Effect of GRK4 on renal gastrin receptor regulation in hypertension

OBJECTIVE

To investigate whether GRK4 regulates the phosphorylation and function of renal CCKBR.

METHODS

GRK4 A142V transgenic mice were used as an animal model of enhanced GRK4 activity, and siRNA was used to silence the GRK4 gene to investigate the regulatory effect of GRK4 on CCKBR phosphorylation and function. Finally, the co-localization and co-connection of GRK4 and CCKBR in RPT cells were observed by laser confocal microscopy and immunoprecipitation to explore the mechanism of GRK4 regulating CCKBR.

RESULTS

Gastrin infusion significantly increased urinary flow and sodium excretion rates in GRK4 WT mice (P < .05). GRK4 siRNA did not affect CCKBR protein expression in WKY RPT cells and SHR RPT cells, but remarkably reduced CCKBR phosphorylation in WKY and SHR RPT cells (P < .05). The inhibitory effect of gastrin on Na+-K+ -ATPase activity in WKY RPT cells was further enhanced by the reduction of GRK4 expression (P < .05), while GRK4 siRNA restored the inhibitory effect of gastrin on Na+-K+ -ATPase activity in SHR RPT cells. Laser confocal and Co-immunoprecipitation results showed that GRK4 and CCKBR co-localized in cultured RPT cells' cytoplasm.

CONCLUSION

GRK4 participates in the development of hypertension by regulating the phosphorylation of renal CCKBR leading to impaired CCKBR function and water and sodium retention. Knockdown of GRK4 restored the function of CCKBR. The enhanced co-connection between GRK4 and CCKBR may be an important reason for the hyperphosphorylation of GRK4 and CCKBR involved in the pathogenesis of hypertension.

Elevated Serum Gastrin Is Associated with Melanoma Progression: Putative Role in Increased Migration and Invasion of Melanoma Cells

Micro-environmental factors, including stromal and immune cells, cytokines, and circulating hormones are well recognized to determine cancer progression. Melanoma cell growth was recently shown to be suppressed by cholecystokinin/gastrin (CCK) receptor antagonists, and our preliminary data suggested that melanoma patients with Helicobacter gastritis (which is associated with elevated serum gastrin) might have an increased risk of cancer progression. Therefore, in the present study, we examined how gastrin may act on melanoma cells. In 89 melanoma patients, we found a statistically significant association between circulating gastrin concentrations and melanoma thickness and metastasis, which are known risk factors of melanoma progression and prognosis. Immunocytochemistry using a validated antibody confirmed weak to moderate CCK2R expression in both primary malignant melanoma cells and the melanoma cell lines SK-MEL-2 and G361. Furthermore, among the 219 tumors in the Skin Cutaneous Melanoma TCGA Pan-Cancer dataset showing gastrin receptor (CCKBR) expression, significantly higher CCKBR mRNA levels were linked to stage III-IV than stage I-II melanomas. In both cell lines, gastrin increased intracellular calcium levels and stimulated cell migration and invasion through mechanisms inhibited by a CCK2 receptor antagonist. Proteomic studies identified increased MMP-2 and reduced TIMP-3 levels in response to gastrin that were likely to contribute to the increased migration of both cell lines. However, the effects of gastrin on tumor cell invasion were relatively weak in the presence of the extracellular matrix. Nevertheless, dermal fibroblasts/myofibroblasts, known also to express CCK2R, increased gastrin-induced cancer cell invasion. Our data suggest that in a subset of melanoma patients, an elevated serum gastrin concentration is a risk factor for melanoma tumor progression, and that gastrin may act on both melanoma and adjacent stromal cells through CCK2 receptors to promote mechanisms of tumor migration and invasion.

Signaling Network Response to Alpha-Particle Targeted Therapy with Actinium-225 Labeled Minigastrin Analogue 225Ac-PP-F11N Reveals Radiosensitizing Potential of HDAC Inhibitors

Alpha-particle emitters have recently been explored as valuable therapeutic radionuclides. Yet, toxicity to healthy organs and cancer radioresistance limit the efficacy of targeted alpha-particle therapy (TAT). Identification of the radiation-activated mechanisms, which drive cancer cell survival, provides opportunities to develop new points for therapeutic interference to improve efficacy and safety of TAT. Methods: Quantitative phosphoproteomics and matching proteomics followed by the bioinformatics analysis were employed to identify alterations in the signaling networks in response to TAT with actinium-225 labeled minigastrin analogue ²²⁵Ac-PP-F11N in A431 cells, which overexpress cholecystokinin B receptor (CCKBR). Western blot (WB) analysis and microscopy verified the activation of the selected signaling pathways. Small-molecule inhibitors were used to validate the potential of the radio-sensitizing combinatory treatments both in vitro and in A431/CCKBR tumor-bearing nude mice. Results: TAT-induced alterations involved in DNA damage response (DDR), cell cycle regulation, signal transduction as well as RNA transcription and processing, cell morphology and transport. WB analysis and microscopy confirmed increased phosphorylations of the key proteins involved in DDR and carcinogenesis including P53, P53BP1 histone deacetylases (HDACs) and H2AX. Inhibition of HDAC class II, ataxia-telangiectasia mutated (ATM) and p38 kinases by TMP269, AZD1390 and SB202190, respectively, sensitized A431/CCKBR cells to ²²⁵Ac-PP-F11N. Combination of ²²⁵Ac-PP-F11N with HDAC inhibitor vorinostat (SAHA) showed significantly reduced viability and increased DNA damage of A431/CCKBR cells as well as the most pronounced tumor growth inhibition and the extended mean survival of A431/CCKBR xenografted nude mice as compared to the control and monotherapies. Conclusion: Our study revealed the cellular responses to TAT and demonstrated the radiosensitizing potential of HDAC inhibitors to ²²⁵Ac-PP-F11N in CCKBR-positive tumors. This proof-of-concept study recommends development of the novel radiosensitizing strategies by targeting TAT-activated and survival-promoting signaling pathways.

Comparative analysis of cancer cell responses to targeted radionuclide therapy (TRT) and external beam radiotherapy (EBRT)

The vast majority of our knowledge regarding cancer radiobiology and the activation of radioresistance mechanisms emerged from studies using external beam radiation therapy (EBRT). Yet, less is known about the cancer response to internal targeted radionuclide therapy (TRT). Our comparative phosphoproteomics analyzed cellular responses to TRT with lutetium-177-labeled minigastrin analogue [¹⁷⁷Lu]Lu-PP-F11N (β-emitter) and EBRT (ɣ-rays) in CCKBR-positive cancer cells. Activation of DNA damage response by p53 was induced by both types of radiotherapy, whereas TRT robustly increased activation of signaling pathways including epidermal growth factor receptor (EGFR), mitogen-activated protein kinases (MAPKs) or integrin receptor. Inhibition of EGFR or integrin signaling sensitized cancer cells to radiolabeled minigastrin. In vivo, EGFR inhibitor erlotinib increased therapeutic response to [¹⁷⁷Lu]Lu-PP-F11N and median survival of A431/CCKBR-tumor bearing nude mice. In summary, our study explores a complex scenario of cancer responses to different types of irradiation and pinpoints the radiosensitizing strategy, based on the targeting survival pathways, which are activated by TRT.

Downregulation of CCKBR Expression Inhibits the Proliferation of Gastric Cancer Cells, Revealing a Potential Target for Immunotoxin Therapy

Background Increased CCKBR expression density or frequency has been reported in many neoplasms. Objective We aimed to investigate whether CCKBR drives the growth of gastric cancer (GC) and its potential as a therapeutic target of immunotoxins. Methods A lentiviral interference system was used to generate CCKBR-knockdown gastric cancer cells. Cell Counting Kit-8 and clonogenic assays were used to evaluate cell proliferation. Wound-healing and cell invasion assays were performed to evaluate cell mobility. Cell cycle was analyzed by flow cytometry. Tumor growth in vivo was investigated using a heterologous tumor transplantation model in nude mice. In addition, we generated the immunotoxin FQ17P and evaluated the combining capacity and tumor cytotoxicity of FQ17P in vitro. Results Stable downregulation of CCKBR expression resulted in reduced proliferation, migration and invasion of BGC-823 and SGC-7901 cells. The impact of CCKBR on gastric cancer cells was further verified through CCKBR overexpression studies. Downregulation of CCKBR expression also inhibited the growth of gastric tumors in vivo. Furthermore, FQ17P killed CCKBR-overexpressing GC cells by specifically binding to CCKBR on the tumor cell surface. Conclusion The CCKBR protein drives the growth, migration, and invasion of gastric cancer cells, and it might be a promising target for immunotoxin therapy based on its aberrant expression, functional binding interactions with gastrin, and subsequent internalization.

Gastrin, via activation of PPARα, protects the kidney against hypertensive injury

Hypertensive nephropathy (HN) is a common cause of end-stage renal disease with renal fibrosis; chronic kidney disease is associated with elevated serum gastrin. However, the relationship between gastrin and renal fibrosis in HN is still unknown. We, now, report that mice with angiotensin II (Ang II)-induced HN had increased renal cholecystokinin receptor B (CCKBR) expression. Knockout of CCKBR in mice aggravated, while long-term subcutaneous infusion of gastrin ameliorated the renal injury and interstitial fibrosis in HN and unilateral ureteral obstruction (UUO). The protective effects of gastrin on renal fibrosis can be independent of its regulation of blood pressure, because in UUO, gastrin decreased renal fibrosis without affecting blood pressure. Gastrin treatment decreased Ang II-induced renal tubule cell apoptosis, reversed Ang II-mediated inhibition of macrophage efferocytosis, and reduced renal inflammation. A screening of the regulatory factors of efferocytosis showed involvement of peroxisome proliferator-activated receptor α (PPAR-α). Knockdown of PPAR-α by shRNA blocked the anti-fibrotic effect of gastrin in vitro in mouse renal proximal tubule cells and macrophages. Immunofluorescence microscopy, Western blotting, luciferase reporter, and Cut&tag-qPCR analyses showed that CCKBR may be a transcription factor of PPAR-α, because gastrin treatment induced CCKBR translocation from cytosol to nucleus, binding to the PPAR-α promoter region, and increasing PPAR-α gene transcription. In conclusion, gastrin protects against HN by normalizing blood pressure, decreasing renal tubule cell apoptosis, and increasing macrophage efferocytosis. Gastrin-mediated CCKBR nuclear translocation may make it act as a transcription factor of PPAR-α, which is a novel signaling pathway. Gastrin may be a new potential drug for HN therapy.

Gastrin Attenuates Renal Ischemia/Reperfusion Injury by a PI3K/Akt/Bad-Mediated Anti-apoptosis Signaling

Ischemic/reperfusion (I/R) injury is the primary cause of acute kidney injury (AKI). Gastrin, a gastrointestinal hormone, is involved in the regulation of kidney function of sodium excretion. However, whether gastrin has an effect on kidney I/R injury is unknown. Here we show that cholecystokinin B receptor (CCKBR), the gastrin receptor, was significantly up-regulated in I/R-injured mouse kidneys. While pre-administration of gastrin ameliorated I/R-induced renal pathological damage, as reflected by the levels of serum creatinine and blood urea nitrogen, hematoxylin and eosin staining and periodic acid-Schiff staining. The protective effect could be ascribed to the reduced apoptosis for gastrin reduced tubular cell apoptosis both in vivo and in vitro. In vitro studies also showed gastrin preserved the viability of hypoxia/reoxygenation (H/R)-treated human kidney 2 (HK-2) cells and reduced the lactate dehydrogenase release, which were blocked by CI-988, a specific CCKBR antagonist. Mechanistically, the PI3K/Akt/Bad pathway participates in the pathological process, because gastrin treatment increased phosphorylation of PI3K, Akt and Bad. While in the presence of wortmannin (1 μM), a PI3K inhibitor, the gastrin-induced phosphorylation of Akt after H/R treatment was blocked. Additionally, wortmannin and Akt inhibitor VIII blocked the protective effect of gastrin on viability of HK-2 cells subjected to H/R treatment. These studies reveals that gastrin attenuates kidney I/R injury via a PI3K/Akt/Bad-mediated anti-apoptosis signaling. Thus, gastrin can be considered as a promising drug candidate to prevent AKI.

Association of GA genotype of SNP rs4680 in COMT gene with psoriasis

Psoriasis is a multigene and multifactorial skin disease with heterogeneous genetic inheritance. Mental disorders participate in the development of psoriasis as predisposing factors; a correlation of dermatological diseases with pathological anxiety and stress was shown. Meanwhile, there are no studies describing molecular mechanisms of the linkages between psycho-emotional disorders and skin diseases. The aim of this study is to find the associations between SNP in genes COMT (rs4680), DBH (rs141116007), CCKAR (rs1800857) and CCKBR (rs1805002), and psoriasis. Patients were selected according to the 10th revision of International Classification of Diseases (L-40). The sample size was 88 patients. The size of the control sample (population control) was 365 people. Genotyping was performed using PCR-RFLP and real-time PCR. Statistical analysis was performed using WinPepi software. Identification of complex genotypes was performed by the Monte Carlo method using APSampler 3.6.1 algorithm. Among the studied genes, only GA genotype of COMT gene is significantly associated with psoriasis [χ² = 19.163 (p = 1.3E-5), F (p) = 1.2E-5, OR 3.47 (CI 99% = 1.61-7.91)]. At the moment, the functional significance of this phenomenon is difficult to explain.

Gastrin Induces Nuclear Export and Proteasome Degradation of Menin in Enteric Glial Cells

BACKGROUND & AIMS

The multiple endocrine neoplasia, type 1 (MEN1) locus encodes the nuclear protein and tumor suppressor menin. MEN1 mutations frequently cause neuroendocrine tumors such as gastrinomas, characterized by their predominant duodenal location and local metastasis at time of diagnosis. Diffuse gastrin cell hyperplasia precedes the appearance of MEN1 gastrinomas, which develop within submucosal Brunner's glands. We investigated how menin regulates expression of the gastrin gene and induces generation of submucosal gastrin-expressing cell hyperplasia.

METHODS

Primary enteric glial cultures were generated from the VillinCre:Men1FL/FL:Sst-/- mice or C57BL/6 mice (controls), with or without inhibition of gastric acid by omeprazole. Primary enteric glial cells from C57BL/6 mice were incubated with gastrin and separated into nuclear and cytoplasmic fractions. Cells were incubated with forskolin and H89 to activate or inhibit protein kinase A (a family of enzymes whose activity depends on cellular levels of cyclic AMP). Gastrin was measured in blood, tissue, and cell cultures using an ELISA. Immunoprecipitation with menin or ubiquitin was used to demonstrate post-translational modification of menin. Primary glial cells were incubated with leptomycin b and MG132 to block nuclear export and proteasome activity, respectively. We obtained human duodenal, lymph node, and pancreatic gastrinoma samples, collected from patients who underwent surgery from 1996 through 2007 in the United States or the United Kingdom.

RESULTS

Enteric glial cells that stained positive for glial fibrillary acidic protein (GFAP+) expressed gastrin de novo through a mechanism that required PKA. Gastrin-induced nuclear export of menin via cholecystokinin B receptor (CCKBR)-mediated activation of PKA. Once exported from the nucleus, menin was ubiquitinated and degraded by the proteasome. GFAP and other markers of enteric glial cells (eg, p75 and S100B), colocalized with gastrin in human duodenal gastrinomas.

CONCLUSIONS

MEN1-associated gastrinomas, which develop in the submucosa, might arise from enteric glial cells through hormone-dependent PKA signaling. This pathway disrupts nuclear menin function, leading to hypergastrinemia and associated sequelae.

Expression of the Cholecystokinin-B Receptor in Neoplastic Gastric Cells

Gastric cancer is an important disease due to its high mortality. Despite the decline in frequency, most cases are discovered late in its course, and most of the cancer patients die within a few years of diagnosis. In addition to Helicobacter pylori gastritis, gastrin is considered an important factor in the development of this disease, and thus, cholecystokinin-B receptor (CCKBR) becomes of interest. The aim of our study was to explore whether CCKBR is expressed in stomach cancers. Thirty-seven tumors from 19 men and 18 women diagnosed with either adenocarcinoma or neuroendocrine neoplasm (NENs) were included in this study. The tumors were classified into 29 adenocarcinomas and eight NENs. Immunohistochemistry with antibodies against chromogranin A (CgA), synaptophysin and CCKBR, and in situ hybridization with probes against CgA, CCKBR and histidine decarboxylase were used to further explore these tumors. Thirty-three (89%) of the tumors expressed CCKBR protein, whereas only 20 (54%) of all tumors expressed CCKBR mRNA. Of the 20 tumors expressing CCKBR mRNA, eight were NENs and 12 were adenocarcinoma. The highest amount of CCKBR was expressed in NEN. Interestingly, a high degree of co-expression of CCKBR and CgA was observed when the two markers were examined together with in situ hybridization. In conclusion, we found that all eight NENs expressed CCKBR and neuroendocrine markers in a majority of tumor cells. The same markers were also expressed in a proportion of adenocarcinomas supporting the view that gastrin is important in the development of gastric cancer.

Assessment of cholecystokinin 2 receptor (CCK2R) in neoplastic tissue

The expression of cholecystokinin 2 receptor (CCK2R, CCKBR or gastrin receptor) has been reported on a diverse range of cancers such as colorectal, liver, lung, pancreatic, ovarian, stomach, thyroid and numerous neuroendocrine/carcinoid tumors. Some cancers of the colorectum, lung, pancreas and thyroid have been shown to overexpress CCK2R in relation to normal matched tissues of the same organ. This reported overexpression has led to the development of a number of CCK2R-ligand targeted imaging and therapeutic agents. However, no comprehensive study comparing the expression of CCK2R in multiple cancers to multiple normal tissues has been performed. Herein, we report the immunohistochemical analysis of cancer samples from gastrointestinal stromal tumor (GIST), hepatocellular carcinoma (HCC), non-small cell lung cancer (NSCLC), pancreatic adenocarcinoma, and thyroid cancer against multiple normal tissue samples from esophagus, liver, lung, pancreas, stomach, spleen and thyroid. These results show that CCK2R expression is present in nearly all cancer and normal samples tested and that none of the cancer samples had expression that was statistically greater than that of all of the normal samples.

Investigating the role of BDNF and CCK system genes in suicidality in a familial bipolar cohort

BACKGROUND

Suicidal behaviour is a phenotype widely associated with psychiatric disorders such as major depressive disorder and bipolar disorder. However, recent evidence indicates that part of the heritability of suicidal behaviour is independent of the heritability of individual psychiatric disorders. This allows investigation into genetic risk factors for suicidal behaviour within a disorder using a candidate gene association approach.

METHODS

We used family-based association testing in a cohort of 130 multiplex bipolar pedigrees, comprising 795 individuals, to look for associations between suicidal behaviour and 32 single nucleotide polymorphisms (SNPs) from across the genes brain-derived neurotrophic factor (BDNF), cholecystokinin (CCK) and the cholecystokinin beta-receptor (CCKBR).

RESULTS

We found associations (p≤0.05) between suicide attempt and 12 SNPs of CCKBR and five SNPs of BDNF. After correction for multiple testing, seven SNPs of CCKBR remained significantly associated. No association was found between CCK and suicidal behaviour.

LIMITATIONS

The study relied on retrospective self-reporting by individuals to determine phenotype, and the sample size was relatively small.

CONCLUSIONS

The results of the study support the hypothesis that some CCKBR polymorphisms may contribute to an underlying predisposition towards suicidal behaviour in bipolar disorder.

Long noncoding RNAs: Novel insights into hepatocelluar carcinoma

Recent advances in non-protein coding part of human genome analysis have discovered extensive transcription of large RNA transcripts that lack of coding protein function, termed long noncoding RNAs (lncRNAs). It is becoming evident that lncRNAs may be an important class of pervasive genes involved in carcinogenesis and metastasis. However, the biological and molecular mechanisms of lncRNAs in diverse diseases are not yet fully understood. Thus, it is anticipated that more efforts should be made to clarify the lncRNAs world. Moreover, accumulating studies have demonstrated that a class of lncRNAs are dysregulated in hepatocellular carcinoma(HCC) and closely related with tumorigenesis, metastasis, prognosis or diagnosis. In this review, we will briefly discuss the regulation and functional role of lncRNAs in HCC, therefore evaluating the potential of lncRNAs as prospective novel therapeutic targets in HCC.