The mitochondrial Ca2+ channel MCU is critical for tumor growth by supporting cell cycle progression and proliferation

Introduction: The mitochondrial uniporter (MCU) Ca²⁺ ion channel represents the primary means for Ca²⁺ uptake by mitochondria. Mitochondrial matrix Ca²⁺ plays critical roles in mitochondrial bioenergetics by impinging upon respiration, energy production and flux of biochemical intermediates through the TCA cycle. Inhibition of MCU in oncogenic cell lines results in an energetic crisis and reduced cell proliferation unless media is supplemented with nucleosides, pyruvate or α-KG. Nevertheless, the roles of MCU-mediated Ca²⁺ influx in cancer cells remain unclear, in part because of a lack of genetic models. Methods: MCU was genetically deleted in transformed murine fibroblasts for study in vitro and in vivo. Tumor formation and growth were studied in murine xenograft models. Proliferation, cell invasion, spheroid formation and cell cycle progression were measured in vitro. The effects of MCU deletion on survival and cell-death were determined by probing for live/death markers. Mitochondrial bioenergetics were studied by measuring mitochondrial matrix Ca²⁺ concentration, membrane potential, global dehydrogenase activity, respiration, ROS production and inactivating-phosphorylation of pyruvate dehydrogenase. The effects of MCU rescue on metabolism were examined by tracing of glucose and glutamine utilization for fueling of mitochondrial respiration. Results: Transformation of primary fibroblasts in vitro was associated with increased MCU expression, enhanced MCU-mediated Ca²⁺ uptake, altered mitochondrial matrix Ca²⁺ concentration responses to agonist stimulation, suppression of inactivating-phosphorylation of pyruvate dehydrogenase and a modest increase of mitochondrial respiration. Genetic MCU deletion inhibited growth of HEK293T cells and transformed fibroblasts in mouse xenograft models, associated with reduced proliferation and delayed cell-cycle progression. MCU deletion inhibited cancer stem cell-like spheroid formation and cell invasion in vitro, both predictors of metastatic potential. Surprisingly, mitochondrial matrix [Ca²⁺], membrane potential, global dehydrogenase activity, respiration and ROS production were unaffected. In contrast, MCU deletion elevated glycolysis and glutaminolysis, strongly sensitized cell proliferation to glucose and glutamine limitation, and altered agonist-induced cytoplasmic Ca²⁺ signals. Conclusion: Our results reveal a dependence of tumorigenesis on MCU, mediated by a reliance on MCU for cell metabolism and Ca²⁺ dynamics necessary for cell-cycle progression and cell proliferation.

Effects of temperature on action potentials and ion conductances in type II taste-bud cells

Temperature strongly influences intensity of taste, but it remains under-studied despite its physiological, hedonic and commercial implications. The relative roles of the peripheral gustatory and somatosensory systems innervating the oral cavity in mediating thermal effects on taste sensation and perception are poorly understood. Type II taste-bud cells, responsible for sensing sweet, bitter umami and appetitive NaCl, release neurotransmitter to gustatory neurons by generation of action potentials, but the effects of temperature on action potentials and the underlying voltage-gated conductances are unknown. Here, we used patch-clamp electrophysiology to explore effects of temperature on acutely isolated type II taste-bud cell electrical excitability and whole-cell conductances. Our data reveal that temperature strongly affects action potential generation, properties and frequency, and suggest that thermal sensitivities of underlying voltage-gated Na⁺ and K⁺ channel conductances provide a mechanism for how and whether voltage-gated Na⁺ and K⁺channels in the peripheral gustatory system contribute to the influence of temperature on taste sensitivity and perception.

The mitochondrial Ca 2+ channel MCU is critical for tumor growth by supporting cell cycle progression and proliferation

The mitochondrial uniporter (MCU) Ca ²⁺ ion channel represents the primary means for Ca ²⁺ uptake into mitochondria. Here we employed in vitro and in vivo models with MCU genetically eliminated to understand how MCU contributes to tumor formation and progression. Transformation of primary fibroblasts in vitro was associated with increased MCU expression, enhanced mitochondrial Ca ²⁺ uptake, suppression of inactivating-phosphorylation of pyruvate dehydrogenase, a modest increase of basal mitochondrial respiration and a significant increase of acute Ca ²⁺ -dependent stimulation of mitochondrial respiration. Inhibition of mitochondrial Ca ²⁺ uptake by genetic deletion of MCU markedly inhibited growth of HEK293T cells and of transformed fibroblasts in mouse xenograft models. Reduced tumor growth was primarily a result of substantially reduced proliferation and fewer mitotic cells in vivo , and slower cell proliferation in vitro associated with delayed progression through S-phase of the cell cycle. MCU deletion inhibited cancer stem cell-like spheroid formation and cell invasion in vitro , both predictors of metastatic potential. Surprisingly, mitochondrial matrix Ca ²⁺ concentration, membrane potential, global dehydrogenase activity, respiration and ROS production were unchanged by genetic deletion of MCU in transformed cells. In contrast, MCU deletion elevated glycolysis and glutaminolysis, strongly sensitized cell proliferation to glucose and glutamine limitation, and altered agonist-induced cytoplasmic Ca ²⁺ signals. Our results reveal a dependence of tumorigenesis on MCU, mediated by a reliance on mitochondrial Ca ²⁺ uptake for cell metabolism and Ca ²⁺ dynamics necessary for cell-cycle progression and cell proliferation.

The ion channel CALHM6 controls bacterial infection-induced cellular cross-talk at the immunological synapse

Membrane ion channels of the calcium homeostasis modulator (CALHM) family promote cell-cell crosstalk at neuronal synapses via ATP release, where ATP acts as a neurotransmitter. CALHM6, the only CALHM highly expressed in immune cells, has been linked to the induction of natural killer (NK) cell anti-tumour activity. However, its mechanism of action and broader functions in the immune system remain unclear. Here, we generated Calhm6-/- mice and report that CALHM6 is important for the regulation of the early innate control of Listeria monocytogenes infection in vivo. We find that CALHM6 is upregulated in macrophages by pathogen-derived signals and that it relocates from the intracellular compartment to the macrophage-NK cell synapse, facilitating ATP release and controlling the kinetics of NK cell activation. Anti-inflammatory cytokines terminate CALHM6 expression. CALHM6 forms an ion channel when expressed in the plasma membrane of Xenopus oocytes, where channel opening is controlled by a conserved acidic residue, E119. In mammalian cells, CALHM6 is localised to intracellular compartments. Our results contribute to the understanding of neurotransmitter-like signal exchange between immune cells that fine-tunes the timing of innate immune responses.

Coupled transmembrane mechanisms control MCU-mediated mitochondrial Ca2+ uptake

Ca2+ uptake by mitochondria regulates bioenergetics, apoptosis, and Ca2+ signaling. The primary pathway for mitochondrial Ca2+ uptake is the mitochondrial calcium uniporter (MCU), a Ca2+-selective ion channel in the inner mitochondrial membrane. MCU-mediated Ca2+ uptake is driven by the sizable inner-membrane potential generated by the electron-transport chain. Despite the large thermodynamic driving force, mitochondrial Ca2+ uptake is tightly regulated to maintain low matrix [Ca2+] and prevent opening of the permeability transition pore and cell death, while meeting dynamic cellular energy demands. How this is accomplished is controversial. Here we define a regulatory mechanism of MCU-channel activity in which cytoplasmic Ca2+ regulation of intermembrane space-localized MICU1/2 is controlled by Ca2+-regulatory mechanisms localized across the membrane in the mitochondrial matrix. Ca2+ that permeates through the channel pore regulates Ca2+ affinities of coupled inhibitory and activating sensors in the matrix. Ca2+ binding to the inhibitory sensor within the MCU amino terminus closes the channel despite Ca2+ binding to MICU1/2. Conversely, disruption of the interaction of MICU1/2 with the MCU complex disables matrix Ca2+ regulation of channel activity. Our results demonstrate how Ca2+ influx into mitochondria is tuned by coupled Ca2+-regulatory mechanisms on both sides of the inner mitochondrial membrane.

Cutaneous Leishmaniasis in Natives of Central Region of Nepal

We report two cases of cutaneous leishmaniasis in natives of central region of Nepal. The first patient in our series, an adult female, presented with a small nodule on the philtrum of upper lip and the second case, a male child, presented with two crusted plaques on forehead. The final diagnosis was based on histopathological findings; however, species characterization was not possible because of its unavailability in the country. These patients responded well to the treatment with Miltefosine (First case) and Fluconazole (second case). Moreover, these cases sparks a question about the origin of diseases in this region and calls for further research in future to find out the cause and prevalence of this disease in Nepal. This case report also emphasizes to consider cutaneous leishmaniasis as differential diagnosis for granulomatous presentations in our context.

The influence of time of birth and seasonal variations on weight loss in breastfeeding neonates

BACKGROUND

Breastfeeding (BF) neonates generally lose weight after birth. Neonatal factors like gestational age, birth weight and mode of delivery can affect the neonatal weight loss after birth. Similarly, maternal age, parity and illness may contribute to newborn weight loss. However, influence of the time of birth and season on changes in weight is not well elucidated.

OBJECTIVE

The aim of this study is to determine the effect of birth time and the seasonal variations on weight loss in BF newborns.

METHODS

In this retrospective study of a prospectively maintained database of two sets of groups, from January 2013 to October 2016, were evaluated- Birth time group and Seasonal group; Birth time of the groups was: night time 7pm to 7am and day time 7am to 7pm; and the seasonal variations groups studies were summer, fall, winter and spring. Weight loss of >5%, 7%, and 10% at <24 hours (h), 48 h and 72 h of birth, respectively, were considered as a significant weight loss. Preterm, exclusively formula fed and neonates admitted to NICU were excluded.

RESULTS

A total of 2044 newborns were analyzed. In the birth time group, babies born during the night time had significantly lost >5% of birth weight at <24 h (p < 0.01) and >7% birth weight at <48 h of life (p < 0.02). Weight loss >10% at <72 h was similar in both birth time cohorts. C-section, prolonged rupture of membrane, and maternal pre-delivery hospital stay for >12 h were significant contributing factors. Whereas, seasonal variations were not associated with weight loss in neonates.

CONCLUSION

BF babies born at night time lose significantly more weight during the first two days of life and seasonal association was not found to affect weight loss in the neonates.

Eckols reduce dental pulp inflammation through the ERK1/2 pathway independent of COX-2 inhibition

OBJECTIVES

The aim of this study was to elucidate the role of 6-6 bieckol (EB1) and pholorofucofuroeckol-A (EB5) from brown seaweed marine algae (Eisenia bicyclis) on lipopolysaccharide (LPS)-induced inflammation in human dental pulp cells (HDPCs).

METHODS

The cytotoxicity of EB1 and EB5 was examined by MTT assay on LPS-induced human dental pulp cells. Their role on expression of inflammatory, odontogenic, and osteogenic molecules was determined by Western blot analysis. The dentin mineralization was checked by alkaline phosphatase activity.

RESULTS

The five compounds from E. bicyclis have different structure with non-cytotoxic in HDPCs. EB1 and EB5 showed anti-inflammatory properties and inhibited phosphorylated-extracellular signal-regulated kinase (p-ERK1/2) and phosphorylated-c-jun N-terminal kinases (p-JNK) without any cytotoxicity. In particular, EB1 inhibited cyclooxygenase-2 (COX-2) and p-ERK1/2 signaling, and EB5 inhibited only p-ERK1/2 signaling but not COX-2. Both compounds inhibited nuclear factor kappa-B (NF-κB) translocation. Furthermore, EB1 and EB5 increased dentinogenic and osteogenic molecules, and dentin mineralized via alkaline phosphatase activity (ALP) in LPS-induced HDPCs.

CONCLUSIONS

This study elucidates that EB1 and EB5 have different types of anti-inflammatory property and help in dentin formation. Therefore, these compounds derived from marine algae of E. bicyclis may be used as selective therapeutic strategies for pulpitis and oral diseases.

Davallialactone from mushroom reduced premature senescence and inflammation on glucose oxidative stress in human diploid fibroblast cells

Mushrooms are both food and a source of natural compounds of biopharmaceutical interest. The purpose of this study was to clarify whether davallialactone from mushroom extract affected the pathogenesis of hyperglycemia oxidative stress and the aging process in human diploid fibroblast (HDF) cells. The high-glucose state with glucose oxidase resulted in glucose oxidative stress, induction of inflammatory molecules, dysfunction of antioxidant molecules, and activation of mitogen-activated protein kinase (MAPKs) and its downstream signaling in old HDF cells. The exposure of glucose oxidative stress in middle-stage cells led to stress-induced premature senescence (SIPS) via senescence-associated β-galactosidase (SA β-gal) activity and displayed replicative senescence phenomena. However, davallialactone reduces the pathogenesis of glucose oxidative stress and the aging process through down-regulation of SA β-gal activity. These results strongly suggest that natural compounds, especially mushroom extract davallialactone, improve the pathogenesis of glucose oxidative stress and the aging process. Hence, davallialactone has potential in the treatment of diabetes mellitus or age-related disease complications.

Hemorrhagic bullae in henoch-schonlein purpura: A case report

We report a case of ten year old male child of Henoch-Schönlein purpura (HSP) who presented initially with predominant hemorrhagic bullae in extremities. Initial presentation with bullae is rare in HSP. The child recovered within two weeks with a course of systemic and topical steroid without any sequel. Journal of College of Medical Sciences-Nepal,2011,Vol-6,No-4, 46-48 DOI: http://dx.doi.org/10.3126/jcmsn.v6i4.6725

Cutaneous leishmaniasis: report of rare cases in Nepal

Cutaneous leishmaniasis is rare in Nepal although visceral leishmaniasis (kala azar) is common in the Terai region. In country like ours where tuberculosis is more prevalent cutaneous leishmaniasis is very likely to be mistreated as cutaneous tuberculosis, especially lupus vulgaris. Here we report a series of four cases of cutaneous leishmaniasis who presented in the out patient department at TUTH in the year 2006.

Herpes zoster in a five month old infant subsequent to intrauterine exposure to varicella infection

Herpes zoster is characterized by painful vesicular eruption in a dermatomal distribution of sensory nerves as a result of reactivation of latent herpes zoster virus in posterior root ganglia. The primary varicella infection is usually acquired in childhood and reactivation usually is seen in elderly. In rare instances herpes zoster can also occur in infancy as a result of reactivation of primary varicella infection acquired in utero or in early infancy. Here, we report a rare case of herpes zoster in a 5 month baby who acquired primary infection in utero from mother who had varicella infection at 6 months of gestation.