Lithium and antidepressants: Stimulating immune function and preventing and reversing infection

Sol-gel synthesis of lithium doped mesoporous bioactive glass nanoparticles and tricalcium silicate for restorative dentistry: Comparative investigation of physico-chemical structure, antibacterial susceptibility and biocompatibility

Introduction: The sol-gel method for production of mesoporous bioactive glass nanoparticles (MBGNs) has been adapted to synthesize tricalcium silicate (TCS) particles which, when formulated with other additives, form the gold standard for dentine-pulp complex regeneration. Comparison of TCS and MBGNs obtained by sol-gel method is critical considering the results of the first ever clinical trials of sol-gel BAG as pulpotomy materials in children. Moreover, although lithium (Li) based glass ceramics have been long used as dental prostheses materials, doping of Li ion into MBGNs for targeted dental applications is yet to be investigated. The fact that lithium chloride benefits pulp regeneration in vitro also makes this a worthwhile undertaking. Therefore, this study aimed to synthesize TCS and MBGNs doped with Li by sol-gel method, and perform comparative characterizations of the obtained particles.

Methods: TCS particles and MBGNs containing 0%, 5%, 10% and 20% Li were synthesized and particle morphology and chemical structure determined. Powder concentrations of 15mg/10 mL were incubated in artificial saliva (AS), Hank’s balanced saline solution (HBSS) and simulated body fluid (SBF), at 37°C for 28 days and pH evolution and apatite formation, monitored. Bactericidal effects against S. aureus and E. coli, as well as possible cytotoxicity against MG63 cells were also evaluated through turbidity measurements.

Results: MBGNs were confirmed to be mesoporous spheres ranging in size from 123 nm to 194 nm, while TCS formed irregular nano-structured agglomerates whose size was generally larger and variable. From ICP-OES data, extremely low Li ion incorporation into MBGNs was detected. All particles had an alkalinizing effect on all immersion media, but TCS elevated pH the most. SBF resulted in apatite formation for all particle types as early as 3 days, but TCS appears to be the only particle to form apatite in AS at a similar period. Although all particles had an effect on both bacteria, this was pronounced for undoped MBGNs. Whereas all particles are biocompatible, MBGNs showed better antimicrobial properties while TCS particles were associated with greater bioactivity.

Conclusion: Synergizing these effects in dental biomaterials may be a worthwhile undertaking and realistic data on bioactive compounds targeting dental application may be obtained by varying the immersion media.

Li-Doped Bioactive Ceramics: Promising Biomaterials for Tissue Engineering and Regenerative Medicine

Lithium (Li) is a metal with critical therapeutic properties ranging from the treatment of bipolar depression to antibacterial, anticancer, antiviral and pro-regenerative effects. This element can be incorporated into the structure of various biomaterials through the inclusion of Li chloride/carbonate into polymeric matrices or being doped in bioceramics. The biocompatibility and multifunctionality of Li-doped bioceramics present many opportunities for biomedical researchers and clinicians. Li-doped bioceramics (capable of immunomodulation) have been used extensively for bone and tooth regeneration, and they have great potential for cartilage/nerve regeneration, osteochondral repair, and wound healing. The synergistic effect of Li in combination with other anticancer drugs as well as the anticancer properties of Li underline the rationale that bioceramics doped with Li may be impactful in cancer treatments. The role of Li in autophagy may explain its impact in regenerative, antiviral, and anticancer research. The combination of Li-doped bioceramics with polymers can provide new biomaterials with suitable flexibility, especially as bio-ink used in 3D printing for clinical applications of tissue engineering. Such Li-doped biomaterials have significant clinical potential in the foreseeable future.

A comparative study on the in vitro formation of hydroxyapatite, cytotoxicity and antibacterial activity of 58S bioactive glass substituted by Li and Sr

Lithium and strontium up to 10 mol% have been substituted for calcium in 58S bioactive glasses in order to enhance specific biological properties such as proliferation, alkaline phosphatase (ALP) activity of cells as well as antibacterial activity. In-vitro formation of hydroxyapatite was studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma atomic emission spectrometry (ICP-AES) and scanning electron microscopy (SEM). Substitution of either Li or Sr for Ca in the composition had a retarding effect on the bioactivity while Li decreased and Sr increased the rate of ion release in the simulated body fluid solution. The dissolution rate showed to be inversely proportional to oxygen density of the bioactive glasses. The proposed mechanisms for the lowered bioactivity are a lower supersaturation degree for nucleation of apatite in Li substituted bioactive glasses and blocking of the active growth sites of calcium phosphate by Sr²⁺ in Sr substituted bioactive glasses. The proliferation rate and alkaline phosphate activity of osteoblast cell line MC3T3-E1 treated with Li and Sr bioactive glasses were studied. 3-(4,5dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and alkaline phosphate assay showed that all synthesized bioactive glasses with exception of 58S with 10 mol% SrO, exhibited statistically significant increase in both cell proliferation and alkaline phosphatase activity. Finally, 58S bioactive glass with 5 mol% Li₂O substitution for CaO was considered as a potential biomaterial in bone repair/regeneration therapies with enhanced biocompatibility, and alkaline phosphate activity, with a negligible loss in the bioactivity compared to the 58S bioglass. At the same time this composition had the highest antibacterial activity against methicillin-resistant Staphylococcus aureus bacteria among all synthesized Li and Sr substituted bioactive glasses.

Depression as an evolutionary strategy for defense against infection

Recent discoveries relating depression to inflammation and immune function may help to solve an important evolutionary puzzle: If depression carries with it so many negative consequences, including notable costs to survival and reproduction, then why is it common and heritable? What countervailing force or compensatory advantage has allowed susceptibility genes for depression to persist in the population at such high rates? A priori, compensatory advantages in combating infection are a promising candidate, given that infection has been the major cause of mortality throughout human history. Emerging evidence on deeply rooted bidirectional pathways of communication between the nervous and immune systems further supports this notion. Here we present an updated review of the "infection-defense hypothesis" of depression, which proposes that moods-with their ability to orchestrate a wide array of physical and behavioral responses-have played an adaptive role throughout human history by helping individuals fight existing infections, as well as helping both individuals and their kin avoid new ones. We discuss new evidence that supports several key predictions derived from the hypothesis, and compare it with other major evolutionary theories of depression. Specifically, we discuss how the infection-defense hypothesis helps to explain emerging data on psychoimmunological features of depression, as well as depression's associations with a diverse array of conditions and illnesses-including nutritional deficiencies, seasonal changes, hormonal fluctuations, and chronic diseases-that previous evolutionary theories of depression have not accounted for. Finally, we note the potential implications of the hypothesis for the treatment and prevention of depression.

Clozapine-induced neutropenia: A review of lithium and other currently available options

Available options are limited for patients with neutropenia needing to be initiated or maintained on clozapine therapy. A common strategy that is often utilized in these patients is the use of lithium as augmentation to clozapine, which enables the health care provider a means of continuing or initiating clozapine therapy. This article reviews the mechanism and literature evidence behind this treatment strategy.

Enhancement of the antimicrobial performance of biocidal formulations used for the preservation of white mineral dispersions

Biocides play an important role in the preservation of white mineral dispersions (WMD). Due to the occurrence of biocide-resistant bacteria and technical limitations in the use of biocides, new preservation strategies are required-like the enhancement of biocides by non-biocidal compounds. The aim of this study was to evaluate the biocide enhancement performance of lithium against various biocide-resistant bacteria in WMD. Subsequently, the minimal enhancing concentration (MEC) of lithium and the bioavailability of lithium in respect to the mode of introduction into WMD were investigated. The antimicrobial performance of biocidal formulations comprising isothiazolinones and formaldehyde releasers or isothiazolinones and glutaraldehyde has been evaluated against the related resistant bacterial spectrum in the presence of lithium. The MEC of lithium ranged from 1,350 to 1,500 ppm (based on the liquid phase weight of a WMD with 75% solids) for formaldehyde releasers and glutaraldehyde-based biocidal formulations, respectively. The biocide enhancing property of lithium was independent of whether lithium was introduced into WMD via a lithium-neutralised dispersant, added during the calcium carbonate grinding step, or dosed into the final product. Lithium is a non-biocidal compound which has been discovered to be a potent and universal biocide enhancer. Lithium boosts the biocidal activity of various biocides and provides a novel technique to overcome biocide resistance in WMD. Such a biocide enhancer represents a breakthrough that offers a potential tool to revolutionise the consumption of biocidal agents in the WMD producing industry.