Lithium isotopes differentially modify mitochondrial amorphous calcium phosphate cluster size distribution and calcium capacity

Evidence for a possible quantum effect on the formation of lithium-doped amorphous calcium phosphate from solution

Differential isotope effects are an emerging tool for discovering possible nontrivial quantum mechanical effects within biological systems. However, it is often nearly impossible to elucidate the exact mechanisms by which a biological isotope effect manifests due to the complexity of these systems. As such, one proposed in vitro system of study for a quantum isotope effect is calcium phosphate aggregation, where symmetric calcium phosphate molecular species, known as Posner molecules, have been theorized to have phosphorus nuclear spin-dependent self-binding rates, which could be differently modulated by doping with stable lithium isotopes. Here, we present in vitro evidence for such a differential lithium isotope effect on the formation and aggregation of amorphous calcium phosphate from solution under certain conditions. Experiments confirm that lithium incorporates into amorphous calcium phosphate, with 7Li found to promote a greater abundance of observable calcium phosphate particles than 6Li under identical solution preparations. These in vitro results offer a potential explanation for in vivo biological studies that have shown differential lithium isotope effects. Given the importance of calcium phosphate in biological systems-ranging from mitochondrial signaling pathways to key biomineralization processes, as well as the proposed role of Posner molecules as a "neural qutrit"-these results present an important step in understanding calcium phosphate nucleation as well as the potential role of calcium phosphate for quantum biology and processing.

Quantum Models of Consciousness from a Quantum Information Science Perspective

This perspective explores various quantum models of consciousness from the viewpoint of quantum information science, offering potential ideas and insights. The models under consideration can be categorized into three distinct groups based on the level at which quantum mechanics might operate within the brain: those suggesting that consciousness arises from electron delocalization within microtubules inside neurons, those proposing it emerges from the electromagnetic field surrounding the entire neural network, and those positing it originates from the interactions between individual neurons governed by neurotransmitter molecules. Our focus is particularly on the Posner model of cognition, for which we provide preliminary calculations on the preservation of entanglement of phosphate molecules within the geometric structure of Posner clusters. These findings provide valuable insights into how quantum information theory can enhance our understanding of brain functions.

A physical perspective on lithium therapy

Lithium salts have strong medical properties in neurological disorders such as bipolar disorder and lithium-responsive headaches. They have recently gathered attention due to their potential preventive effect in viral infections. Though the therapeutic effect of lithium was documented by Cade in the late 1940s, its underlying mechanism of action is still disputed. Acute lithium exposure has an activating effect on excitable organic tissue and organisms, and is highly toxic. Lithium exposure is associated with a strong metabolic response in the organism, with large changes in phospholipid and cholesterol expression. Opposite to acute exposure, this metabolic response alleviates excessive cellular activity. The presence of lithium ions strongly affects lipid conformation and membrane phase unlike other alkali ions, with consequences for membrane permeability, buffer property and excitability. This review investigates how lithium ions affect lipid membrane composition and function, and how lithium response might in fact be the body's attempt to counteract the physical presence of lithium ions at cell level. Ideas for further research in microbiology and drug development are discussed.

Selective inhibitor of sodium-calcium exchanger, SEA0400, affects NMDA receptor currents and abolishes their calcium-dependent block by tricyclic antidepressants

The open-channel block of N-methyl-D-aspartate receptors (NMDARs) and their calcium-dependent desensitization (CDD) represent conventional mechanisms of glutamatergic synapse regulation. In neurotrauma, neurodegeneration, and neuropathic pain the clinical benefits of cure with memantine, ketamine, Mg2+, and some tricyclic antidepressants are often attributed to NMDAR open-channel block, while possible involvement of NMDAR CDD in the therapy is not well established. Here the effects of selective high-affinity sodium-calcium exchanger (NCX) isoform 1 inhibitor, SEA0400, on NMDA-activated whole-cell currents and their block by amitriptyline, desipramine and clomipramine recorded by patch-clamp technique in cortical neurons of primary culture were studied. We demonstrated that in the presence of extracellular Ca2+, 50 nM SEA0400 caused a reversible decrease of the steady-state amplitude of NMDAR currents, whereas loading neurons with BAPTA or the removal of extracellular Ca2+ abolished the effect. The decrease did not exceed 30% of the amplitude and did not depend on membrane voltage. The external Mg2+ block and 50 nM SEA0400 inhibition of currents were additive, suggesting their independent modes of action. In the presence of Ca2+ SEA0400 speeded up the decay of NMDAR currents to the steady state determined by CDD. The measured IC50 value of 27 nM for SEA0400-induced inhibition coincides with that for NCX1. Presumably, SEA0400 effects are induced by an enhancement of NMDAR CDD through the inhibition of Ca2+ extrusion by NCX1. SEA0400, in addition, at nanomolar concentrations could interfere with Ca2+-dependent effect of tricyclic antidepressants. In the presence of 50 nM SEA0400, the IC50s for NMDAR inhibition by amitriptyline and desipramine increased by about 20 folds, as the Ca2+-dependent NMDAR inhibition disappeared. This observation highlights NCX1 involvement in amitriptyline and desipramine effects on NMDARs and unmasks competitive relationships between SEA0400 and these antidepressants. Neither amitriptyline nor desipramine could affect NCX3. The open-channel block of NMDARs by these substances was not affected by SEA0400. In agreement, SEA0400 did not change the IC50 for clomipramine, which acts as a pure NMDAR open-channel blocker. Thus, NCX seems to represent a promising molecular target to treat neurological disorders, because of the ability to modulate NMDARs by decreasing the open probability through the enhancement of their CDD.

Effects of lithium isotopes on sodium/lithium co-transport and calcium efflux through the sodium/calcium/lithium exchanger in mitochondria

The effects of lithium (Li) isotopes and their impact on biological processes have recently gained increased attention due to the significance of Li as a pharmacological agent and the potential that Li isotopic effects in neuroscience contexts may constitute a new example of quantum effects in biology. Previous studies have shown that the two Li isotopes, which differ in mass and nuclear spin, have unusual different effects in vivo and in vitro and, although some molecular targets for Li isotope fractionation have been proposed, it is not known whether those result in observable downstream neurophysiological effects. In this work we studied fluxes of Li+, sodium (Na+) and calcium (Ca2+) ions in the mitochondrial sodium/calcium/lithium exchanger (NCLX), the only transporter known with recognized specificity for Li+. We studied the effect of Li+ isotopes on Ca2+ efflux from heart mitochondria in comparison to natural Li+ and Na+ using Ca2+-induced fluorescence and investigated a possible Li isotope fractionation in mitochondria using inductively coupled plasma mass spectrometry (ICP-MS). Our fluorescence data indicate that Ca2+ efflux increases with higher concentrations of either Li+ or Na+. We found that the simultaneous presence of Li+ and Na+ increases Ca2+ efflux compared to Ca2+ efflux caused by the same concentration of Li+ alone. However, no differentiation in the Ca2+ efflux between the two Li+ isotopes was observed, either for Li+ alone or in mixtures of Li+ and Na+. Our ICP-MS data demonstrate that there is selectivity between Na+ and Li+ (greater Na+ than Li+ uptake) and, most interestingly, between the Li+ isotopes (greater 6Li+ than 7Li+ uptake) by the inner mitochondrial membrane. In summary, we observed no Li+ isotope differentiation for Ca2+ efflux in mitochondria via NCLX but found a Li+ isotope fractionation during Li+ uptake by mitochondria with NCLX active or blocked. Our results suggest that the transport of Li+ via NCLX is not the main pathway for Li+ isotope fractionation and that this differentiation does not affect Ca2+ efflux in mitochondria. Therefore, explaining the puzzling effects of Li+ isotopes observed in other contexts will require further investigation to identify the molecular targets for Li+ isotope differentiation.