Lithium transport in the mouse brain

SPIRAL MRI for in vivo lithium-7 imaging: a feasibility study in mice after oral lithium treatment

Lithium has been the frontline treatment for bipolar disorder for over 60 years. However, its mode of action and distribution in the brain is still incompletely understood. The primary isotope of lithium, lithium-7 (7Li), is a magnetic resonance (MR) active, spin-3/2 nucleus. However, its low MR sensitivity and the small brain size of mice make 7Li MR imaging (MRI) difficult in preclinical research. We tested four MRI sequences (FLASH, RARE, bSSFP, and SPIRAL) on lithium-containing phantoms, and bSSFP and SPIRAL on orally lithium-treated adult C57BL/6 mice. 7Li MR spectroscopy was acquired weekly at 9.4T to monitor the lithium uptake. The in vivo T1 relaxation time of 7Li was estimated in four mice. 4-h SPIRAL 7Li MRI was acquired in ten mice at a resolution of 2 × 2 × 3 mm3. SPIRAL MRI provided the highest signal-to-noise ratio (SNR) per unit acquisition time and the best image quality. We observed a non-homogeneous distribution of lithium in the mouse brain, with the highest concentrations in the cortex, ventricles, and basal brain regions. Almost no lithium signal was detected in the olfactory bulb and the cerebellum. We showed that in vivo 7Li MRI in mice is feasible, although with limited spatial resolution and SNR.

DNAzyme-Based Lithium-Selective Imaging Reveals Higher Lithium Accumulation in Bipolar Disorder Patient-Derived Neurons

Lithium has been a drug for bipolar disorders (BD) for over 70 years; however, its usage has been limited by its narrow therapeutic window (between 0.6 and 1.2 mM). Understanding the cellular distribution of lithium ions (Li+) in patient cells will offer deep insight into this limitation, but selective imaging of Li+ in living cells under biomedically relevant concentration ranges has not been achieved. Herein, we report in vitro selection and development of a Li+-specific DNAzyme fluorescent sensor with >100-fold selectivity over other biorelevant metal ions. This sensor allows comparative Li+ visualization in HeLa cells, human neuronal progenitor cells (NPCs), and neurons derived from BD patients and healthy controls. Strikingly, we detected enhanced accumulation of Li+ in cells derived from BD patients compared with healthy controls in differentiated neurons but not NPCs. These results establish the DNAzyme-based sensor as a novel platform for biomedical research into BD and related areas using lithium drugs.

Resurrecting the discussion on neurotoxicity of lithium at therapeutic levels

Lithium is widely used in the treatment of bipolar disorder. Here we describe the syndrome of irreversible lithium-effectuated neurotoxicity in a patient within therapeutic doses and levels, which persisted after discontinuation of Lithium. A 50-year-old gentleman with Bipolar disorder presented with symptoms of Mania following drug default. Lithium was initiated as a mood stabilizer. On day 4, the patient developed abdominal pain, itching, and sore throat. On day 5, lithium levels were 0.9 mEq/L. Subsequently, the patient was noted to have slurring of speech, dysarthria, past pointing, and dysdiadochokinesis. Lithium was withdrawn on day 7. When lithium was re-introduced at a lower dose, the neurological symptoms re-appeared after 2 days and lithium was discontinued. Mild degree of slurring of speech persisted at 2-month follow-up. The patient had no history of side effects with antipsychotics in the past or current episode. In the absence of predisposing factors, Lithium has resulted in neurotoxicity at therapeutic doses and levels. Slurring of speech persisted despite adequate dose of anticholinergics. In addition to presumed neuroprotective effects of lithium, it can produce neurotoxic symptoms at therapeutic doses and levels.

Lithium Accumulates in Neurogenic Brain Regions as Revealed by High Resolution Ion Imaging

Lithium (Li) is a potent mood stabilizer and displays neuroprotective and neurogenic properties. Despite extensive investigations, the mechanisms of action have not been fully elucidated, especially in the juvenile, developing brain. Here we characterized lithium distribution in the juvenile mouse brain during 28 days of continuous treatment that result in clinically relevant serum concentrations. By using Time-of-Flight Secondary Ion Mass Spectrometry- (ToF-SIMS) based imaging we were able to delineate temporospatial lithium profile throughout the brain and concurrent distribution of endogenous lipids with high chemical specificity and spatial resolution. We found that Li accumulated in neurogenic regions and investigated the effects on hippocampal neurogenesis. Lithium increased proliferation, as judged by Ki67-immunoreactivity, but did not alter the number of doublecortin-positive neuroblasts at the end of the treatment period. Moreover, ToF-SIMS revealed a steady depletion of sphingomyelin in white matter regions during 28d Li-treatment, particularly in the olfactory bulb. In contrast, cortical levels of cholesterol and choline increased over time in Li-treated mice. This is the first study describing ToF-SIMS imaging for probing the brain-wide accumulation of supplemented Li in situ. The findings demonstrate that this technique is a powerful approach for investigating the distribution and effects of neuroprotective agents in the brain.

Cerebellar syndrome in a patient with pneumonia under lithium treatment: A case report

We report the case of a 31-year-old man with bipolar disorder who was on a combination therapy of lithium, lamotrigine and escitalopram. Serum lithium level was within therapeutic range. Cerebellar symptoms such as dysarthria, ataxia, and dyskinesia developed in the patient following the pneumonia. Cerebellar syndrome was most likely due to lithium neurotoxicity, which was associated with additional factors such as acute febrile pneumonia, fever and hyponatremia. The reported case suggests that infections may increase the risk of cerebellar toxicity of lithium, even in the therapeutic doses.

Lithium-induced neurotoxicity at serum lithium levels within the therapeutic range

OBJECTIVE

To report the occurrence of lithium-induced neurotoxicity and extrapyramidal symptoms at serum lithium levels within the therapeutic range.

CLINICAL PICTURE

On two occasions, a 73-year-old patient presented with symptoms of lithium-induced neurotoxicity and extrapyramidal symptoms when her serum lithium levels were within the therapeutic range.

TREATMENT AND OUTCOME

Both lithium-induced neurotoxicity and extrapyramidal symptoms resolved when lithium was withdrawn.

CONCLUSION

Even when serum lithium levels are within the therapeutic range, lithium-induced neurotoxicity may occur. Patients on neuroleptics and the elderly in particular may be more vulnerable to these side effects.

Mass spectrometry of trace elements in biological samples

Mass spectrometry is a powerful analytical tool for determining the isotope ratios and concentrations of trace elements in various samples at levels ranging from major constituents to subparts per billion. Because isotope dilution is free from matrix effects, it has the potential of being incorporated into a definitive analytical approach that can provide reference values for concentrations in physiological and pathological conditions. In addition, isotope dilution mass spectrometry results are free from the constraints of quantitative recovery of the analyte, an essential requirement in other analytical techniques that is difficult to achieve with complex biological samples. A variety of mass spectrometric approaches have been used for determining the concentration of trace elements in biological samples. The more commonly used are thermal ionization mass spectrometry, inductively coupled plasma mass spectrometry, fast atom bombardment mass spectrometry, and gas chromatography mass spectrometry. This article reviews the work on trace element determination in biological samples using different mass spectrometric techniques and highlights the experiments performed by the authors in establishing gas chromatography mass spectrometry.