The wakefulness promoting drug Modafinil causes adenosine receptor-mediated upregulation of receptor activator of nuclear factor κB ligand in osteoblasts: Negative impact of the drug on peak bone accrual in rats

The Role of the Receptor Activator of Nuclear Factor Kappa-B Ligand/Osteoprotegerin Ratio in Vascular Diseases: A Therapeutic Approach

Cardiovascular and bone diseases contribute independently to mortality and global health. The exact mechanisms involved in the pathophysiology shared between bone and vascular diseases are not well defined. Endothelial cells and osteoblasts communicate during osteogenesis, thus establishing a connection between angiogenesis and osteogenesis. One shared mechanism may involve osteoprotegerin (OPG) and its ligand Receptor Activator of NF-κB Ligand (RANKL). The RANKL/OPG ratio is an important modulator for the skeletal, immunological, and vascular systems. OPG levels are elevated due to either osteogenic causes or inflammatory responses in the vasculature. The data obtained from clinical and in vitro studies support the role of the RANKL/OPG ratio as a potential marker for the progression of endothelial damage. Therefore, determining the therapeutic approaches for the targeting RANKL/OPG ratio and evaluating its usage as a biomarker in cardiovascular and bone pathophysiology are needed. By integrating the protective and disease-causing role of OPG with its ligand, this review outlines the role of the RANKL/OPG ratio at the molecular level. We also consider targeted therapeutic approaches.

Modafinil exerts anti-inflammatory and anti-fibrotic effects by upregulating adenosine A2A and A2B receptors

Adenosine receptor (AR) suppresses inflammation and fibrosis by activating cyclic adenosine monophosphate (cAMP) signaling. We investigated whether altered AR expression contributes to the development of fibrotic diseases and whether A2AAR and A2BAR upregulation inhibits fibrotic responses. Primary human lung fibroblasts (HLFs) from normal (NHLFs) or patients with idiopathic pulmonary fibrosis (DHLF) were used for in vitro testing. Murine models of fibrotic liver or pulmonary disease were developed by injecting thioacetamide intraperitoneally, by feeding a high-fat diet, or by intratracheal instillation of bleomycin. Modafinil, which activates cAMP signaling via A2AAR and A2BAR, was administered orally. The protein amounts of A2AAR, A2BAR, and exchange protein directly activated by cAMP (Epac) were reduced, while collagen and α-smooth muscle actin (α-SMA) were elevated in DHLFs compared to NHLFs. In liver or lung tissue from murine models of fibrotic diseases, A2AAR and A2BAR were downregulated, but A1AR and A3AR were not. Epac amounts decreased, and amounts of collagen, α-SMA, KCa2.3, and KCa3.1 increased compared to the control. Modafinil restored the amounts of A2AAR, A2BAR, and Epac, and reduced collagen, α-SMA, KCa2.3, and KCa3.1 in murine models of fibrotic diseases. Transforming growth factor-β reduced the amounts of A2AAR, A2BAR, and Epac, and elevated collagen, α-SMA, KCa2.3, and KCa3.1 in NHLFs; however, these alterations were inhibited by modafinil. Our investigation revealed that A2AAR and A2BAR downregulation induced liver and lung fibrotic diseases while upregulation attenuated fibrotic responses, suggesting that A2AAR and A2BAR-upregulating agents, such as modafinil, may serve as novel therapies for fibrotic diseases.

Psychostimulants Modafinil, Atomoxetine and Guanfacine Impair Bone Cell Differentiation and MSC Migration

Attention deficit hyperactivity disorder (ADHD) is one of the most common worldwide mental disorders in children, young and adults. If left untreated, the disorder can continue into adulthood. The abuse of ADHD-related drugs to improve mental performance for studying, working and everyday life is also rising. The potentially high number of subjects with controlled or uncontrolled use of such substances increases the impact of possible side effects. It has been shown before that the early ADHD drug methylphenidate influences bone metabolism negatively. This study focused on the influence of three more recent cognitive enhancers, modafinil, atomoxetine and guanfacine, on the differentiation of mesenchymal stem cells to osteoblasts and on their cell functions, including migration. Human mesenchymal stem cells (hMSCs) were incubated with a therapeutic plasma dosage of modafinil, atomoxetine and guanfacine. Gene expression analyses revealed a high beta-2 adrenoreceptor expression in hMSC, suggesting it as a possible pathway to stimulate action. In bone formation assays, all three cognitive enhancers caused a significant decrease in the mineralized matrix and an early slight reduction of cell viability without triggering apoptosis or necrosis. While there was no effect of the three substances on early differentiation, they showed differing effects on the expression of osterix (OSX), receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG) in the later stages of osteoblast development, suggesting alternative modes of action. All three substances significantly inhibited hMSC migration. This effect could be rescued by a selective beta-blocker (Imperial Chemical Industries ICI-118,551) in modafinil and atomoxetine, suggesting mediation via beta-2 receptor stimulation. In conclusion, modafinil, atomoxetine and guanfacine negatively influence hMSC differentiation to bone-forming osteoblasts and cell migration through different intracellular pathways.

Oral Administration of Isovitexin, a Naturally Occurring Apigenin Derivative Showed Osteoanabolic Effect in Ovariectomized Mice: A Comparative Study with Teriparatide

Isovitexin (apigenin-6C-glucopyranose) is found in several food items and medicinal plants. Recently, we showed that isovitexin stimulated osteoblast differentiation through mitochondrial biogenesis and respiration that required adiponectin receptors (AdipoRs). Here, we studied whether oral isovitexin has a bone anabolic effect in vivo. At first, using a femur osteotomy model in adult mice, we compared the bone regenerative effect of isovitexin and apigenin. Whereas isovitexin-stimulated bone formation at the osteotomy site at 2.5 mg/kg and 5 mg/kg dose, apigenin had no effect. Subsequently, we tested the effect of isovitexin (5 mg/kg) in ovariectomized (OVX) osteopenic mice and observed that it restored bone mass and architecture of trabecular bones (femur metaphysis and fifth lumbar vertebra/L5) and cortical bones (femur diaphysis). Isovitexin completely restored bone strength at L5 (compressive strength) and femur (bending strength) in OVX mice. The bone anabolic effect of isovitexin was demonstrated by the increased surface referent bone formation parameters, increased expression of osteogenic genes (Runx2, bone morphogenetic protein-2 and type 1 collagen) in bones, and increased serum procollagen type 1N-terminal propeptide in OVX mice and these were on a par with teriparatide. Isovitexin inhibited bone and serum sclerostin as well as the serum type I collagen cross-linked C-telopeptide in OVX mice. Isovitexin has an oral bioavailability of 14.58%. Taken together, our data show that isovitexin had a significant oral bioavailability that translated to osteoanabolic effect equivalent to teriparatide and inhibited bone resorption, which implied a durable effect over teriparatide.

Anti-inflammatory and anti-fibrotic effects of modafinil in nonalcoholic liver disease

Small- and intermediate-conductance Ca²⁺-activated K⁺ channels, K_Ca2.3 and K_Ca3.1, are involved in cellular signaling processes associated with inflammation and fibrosis. K_Ca2.3 and K_Ca3.1 are upregulated by proinflammatory cytokines and profibrotic growth factors. Cyclic AMP, which downregulates K_Ca2.3 and K_Ca3.1, is elevated by modafinil in cells; accordingly, we investigated whether modafinil exerts anti-inflammatory and anti-fibrotic responses via K_Ca2.3- and K_Ca3.1-mediated pathways in high-fat diet (HFD)- or thioacetamide-induced liver disease models in mice. Modafinil was administered orally in the form of a racemate, (R)-isomer, or (S)-isomer. We also determined whether the treatment targeted the profibrotic activity of hepatic stellate cells using immortalized human hepatic stellate cells (LX-2 cells). Modafinil improved HFD- or thioacetamide-induced changes compared to the control, leading to a reduced inflammatory response, collagen deposition, and α-smooth muscle actin expression both in vivo and in vitro. However, modafinil did not relieve HFD-induced steatosis. There were no significant differences in the effects of the (R)- and (S)-isomers of modafinil. K_Ca2.3 and K_Ca3.1 were upregulated and catalase was downregulated in liver tissues from thioacetamide- or HFD-induced liver disease models or in TGF-β-treated LX-2 cells. TGF-β-induced upregulation of K_Ca2.3, K_Ca3.1, collagen, and α-smooth muscle actin and downregulation of catalase were reversed by modafinil, polyethylene glycol catalase, N-acetylcysteine, siRNA against K_Ca2.3 or K_Ca3.1, and Epac inhibitors. Our investigation revealed that modafinil attenuated inflammatory and fibrotic progression via K_Ca2.3- and K_Ca3.1-mediated pathways in nonalcoholic hepatitis, suggesting that inhibiting K_Ca2.3- and K_Ca3.1-mediated signaling may serve as a novel therapeutic approach for inflammatory and fibrotic liver diseases.

Mass Spectrometry Imaging Shows Modafinil, A Student Study Drug, Changes the Lipid Composition of the Fly Brain

Modafinil, a widely used psychoactive drug, has been shown to exert a positive impact on cognition and is used to treat sleep disorders and hyperactivity. Using time-of-flight secondary ion mass spectrometric imaging, we studied the changes of brain lipids of Drosophila melanogaster induced by modafinil to gain insight into the functional mechanism of modafinil in the brain. We found that upon modafinil treatment, the abundance of phosphatidylcholine and sphingomyelin species in the central brain of Drosophila is significantly decreased, whereas the levels of phosphatidylethanolamine and phosphatidylinositol in the brains show significant enhancement compared to the control flies. The alteration of brain lipids caused by modafinil is consistent with previous studies about cognition-related drugs and offers a plausible mechanism regarding the action of modafinil in the brain as well as a potential target for the treatment of certain disorders.

Moderate/subclinical calcium deficiency attenuates trabecular mass, microarchitecture and bone growth in growing rats

Adequate dietary calcium (Ca) intake is essential for bone accretion, peak bone mass (PBM) attainment, bone quality and strength during the mammalian growth period. Severe Ca deficiency during growing age results in secondary hyperparathyroidism (SHPT) and poor bone quality and strength. However, the impact of moderate Ca deficiency during rats early growth period on bone health and the reversibility with supplementing calcium later in adult life remains unclear. Female Sprague-Dawley (SD) rats (postnatal 28th day, P28) were initiated either with a moderate calcium-deficient diet (MCD, 0.25% w/w Ca) or a control diet (0.8% w/w Ca, control group) till P70. Thereafter, MCD rats were continued either with MCD diet or supplemented with calcium diet (0.8% w/w Ca, calcium supplemented group, CaS) till P150. Another group (control rats) were fed 0.8% w/w Ca containing diet from P28 till P150.

MCD group, as compared to the control group, had significantly reduced serum ionized Ca and procollagen type 1 N-terminal propeptide (P1NP) at P70 while no significant change was observed in serum corrected Ca, inorganic phosphate (P), alkaline phosphatase (ALP), 25-hydroxy vitamin D [25(OH)D], intact parathyroid hormone (iPTH), and urinary C-terminal telopeptide of collagen 1 (CTX-1), Ca, and P. Femoral and tibial metaphysis in MCD rats had significantly reduced linear growth, cortical and trabecular volumetric BMD (vBMD), trabecular microarchitecture (BV/TV%, trabecular thickness, separation and number, structural model index and connectivity density), cortical thickness, and bone stiffness despite the absence of secondary hyperparathyroidism (SHPT). Continued MCD at P70–P150 results in persistence of compromised bone strength while calcium supplementation (CaS group) improved all the parameters related to bone strength and microarchitecture. Our results indicate that uncorrected moderate/subclinical calcium deficiency in growing rats can result in poor bone quality and strength despite the absence of SHPT. This finding could have relevance in children with poor calcium intake in childhood and adolescence.

•

Moderate Ca intake impairs bone growth and stiffness in critical growth phase via subclinical Ca deficiency.

•

Ca supplementaion reverses the effects subclinical Ca deficiency on bone health.

•

Conclusively, moderate Ca intake imposes different effects on the bone at different phases of life.

Prolonged caffeine intake decreases alveolar bone damage induced by binge-like ethanol consumption in adolescent female rats

Ethanol consumption has been reported to negatively impact on periodontal disease. In particular, oral cavity disorders occur upon ethanol exposure during adolescence, a life period associated with particular patterns of short and intense ('binge-like') ethanol consumption that is most deleterious to oral health. The hazardous central effects of ethanol have been linked to the overfunction of adenosine receptors, which are antagonized by caffeine, a bioactive substance present in numerous natural nutrients, which can also modify bone metabolism. The aim of this study was to investigate the effects of caffeine on alveolar bone damage induced by an ethanol binge drinking paradigm during adolescence. Female Wistar rats (35 days old; n = 30) were allocated to six groups: control (vehicle), ethanol (3 g/kg/day; 3 days On-4 days Off challenge), caffeine (10 mg/kg/day), caffeine plus ethanol, SCH58261 (0.1 mg/kg/day, an antagonist of A_2A receptors), and SCH58261 plus ethanol. Bone micromorphology and vertical bone loss were analyzed by computed microtomography. Our data showed that ethanol binge drinking reduced alveolar bone quality, with repercussion on alveolar bone size. This ethanol-induced alveolar bone deterioration was abrogated upon treatment with caffeine, but not with SCH58261. This shows that caffeine prevented the periodontal disorder caused by ethanol binge drinking during adolescence, an effect that was not mediated by adenosine A_2A receptor blockade.

Pharmacokinetic and pharmacodynamic of the cognitive enhancer modafinil: Relevant clinical and forensic aspects

Modafinil is a nonamphetamine nootropic drug with an increasingly therapeutic interest due to its different sites of action and behavioral effects in comparison to cocaine or amphetamine. A review of modafinil (and of its prodrug adrafinil and its R-enantiomer armodafinil) chemical, pharmacokinetic, pharmacodynamic, toxicological, clinical and forensic aspects was performed, aiming to better understand possible health problems associated to its unconscious and unruled use. Modafinil is a racemate metabolized mainly in the liver into its inactive acid and sulfone metabolites, which undergo primarily renal excretion. Although not fully clarified, major effects seem to be associated to inhibition of dopamine reuptake and modulation of several other neurochemical pathways, namely noradrenergic, serotoninergic, orexinergic, histaminergic, glutamatergic and GABAergic. Due its wake-promoting effects, modafinil is used for the treatment of daily sleepiness associated to narcolepsy, obstructive sleep apnea and shift work sleep disorder. Its psychotropic and cognitive effects are also attractive in several other pathologies and conditions that affect sleep structure, induce fatigue and lethargy, and impair cognitive abilities. Additionally, in health subjects, including students, modafinil is being used off-label to overcome sleepiness, increase concentration and improve cognitive potential. The most common adverse effects associated to modafinil intake are headache, insomnia, anxiety, diarrhea, dry mouth and raise in blood pressure and heart rate. Infrequently, severe dermatologic effects in children, including maculopapular and morbilliform rash, erythema multiforme and Stevens-Johnson Syndrome have been reported. Intoxication and dependence associated to modafinil are uncommon. Further research on effects and health implications of modafinil and its analogs is steel needed to create evidence-based policies.

Effect of acute modafinil ingestion on cognitive and physical performance following mental exertion

OBJECTIVE

Modafinil is a psychostimulant that has been shown to enhance cognitive and physical performance. Given its long half-life, it may provide operational advantages if it can improve tolerance to the deleterious effects of prolonged mental exertion.

METHODS

Physically active males (n = 13, 23 ± 4 years, peak oxygen consumption 45.3 ± 3.2 ml kg^-1  min^-1 ) took part in a placebo controlled, double-blind randomised crossover study to investigate if modafinil could improve cognitive and physical performance following a prolonged period of mental exertion.

RESULTS

Overall modafinil improved performance on a task of executive function over time (p = .023; η²  = 0.376) but did not improve subsequent physical endurance performance (mean difference 2.3 ± 11.5%, p = .50), despite improvement in 10 out of the 13 participants. Task demand was reported as lower with modafinil, although perceptual measures of fatigue and motivation did not consistently improve. Heart rate during submaximal exercise was higher (134 ± 11 vs. 119 ± 14 bpm, p < .001), and sleep was reduced (5.5 ± 1.4 vs. 7.5 ± 1.4 hr, p < .001) and less efficient (64 ± 13 vs. 83 ± 9%, p < .001) compared with placebo.

CONCLUSIONS

Operationally, modafinil may offer advantages given the established longer half-life than other psychostimulants, despite the variable response. The impact of higher heart rates and disrupted sleep on performance must also be considered.