⁷Li Nuclear Magnetic Resonance Study for the Determination of Li⁺ Properties in Neuroblastoma SH‐SY5Y Cells

Abstract

Lithium has been used clinically in the treatment of manic depression. However, its pharmacologic mode of action remains unclear. Characteristics of Li ± interactions in red blood cells (RBCs) have been identified. We investigated Li + interactions on human neuroblastoma SH-SY5Y cells by developing a novel 7Li NMR method that provided a clear estimation of the intra-and extracellular amounts of LV in the presence of the shift reagent thulium-1,4,7,10tetrazacyclododecane-N , N', N", N"-tetramethylene phosphonate (HTmDOTP4). The first-order rate constants of Li + influx and efflux for perfused, agarose-embedded SH-SY5Y cells in the presence of 3 mM HTmDOTP4 were 0.055 ±0.006 (n = 4) and -0.025 ±0.006 min~1(n = 3), respectively. Significant increases in the rate constants of Li + influx and efflux in the presence of 0.05 mM veratridine indicated the presence of Nachannel-mediated Litransport in SH-SY5Y cells. 7Li NMR relaxation measurements showed that Li~is immobilized more in human neuroblastoma SH-SY5Y cells than in human RBCs. A 0, starting area of the intracellular resonance of Li * -loaded cells in Li + efflux measurements; A~, intracellular resonance area at time t; AA, atomic absorption; DIDS, 4,4 '-diisothiocyanatostilbene-2,2 '-disulfonic acid; DMEM, Dulbecco's modified Eagle's medium; HTmDOTP 4~, thulium-1,4,7,1 0-tetrazacyclododecane-N, N', N", N"-tetramethylenephosphonate; PCr, phosphocreatine; P,, inorganic phosphorus; ppm, parts per million; RBC, red blood cell; T,, spin-lattice relaxation value; T 2, spin-spin relaxation value; v0, initial rate of Li * influx.

Biomedical applications of7Li NMR

“…Repeat T 2 measurements separated by 10 days in four rats detected no individual change with time. Consistent with the above in vivo results, Nikolakopoulos et al 42 found T 1 and T 2 values of 5.1 s and 50 ms, respectively, for 7 Li in cultured neuroblastoma SH-SY5Y cells.…”

“…Mota de Freitas and coworkers 42 have continued their work on neuroblastoma SH-SY5Y cells as a CNS model. Figure 3 shows 7 Li NMR spectra of Li influx and efflux for perfused neuroblastoma SH-SY5Y cells in agarose threads in the presence of HTmDOTP 4À shift reagent.…”

Effects of Li+ transport and Li+ immobilization on Li+/Mg2+ competition in cells: implications for bipolar disorder

“…countertransport (for both phloretin and HMA) pathways, respectively [10,18]. The Na þ channel activator, veratridine (at 0.50 mmol/L), was also tested in these transport experiments [10].…”

“…The Na þ channel activator, veratridine (at 0.50 mmol/L), was also tested in these transport experiments [10].…”

“…These increases are small; however, larger increases in [Mg 2þ ] f would be toxic to cells [7], and are not required to have a significant effect on the activity of signal-transduction processes [8,9]. It is necessary to determine the dependence of Li þ /Mg 2þ competition on the kinetic and thermodynamic properties of [Li þ ] i , because these properties are known to vary among different cell types [10]. Specific sites of enzyme inhibition by Li þ have been proposed for inositol monophosphatase [11], glycogen synthase kinase-3b [12][13][14], adenylate cyclase [15], and guanine-nucleotide binding proteins [9], in which each of the proteins is Mg 2þ -dependent.…”