Dihydroxyacetone suppresses mTOR nutrient signaling and induces mitochondrial stress in liver cells.

Dihydroxyacetone (DHA) is the active ingredient in sunless tanning products and a combustion product from e-juices in electronic cigarettes (e-cigarettes). DHA is rapidly absorbed in cells and tissues and incorporated into several metabolic pathways through its conversion to dihydroxyacetone phosphate (DHAP). Previous studies have shown DHA induces cell cycle arrest, reactive oxygen species, and mitochondrial dysfunction, though the extent of these effects is highly cell-type specific. Here, we investigate DHA exposure effects in the metabolically active, HepG3 (C3A) cell line. Metabolic and mitochondrial changes were evaluated by characterizing the effects of DHA in metabolic pathways and nutrient-sensing mechanisms through mTOR-specific signaling. We also examined cytotoxicity and investigated the cell death mechanism induced by DHA exposure in HepG3 cells. Millimolar doses of DHA were cytotoxic and suppressed glycolysis and oxidative phosphorylation pathways. Nutrient sensing through mTOR was altered at both short and long time points. Increased mitochondrial reactive oxygen species (ROS) and mitochondrial-specific injury induced cell cycle arrest and cell death through a non-classical apoptotic mechanism. Despite its carbohydrate nature, millimolar doses of DHA are toxic to liver cells and may pose a significant health risk when higher concentrations are absorbed through e-cigarettes or spray tanning.

Dihydroxyacetone Exposure Alters NAD(P)H and Induces Mitochondrial Stress and Autophagy in HEK293T Cells.

Dihydroxyacetone phosphate (DHAP) is the endogenous byproduct of fructose metabolism. Excess DHAP in cells can induce advanced glycation end products and oxidative stress. Dihydroxyacetone (DHA) is the triose precursor to DHAP. DHA is used as the active ingredient in sunless tanning products, including aerosolized spray tans, and is formed by the combustion of solvents found in electronic cigarettes. Human exposure to DHA has been increasing as the popularity of sunless tanning products and electronic cigarettes has grown. Topically applied DHA is absorbed through the viable layers of the skin and into the bloodstream. Exogenous exposure to DHA is cytotoxic in immortalized keratinocytes and melanoma cells with cell cycle arrest induced within 24 h and cell death occurring by apoptosis at consumer-relevant concentrations of DHA within 72 h. Less is known about systemic exposures to DHA that occur following absorption through skin, and now through inhalation of the aerosolized DHA used in spray tanning. In the present study, HEK293T cells were exposed to consumer-relevant concentrations of DHA to examine the cytotoxicity of systemic exposures. HEK293T cells were sensitive to consumer-relevant doses of DHA with an IC50 value of 2.4 ± 0.3 mM. However, cell cycle arrest did not begin until 48 h after DHA exposure. DHA-exposed cells showed altered metabolic activity with decreased mitochondrial function and decreased lactate and ATP production observed within 24 h of exposure. Autofluorescent imaging and NAD+ sensors also revealed an imbalance in the redox cofactors NAD+/NADH within 24 h of exposure. Cell death occurred by autophagy indicated by increases in LC3B and SIRT1. Despite DHA's ability to be converted to DHAP and integrated into metabolic pathways, the metabolic dysfunction and starvation responses observed in the HEK293T cells indicate that DHA does not readily contribute to the energetic pool in these cells.

Dihydroxyacetone induces G2/M arrest and apoptotic cell death in A375P melanoma cells.

The active ingredient in sunless tanning products (STPs) is a simple sugar, dihydroxyacetone (DHA). Several studies have demonstrated that DHA is absorbed within the viable layers of skin and not fully contained within the stratum corneum. Additionally, spray tanning and other aerosolized application methods have increased the risk of internal exposure through mucous membranes and inhalation. Beyond its presence in STPs, DHA also occurs as an endogenous by-product of fructose metabolism, and an excess of DHA in cells can induce advanced glycation end (AGE) products and oxidative stress. Therefore, exogenous and endogenous exposures to DHA may be harmful to cells, and it has already been demonstrated that exogenous exposure to DHA is cytotoxic in immortalized keratinocytes. Still, little is known about the exogenous DHA exposure effects on other skin components. In this study, we explore the effects of exogenous DHA exposure in a human melanoma cell line, A375P. Melanoma cells were sensitive to DHA and displayed a transient burst of reactive oxygen species within an hour of exposure. Cell cycle arrest at G2/M was observed within 24 h of exposure, and apoptosis, monitored by the cleavage of PARP-1 and Caspase-3, was detected within 72 h of exposure to DHA. Together, these demonstrate that exogenous exposure to DHA has cytotoxic effects in our selected cell model and indicates the need to further investigate the exogenous exposure effects of DHA in other relevant exposure models.

miR-125b regulates differentiation and metabolic reprogramming of T cell acute lymphoblastic leukemia by directly targeting A20.

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematopoietic malignancy. Although it has been reported that overexpression of miR-125b leads to T-ALL development, the underlying mechanisms of miR-125b action are still unclear. The goal of this study is to delineate the role of miR-125b in T-ALL development. We found that miR-125b is highly expressed in undifferentiated leukemic T cells (CD4-negative) while its expression is low in differentiated T cells (CD4-positive). Overexpression of miR-125b increased the CD4-negative population in T cells, whereas depletion of miR-125b by miR-125b-sponge decreased the CD4-negative cell population. We identified that A20 (TNFAIP3) is a direct target of miR-125b in T cells. Overexpression of miR-125b also increased glucose uptake and oxygen consumption in T cells through targeting A20. Furthermore, restoration of A20 in miR-125b-overexpressing cells decreased the CD4-negative population in T cell leukemia, and decreased glucose uptake and oxygen consumption to the basal level of T cells transfected with vector. In conclusion, our data demonstrate that miR-125b regulates differentiation and reprogramming of T cell glucose metabolism via targeting A20. Since both de-differentiation and dysregulated glucose metabolism contribute to the development of T-cell leukemia, these findings provide novel insights into the understanding and treatment of T-ALL.

Regulation of mitochondrial functions by protein phosphorylation and dephosphorylation.

The mitochondria are double membrane-bound organelles found in most eukaryotic cells. They generate most of the cell's energy supply of adenosine triphosphate (ATP). Protein phosphorylation and dephosphorylation are critical mechanisms in the regulation of cell signaling networks and are essential for almost all the cellular functions. For many decades, mitochondria were considered autonomous organelles merely functioning to generate energy for cells to survive and proliferate, and were thought to be independent of the cellular signaling networks. Consequently, phosphorylation and dephosphorylation processes of mitochondrial kinases and phosphatases were largely neglected. However, evidence accumulated in recent years on mitochondria-localized kinases/phosphatases has changed this longstanding view. Mitochondria are increasingly recognized as a hub for cell signaling, and many kinases and phosphatases have been reported to localize in mitochondria and play important functions. However, the strength of the evidence on mitochondrial localization and the activities of the reported kinases and phosphatases vary greatly, and the detailed mechanisms on how these kinases/phosphatases translocate to mitochondria, their subsequent function, and the physiological and pathological implications of their localization are still poorly understood. Here, we provide an updated perspective on the recent advancement in this area, with an emphasis on the implications of mitochondrial kinases/phosphatases in cancer and several other diseases.

Epimacular brachytherapy for neovascular age-related macular degeneration (CABERNET): fluorescein angiography and optical coherence tomography.

PURPOSE: To report the fluorescein angiography (FA) and optical coherence tomography (OCT) results of a clinical trial of epimacular brachytherapy (EMBT) used for the treatment of neovascular age-related macular degeneration (AMD). DESIGN: Pivotal multicenter, active-controlled, randomized clinical trial. PARTICIPANTS: A total of 494 participants with treatment-naïve, neovascular AMD. METHODS: Participants with classic, minimally classic, and occult lesions were randomized to receive (a) EMBT and 2 mandated monthly ranibizumab injections followed by pro re nata (PRN) ranibizumab or (b) 3 mandated monthly ranibizumab injections followed by mandated quarterly plus PRN ranibizumab. Participants underwent FA at screening and at months 1, 6, 12, 18, and 24. Optical coherence tomography scans were undertaken monthly for 24 months. The FA and OCT images were analyzed at respective independent reading centers. MAIN OUTCOME MEASURES: Change at 24 months in mean FA total lesion size and choroidal neovascularization (CNV) size and change in mean OCT centerpoint thickness. RESULTS: The mean (standard deviation) changes in FA total lesion size in the EMBT and control arms were +1.9 (8.7) and -3.0 (7.2) mm(2), respectively, with a mean change in total CNV size of +0.4 (8.4) and -4.7 (6.5) mm(2), respectively. Mean (standard deviation) changes in OCT centerpoint thickness were -144 (246) and -221 (185) µm, respectively. Retrospective subgroup analyses showed no significant difference between treatment arms in mean centerpoint thickness in some subgroups, including eyes with classic lesions. The control arm showed a significantly larger reduction in mean total lesion size and mean CNV size than the EMBT arm in all subgroups analyzed. Nine eyes in the EMBT arm showed features consistent with mild, nonproliferative radiation retinopathy, but with a mean gain of 5.0 Early Treatment Diabetic Retinopathy Study letters. CONCLUSIONS: Both FA and OCT suggest that EMBT with PRN ranibizumab results in an inferior structural outcome than quarterly plus PRN ranibizumab. Some subgroup analyses suggest that classic lesions may be more responsive than occult lesions, although generally both subgroups are inferior to ranibizumab. A non-vision-threatening radiation retinopathy occurs in 2.9% of eyes over 24 months, but longer follow-up is needed. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

Developmental exposure to cadmium alters responsiveness to cocaine in the rat.

The purpose of the present report was to investigate the potential interactive relation between perinatal (gestation/lactation) cadmium exposure and changes in responsiveness to cocaine. In Experiment 1, adult female rats were exposed to a diet containing 50 ppm cadmium (as cadmium chloride) or a diet containing no added cadmium for 30 days prior to breeding with nonexposed males. The metal-exposure regimen continued throughout gestation, and for 15 days of lactation, at which time all animals were placed on standard rat chow diets containing no added cadmium for the remainder of the investigation. Atomic absorption assays confirmed that cadmium concentrations were significantly elevated in metal-exposed dams, littermates, and test animals. Offspring were weaned on postnatal day (PND) 21 and commenced cocaine sensitization testing on PND 70. Testing operations for controls and animals perinatally exposed to cadmium consisted of 21 daily i.p. injections of vehicle (saline) or 10 mg/kg cocaine HCl, and subsequent recording of locomotor activity. Subsequently, across successive days, all animals received 0, 10, and 20 mg/kg cocaine challenges. The results showed that cocaine sensitization was attenuated in animals perinatally exposed to cadmium. A similar pattern of antagonism was observed in Experiment 2 where a higher dose of cocaine was required to produce conditioned place preference (CPP) in cadmium-exposed animals. The implications of these findings with respect to the interactive role of cadmium in the dynamics of cocaine use/abuse remain unclear.

The effects of developmental cadmium exposure on morphine sensitization and challenge with selective D(1) and D(2) antagonists.

The purpose of this investigation was to determine the effects of developmental (perinatal) cadmium exposure on the development and expression of behavioral sensitization to morphine. Adult female rats were maintained ad libitum on diets containing 0, 25, or 50 ppm added cadmium (administered as cadmium chloride) for 30 days prior to breeding with nonexposed males. This exposure regimen continued throughout the gestational period and for 15 days postnatally during lactation, at which time regular rat chow was provided. On postnatal day (PND) 21, male pups from the respective litters were weaned and placed on an unadulterated food supply (no added cadmium) and tap water for the remainder of the study. Beginning on PND 70, animals from each exposure condition (0, 25, 50 ppm exposure conditions) received, for 21 consecutive days, either vehicle (distilled water) or 10 mg/kg morphine sulfate injections (ip) prior to being monitored for locomotor activity during 80-min test sessions. Following this 21-day period of morphine sensitization training, dose-effect profiles were determined for each exposure condition with successive daily challenges of 0, 10, and 20 mg/kg morphine. Subsequently, different doses of the D(1) antagonist SCH 23390 (0.01, 0.056, and 0.10 mg/kg) and the D(2) antagonist eticlopride (0.01 and 0.056 mg/kg) were presented prior to administration of the training dose of morphine (10 mg/kg). The results of the investigation revealed that developmental cadmium exposure attenuated the development/expression of morphine sensitization. Furthermore, it was found that the suppressive effects of the D(2) antagonist eticlopride were decreased by early cadmium exposure.