In conclusion, the current data provide the novel observation that alcohol impairs the response of MPS in exercise recovery in human skeletal muscle despite optimal nutrient provision. The quantity of alcohol consumed in the current study was based on amounts reported during binge drinking by athletes. However, published reports suggest intakes of some individuals can be significantly greater , , which is of concern for many reasons related to health and safety . Regrettably, there has been difficulty in finding an educational message with alcohol consumption related to sports performance that has resonance with athletes. Given the need to promote protein synthesis that underpins adaptation, repair and regeneration of skeletal muscle the results of the current study provide clear evidence of impaired recovery when alcohol is consumed after concurrent (resistance, continuous and intermittent high-intensity) exercise even in the presence of optimal nutritional conditions. We propose our data is of paramount interest to athletes and coaches. Our findings provide an evidence-base for a message of moderation in alcohol intake to promote recovery after exercise with the potential to alter current sports culture and athlete practices.
HLB is the most devastating citrus disease worldwide [18, 19]. The disease is caused by the gram-negative, phloem-limited, alpha-proteobacteria Candidatus Liberibacter spp., i.e., Ca. L. asiaticus (Las), Ca. L. africanus (Laf), and Ca. L. americanus (Lam) [18, 19]. HLB impairs phloem transportation of photoassimilates  and causes root decline . Las living in the phloem prevents direct interactions with other microbes on the rhizoplane and in the rhizosphere. Instead, Las causes decreased photoassimilate transportation, likely reducing plant resource availability for the root-associated microbiome. Our previous results suggested that HLB significantly altered the structure or functional potential of the citrus endosphere (leaves or roots) or rhizosphere bacterial community based on cultivation, 16S rDNA clone library, PhyloChip, or the GeoChip method [21,22,23,24]. However, the low-throughput-based methods used in these previous studies limited our understanding of the citrus microbiome. Additionally, these studies focused on the bacterial community colonized on a single layer, either the rhizosphere or endosphere. How HLB affects the microbiome assembly process, particularly the process from the less tightly associated rhizosphere to the rhizoplane component, of the citrus root-associated microbiome remains unknown. In this study, we obtained snapshots of the citrus root microbiome using metagenomic (MG) and metatranscriptomic (MT) approaches to investigate the rhizosphere-to-rhizoplane-enriched taxa and functions and how HLB affects those enriched taxonomic and functional attributes.
Overall, we demonstrate that the functional properties involved in host-microbe interactions are critical for the microbiome-inhabiting plant root surfaces and are influenced dramatically by the availability of plant exudates. These rhizoplane-enriched functional properties can subsequently benefit the plant host. HLB not only alters the physiology of the citrus host but also impairs the microbiome-host interaction. Our study provides novel insights for understanding the composition and function of the plant rhizoplane-enriched microbiome and its effect on plant health.
Gabriela Assis-de-Lemos, Jamila Monteiro, Viviane M. Oliveira-Valença, Guilherme A. Melo, Ricardo A. de Melo Reis, Stevens K. Rehen, Mariana S. Silveira, Antonio Galina; Dopamine signaling impairs ROS modulation by mitochondrial hexokinase in human neural progenitor cells. Biosci Rep 22 December 2021; 41 (12): BSR20211191. doi:
Dopamine signaling has numerous roles during brain development. In addition, alterations in dopamine signaling may be also involved in the pathophysiology of psychiatric disorders. Neurodevelopment is modulated in multiple steps by reactive oxygen species (ROS), byproducts of oxidative metabolism that are signaling factors involved in proliferation, differentiation, and migration. Hexokinase (HK), when associated with the mitochondria (mt-HK), is a potent modulator of the generation of mitochondrial ROS in the brain. In the present study, we investigated whether dopamine could affect both the activity and redox function of mt-HK in human neural progenitor cells (NPCs). We found that dopamine signaling via D1R decreases mt-HK activity and impairs ROS modulation, which is followed by an expressive release of H2O2 and impairment in calcium handling by the mitochondria. Nevertheless, mitochondrial respiration is not affected, suggesting specificity for dopamine on mt-HK function. In neural stem cells (NSCs) derived from induced-pluripotent stem cells (iPSCs) of schizophrenia patients, mt-HK is unable to decrease mitochondrial ROS, in contrast with NSCs derived from healthy individuals. Our data point to mitochondrial hexokinase as a novel target of dopaminergic signaling, as well as a redox modulator in human neural progenitor cells, which may be relevant to the pathophysiology of neurodevelopmental disorders such as schizophrenia.
Crosstalk between dopamine and HK activity in NPCs was investigated by the analysis of classes of dopamine receptors important for the regulation of mt-HK activity. Initially, we demonstrated that human NPCs express both dopamine receptors type 1 (D1R) and 2 (D2R) (Figure 4A). D1R and D2R were blocked with specific antagonists (SCH 23390 and raclopride, respectively), and mitochondrial HK coupled activity was selectively analyzed by generation of G6P in a system stimulated by succinate + ADP + Pi, in which mitochondrial ATP is used as a substrate for mt-HK phosphorylation of glucose (Figure 4B) . Control treatment with oligomycin, a specific inhibitor of F1FO-ATP synthase, completely abrogated mt-HK-dependent generation of G6P (Figure 4C). In addition to total HK activity, dopamine treatment induced a 60% decrease in mt-HK coupled activity (Figure 4C,D). The inhibition of mt-HK coupled activity was blocked by pretreatment with a D1R antagonist (SCH23390), but not with D2R antagonist (raclopride) (Figure 4C,D), demonstrating that dopamine specifically impairs mt-HK through the activation of D1R.
Mitochondria play an essential role in calcium homeostasis through the uptake of cytosolic calcium. Recently, de-Souza-Ferreira (2019) demonstrated that mt-HK plays an important role in calcium uptake by brain mitochondria because mt-HK inhibition by G6P impairs mitochondrial uptake of calcium, whereas mt-HK activation by 2-DOG improves the uptake . Treatment with dopamine decreased mt-HK coupled activity (Figure 4C,D); hence, we investigated whether the uptake of calcium by the mitochondria is changed in NPCs exposed to dopamine. We assessed the uptake in permeabilized NPCs using Calcium Green-5N fluorescence . In control NPCs, activation of mt-HK by 2-DOG enhanced calcium retention capacity of mitochondria measured as Calcium Green fluorescence after calcium pulses (Figure 5A). The amount of calcium retained by the mitochondria represents a balance between the influx and efflux rates. The influx rate was derived from the decay of the signal of Calcium Green fluorescence. On the other hand, the accumulation of calcium in the medium results from inhibition of the influx and/or an increase in the efflux of calcium by mitochondria. The rate of calcium influx in control NPCs was gradually inhibited by calcium added to the reaction (Figure 5B, black circles); this effect was detected only at higher concentrations of calcium in NPCs exposed to 2-DOG (Figure 5B, red circles). A reduction in the accumulation of calcium outside of mitochondria upon stimulation with 2-DOG compared with that in unstimulated control NPCs indicated more efficient calcium uptake in the presence of 2-DOG (Figure 5C'). Conversely, after treatment with dopamine, the stimulation of mt-HK activity did not improve the uptake of calcium by the mitochondria because 2-DOG did not alter calcium accumulation outside of mitochondria (Figure 5C''). These data are summarized as the magnitude of the effect of 2-DOG on the decrease in the amount of calcium outside of mitochondria in control and dopamine-treated NPCs (Figure 5D).
The present study showed that dopamine impairs the modulation of mitochondrial ROS by decreasing mt-HK activity via D1R-dependent signaling in human NPCs. This effect resulted in an increase in extracellular H2O2 and impairment of mitochondrial calcium dynamics in dopamine-treated NPCs.
Overall, our data highlight the role of mitochondrial hexokinase, a potent redox modulator in mature neurons, as an equally relevant redox modulator in human neural progenitor cells. Importantly, we propose that mt-HK is a novel target of D1R-mediated dopaminergic signalling, which impairs the role of mt-HK as a redox modulator in NPCs. Similarly, impaired control of ROS production by mt-HK was shown in NSCs derived from schizophrenia patients; these findings may indicate a correlation between dysregulation of dopaminergic signalling during neurodevelopment with pathophysiology of schizophrenia. Applicability of these findings to other cell types in addition to neural progenitor cells used in the present study remains to be determined. The results of the present study obtained using various approaches suggest that redox balance fine-tuned by mt-HK may be disrupted by dopamine signalling in human brain cells. 350c69d7ab