Replies to post #306958 on Elite Pharmaceuticals Inc (ELTP)

[dr_lowenstein]

sorry that is flat out wrong:

Lower Affinity of Isradipine for L-Type Ca2+ Channels during Substantia Nigra Dopamine Neuron-Like Activity: Implications for Neuroprotection in Parkinson's Disease.
Ortner NJ1, Bock G1, Dougalis A2, Kharitonova M1, Duda J2, Hess S3, Tuluc P1, Pomberger T1, Stefanova N4, Pitterl F5, Ciossek T6, Oberacher H5, Draheim HJ6, Kloppenburg P3, Liss B2, Striessnig J7.
Author information
1
Department of Pharmacology and Toxicology, Center for Molecular Biosciences, University of Innsbruck, 6020 Innsbruck, Austria.
2
Institute of Applied Physiology, University of Ulm, 89081 Ulm, Germany.
3
Biocenter, Institute for Zoology, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50674 Cologne, Germany.
4
Department of Neurology and.
5
Institute of Legal Medicine and Core Facility Metabolomics, Medical University of Innsbruck, 6020 Innsbruck, Austria.
6
Boehringer Ingelheim Pharma GmbH & Co KG, CNS Research, 88400 Biberach an der Riss, Germany, and.
7
Department of Pharmacology and Toxicology, Center for Molecular Biosciences, University of Innsbruck, 6020 Innsbruck, Austria, [e-mail].
Abstract
Ca2+-influx through L-type Ca2+-channels (LTCCs) is associated with activity-related stressful oscillations of Ca2+ levels within dopaminergic (DA) neurons in the substantia nigra (SN), which may contribute to their selective degeneration in Parkinson's disease (PD). LTCC blockers were neuroprotective in mouse neurotoxin models of PD, and isradipine is currently undergoing testing in a phase III clinical trial in early PD. We report no evidence for neuroprotection by in vivo pretreatment with therapeutically relevant isradipine plasma levels, or Cav1.3 LTCC deficiency in 6-OHDA-treated male mice. To explain this finding, we investigated the pharmacological properties of human LTCCs during SN DA-like and arterial smooth muscle (aSM)-like activity patterns using whole-cell patch-clamp recordings in HEK293 cells (Cav1.2 a1-subunit, long and short Cav1.3 a1-subunit splice variants; ß3/a2d1). During SN DA-like pacemaking, only Cav1.3 variants conducted Ca2+ current (ICa) at subthreshold potentials between action potentials. SN DA-like burst activity increased integrated ICa during (Cav1.2 plus Cav1.3) and after (Cav1.3) the burst. Isradipine inhibition was splice variant and isoform dependent, with a 5- to 11-fold lower sensitivity to Cav1.3 variants during SN DA-like pacemaking compared with Cav1.2 during aSM-like activity. Supratherapeutic isradipine concentrations reduced the pacemaker precision of adult mouse SN DA neurons but did not affect their somatic Ca2+ oscillations. Our data predict that Cav1.2 and Cav1.3 splice variants contribute differentially to Ca2+ load in SN DA neurons, with prominent Cav1.3-mediated ICa between action potentials and after bursts. The failure of therapeutically relevant isradipine levels to protect SN DA neurons can be explained by weaker state-dependent inhibition of SN DA LTCCs compared with aSM Cav1.2.SIGNIFICANCE STATEMENT The high vulnerability of dopamine (DA) neurons in the substantia nigra (SN) to neurodegenerative stressors causes Parkinson's disease (PD). Ca2+ influx through voltage-gated L-type Ca2+ channels (LTCCs), in particular Cav1.3, appears to contribute to this vulnerability, and the LTCC inhibitor isradipine is currently being tested as a neuroprotective agent for PD in a phase III clinical trial. However, in our study isradipine plasma concentrations approved for therapy were not neuroprotective in a PD mouse model. We provide an explanation for this observation by demonstrating that during SN DA-like neuronal activity LTCCs are less sensitive to isradipine than Cav1.2 LTCCs in resistance blood vessels (mediating dose-limiting vasodilating effects) and even at supratherapeutic concentrations isradipine fails to reduce somatic Ca2+ oscillations of SN DA neurons.

[dr_lowenstein]

and this:


Brain Res. 2014 Sep 18;1581:1-11. doi: 10.1016/j.brainres.2014.07.014. Epub 2014 Jul 16.
Nifedipine and nimodipine protect dopaminergic substantia nigra neurons against axotomy-induced cell death in rat vibrosections via modulating inflammatory responses.
Daschil N1, Humpel C2.
Author information
Abstract

Neurodegeneration of cholinergic and dopaminergic neurons is a major hallmark in Alzheimer's or Parkinson's disease, respectively. A dysregulation in calcium homeostasis may be part of this process and counteracting calcium influx may have neuroprotective properties in both diseases. Therefore, we investigated the putative neuroprotective or neurotoxic activity of L-type calcium channel (LTCC) inhibitors on cholinergic and dopaminergic neurons in a rat organotypic vibrosection model. Sagittal or coronal vibrosections (200 µm thick) of postnatal day 10 rats were cultured on 0.4 µm semipermeable membranes for 2 weeks with 10 ng/ml nerve growth factor (NGF) and/or glial-cell line derived neurotrophic factor (GDNF) to maintain survival of cholinergic or dopaminergic neurons, respectively. Thereafter, sections were incubated with 0.1, 1 or 10 µM isradipine, nicardipine or verapamil for 2 weeks to explore cytotoxicity. Alternatively, in order to explore neuroprotective activity, vibrosections were incubated without growth factors but with isradipine or verapamil or with nicardipine, nimodipine or nifedipine from the beginning for 4 weeks. Our data show that all LTCC inhibitors exhibited no neurotoxic effect on cholinergic and dopaminergic neurons. Further, LTCC inhibitors did not have any neuroprotective activity on cholinergic neurons. However, nimodipine and nifedipine significantly enhanced the survival of dopaminergic substantia nigra (SN) but not ventral tegmental area (VTA) neurons, while nicardipine, isradipine and verapamil had no effect. Nifedipine (and more potently GDNF) reduced inflammatory cytokines (macrophage inflammatory protein-2, tumor necrosis factor-a), but did not influence oxidative stress or caspase-3 activity and did not interfere with iron-mediated overload. Our data show that nifedipine and nimodipine are very potent to enhance the survival of axotomized SN neurons, possibly influencing inflammatory processes.

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ChaChing $$$
Isradapine Parkinson"s Study completed.

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