Calcineurin regulates aldosterone production via dephosphorylation of NFATC4

The mineralocorticoid aldosterone, secreted by the adrenal zona glomerulosa (ZG), is critical for life, maintaining ion homeostasis and blood pressure. Therapeutic inhibition of protein phosphatase 3 (calcineurin, Cn) results in inappropriately low plasma aldosterone levels despite concomitant hyperkalemia and hyperreninemia. We tested the hypothesis that Cn participates in the signal transduction pathway regulating aldosterone synthesis. Inhibition of Cn with tacrolimus abolished the potassium-stimulated (K+-stimulated) expression of aldosterone synthase, encoded by CYP11B2, in the NCI-H295R human adrenocortical cell line as well as ex vivo in mouse and human adrenal tissue. ZG-specific deletion of the regulatory Cn subunit CnB1 diminished Cyp11b2 expression in vivo and disrupted K+-mediated aldosterone synthesis. Phosphoproteomics analysis identified nuclear factor of activated T cells, cytoplasmic 4 (NFATC4), as a target for Cn-mediated dephosphorylation. Deletion of NFATC4 impaired K+-dependent stimulation of CYP11B2 expression and aldosterone production while expression of a constitutively active form of NFATC4 increased expression of CYP11B2 in NCI-H295R cells. Chromatin immunoprecipitation revealed NFATC4 directly regulated CYP11B2 expression. Thus, Cn controls aldosterone production via the Cn/NFATC4 pathway. Inhibition of Cn/NFATC4 signaling may explain low plasma aldosterone levels and hyperkalemia in patients treated with tacrolimus, and the Cn/NFATC4 pathway may provide novel molecular targets to treat primary aldosteronism.

Calcineurin-NFATc4 Pathway Is Activated Upon K+-stimulation of Adrenal Aldosterone Production

The mineralocorticoid aldosterone secreted by the adrenal zona glomerulosa (ZG) cells promote renal K⁺ secretion and Na⁺ reabsorption; thereby it is critical for the control of ion homeostasis and blood pressure. While the Ca²⁺/calmodulin-dependent protein kinase (CAMK) pathway regulating K⁺ stimulated aldosterone production is well studied, little is known about the potentially involved phosphatases. Interestingly, immunosuppression therapy of transplanted patients with protein phosphatase 3 (calcineurin) inhibitors often results in rather low plasma aldosterone levels despite a concomitant hyperkalemia and hyperreninemia. Calcineurin (Cn) is a calcium and calmodulin-dependent protein phosphatase expressed in the adrenal cortex. We tested the hypothesis that Cn participates in the signal transduction pathway mediating the K⁺-dependent stimulation of aldosterone production. To address this question, we used the adrenocortical cell model NCI-H295R, mouse and human ex vivo adrenal preparations and a ZG-specific and inducible Cn knockout mouse model (ZG-CnB1-KO). Inhibition of Cn with tacrolimus abolished the K⁺-stimulated expression of CYP11B2 in NCI-H295R cell line as well as mouse and human adrenal pieces, ex vivo. Using a phosphoproteomics analysis, we identified nuclear factor of activated T-cells, cytoplasmic 4 (NFATc4) as a critical downstream factor mediating Cn function. In support of this result, genetic deletion of NFATc4 reduced the basal expression of CYP11B2 and impaired the K⁺-stimulated expression of this gene. Conversely, the expression of a constitutively active form of NFATc4 drastically increased the expression of CYP11B2 in NCI-H295R cells which remained unaltered upon treatment with K⁺ or tacrolimus. Finally, preliminary experiments using ZG-CnB1-KO mice suggest that Cn deletion in the ZG blunts the increase in aldosterone excretion triggered by high K⁺ diet. Altogether, our data indicate that Cn function is indispensable for the physiological regulation of aldosterone production. Moreover, Cn may represent a novel molecular target for the pharmacological treatment of primary aldosteronism.

SAT-LB23 Paraneoplastic Hypercalcemia in a PTH Producing Adrenocortical Carcinoma - a Rare and Deadly Condition

Background: Hypercalcemia is a commonly encountered paraneoplastic manifestation of certain cancers with or without endocrine differentiation. However, the association between adrenocortical carcinoma (ACC) with paraneoplastic hypercalcemia is very rare, and therefore little is known about the cause and its relevance in the disease. Clinical Case: A 40-year-old woman presented in the hospital with a 5-month history of progressive flank pain with unintentional weight loss of 6 kg. MRI revealed a mass of 9x8.1x4.8 cm of the right adrenal gland with inhomogeneous contrast enhancement. Biochemical investigations provided evidence of endogenous hypercortisolism (24-hour urinary cortisol excretion [490 µg, n<236 µg/l], 1mg dexamethasone suppression test [199 nmol/l, n<50 nmol/l], ACTH [28 ng/l, n<61 ng/l]) although the patient did not show any specific clinical sign of overt hypercortisolism. In addition, laboratory testing revealed an exceptionally high plasma level of calcium [max 3.67 mmol/l (albumin-corrected)] and low phosphate [min 0.26 mmol/l] in the setting of low PTH [6.4 ng/l, n>15 ng/l] and PTHrP levels [<0.50 pmol/l]. However, subsequent dilution unmasked a highly elevated PTH concentration of 2171.5 ng/l with persistent low PTHrP levels, indicating false low values due to a hook effect in the initial measurement. Levels of 1,25-dihydroxy vitamin D and 25-hydroxy vitamin D were in the normal range. A PET-CT provided no indications of metabolically active (osseous) metastases. After correction of the serum calcium towards tolerable values, the tumor was removed by open en bloc adrenalectomy. Histologic evaluation confirmed an ACC (TNM pT4 pN1 (2/3), L1, V1, high grade) despite missing immunohistochemically expression of classical adrenal markers (diagnosis of exclusion). Supplemental quantitative RT-PCR studies support the diagnosis of ACC by detecting significant SF-1 and CYP11B2 expression in the tumor cells. Further analyses provided evidence that the mRNA expression of PTH, but not PTHrP, was moderately increased in the ACC sample compared to NCI H295R cells. Upon tumor resection, serum calcium levels swiftly normalized indicating the tumor as the sole source of PTH secretion. Despite initiation of adjuvant mitotane- and salvage chemo-therapy, the patient died 3 months later upon of a massive tumor relapse with a recurrence of severe hypercalcemia. Conclusion: This case demonstrates paraneoplastic hypercalcemia in a PTH producing ACC. PTH may induce hypercalcemia, impair adrenal steroid synthesis and act as an autocrine growth factor in ACC, as described in few individual cases for PTHrp producing ACC [1]. This suggests a poor prognosis for this rare entity.

1. Rizk-Rabin, M., et al., Differential Expression of Parathyroid Hormone-Related Protein in Adrenocortical Tumors: Autocrine/Paracrine Effects on the Growth and Signaling Pathways in H295R Cells. 2008.

NLRC3 protein inhibits inflammation by disrupting NALP3 inflammasome assembly via competition with the adaptor protein ASC for pro-caspase-1 binding

Inflammasomes are multiprotein complexes that sense pathogen-associated and danger-associated molecular patterns and induce inflammation in cells. The NALP3 inflammasome is tightly regulated by recently discovered control mechanisms, but other modulators still remain to be characterized. NLR family CARD-containing 3 (NLRC3) protein, a caspase recruitment domain (CARD)-containing member of the nucleotide oligomerization domain-like receptor (NLR) family, was found to down-regulate the NF-κB pathway and stimulator of interferon genes (STING)-dependent cytokine secretion. However, the effect of NLRC3 on the NALP3 inflammasome or other inflammasomes is still unknown. We hypothesized that NLRC3 might inhibit NALP3 inflammasome complex assembly. Toward this end, we tested whether NLRC3 overexpression or knockdown influences NALP3 activity in human monocyte and HEK293FT cells when the complex is ectopically reconstituted. We found that NLRC3 indeed decreases NALP3-induced IL-1β maturation and secretion, pro-caspase-1 cleavage, and speck formation by apoptosis-associated speck-like protein containing a CARD (ASC) protein in response to NALP3 activators. We also show that endogenous NLRC3 interacts with both ASC and pro-caspase-1 but not with NALP3, disrupts ASC speck formation through its CARD, and impairs the ASC and pro-caspase-1 interaction. Moreover, the NLRC3 CARD alone could dampen IL-1β secretion and ASC speck formation induced by NALP3 mutants associated with autoinflammatory diseases. In conclusion, we show here that, besides its role in the inhibition of the NF-κB pathway, NLRC3 interferes with the assembly and activity of the NALP3 inflammasome complex by competing with ASC for pro-caspase-1 binding.

Impact of early weight loss on growth of Caesarean delivered babies: how long does it last?

BACKGROUND

We hypothesized that Caesarean delivered babies might experience excessive weight loss during neonatal period.

AIM

To investigate amount of weight loss among Caesarean delivered babies with exclusive breastfeeding and to identify role of relative weight change (RWC) in early postnatal period on the growth of infants in subsequent months.

METHODS

We studied healthy infants born ≥36 completed weeks, by Caesarean section between September 2008 and August 2009, with Apgar scores >7. Weight measurements were performed at birth, at 24 h postpartum and at days 2, 4, 7, 14, 30 and monthly up to 6 months. Predictive roles of RWC at each assessment on detecting excessive weight loss and poor weight gain in 1st month, as well as bodyweight z scores in subsequent months were assessed.

RESULTS

We studied 160 infants (88 female, 72 male) with a mean gestational age of 38.01 ± 1 weeks and birthweight of 3239 ± 421 g. Overall, 22.5% of infants lost >10% of birthweight; 11.9% at day 2, 16.9% at day 4 and 6.6% at day 7. Degree of weight loss was not related with parity, gestational age, birthweight or type of anaesthesia. Predictive values of RWCs in detecting poor weight gain in 0-30 days were: 2nd day; limit =-9.4%, specificity = 91.5%, 4th day; limit =-10.2%, specificity = 89.4%, 7th day; limit =-6.3%, specificity = 85%, sensitivity = 78%, 14th day; limit =+0.8%, specificity = 91.5%, sensitivity = 83.3%. Adjusting for birthweight z scores, RWC at 14th day had a significant influence on 1st and 2nd month bodyweight z scores. Bodyweight z scores were significantly correlated with the z scores of bodyweight in 1-5 months but not with that of 6 months.

CONCLUSION

Incidence of excessive weight loss is very high among Caesarean delivered babies. RWC at earlier measurements proves satisfactory in predicting poor infant growth. Management strategies based on identifying infants at risk could prevent excessive weight loss and improve future growth of those infants.

The effect of economic status on height, insulin-like growth factor (IGF)-I and IGF binding protein-3 concentrations in healthy Turkish children

OBJECTIVES

The effect of economic status (ES) on growth, insulin-like growth factor (IGF)-I and IGF-binding protein (IGFBP)-3 in healthy children is not well characterized. We aimed to study the interrelationship between height, weight, IGF-I, IGFBP-3, mid-parental height (MPH) and ES.

DESIGN/SUBJECTS

Eight hundred and fourteen healthy children (428 boys, 386 girls; age 3-18 years) were classified according to income of the families as low, middle and high. Standard deviation scores (SDSs) of height, weight, MPH, IGF-I and IGFBP-3 were compared between the groups. The combined effect of these parameters and ES on height SDS was investigated with complex statistical models.

RESULTS

There was a significant trend for height and weight SDSs to increase with higher income levels in boys, but not in girls. Body mass index (BMI) SDSs were similar in three groups. There was a general trend for MPH SDS to increase with income levels in both sexes. In boys, IGF-I SDS was significantly higher in high ES group than low ES. In girls, IGFBP-3 SDSs were significantly higher in high ES group than in middle ES group. For both genders, height SDS was highly correlated with weight SDS and moderately correlated with BMI SDS, MPH SDS and IGF-1 SDS. All correlations were significant and positive. Complex models showed that MPH (19%), IGF-I (13%) and ES (3%) in boys, and MPH (16%) and IGF-I (7%) in girls have significant contribution to height SDSs.

CONCLUSIONS

ES per se, independent of overt malnutrition, affects height, weight, IGF-I and IGFBP-3 with some gender differences in healthy children. Influence of income on height and weight show sexual dimorphism, a slight but significant effect is observed only in boys. MPH is the most prominent variable effecting height in healthy children. Higher height and MPH SDSs observed in higher income groups suggest that secular trend in growth still exists, at least in boys, in a country of favorable economic development.