Essential role for GABARAP autophagy proteins in interferon-inducible GTPase-mediated host defense.

Mammalian autophagy-related 8 (Atg8) homologs consist of LC3 proteins and GABARAPs, all of which are known to be involved in canonical autophagy. In contrast, the roles of Atg8 homologs in noncanonical autophagic processes are not fully understood. Here we show a unique role of GABARAPs, in particular gamma-aminobutyric acid (GABA)-A-receptor-associated protein-like 2 (Gabarapl2; also known as Gate-16), in interferon-γ (IFN-γ)-mediated antimicrobial responses. Cells that lacked GABARAPs but not LC3 proteins and mice that lacked Gate-16 alone were defective in the IFN-γ-induced clearance of vacuolar pathogens such as Toxoplasma. Gate-16 but not LC3b specifically associated with the small GTPase ADP-ribosylation factor 1 (Arf1) to mediate uniform distribution of interferon-inducible GTPases. The lack of GABARAPs reduced Arf1 activation, which led to formation of interferon-inducible GTPase-containing aggregates and hampered recruitment of interferon-inducible GTPases to vacuolar pathogens. Thus, GABARAPs are uniquely required for antimicrobial host defense through cytosolic distribution of interferon-inducible GTPases.

Heterozygous variants in SIX3 and POU1F1 cause pituitary hormone deficiency in mouse and man.

Congenital hypopituitarism is a genetically heterogeneous condition that is part of a spectrum disorder that can include holoprosencephaly. Heterozygous mutations in SIX3 cause variable holoprosencephaly in humans and mice. We identified two children with neonatal hypopituitarism and thin pituitary stalk who were doubly heterozygous for rare, likely deleterious variants in the transcription factors SIX3 and POU1F1. We used genetically engineered mice to understand the disease pathophysiology. Pou1f1 loss-of-function heterozygotes are unaffected; Six3 heterozygotes have pituitary gland dysmorphology and incompletely ossified palate; and the Six3+/-; Pou1f1+/dw double heterozygote mice have a pronounced phenotype, including pituitary growth through the palate. The interaction of Pou1f1 and Six3 in mice supports the possibility of digenic pituitary disease in children. Disruption of Six3 expression in the oral ectoderm completely ablated anterior pituitary development, and deletion of Six3 in the neural ectoderm blocked the development of the pituitary stalk and both anterior and posterior pituitary lobes. Six3 is required in both oral and neural ectodermal tissues for the activation of signaling pathways and transcription factors necessary for pituitary cell fate. These studies clarify the mechanism of SIX3 action in pituitary development and provide support for a digenic basis for hypopituitarism.

High-throughput splicing assays identify missense and silent splice-disruptive POU1F1 variants underlying pituitary hormone deficiency.

Pituitary hormone deficiency occurs in ∼1:4,000 live births. Approximately 3% of the cases are due to mutations in the alpha isoform of POU1F1, a pituitary-specific transcriptional activator. We found four separate heterozygous missense variants in unrelated individuals with hypopituitarism that were predicted to affect a minor isoform, POU1F1 beta, which can act as a transcriptional repressor. These variants retain repressor activity, but they shift splicing to favor the expression of the beta isoform, resulting in dominant-negative loss of function. Using a high-throughput splicing reporter assay, we tested 1,070 single-nucleotide variants in POU1F1. We identified 96 splice-disruptive variants, including 14 synonymous variants. In separate cohorts, we found two additional synonymous variants nominated by this screen that co-segregate with hypopituitarism. This study underlines the importance of evaluating the impact of variants on splicing and provides a catalog for interpretation of variants of unknown significance in POU1F1.

Newer parameters of the octreotide test in patients with acromegaly.

PURPOSE: Predicting the therapeutic effects of first-generation somatostatin receptor ligands (fg-SRLs) is important when assessing or planning effective treatment strategies in patients with acromegaly. The oft-used maximum growth hormone (GH) suppression rate parameter of the octreotide test has a suboptimal predictive value. Therefore, this study explored newer parameters of the octreotide test for predicting the therapeutic effect of long-acting fg-SRLs. METHODS: In this single-center retrospective study, the octreotide test parameters and the therapeutic effects of fg-SRL at 3 months were investigated in 45 consecutive treatment-naïve patients with acromegaly between April 2008 and March 2023. Additionally, the relationship between the octreotide test parameters and the therapeutic effects of fg-SRLs was investigated. Tumor shrinkage was evaluated based on changes in the longitudinal diameter of the macroadenomas. The area GH suppression rate-time under the curve (AUC) and the time to nadir GH level were calculated and compared with the maximum GH suppression rate. RESULTS: The AUC estimated reductions in serum insulin-like growth factor I, and tumor shrinkage. The time to nadir GH level predicted tumor shrinkage more robustly than the maximum GH suppression rate in patients with macroadenoma. CONCLUSION: The AUC and time to nadir GH level may potentially be newer parameters of the octreotide test for estimating the therapeutic effect of fg-SRLs.

Composite paraganglioma-ganglioneuroma with atypical catecholamine profile and phenylethanolamine N-methyltransferase expression: a case report and literature review.

Pheochromocytomas and paragangliomas (PPGLs) are rare tumors that secrete catecholamines and arise from the adrenal medulla or extra-adrenal sympathetic ganglia. These tumors secrete adrenaline and noradrenaline, but paragangliomas usually produce only noradrenaline because of the lack of phenylethanolamine N-methyltransferase (PNMT) expression. Composite paragangliomas, which are complex tumors consisting of multiple types of neuroblastic cells, are extremely rare. We present the case of a 46-year-old woman with an atypical catecholamine profile who was preoperatively diagnosed with pheochromocytoma. However, postoperative pathology revealed that the patient had an extra-adrenal paraganglioma accompanied by a ganglioneuroma, which led to the diagnosis of a composite tumor. Interestingly, PNMT is expressed in both paragangliomas and ganglioneuromas. In addition, we reviewed reported composite paragangliomas and compared their clinical features with those of composite pheochromocytomas. We also discuss various aspects of the etiology of composite paragangliomas and the mechanism by which PNMT is expressed in tumors.

Human GBP1 is a microbe-specific gatekeeper of macrophage apoptosis and pyroptosis.

The guanylate binding protein (GBP) family of interferon-inducible GTPases promotes antimicrobial immunity and cell death. During bacterial infection, multiple mouse Gbps, human GBP2, and GBP5 support the activation of caspase-1-containing inflammasome complexes or caspase-4 which trigger pyroptosis. Whether GBPs regulate other forms of cell death is not known. The apicomplexan parasite Toxoplasma gondii causes macrophage death through unidentified mechanisms. Here we report that Toxoplasma-induced death of human macrophages requires GBP1 and its ability to target Toxoplasma parasitophorous vacuoles through its GTPase activity and prenylation. Mechanistically, GBP1 promoted Toxoplasma detection by AIM2, which induced GSDMD-independent, ASC-, and caspase-8-dependent apoptosis. Identical molecular determinants targeted GBP1 to Salmonella-containing vacuoles. GBP1 facilitated caspase-4 recruitment to Salmonella leading to its enhanced activation and pyroptosis. Notably, GBP1 could be bypassed by the delivery of Toxoplasma DNA or bacterial LPS into the cytosol, pointing to its role in liberating microbial molecules. GBP1 thus acts as a gatekeeper of cell death pathways, which respond specifically to infecting microbes. Our findings expand the immune roles of human GBPs in regulating not only pyroptosis, but also apoptosis.

Instability of harmonized thyroid-stimulating hormone immunoassays in clinical practice.

OBJECTIVE: Thyroid-stimulating hormone (TSH) harmonization is effective in minimizing differences between the results of immunoassays in healthy subjects. However, the effectiveness of TSH harmonization in clinical practice has not been investigated. The aim of this study was to evaluate the instability of TSH harmonization in clinical practice. METHODS: We compared the reactivities of four harmonized TSH immunoassays using combined difference plots of 431 patients. We selected patients with statistically significant deviations in TSH levels and analyzed their thyroid hormone levels and clinical characteristics. RESULTS: The combined difference plots showed that one harmonized TSH immunoassay exhibited markedly different reactivity even after TSH harmonization compared with the other three immunoassays. Among 109 patients with mild-to-moderate elevation of TSH levels, we selected 15 patients with statistically significant deviations in TSH levels according to the difference plots of three harmonized TSH immunoassays, excluding one immunoassay that showed different reactivity. The thyroid hormone levels of three patients were misclassified as hypothyroidism or normal due to deviating TSH levels. In terms of clinical characteristics, these patients were in poor nutritional status and general condition, possibly due to their severe illness (e.g., advanced metastatic cancer). CONCLUSION: We have confirmed that TSH harmonization in clinical practice is relatively stable. However, some patients showed deviating TSH levels in the harmonized TSH immunoassays, indicating the need for caution, particularly in poorly nourished patients. This finding suggests the presence of factors that contribute to the instability of TSH harmonization in such cases. Further investigation is warranted to validate these results.

A new insight into GH regulation and its disturbance from nutrition and autoimmune perspectives.

GH activates GH receptors, which activates IGF-1 in the liver through a cascade of processes. The GH/IGF-1 axis plays an important role in the regulation of metabolism. Insufficient GH secretion results in short stature in childhood, while adult GH deficiency (AGHD) is observed in adulthood. The early diagnosis of AGHD is important for early initiation of GH replacement therapy. This review described the regulatory mechanisms of GH signaling based on nutritional status and a novel disease concept pathogenesis that causes AGHD. GH-dependent IGF-1 production in the liver is regulated by a complex interplay between nutritional status, hormones, and growth factors. GH resistance is an adaptive response that enhances survival during starvation and malnutrition. Sirtuin 1 (SIRT1) negatively regulates GH-induced IGF-I production in the liver by directly inhibiting STAT5 activation, which causes GH resistance under starvation and malnutrition. The presence of autoantibodies is strongly associated with the disruption of immune tolerance in pituitary cells. Pituitary-specific transcription factors (PIT-1) are essential for the development, differentiation, and maintenance of GH, PRL, and TSH producing cells. However, the underlying mechanism that causes immune intolerance to PIT-1 remain unclear. The GH-IGF-1 system plays a pivotal role in growth, and the involvement of SIRT1 in this regulatory mechanism presents an intriguing perspective on the interplay between nutrient metabolism and lifespan. The discovery of the anti-PIT-1 pituitary antibody, a novel disease concept associated with AGHD, has provided valuable insights, which serves as a significant milestone towards unraveling the complete pathogenesis of the disease.

Successful diagnosis and treatment of pheochromocytoma during severe coronavirus disease 2019 (COVID-19): a case report.

Pheochromocytoma is a rare but life-threatening condition due to catecholamine release induced by drug treatments such as ß-blockers or glucocorticoids. We present a case of hypertensive crisis due to pheochromocytoma, induced after the initiation of dexamethasone and landiolol during intensive care for severe coronavirus disease 2019 (COVID-19). Based on a detailed medical history review, the patient was previously diagnosed with primary aldosteronism by confirmatory tests, moreover, an abdominal computed tomography scan identified an adrenal tumor 2 years before current admission. We tentatively diagnosed the patient with pheochromocytoma and initiated α-blockers without conducting a catecholamine report, leading to stable hemodynamics. We present a successfully managed case of pheochromocytoma concomitant with COVID-19, which has become a global crisis.

Survey of glucocorticoid dose escalation in patients with adrenal insufficiency during the peri-COVID-19 vaccination period.

There is uncertainty regarding the need for COVID-19 peri-vaccination glucocorticoid coverage in patients with adrenal insufficiency. In this survey conducted in a single tertiary medical institution, 167 consecutive outpatients taking physiological glucocorticoids because of adrenal insufficiency were included. The patients declared if they developed an adrenal crisis after vaccination, and the amount and duration of an increase in their glucocorticoid dosage, if any. None of the patients without preventive glucocorticoid increase suffered an adrenal crisis after COVID-19 vaccination. Only 8.3% (14 cases) and 27.5% (46 cases) of the patients needed to escalate the dose of glucocorticoids when systemic symptoms appeared after the first and second injections, respectively. Glucocorticoids were increased in patients <60 years of age more than in patients ≥60 years of age at the time of both the first (p = 0.026) and second injections (p = 0.005). Sex and the causes of adrenal insufficiency were not associated with the frequency of the patients who needed glucocorticoid dose escalation. In the cases with increased glucocorticoids, the median dosage for escalation was 10 mg (hydrocortisone equivalent). In conclusion, even without prophylactic glucocorticoid administration, adrenal crisis did not occur during the peri-COVID-19 vaccination period. The dose escalation of steroid was more frequent in younger patients following the second vaccination. Careful monitoring of adverse effects and the appropriate management of glucocorticoids when necessary are essential following COVID-19 vaccinations.

Otx2b mutant zebrafish have pituitary, eye and mandible defects that model mammalian disease.

Combined pituitary hormone deficiency (CPHD) is a genetically heterogeneous disorder caused by mutations in over 30 genes. The loss-of-function mutations in many of these genes, including orthodenticle homeobox 2 (OTX2), can present with a broad range of clinical symptoms, which provides a challenge for predicting phenotype from genotype. Another challenge in human genetics is functional evaluation of rare genetic variants that are predicted to be deleterious. Zebrafish are an excellent vertebrate model for evaluating gene function and disease pathogenesis, especially because large numbers of progeny can be obtained, overcoming the challenge of individual variation. To clarify the utility of zebrafish for the analysis of CPHD-related genes, we analyzed the effect of OTX2 loss of function in zebrafish. The otx2b gene is expressed in the developing hypothalamus, and otx2bhu3625/hu3625 fish exhibit multiple defects in the development of head structures and are not viable past 10 days post fertilization (dpf). Otx2bhu3625/hu3625 fish have a small hypothalamus and low expression of pituitary growth hormone and prolactin (prl). The gills of otx2bhu3625/hu3625 fish have weak sodium influx, consistent with the role of prolactin in osmoregulation. The otx2bhu3625/hu3625 eyes are microphthalmic with colobomas, which may underlie the inability of the mutant fish to find food. The small pituitary and eyes are associated with reduced cell proliferation and increased apoptosis evident at 3 and 5 dpf, respectively. These observations establish the zebrafish as a useful tool for the analysis of CPHD genes with variable and complex phenotypes.

Responsiveness to DDAVP in Cushing's disease is associated with USP8 mutations through enhancing AVPR1B promoter activity.

PURPOSE: To clarify the characteristics of Cushing's disease (CD) patients who respond to the desmopressin (DDAVP) test and its underlying mechanisms. METHODS: Forty-seven patients with CD who underwent DDAVP testing were included. Patients were divided into two groups: DDAVP test (+) (adrenocorticotropic hormone [ACTH] levels increased by ≥ 1.5-fold during the DDAVP test) and DDAVP test (-) (ACTH levels increased by < 1.5-fold). AVP receptor expression levels in these tumors were quantified using quantitative RT-PCR and immunohistochemistry. AVP receptor promoter activity was analyzed using a dual-luciferase reporter assay system. RESULTS: Females (96.9%) and USP8 mutants (85.7%) were more prevalent in the DDAVP test (+) than in the DDAVP test (-). Indeed, the ACTH and cortisol responsiveness to DDAVP was greater in USP8 mutation positive tumors than that in USP8 wild type tumors (3.0-fold vs. 1.3-fold, 1.6-fold vs. 1.1-fold, respectively). Responsiveness to DDAVP was correlated with the expression levels of AVPR1B, but not with those of AVPR2. Comparably, Avpr1b promoter activity was enhanced by the overexpression of mutant USP8 compared to the wild type. CONCLUSIONS: We found that the responsiveness of ACTH to DDAVP in CD was greater in tumors with USP8 mutations. The present data suggest that USP8 mutations upregulate the AVPR1B promoter activity. Additionally, we showed that the DDAVP test can predict the presence of USP8 mutations.

Mechanistic insights into immune checkpoint inhibitor-related hypophysitis: a form of paraneoplastic syndrome.

BACKGROUND: Immune checkpoint inhibitors (ICIs) as a cancer immunotherapy have emerged as a treatment for multiple advanced cancer types. Because of enhanced immune responses, immune-related adverse events (irAEs), including endocrinopathies such as hypophysitis, have been associated with the use of ICIs. Most underlying mechanisms of ICI-related hypophysitis remain unclear, especially for programmed cell death-1 (PD-1)/PD-1 ligand 1 (PD-L1) inhibitors. We hypothesized that ICI-related hypophysitis is associated with paraneoplastic syndrome caused by ectopic expression of pituitary-specific antigens. METHODS: Twenty consecutive patients with ICI-related hypophysitis between 2017 and 2019 at Kobe University Hospital were retrospectively analyzed. Circulating anti-pituitary antibodies were detected using immunofluorescence staining and immunoblotting. Ectopic expression of pituitary autoantigens in tumor specimens was also examined. RESULTS: Eighteen patients were treated with PD-1/PD-L1 inhibitors, and two were treated with a combination of cytotoxic T-lymphocyte antigen-4 (CTLA-4) and PD-1 inhibitors. All patients showed adrenocorticotropic hormone (ACTH) deficiency and additionally, three showed thyroid-stimulating hormone (TSH) deficiency, and one showed gonadotropin-releasing hormone (GnRH) deficiency. Among these patients, three exhibited anti-pituitary antibodies, two with anti-corticotroph antibody and one with anti-somatotroph antibody. Interestingly, the anti-corticotroph antibody recognized proopiomelanocortin (POMC) and those two patients exhibited ectopic ACTH expression in the tumor, while the patients without anti-corticotroph antibody did not. CONCLUSIONS: We demonstrated 10% of PD-1/PD-L1 inhibitors-related hypophysitis were associated with the autoimmunity against corticotrophs and maybe caused as a form of paraneoplastic syndrome, in which ectopic expression of ACTH in the tumor was observed. It is also suggested that the pathophysiology is heterogenous in ICI-related hypophysitis.

Patients with pheochromocytoma exhibit low aldosterone renin ratio-preliminary reports.

BACKGROUND: Plasma renin activity (PRA) is generally increased in patients with pheochromocytoma (PCC) due to low circulating plasma volume and activation of ß-1 adrenergic receptor signaling. However, there has been no study on the aldosterone renin ratio (ARR) in patients with PCC. To elucidate the issue, this study aimed to determine the PRA, plasma aldosterone concentration (PAC), and ARR in patients with PCC and compare them with those in patients with subclinical Cushing's syndrome (SCS) and non-functioning adrenal adenoma (NFA). METHODS: In this retrospective single-center, cross-sectional study, 67 consecutive patients with adrenal tumors (PCC (n = 18), SCS (n = 18), and NFA (n = 31)) diagnosed at Kobe University Hospital between 2008 and 2014 were enrolled. RESULTS: PRA was significantly higher in patients with PCC than in those with SCS and NFA (2.1 (1.3 ~ 2.8) vs. 0.7 (0.5 ~ 1.8) and 0.9 (0.6 ~ 1.4) ng/mL/h; p = 0.018 and p = 0.025). Although PACs were comparable among the three groups, ARR was significantly lower in patients with PCC than in those with SCS and NFA (70.5 (45.5 ~ 79.5) vs. 156.0 (92.9 ~ 194.5) and 114.9 (90.1 ~ 153.4); p = 0.001 and p < 0.001). Receiver operating characteristic curve analysis demonstrated that, in differentiating PCC from NFA, PRA > 1.55 ng/mL/h showed a sensitivity of 70.0% and specificity of 80.6%. Interestingly, ARR < 95.4 showed a sensitivity of 83.3% and specificity of 86.7%, which were higher than those in PRA. CONCLUSIONS: ARR decreased in patients with PCC, which was a more sensitive marker than PRA. Further study is necessary to understand the usefulness of this convenient marker in the detection of PCC. TRIAL REGISTRATION: This study was not registered because of the retrospective analysis.

IgG4-related hypophysitis in patients with autoimmune pancreatitis.

PURPOSE: IgG4-related disease involves various organs including the pituitary and pancreas. The prevalence of IgG4-related hypophysitis is relatively rare compared with IgG4-related pancreatitis (autoimmune pancreatitis). Although several cases demonstrating both autoimmune pancreatitis and hypophysitis have been reported, the prevalence of IgG4-related hypophysitis in patients with autoimmune pancreatitis remains unknown. This study aimed at screening for IgG4-related hypophysitis to accurately determine its prevalence in patients with autoimmune pancreatitis. METHODS: In this cohort study, we screened IgG4-related hypophysitis via pituitary magnetic resonance imaging (MRI) and endocrinological examination in 27 patients who were undergoing follow-up for autoimmune pancreatitis at Kobe University Hospital between 2014 and 2018. RESULTS: Among 27 patients with autoimmune pancreatitis, 5 patients exhibited morphological abnormalities in the pituitary (18.5%). Among them, one patient (3.7%) met the criteria for hypophysitis with an enlarged pituitary and stalk concomitant with hypopituitarism. After glucocorticoid treatment, the enlarged pituitary shrank and became empty sella during the clinical course. Four patients (14.8%) revealed empty sella without obvious pituitary dysfunction. Four of 5 patients with morphological pituitary abnormalities showed multiple organ involvement in addition to pancreatic and pituitary involvement. Accordingly, multiple organ involvement was more prevalent in patients with morphological pituitary abnormalities (80%) compared to those without (48%). CONCLUSIONS: Although a large-scale study is necessary to validate these results, these data suggest that the prevalence of hypophysitis in patients with autoimmune pancreatitis may be underestimated. Based on our findings, we recommend screening for hypophysitis, especially in patients with multiple organ involvement.

Acromegaly caused by a somatotroph adenoma in patient with neurofibromatosis type 1.

Although acromegaly has been reported in patients with Neurofibromatosis type 1 (NF1), these cases have not been associated with growth hormone (GH)-producing somatotroph adenoma, but with optic pathway glioma. A 68 year-old Japanese woman, who had been clinically diagnosed with NF1, was referred to our hospital due to a thyroid tumor and hypercalcemia. Acromegaly was suspected due to her facial features, and subsequent examinations revealed the presence of GH excess with a pituitary tumor, leading to the diagnosis of acromegaly. Histological and immunohistochemical analysis demonstrated an eosinophilic pituitary adenoma with diffuse positivity for GH, indicating typical somatotroph adenoma. In addition, her thyroid tumor was diagnosed histologically as follicular thyroid carcinoma (FTC) with primary hyperparathyroidism (PHPT). To investigate the pathogenesis of this untypical multiple endocrine tumor case of NF1, genetic analysis was performed using peripheral leukocytes and tissue of resected tumors. A heterozygous novel germline nonsense mutation (p.Arg1534*) in exon 35 of the NF1 gene was detected from peripheral leukocytes, which results in a truncated protein lacking the critical domain for GTPase activity, strongly suggesting its causal role in NF1. The loss of heterozygosity (LOH) in exon 35 of the NF1 gene was not detected in the somatotroph adenoma, parathyroid adenoma, and FTC. Although any mutations of the following genes; MEN1, CDKN1B, and PAX8-PPARγ were not detected, a heterozygous GNAS R201C mutation was detected in the somatotroph adenoma. To our knowledge, this is the first rare MEN1-like case of genetically diagnosed NF1 complicated with acromegaly caused by a somatotroph adenoma.

Isolated adrenocorticotropic hormone deficiency as a form of paraneoplastic syndrome.

PURPOSE: In isolated adrenocorticoropic hormone (ACTH) deficiency (IAD), autoimmunity against corticotrophs has been suggested; however, the pathogenesis remains largely unknown. Large cell neuroendocrine carcinoma (LCNEC) of the lung is a pulmonary tumor of high-grade malignant neuroendocrine tumor and it reportedly caused paraneoplastic syndrome by autoimmunity in several cases. METHODS: A 42-year-old woman with isolated adrenocorticotropic (ACTH) hormone deficiency (IAD) was diagnosed with large cell neuroendocrine carcinoma (LCNEC) 3 years after being diagnosed with IAD. We hypothesized that the LCNEC played a causal role in the development of IAD as a paraneoplastic syndrome and analyzed the autoimmunity. We also analyzed another case of ectopic ACTH syndrome to prove this hypothesis. RESULTS: The LCNEC tissue revealed an ectopic ACTH expression and lymphocyte infiltration. Interestingly, autoantibody against the proopiomelanocortin (POMC) protein was detected in the peripheral blood. Although, patient's serum did not show any effects on cell viability, proliferation, nor pomc expression in a corticotroph cell line, AtT20 cells, patient's lymphocytes in the peripheral blood specifically reacted toward POMC protein, indicating a presence of cytotoxic T lymphocytes (CTLs). In addition, the analysis of another case of ectopic ACTH syndrome showed lymphocyte infiltration not only in the metastatic liver tumors but also in the pituitary. Moreover, most CD8-positive cells resided adjacent to corticotrophs. CONCLUSIONS: These data indicate that the ectopic ACTH expression in the tumor evoked the autoimmunity to corticotrophs and caused IAD as a form of paraneoplastic syndrome.

RabGDIα is a negative regulator of interferon-γ-inducible GTPase-dependent cell-autonomous immunity to Toxoplasma gondii.

IFN-γ orchestrates cell-autonomous host defense against various intracellular vacuolar pathogens. IFN-γ-inducible GTPases, such as p47 immunity-related GTPases (IRGs) and p65 guanylate-binding proteins (GBPs), are recruited to pathogen-containing vacuoles, which is important for disruption of the vacuoles, culminating in the cell-autonomous clearance. Although the positive regulation for the proper recruitment of IRGs and GBPs to the vacuoles has been elucidated, the suppressive mechanism is unclear. Here, we show that Rab GDP dissociation inhibitor α (RabGDIα), originally identified as a Rab small GTPase inhibitor, is a negative regulator of IFN-γ-inducible GTPases in cell-autonomous immunity to the intracellular pathogen Toxoplasma gondii. Overexpression of RabGDIα, but not of RabGDIß, impaired IFN-γ-dependent reduction of T. gondii numbers. Conversely, RabGDIα deletion in macrophages and fibroblasts enhanced the IFN-γ-induced clearance of T. gondii. Furthermore, upon a high dose of infection by T. gondii, RabGDIα-deficient mice exhibited a decreased parasite burden in the brain and increased resistance in the chronic phase than did control mice. Among members of IRGs and GBPs important for the parasite clearance, Irga6 and Gbp2 alone were more frequently recruited to T. gondii-forming parasitophorous vacuoles in RabGDIα-deficient cells. Notably, Gbp2 positively controlled Irga6 recruitment that was inhibited by direct and specific interactions of RabGDIα with Gbp2 through the lipid-binding pocket. Taken together, our results suggest that RabGDIα inhibits host defense against T. gondii by negatively regulating the Gbp2-Irga6 axis of IFN-γ-dependent cell-autonomous immunity.

Cross-sectional prevalence of pancreatic cystic lesions in patients with acromegaly, a single-center experience.

PURPOSE: Acromegaly is a disease associated with an increased risk for several kinds of neoplasms including colon and thyroid cancer. Although the association between acromegaly and pancreatic neoplasms has not been elucidated, it has recently been reported that GNAS gene mutations were found in 58% of intraductal papillary mucinous neoplasms (IPMNs), which are representative pancreatic cystic lesions, suggesting a link between IPMNs and acromegaly. To assess the prevalence of pancreatic cystic lesions in patients with acromegaly, we performed a retrospective cross-sectional single institute study. METHODS: Thirty consecutive acromegalic patients (20 females and 10 males; mean age, 60.9 ± 11.9 years) who underwent abdominal contrast-enhanced computed tomography or magnetic resonance imaging between 2007 and 2015 at Kobe University Hospital were recruited. We also analyzed the relationship between presence of pancreatic cystic lesions and somatic GNAS mutations in pituitary tumors. RESULTS: Seventeen of 30 (56.7%) patients studied had pancreatic cystic lesions. Nine of 17 patients (52.9%) were diagnosed with IPMNs based on imaging findings. These results suggest that the prevalence of IPMNs may be higher in acromegalic patients in acromegalic patients than historically observed in control patients (up to 13.5%). In patients with pancreatic cystic lesions, the mean patient age was higher and the duration of disease was longer than in those without pancreatic cystic lesions (67.0 ± 2.3 vs. 53.0 ± 2.7 years, p < 0.001, 15.5 ± 2.4 vs. 7.3 ± 2.8 years, p = 0.04). There were no differences in serum growth hormone levels or insulin-like growth factor standard deviation scores between these two groups (21.3 ± 6.4 vs. 23.0 ± 7.4 ng/ml, p = 0.86, 6.6 ± 0.5 vs. 8.0 ± 0.6, p = 0.70). Neither the presence of somatic GNAS mutation in a pituitary tumor nor low signal intensity of the tumor in T2 weighted magnetic resonance imaging was associated with the presence of pancreatic cystic lesions. CONCLUSIONS: These data demonstrate that old or long-suffering patients with acromegaly have a higher prevalence of pancreatic cystic lesions. Moreover, the prevalence of pancreatic cystic lesions may be increased in acromegalic patients.

Genetic and clinical characteristics of Japanese patients with sporadic somatotropinoma.

Most of acromegaly is caused by a sporadic somatotropinoma and a couple of novel gene mutations responsible for somatotropinoma have recently been reported. To determine the cause of sporadic somatotropinoma in Japanese patients, we analyzed 61 consecutive Japanese patients with somatotropinoma without apparent family history. Comprehensive genetic analysis revealed that 31 patients harbored guanine nucleotide-binding protein, alpha stimulating (GNAS) mutations (50.8%) and three patients harbored aryl hydrocarbon receptor interacting protein (AIP) mutations (4.9%). No patients had G protein-coupled receptor 101 (GPR101) mutations. The patients in this cohort study were categorized into three groups of AIP, GNAS, and others and compared the clinical characteristics. The AIP group exhibited significantly younger age at diagnosis, larger tumor, and higher nadir GH during oral glucose tolerance test. In all patients with AIP mutation, macro- and invasive tumor was detected and repetitive surgery or postoperative medical therapy was needed. One case showed a refractory response to postoperative somatostatin analogue (SSA) but after the addition of cabergoline as combined therapy, serum IGF-I levels were controlled. The other case showed a modest response to SSA and the switching to cabergoline monotherapy was also effective. These data suggest that although resistance to SSA has been reported in patients with AIP mutations, the response to dopamine agonist (DA) may be retained. In conclusion, the cause of sporadic somatotropinoma in Japanese patients was comparable with the previous reports in Caucasians, patients with AIP mutations showed unique clinical characteristics, and DA may be a therapeutic option for patients with AIP mutations.