Ca(2+) concentration of intact cultured cells. CPA produced cytosolic Ca(2+) transients in cultured endothelial and smooth muscle cells. Pre-treatment with peroxynitrite (200 microM) inhibited the Ca(2+) transients in the smooth muscle but not in the endothelial cells. CPA contracts de-endothelialized artery rings and relaxes precontracted arteries with intact endothelium. Peroxynitrite (250 microM) pre-treatment inhibited contraction in the de-endothelialized artery rings, but not the endothelium-dependent relaxation. Thus, endothelial cells appear to be more resistant than smooth muscle to the effects of peroxynitrite at the levels of SERCA pump activity, CPA-induced Ca(2+) transients in cultured cells, and the effects of CPA on contractility. The greater resistance of endothelium to peroxynitrite may play a protective role in pathological conditions such as ischemia-reperfusion when excess free radicals are produced.

Role of transient receptor potential canonical 6 (TRPC6) in non-transferrin-bound iron uptake in neuronal phenotype PC12 cells

Cells take up transferrin-bound iron or NTBI (non-transferrin-bound iron). After treatment with NGF (nerve growth factor), PC12 cells exhibited a neuronal phenotype and an increase in the NTBI uptake (55Fe2+ or 55Fe3+). We loaded the cells with the dye calcein, whose fluorescence increases in the presence of Ca2+ but is quenched with Fe2+ or Fe3+. When examined using calcein fluorescence or radioactive iron, DAG (diacylglycerol)-stimulated NTBI entry was more in NGF-treated PC12 cells compared with untreated cells. All experiments were performed at 1.5 mM extracellular Ca2+. Nramp2 (natural-resistance-associated macrophage protein 2) mRNA expression did not change after the NGF treatment. Expression of the bivalent cation entry protein TRPC6 (transient receptor potential canonical 6) was detected only in the NGF-treated cells. To verify that increased NTBI uptake depended on TRPC6, we examined whether transfecting HEK-293 (human embryonic kidney 293) cells with TRPC6 also increased the NTBI (55Fe) uptake. We also cotransfected HEK-293 cells with two plasmids, one expressing TRPC6 and the other expressing the fluorescent protein DsRED2 to identify the transfected cells. Challenging the calcein-loaded HEK-293 cells (which intrinsically express the a1-adrenergic receptors) with phenylephrine or a cell-permeant DAG increased the fluorescence signal more rapidly in transfected cells compared with untransfected cells. However, when iron (Fe2+ and Fe3+) was added before adding phenylephrine or DAG, the fluorescence intensity decreased more rapidly in transfected cells compared with untransfected cells, thereby indicating a greater stimulation of the NTBI uptake in cells expressing TRPC6. We postulate that the increase in the NTBI entry into neuronal PC12 cells is through TRPC6, a pathway that is unique since it is receptor-stimulated. Since neuronal cells express TRPC6, this pathway may have a role in neurotoxicity.

Sarcoplasmic reticulum Ca2+ pump mRNA stability in cardiac and smooth muscle: role of poly A+ tail length

Transcripts of the sarco/endoplasmic reticulum Ca2+ pump SERCA2 are alternatively spliced to produce SERCA2a (expressed in left ventricular muscle (LVM)) and SERCA2b (in stomach smooth muscle (SSM)) mRNA that use different polyadenylation sequences. SERCA2 mRNA in LVM is more stable than in SSM. Here, we report that the SERCA2 poly A+ tail length in LVM (32 +/- 2 bases) is longer than in SSM (20 +/- 1). In the in vitro decay assays, the 3'-region mRNA of SERCA2a or SERCA2b is more stable when the poly A+ tail is longer. However, when the poly A+ tail length is similar for SERCA2a and SERCA2b, the SERCA2a RNA is more stable. Thus, the longer poly A+ tail may contribute to, but does not appear to be the sole determinant of, greater stability of SERCA2 mRNA in LVM than in SSM.

Effects of peroxynitrite on sarco/endoplasmic reticulum Ca2+ pump isoforms SERCA2b and SERCA3a

Sarco(endo)plasmic reticulum Ca2+ (SERCA) pumps are important for cell signaling. Three different genes, SERCA1, 2, and 3, encode these pumps. Most tissues, including vascular smooth muscle, express a splice variant of SERCA2 (SERCA2b), whereas SERCA3a is widely distributed in tissues such as vascular endothelium, tracheal epithelium, mast cells, and lymphoid cells. SERCA2b protein is readily inactivated by peroxynitrite that may be formed during cardiac ischemia reperfusion or during immune response after infection. Here, we compared the peroxynitrite sensitivity of SERCA2b and SERCA3a by using microsomes prepared from HEK-293T cells overexpressing the pumps. We incubated the microsomes with different concentrations of peroxynitrite and determined Ca2+ uptake, Ca2+-Mg2+-ATPase, Ca2+-dependent formation of acylphosphate intermediate, and protein mobility in Western blots. Ca2+ uptake, Ca2+-Mg2+-ATPase, and Ca2+-dependent formation of acylphosphate intermediate were inactivated for both SERCA2b and SERCA3a, but the latter was more resistant to the inactivation. Western blots showed that SERCA2b and SERCA3a proteins oligomerized after treatment with peroxynitrite, but each with a slightly different pattern. Compared with monomers, the oligomers may be less efficient in forming the acylphosphate intermediate and in conducting the remainder of the steps in the reaction cycle. We conclude that the resistance of SERCA3a to peroxynitrite may aid the cells expressing them in functioning during exposure to oxidative stress.

Endothelium and smooth muscle of pig coronary artery: differences in metabolism

Here, we report that the smooth muscle and endothelium of the pig coronary artery differ in the profiles of energy metabolism nucleotides. ATP levels in the freshly isolated smooth muscle (1490 +/- 93, all the values are in pmol/mg protein) were significantly greater than in the endothelium (418 +/- 68). In contrast, endothelium contained higher levels of NADH (328 +/- 21), NAD+ (1210 -/+ 28), NADPH (87 +/- 2), and NADP+ (77 +/- 4) than smooth muscle (17 +/- 2, 96 +/- 14, 7 +/- 1, and 8 +/- 1, respectively). However, smooth muscle and endothelium do not differ from each other in the ratios of NADH/NAD+ or NADPH/NADP+. Cells cultured from smooth muscle and endothelium contained less ATP (93 +/- 2, 141 +/- 6) and had lower ratios of NADH/ NAD+ than the freshly isolated tissues but the NADPH/NADP+ ratios remained similar. We conclude that (a) freshly isolated smooth muscle and endothelium differ in their profiles of the energy metabolism nucleotides, and (b) culturing the cells alters the profile.

Effects of peroxynitrite on pig coronary artery smooth muscle

We examined the effects of peroxynitrite pretreatment of pig coronary arteries on their sarcoplasmic reticulum (SR) Ca(2+) pump function. Pretreating rings from de-endothelialized arteries with peroxynitrite, followed by a wash to remove this agent, led to a decrease in the force of contraction produced in response to the SR Ca(2+) pump inhibitor cyclopiazonic acid (CPA, IC(50) = 87 +/- 6 microM). Inclusion of catalase and superoxide dismutase with the peroxynitrite did not alter its effect indicating that the inhibition was produced by peroxynitrite. Contractions produced by 30 mM KCl were not affected by up to 250 microM peroxynitrite. Smooth muscle cells cultured from this artery gave a transient increase in cytosolic Ca(2+) in response to CPA. Treating the cells with peroxynitrite inhibited this increase. Treating the SR-enriched isolated subcellular membrane fraction with peroxynitrite produced an inhibition of the ATP-dependent azide-insensitive oxalate-stimulated Ca(2+) uptake. Thus, peroxynitrite damages the SR Ca(2+)pump in the coronary artery, and this inhibition appears to lead to an inability of the arteries to respond to CPA. Thus, peroxynitrite produced from superoxide and NO in the arteries may compromise regulation of coronary tone which requires mobilization of Ca(2+) from the SR.

Mechanism of action of the novel plasma membrane Ca(2+)-pump inhibitor caloxin

Caloxin 2A1 is a novel inhibitor of the plasma membrane (PM) Ca(2+)-pump [Am. J. Physiol. Cell Physiol. 280 (2001) C1027]. The PM Ca(2+)-pump is a Ca(2+)-Mg(2+)-ATPase that expels Ca(2+) from cells to help them maintain low concentrations of cytosolic Ca(2+). Caloxin 2A1 inhibits Ca(2+)-Mg(2+)-ATPase in human erythrocyte leaky ghosts. Here we report that this inhibition is non-competitive with respect to the substrates Ca(2+) and ATP and the activator calmodulin. This was anticipated since the high affinity binding site for Ca(2+) and sites for ATP and calmodulin are intracellular whereas caloxin 2A1 is a peptide selected for binding to the second extracellular domain of the pump. Caloxin 2A1 also inhibited the Ca(2+)-dependent formation of the acid stable 140 kDa acylphosphate intermediate from 32P-gamma-ATP. However, it did not inhibit the formation of the acylphosphate intermediate in the reverse direction-from 32P-orthophosphate. Consistent with results on mutagenesis of transmembrane residues in the pump protein, we suggest that caloxin 2A1 inhibits conformational changes required during the reaction cycle of the pump.

Peroxynitrite and nitric oxide differ in their effects on pig coronary artery smooth muscle

Peroxynitrite generated in arteries from superoxide and nitric oxide (NO) may damage their function. Here, we compare the effects of peroxynitrite and peroxynitrite/NO-generating agents SIN-1 (3-morpholinosydnonimine hydrochloride), SNAP (S-nitroso-N-acetyl-penicillamine), SNP (sodium nitroprusside), and NONOate (spermine NONOate) on pig coronary artery. Deendothelialized artery rings were pretreated with these agents and then washed before examining their contractility. Pretreatment with all agents (200 microM) results in a decrease in the force of contraction in response to the sarco(endo)plasmic Ca(2+) (SERCA) pump inhibitor cyclopiazonic acid (CPA): SNAP > NONOate > or = peroxynitrite > or = SIN-1 > SNP. Pretreatment with SNAP, NONOate, or SIN-1 also inhibits the force of contraction produced with 30 mM KCl, with SNAP being the most potent. Including catalase plus superoxide dismutase (SOD) during the preincubation has no effect. Including an NO scavenger [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] or a guanylate cyclase inhibitor (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one) partially protects against SNAP. Pretreatment of cultured cells with peroxynitrite, but not with SNAP, inhibits the Ca(2+) transients produced in response to CPA. Pretreating isolated membrane vesicles with peroxynitrite inhibits the Ca(2+) uptake due to the SERCA pump, with all the other agents being less effective. Thus peroxynitrite and NO both inhibit the CPA-induced contractions in deendothelialized artery rings, peroxynitrite by damage to the SERCA pump and NO possibly by a step downstream from the increase in cytosolic Ca(2+).