Changes in alpha-1 and beta-2 adrenoceptor density in human hepatocellular carcinoma

A universal co-expression gene network and prognostic model for hepatic-biliary-pancreatic cancers identified by integrative analyses

Hepatic, biliary and pancreatic cancers are a diverse set of malignancies with poor prognoses. It is possible that common molecular mechanisms are involved in the carcinogenesis of these cancers. Here, we identified LINC01537 and seven protein-coding genes by integrative analysis of transcriptomes of mRNAs, microRNAs and long non-coding RNAs from cholangiocarcinoma, hepatocellular carcinoma and pancreatic adenocarcinoma cohorts in TCGA. A predictive model constructed from seven biomarkers was established to successfully predict the survival rate of patients, which was then further verified in external cohorts. Additionally, patients with high-risk scores in our model were prone to epithelial-mesenchymal transition. Finally, activation of the biomarker PDE2A significantly attenuated migration and epithelial-mesenchymal transition in the HepG2 liver cancer cell line.

The Role of Catecholamines in Pathophysiological Liver Processes

Over the last few years, the number of research publications about the role of catecholamines (epinephrine, norepinephrine, and dopamine) in the development of liver diseases such as liver fibrosis, fatty liver diseases, or liver cancers is constantly increasing. However, the mechanisms involved in these effects are not well understood. In this review, we first recapitulate the way the liver is in contact with catecholamines and consider liver implications in their metabolism. A focus on the expression of the adrenergic and dopaminergic receptors by the liver cells is also discussed. Involvement of catecholamines in physiological (glucose metabolism, lipids metabolism, and liver regeneration) and pathophysiological (impact on drug-metabolizing enzymes expression, liver dysfunction during sepsis, fibrosis development, or liver fatty diseases and liver cancers) processes are then discussed. This review highlights the importance of understanding the mechanisms through which catecholamines influence liver functions in order to draw benefit from the adrenergic and dopaminergic antagonists currently marketed. Indeed, as these molecules are well-known drugs, their use as therapies or adjuvant treatments in several liver diseases could be facilitated.

Hepatic Arterial Blood Flow Modulation in Patients with Hepatocellular Carcinoma: A Pilot Study of the Influence of Intraarterial Norepinephrine Assessed with CT Perfusion

PURPOSE

This pilot study aims to evaluate the effect of hepatic intraarterial norepinephrine injection in vasculature modulation for hepatocellular carcinoma (HCC) tumors.

MATERIALS AND METHODS

This is a single-center prospective study of patients with HCC with proven single-lobe tumors > 3 cm. Eight patients were included, with a mean age of 63 y ± 8. All patients had Barcelona Clinic Liver Cancer stage B HCC and an Eastern Cooperative Oncology Group performance status of 0. Mean tumor size was 6.1 cm ± 1.8; all tumors were hypervascular. Patients underwent CT hepatic perfusion before and after injection of 24 μg of norepinephrine intraarterially (4 μg/mL; total 6 mL injected at a rate of 1 mL/s). Color-coded perfusion maps were used to assess the effects of local therapy on hepatic perfusion values. Tumor-to-liver ratio (TLR) was calculated from the ratio of tumor perfusion to background liver perfusion value.

RESULTS

Seven of 8 patents had significant (P = .04) absolute increase in tumor perfusion vs background liver, varying from incremental (-2 mL/min/100 mL) to 290 mL/min/100 mL. There was a nonsignificant increase in TLR from 2.7 ± 1.3 to 2.9 ± 1.4 after norepinephrine injection (P = .8). Mean peak time to maximal increase in tumor perfusion after injection was 6.1 s (range, 4.5-9.1 s). Norepinephrine injection was well tolerated without major adverse events.

CONCLUSIONS

Norepinephrine causes increased blood flow toward HCC tumors, but with a corresponding smaller increase in blood flow to noncancerous liver tissue, with no observed systemic side effects.

Beta-adrenergic receptor blockers and liver cancer mortality in a national cohort of hepatocellular carcinoma patients

Background: β-adrenergic signaling has been implicated in the pathology of hepatocellular carcinoma (HCC), but the evidence from clinical studies is limited. In this national population-based cohort study, we investigated the possible association of β-adrenergic receptor blockers and cancer-specific mortality among patients with primary HCC diagnosed in Sweden between 2006 and 2014.Methods: Patients were identified from the Swedish Cancer Register (n = 2104) and followed until 31 December 2015. We used Cox regression to evaluate the association of β-blockers dispensed within 90 days prior to cancer diagnosis, ascertained from the national Prescribed Drug Register, with liver cancer mortality identified from the Cause of Death Register, while controlling for socio-demographic factors, tumor characteristics, comorbidity, other medications and treatment procedures.Results: Over a median follow-up of 9.9 months, 1601 patients died (of whom 1309 from liver cancer). Compared with non-use, β-blocker use at cancer diagnosis [n = 714 (predominantly prevalent use, 93%)] was associated with lower liver cancer mortality [0.82 (0.72-0.94); p = .005]. Statistically significant associations were observed for non-selective [0.71 (0.55-0.91); p = .006], β1-receptor selective [0.86 [0.75-1.00); p = .049] and lipophilic [0.78 (0.67-0.90); p = .001] β-blockers. No association was observed for hydrophilic β-blockers [1.01 (0.80-1.28); p = .906] or other antihypertensive medications. Further analysis suggested that the observed lower liver cancer mortality rate was limited to patients with localized disease at diagnosis [0.82 (0.67-1.01); p = .062].Conclusion: β-blocker use was associated with lower liver cancer mortality rate in this national cohort of patients with HCC. A higher-magnitude inverse association was observed in relation to non-selective β-blocker use.

Norepinephrine-stimulated HSCs secrete sFRP1 to promote HCC progression following chronic stress via augmentation of a Wnt16B/β-catenin positive feedback loop

Background

Sustained adrenergic signaling secondary to chronic stress promotes cancer progression; however, the underlying mechanisms for this phenomenon remain unclear. Hepatocellular carcinoma (HCC) frequently develops within fibrotic livers rich in activated hepatic stellate cells (HSCs). Here, we examined whether the stress hormone norepinephrine (NE) could accelerate HCC progression by modulating HSCs activities.

Methods

HCC cells were exposed to conditioned medium (CM) from NE-stimulated HSCs. The changes in cell migration and invasion, epithelial-mesenchymal transition, parameters of cell proliferation, and levels of cancer stem cell markers were analyzed. Moreover, the in vivo tumor progression of HCC cells inoculated with HSCs was studied in nude mice subjected to chronic restraint stress.

Results

CM from NE-treated HSCs significantly promoted cell migration and invasion, epithelial-mesenchymal transition (EMT), and expression of cell proliferation-related genes and cancer stem cell markers in HCC cells. These pro-tumoral effects were markedly reduced by depleting secreted frizzled related protein 1 (sFRP1) in CM. The pro-tumoral functions of sFRP1 were dependent on β-catenin activation, and sFRP1 augmented the binding of Wnt16B to its receptor FZD7, resulting in enhanced β-catenin activity. Additionally, sFRP1 enhanced Wnt16B expression, reinforcing an autocrine feedback loop of Wnt16B/β-catenin signaling. The expression of sFRP1 in HSCs promoted HCC progression in an in vivo model under chronic restraint stress, which was largely attenuated by sFRP1 knockdown.

Conclusions

We identify a new mechanism by which chronic stress promotes HCC progression. In this model, NE activates HSCs to secrete sFRP1, which cooperates with a Wnt16B/β-catenin positive feedback loop. Our findings have therapeutic implications for the treatment of chronic stress-promoted HCC progression.

Promoter aberrant methylation status of ADRA1A is associated with hepatocellular carcinoma

The aim of our study was to explore the relationship between the methylation status of the alpha-1A adrenergic receptor (ADRA1A) gene and hepatocellular carcinoma (HCC). We combined our in-house data-set with the Cancer Genome Atlas (TCGA) data-set to screen and identify the methylation status and expression of adrenergic receptor (AR) genes in HCC. Immunohistochemistry and western blot were performed to assess the expression of ADRA1A in HCC cell lines and tissues. We further evaluated the methylation levels of the ADRA1A promoter region in 160 HCC patients using the Sequenom MassARRAY® platform and investigated the association between methylation of ADRA1A and clinical characteristics. The expression levels of ADRA1A mRNA and protein were significantly decreased in HCC tissues. Compared with that in paired normal tissues, the mean methylation level of the ADRA1A promoter region was significantly increased in tumour tissues from 160 HCC patients (25.2% vs. 17.0%, P < 0.0001). We found that a DNA methyltransferase inhibitor (decitabine) could increase the expression of ADRA1A mRNA in HCC cell lines. Moreover, hypermethylation of the ADRA1A gene in HCC samples was associated with clinical characteristics, including alcohol intake (P = 0.0097) and alpha-fetoprotein (P = 0.0411). Receiver operator characteristic (ROC) curve analysis demonstrated that the mean methylation levels of ADRA1A could discriminate between HCC tissues and adjacent non-cancerous tissues (AUC = 0.700, P < 0.0001). mRNA sequencing indicated that the main enriched pathways were pathways in cancer, cytokine-cytokine receptor interaction and metabolic pathways (P < 0.01). ADRA1A gene hypermethylation might contribute to HCC initiation and is a promising biomarker for the diagnosis of HCC.

Propranolol suppresses the proliferation and induces the apoptosis of liver cancer cells

An increasing amount of evidence indicates that the inhibition of β adrenergic signaling can result in the inhibition of tumor growth. However, the role of propranolol in liver cancer and the underlying mechanism remain to be elucidated. The present study aimed to investigate the role of propranolol in liver cancer cell lines and provide evidence for further clinical study. Propranolol was added at different concentrations to HepG2 and HepG2.2.15 liver cancer cells and HL-7702 normal human liver cells. The proliferation of the cell lines was monitored by live-cell imaging at a range of time intervals. Immunofluorescence using DAPI and Hoechst 33342/propidium iodide (PI) staining, Annexin V-FITC/PI double-staining flow cytometry, western blotting and reverse transcription-quantitative polymerase chain reaction were used to investigate the effect of propranolol on liver cancer cell apoptosis. The proliferation of HepG2 and HepG2.2.15 cells was inhibited by 40 and 80 µmol/l propranolol. However, the proliferation of HL-7702 cells was not affected by <160 µmol/l propranolol. Propranolol treatment decreased the expression of adrenergic receptor β-2 to a greater extent than adrenergic receptor β-1, and induced apoptosis in the liver cancer cells. The apoptotic rates of HepG2 and HepG2.2.15 cells increased following treatment with propranolol, while the apoptotic rate of HL-7702 cells was not affected. Propranolol promoted poly (ADP-ribose) polymerase cleavage and decreased the expression of full-length caspase-3 in liver cancer cell lines; it induced S-phase arrest in HepG2 and HepG2.2.15 cell lines, while HL-7702 cells were arrested at the G₀/G₁ phase of the cell cycle. Thus, it was demonstrated that propranolol inhibited proliferation, promoted apoptosis and induced S-phase arrest in HepG2 and HepG2.2.15 cells.

Sympathetic nervous system promotes hepatocarcinogenesis by modulating inflammation through activation of alpha1-adrenergic receptors of Kupffer cells

The sympathetic nervous system (SNS) is known to play a significant role in tumor initiation and metastasis. Hepatocellular carcinoma (HCC) frequently occurs in cirrhotic livers after chronic inflammation, and the SNS is hyperactive in advanced liver cirrhosis. However, it remains unclear whether the SNS promotes hepatocarcinogenesis by modulating chronic liver inflammation. In this study, a retrospective pathological analysis and quantification of sympathetic nerve fiber densities (tyrosine hydroxylase, TH⁺) in HCC patients, and diethylnitrosamine (DEN)-induced hepatocarcinogenesis in rats were performed. Our data showed that high density of sympathetic nerve fibers and α1-adrenergic receptors (ARs) of Kupffer cells (KCs) were associated with a poor prognosis of HCC. Sympathetic denervation or blocking of α1-ARs decreased DEN-induced HCC incidence and tumor development. In addition, synergistic effects of interleukin-6 (IL-6) and transforming growth factor-beta (TGF-β) in hepatocarcinogenesis were observed. The suppression of the SNS reduced IL-6 and TGF-β expression, which suppressed hepatocarcinogenesis, and KCs play a key role in this process. After the ablation of KCs, IL-6 and TGF-β expression and the development of HCC were inhibited. This study demonstrates that sympathetic innervation is crucial for hepatocarcinogenesis and that the SNS promotes hepatocarcinogenesis by activating α1-ARs of KCs to boost the activation of KCs and to maintain the inflammatory microenvironment. These results indicate that sympathetic denervation or α1-ARs blockage may represent novel treatment approaches for HCC.

β2-adrenergic receptor activation promotes the proliferation of A549 lung cancer cells via the ERK1/2/CREB pathway

Lung cancer is one of the most common cancers worldwide and accounts for 28% of all cancer-related deaths. The expression of the β2‑adrenergic receptor (β2‑AR), one of the stress‑inducible receptors, has been reported to be closely correlated with malignant tumors. However, the role of β2‑AR activation in human lung epithelial‑derived cancer A549 cells and the underlying mechanisms are not fully understood. In the present study, we found that activation of β2‑AR but not β1‑AR promoted the proliferation of A549 cells. Isoproterenol (ISO) stimulation of β2‑AR induced extracellular signal‑regulated kinase 1/2 (ERK1/2) and cyclic adenosine monophosphate response element‑binding protein (CREB) phosphorylation. Blocking the ERK1/2 pathway by U0126 inhibited CREB phosphorylation and also suppressed A549 cell proliferation. Moreover, ISO treatment enhanced the expression of matrix metalloproteinase (MMP) family proteins such as MMP‑2, MMP‑9, and also vascular endothelial growth factor (VEGF), which were able to be blocked by knockdown of CREB. In conclusion, our data revealed that β2‑AR induced ERK1/2 phosphorylation which in turn activated CREB to promote A549 cell proliferation. These findings elucidate potential therapeutic targets for lung cancer treatment.

Disrupting circadian homeostasis of sympathetic signaling promotes tumor development in mice

Background

Cell proliferation in all rapidly renewing mammalian tissues follows a circadian rhythm that is often disrupted in advanced-stage tumors. Epidemiologic studies have revealed a clear link between disruption of circadian rhythms and cancer development in humans. Mice lacking the circadian genes Period1 and 2 (Per) or Cryptochrome1 and 2 (Cry) are deficient in cell cycle regulation and Per2 mutant mice are cancer-prone. However, it remains unclear how circadian rhythm in cell proliferation is generated in vivo and why disruption of circadian rhythm may lead to tumorigenesis.

Methodology/Principal Findings

Mice lacking Per1 and 2, Cry1 and 2, or one copy of Bmal1, all show increased spontaneous and radiation-induced tumor development. The neoplastic growth of Per-mutant somatic cells is not controlled cell-autonomously but is dependent upon extracellular mitogenic signals. Among the circadian output pathways, the rhythmic sympathetic signaling plays a key role in the central-peripheral timing mechanism that simultaneously activates the cell cycle clock via AP1-controlled Myc induction and p53 via peripheral clock-controlled ATM activation. Jet-lag promptly desynchronizes the central clock-SNS-peripheral clock axis, abolishes the peripheral clock-dependent ATM activation, and activates myc oncogenic potential, leading to tumor development in the same organ systems in wild-type and circadian gene-mutant mice.

Conclusions/Significance

Tumor suppression in vivo is a clock-controlled physiological function. The central circadian clock paces extracellular mitogenic signals that drive peripheral clock-controlled expression of key cell cycle and tumor suppressor genes to generate a circadian rhythm in cell proliferation. Frequent disruption of circadian rhythm is an important tumor promoting factor.

Alpha1-and beta2-adrenoceptors in the human liver with mass-forming intrahepatic cholangiocarcinoma: density and coupling to adenylate cyclase and phospholipase C

Besides the regulation of hepatic metabolic pathways in which adrenoceptors are mainly involved, their effect on the second messenger cAMP is thought to be related to the growth and differentiation of neoplastic cells. However, few studies have been done on the status of these structures in the human liver affected by cholangiocarcinoma (CC). Thus, in this study, changes in densities of alpha1- and beta2-adrenoceptors (alpha1-and beta2-ARs) were investigated in membranes of human liver with cholangiocarcinoma, and for comparison, in membranes of non-adjacent non-tumour liver using the potent antagonists [3H]-prazosin and [1I]-iodocyanopindolol (ICYP) respectively. In addition, the activity of membrane-bound phospholipase C (PLC) and adenylate cyclase (AC) was also studied. In CC liver, the density of alpha1-and beta2-ARs was significantly reduced, compared with non-tumour liver tissues (alpha1-ARs: 23.38+/-4.69 vs 80.35+/-10.52, P=0.0002 beta2-ARs: 14.27+/-2.93 vs 33.22+/-4.32 fmol/mg protein, P=0.03), whereas the ligand affinities (KD) remained unchanged. The beta2-selective antagonist ICI 118,551 was about 100 times more potent in inhibiting ICYP binding than the beta1-selective antagonist CGP 20712A; thus, more than 98% of the beta-ARs were of the beta2-subtypes. The AC activity upon stimulants acting on beta-AR (isoprenaline), G-protein (GTP, NaF) and AC (forskolin) was decreased in CC liver. Similarly, noradrenaline-stimulated PLC activity was significantly reduced in tumour tissues. In conclusion, in CC liver the alpha1- and beta2-ARs density was down-regulated and the neoplastic invasion blunted AC and PLC activity. These quantitative changes may help to elucidate not fully understood pathogenetic mechanisms of disturbed hepatic metabolic processes, such as hypoglycemia during cancer in human liver.

Colorectal cancer metastases affect the biochemical characteristics of the human liver beta-adrenoceptor-G-protein-adenylate cyclase system

The sympathetic-catecholamine system is involved in the regulation of hepatic metabolic pathways mainly through cAMP-linked beta2-adrenoceptors (beta2-ARs) in humans and to a lesser extent through cAMP-independent mechanisms, but no information is available about the possible biochemical changes of beta2-ARs and their signalling pathways in human colorectal cancer (CRC) and colorectal cancer hepatic metastases (CRCHM). Changes in density and distribution of beta-ARs as well as in post-receptor signalling components were studied in membranes of human liver with CRCHM, and for comparison, in membranes of nonadjacent, non-metastatic human liver (NA-NM) obtained from 13 patients, using binding and competition binding studies. Studies were also carried out using normal and cancerous human colon tissues. In CRCHM, the density of beta-ARs (B(max)) was significantly reduced, compared to NA-NM liver tissues (40.09+/-2.83 vs. 23.09+/-3.24 fmol/mg protein; P<0.001). A similar decrease in the beta-AR density was observed in the colon with primary colorectal cancer compared to healthy colon (37.6+/-2.2 vs. 23.8+/-3.5 fmol/mg protein), whereas the affinity of ICYP binding to the receptor remained unaffected. Desensitized beta-ARs were uncoupled from stimulatory G-protein (G(S)), as total density of beta-adrenoceptors in the high affinity state was significantly reduced. Concomitantly, CRCHM elicited decrease in the catalytic adenylate cyclase (AC) activity (cAMP formation) in response to isoproterenol plus GTP or forskolin or NaF. In NA-NM and CRCHM liver, the inhibition-concentration curves of ICI 118.551 showed the presence of a homogeneous population of the beta2-AR subtypes. Neither the binding patterns nor the inhibition constant (K(i)) of ICI 118.551 were altered in CRCHM. In CRCHM, the hepatic beta-AR-G-protein(s)-AC signalling system was markedly impaired, thus, these changes may well influence beta-AR-mediated functions in both organs.

Activation of mitogen-activated protein kinases is required for alpha1-adrenergic agonist-induced cell scattering in transfected HepG2 cells

Activation of alpha1B-adrenergic receptors ((alpha1B)AR) by phenylephrine (PE) induces scattering of HepG2 cells stably transfected with the (alpha1B)AR (TFG2 cells). Scattering was also observed after stimulation of TFG2 cells with phorbol myristate acetate (PMA) but not with hepatocyte growth factor/scatter factor, epidermal growth factor, or insulin. PMA but not phenylephrine rapidly activated PKCalpha in TFG2 cells, and the highly selective PKC inhibitor bisindolylmaleimide (GFX) completely abolished PMA-induced but not PE-induced scattering. PE rapidly activated p44/42 mitogen-activated protein kinase (MAPK), p38 MAPK, c-Jun N-terminal kinase (JNK), and AP1 (c-fos/c-jun). Selective blockade of p42/44 MAPK activity by PD98059 or by transfection of a MEK1 dominant negative adenovirus significantly inhibited the PE-induced scattering of TFG2 cells. Selective inhibition of p38 MAPK by SB203850 or SB202190 also blocked PE-induced scattering, whereas treatment of TFG2 cells with the PI3 kinase inhibitors LY294002 or wortmannin did not inhibit PE-induced scattering. Blocking JNK activation with a dominant negative mutant of JNK or blocking AP1 activation with a dominant negative mutant of c-jun (TAM67) significantly inhibited PE-induced cell scattering. These data indicate that PE-induced scattering of TFG2 cells is mediated by complex mechanisms, including activation of p42/44 MAPK, p38 MAPK, and JNK. Cell spreading has been reported to play important roles in wound repair, tumor invasion, and metastasis. Therefore, catecholamines acting via the (alpha1)AR may modulate these physiological and pathological processes.

Patterns of adrenoceptor change during liver regeneration of the Wistar Kyoto rat: a binding study

BACKGROUND

Adrenoceptors have been involved in the regulation of hepatocyte proliferation after partial hepatectomy, as well as in primary culture. This report characterizes alpha 1- and beta-adrenoceptor change during the time-course of liver regeneration in adult Wistar Kyoto rats.

METHODS

Saturation binding assays with [3H]prazosin or [3H]dihydroalprenolol (for alpha 1- and beta-adrenoceptors, respectively) were done in liver plasma membranes from 6-month-old rats subjected to 70% hepatectomy followed by hepatic regeneration.

RESULTS

[3H]Prazosin and [3H]dihydroalprenolol binding gave control Bmax values of 101 +/- 10 and 12 +/- 1 fmol/mg protein and Kd of 0.50 +/- 0.10 and 4.1 +/- 0.4 nM for alpha 1- and beta-adrenoceptors, respectively. alpha 1-Adrenoceptor number and Kd increased at 24 and 48 h and returned to control values at 72 and 96 h after surgery, whereas beta-adrenoceptors augmented at 48 and 72 h, with a Kd change at 24 and 48 h posthepatectomy.

CONCLUSIONS

These results suggest that dual control of alpha 1- and beta-adrenoceptor membrane expression could be involved in different steps during hepatocyte proliferation, and that Wistar Kyoto rats have a different adrenoceptor pattern expression from other rat strains.

beta2-adrenergic receptor-selective agonist clenbuterol prevents Fas-induced liver apoptosis and death in mice

Stimulation of the cAMP-signaling pathway modulates apoptosis in several cell types and inhibits Jo2-mediated apoptosis in cultured rat hepatocytes. No information is yet available as to whether the hepatic beta2-adrenergic receptor (AR) expression level, including beta2-AR-dependent adenylyl cyclase activation, modulates hepatocyte sensitivity to apoptosis in vivo or whether this sensitivity can be modified by beta2-AR ligands. We have examined this using C57BL/6 mice, in which hepatic beta2-AR densities are low, and transgenic F28 mice, which overexpress beta2-ARs and have elevated basal liver adenylyl cyclase activity. The F28 mice were resistant to Jo2-induced liver apoptosis and death. The beta-AR antagonist propranolol sensitized the F28 livers to Jo2. In normal mice clenbuterol, a beta2-AR-specific agonist, considerably reduced Jo2-induced liver apoptosis and death; salbutamol, another beta2-AR-selective agonist, also reduced Jo2-induced apoptosis and retarded death but with less efficacy than clenbuterol; and propranolol blocked the protective effect of clenbuterol. This indicates that the expression level of functional beta2-ARs modulates Fas-regulated liver apoptosis and that this apoptosis can be inhibited in vivo by giving beta2-AR agonists. This may well form the basis for a new therapeutic approach to diseases involving abnormal apoptosis.

Alpha-adrenergic inhibition of proliferation in HepG2 cells stably transfected with the alpha1B-adrenergic receptor through a p42MAPkinase/p21Cip1/WAF1-dependent pathway

Activation of alpha1B adrenergic receptors (alpha(1B)AR) promotes DNA synthesis in primary cultures of hepatocytes, yet expression of alpha(1B)AR in hepatocytes rapidly declines during proliferative events. HepG2 human hepatoma cells, which do not express alpha(1B)AR, were stably transfected with a rat alpha1B(AR) cDNA (TFG2 cells), in order to study the effects of maintained alpha(1B)AR expression on hepatoma cell proliferation. TFG2 cells had a decreased rate of growth compared to mock transfected HepG2 cells as revealed by a decrease in [3H]thymidine incorporation into DNA. Stimulation of alpha(1B)AR with phenylephrine caused a further large reduction in TFG2 cell growth, whereas no effect on growth was observed in mock transfected cells. Reduced cell growth correlated with increased percentages of cells found in G0/G1 and G2/M phases of the cell cycle. In TFG2 cells, phenylephrine increased p42MAPkinase activity by 1.5- to 2.0-fold for up to 24 h and increased expression of the cyclin dependent kinase inhibitor protein p21Cip1/WAF1. Treatment of TFG2 cells with the specific MEKI inhibitor PD98059, or infection with a -/- MEK1 recombinant adenovirus permitted phenylephrine to increase rather than decrease [3H]thymidine incorporation. In addition, inhibition of MAP kinase signaling by PD98059 or MEK1 -/- blunted the ability of phenylephrine to increase p21Cip1/WAF1 expression. In agreement with a role for increased p21Cip1/WAF1 expression in causing growth arrest, infection of TFG2 cells with a recombinant adenovirus to express antisense p21Cip1/WAF1 mRNA blocked the ability of phenylephrine to increase p21Cip1/WAF1 expression and to inhibit DNA synthesis. Antisense p21Cip1/WAF1 permitted phenylephrine to stimulate DNA synthesis in TFG2 cells, and abrogated growth arrest. These results suggest that transformed hepatocytes may turn off the expression of alpha1B(ARs) in order to prevent the activation of a growth inhibitory pathway. Activation of this inhibitory pathway via alpha1B(AR) appears to be p42MAPkinase and p21Cip1/WAF1 dependent.

Transcriptional regulation of alpha(1b) adrenergic receptors (alpha(1b)AR) by nuclear factor 1 (NF1): a decline in the concentration of NF1 correlates with the downregulation of alpha(1b)AR gene expression in regenerating liver

The 5' upstream region from --490 to --540 (footprint II) within the dominant P2 promoter of the rat alpha(1b) adrenergic receptor (alpha(1b)AR) gene is recognized by a sequence-specific DNA-binding protein (B. Gao, M. S. Spector, and G. Kunos, J. Biol. Chem. 270:5614-5619, 1995). This protein, detectable in Southwestern (DNA-protein) blots of crude nuclear extracts as 32- and 34-kDa bands, has been purified 6,000-fold from rat livers by DEAE-Sepharose, heparin-Sepharose, and DNA affinity chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and UV cross-linking of the purified protein indicated the same molecular mass as that in crude extracts. Methylation interference analysis revealed strong contact with a TTGGCT hexamer and weak contact with a TGGCGT hexamer in the 3' and 5' portions of footprint II, respectively. Nucleotide substitutions within these hexamers significantly reduced protein binding to footprint II and the promoter activity of P2 in Hep3B cells. The purified protein also bound to the nuclear factor 1 (NF1)/CTF consensus sequence, albeit with lower affinity. Gel mobility supershift and Western blotting (immunoblotting) analyses using an antibody against the NF1/CTF protein identified the purified 32- and 34-kDa polypeptides as NF1 or a related protein. Cotransfection into Hep3B cells or primary rat hepatocytes of cDNAs of the NF1-like proteins NF1/L, NF1/X, and NF1/Redl resulted in a three- to fivefold increase in transcription directed by wild-type P2 but not by the mutated P2. Partial hepatectomy markedly decreased the levels of NF1 in the remnant liver and its binding to P2, which paralleled declines in the rate of transcription of the alpha(1b)AR gene and in the steady-state levels of its mRNA. These observations indicate that NF1 activates transcription of the rat alpha(1b)AR gene via interacting with its P2 promoter and that a decline in the expression of NF1 is one of the mechanisms responsible for the reduced expression of the alpha(1b)AR gene during liver regeneration.

Nimesulide decreases superoxide production by inhibiting phosphodiesterase type IV

Nimesulide, the prototype of a new class of anti-inflammatory drugs, dose-dependently decreases the production of the superoxide anion (O2-.) in N-formyl-methionyl-leucyl-phenylalanine (fMLP)- and in phorbol myristate acetate (PMA)-stimulated polymorphonuclear leukocytes. The inhibition of O2-. is possibly related to its inhibitory effect on polymorphonuclear leukocyte cytosolic phosphodiesterase type IV (IC50 = 39 +/- 2 microM), to the related increase in cAMP (P < 0.01 at 1 microM) and the subsequent increase in protein kinase A activity. In fact H-89, a specific protein kinase A inhibitor, counteracts the inhibitory effect of nimesulide on O2-. production by fMLP and PMA. The activation of protein kinase A may prompt the phosphorylation of a number of substrates, thus inhibiting the assembly of NADPH-oxidase in the plasma membrane. Accordingly, nimesulide decreases PMA-induced assembly of NADPH-oxidase in polymorphonuclear leukocytes plasma membranes by about 35%. Protein kinase A activation may also interfere with chemotaxis. Nimesulide inhibits stimulated chemotaxis and the effect is decreased by H-89. Inhibition of phosphodiesterase type IV may explain many of nimesulide's effects.

Rapid inverse changes in alpha 1B- and beta 2-adrenergic receptors and gene transcripts in acutely isolated rat liver cells

In vitro incubation of hepatocytes acutely isolated from adult male rats leads to a rapid conversion of the adrenergic activation of glycogenolysis from an alpha 1-receptor (alpha 1AR) to a beta 2-receptor (beta 2AR) mediated response within 4 h. In order to understand the underlying mechanism, we examined time-dependent changes in alpha 1- and beta 2-adrenergic activation of glycogenolysis and second messenger systems, the cellular density and affinity of alpha 1AR and beta 2AR, and the steady state levels of alpha 1BAR and beta 2AR mRNAs. Incubation of hepatocytes for 4 h resulted in a decrease in phosphorylase activation and inositol 1,4,5 trisphosphate accumulation in response to phenylephrine, a 40% decrease in alpha 1AR density, and a 70% decrease in alpha 1BAR mRNA levels. Incubation of hepatocytes for 4 h also resulted in the emergence of a phosphorylase response to isoproterenol, an increase in isoproterenol-induced but not in glucagon- or forskolin-induced cAMP accumulation, no significant change in beta 2AR density, and a twofold increase in beta 2AR mRNA levels. Exposure of cells to cycloheximide, 2 microM throughout the 4 h incubation, prevented the emergence of the phosphorylase response to isoproterenol and reduced beta 2AR densities, while the decrease in alpha 1AR density was not affected and the decrease in phosphorylase activation by phenylephrine was attenuated. The results indicate that dissociation of rat liver cells triggers a rapidly developing decrease in alpha 1BAR mRNA and increase in beta 2AR mRNA levels and corresponding inverse changes in the synthesis of alpha 1BAR and beta 2AR which account, at least in part, for the rapid conversion from alpha 1- to beta 2-adrenergic glycogenolysis.