α1 -Adrenergic receptor-induced cytoskeletal organization and cell motility in CCL39 fibroblasts requires phospholipase D1

Stimulation of alpha-1 adrenoceptors may intensify cutaneous inflammation in complex regional pain syndrome

ABSTRACT

Alpha-1 adrenoceptors are overexpressed in the epidermis of a subgroup of patients with complex regional pain syndrome (CRPS). Activating α 1 -adrenoceptors in epidermal cells increases production of the proinflammatory cytokine interleukin-6 (IL-6), a mediator of inflammation. To investigate whether this might exacerbate inflammation in CRPS, primary keratinocytes or dermal fibroblasts were cultured from skin biopsies obtained from the affected limb of 25 patients and a similar site in 28 controls. The fundamental proinflammatory cytokine, tumor necrosis factor alpha, was administered for 24 hours to initiate inflammation. After this, cells were incubated for 6 hours with the α 1 -adrenoceptor agonist phenylephrine. Exposure to tumor necrosis factor alpha induced proinflammatory cytokine mRNA production and protein secretion in keratinocytes and fibroblasts and enhanced α 1B -adrenoceptor mRNA expression in keratinocytes. Additional stimulation of α 1 adrenoceptors with phenylephrine increased the production of IL-6 mRNA and protein secretion in both cell types. Under all conditions, gene and protein α 1 -adrenoceptor levels and cytokine gene expression and protein secretion were similar, overall, in patients and controls, except for abnormally high α 1 -adrenoceptor protein levels in the keratinocytes of 3 of 17 patients. These findings suggest that persistent inflammation in CRPS is not due to dysfunction of skin cells but is a normal response to extrinsic signals. After α 1 -adrenoceptor stimulation of keratinocytes, increases in IL-6 mRNA but not protein were proportional to basal α 1 -adrenoceptor protein levels. Skin cells play an important role in persistent inflammation in CRPS. Potentially, a positive feedback loop between α 1 -adrenoceptors and IL-6 production in skin cells contributes to this inflammatory state.

α1 adrenergic receptors in serum and saliva of patients with oral squamous cell carcinoma

BACKGROUND

Neurotransmitters released from the sympathetic nervous system attach to the adrenergic receptors on the surface of tumoral cells in response to stress, and alter the expression of genes programming cellular activity. This study aimed to assess the expression of α1 adrenergic receptors in the serum and saliva of patients with oral squamous cell carcinoma (OSCC) compared with healthy controls.

MATERIALS AND METHODS

In this case-control study, serum and stimulated and unstimulated saliva samples were collected from 26 OSCC patients and 26 healthy controls. ELISA kits were used for measurement of the serum and salivary levels of α1 adrenergic receptors.

RESULTS

The level of α1 adrenergic receptors was significantly higher in the stimulated and unstimulated saliva of OSCC patients than healthy controls (P = 0.000). However, their serum level was not significantly different between the two groups (P = 0.389). The serum level of α1 adrenergic receptors significantly increased by an increase in OSCC grade. No significant correlation was noted between the serum and salivary levels of α1 adrenergic receptors in OSCC patients. The salivary level of α1 adrenergic receptors was significantly higher in patients with tumors located in the gingiva, compared with other sites.

CONCLUSION

Significantly higher salivary level of α1 adrenergic receptors in OSCC patients compared with healthy controls, and no significant difference in their serum level between the two groups may indirectly indicate the over-expression of these receptors in OSCC cells, compared with normal oral mucosa. Further studies and particularly histological analyses are required to confirm this finding.

The in vitro effects of phospholipase D1-mTOR axis in liver fibrogenesis

AIMS

The activation of hepatic stellate cells (HSCs) plays a central role in liver fibrosis progression. Phospholipase D (PLD) enzymes participate in multiple cellular activities. However, whether and how PLD regulates HSCs activation remain elusive.

MAIN METHODS

The expression of intrahepatic PLD1 and PLD2 was determined in CCl₄-induced mouse liver fibrosis models by western blot and immunohistochemistry. Cell model of liver fibrogenesis was constructed using rat HSCs line (HSC-T6) treated with recombinant transforming growth factor β1 (TGFβ1). Fibrogenesis was evaluated on the aspects of proliferation, expression of pro-fibrogenic markers and migration. The effects mediated by PLD1-mTOR axis on TGFβ1-induced fibrogenesis were evaluated using HSC-T6 treated with small-molecular PLD1 inhibitors, PLD1-SiRNA, rapamycin (mTOR inhibitor) and MHY1485 (mTOR activator).

KEY FINDINGS

Significant increase of PLD1, not PLD2 was documented in CCl₄-induced cirrhotic compared to normal liver tissues. Suppression of PLD1 activities by PLD inhibitors or down-regulation of PLD1 expression in HSC-T6 could significantly restrain TGFβ1-induced fibrogenesis, as reflected by decreased cell proliferation and reduced expression of pro-fibrogenic markers. Besides, either PLD1 inhibitor or PLD1-SiRNA significantly inhibited mTOR activity of HSC-T6. Moreover, PLD1 inhibitors not only exhibited similar effects with rapamycin in TGFβ1-induced fibrogenesis, but also blunted MHY1485 enhanced cell proliferation of HSC-T6.

SIGNIFICANCE

The PLD1-mTOR axis of HSCs could be therapeutically targeted in advanced liver fibrosis.

Up-regulation of α1-adrenoceptors in burn and keloid scars

Stimulation of α₁-adrenoceptors evokes inflammatory cytokine production, boosts neurogenic inflammation and pain, and influences cellular migration and proliferation. Hence, these receptors may play a role both in normal and abnormal wound healing. To investigate this, the distribution of α₁-adrenoceptors in skin biopsies of burn scars (N=17), keloid scars (N=12) and unscarred skin (N=17) was assessed using immunohistochemistry. Staining intensity was greater on vascular smooth muscle in burn scars than in unscarred tissue, consistent with heightened expression of α₁-adrenoceptors. In addition, expression of α₁-adrenoceptors was greater on dermal nerve fibres, blood vessels and fibroblasts in keloid scars than in either burn scars or unscarred skin. These findings suggest that increased vascular expression of α₁-adrenoceptors could alter circulatory dynamics both in burn and keloid scars. In addition, the augmented expression of α₁-adrenoceptors in keloid tissue may contribute to processes that produce or maintain keloid scars, and might be a source of the uncomfortable sensations often associated with these scars.

Up-regulation of cutaneous α1-adrenoceptors after a burn

Stimulation of α1-adrenoceptors evokes inflammatory cytokine production, boosts neurogenic inflammation and pain, and influences cellular migration and proliferation. As expression of α1-adrenoceptors increases on dermal nerves and keratinocytes after peripheral nerve injury, the aim of this study was to determine whether another form of tissue injury (a cutaneous burn) triggered a similar response. In particular, changes in expression of α1-adrenoceptors were investigated on dermal nerve fibres, keratinocytes and fibroblast-like cells using immunohistochemistry 2-12 weeks after a full thickness burn in Wistar rats. Within two weeks of the burn, local increases in α1-adrenoceptor expression were seen in the re-forming epidermis, in dense bands of spindle-shaped cells in the upper dermis (putatively infiltrating immune cells and fibroblasts), and on nerve fibres in the deep dermis. In addition, nerve fibre density increased approximately three-fold in the deep dermis, and this response persisted for several more weeks. In contrast, α1-adrenoceptor labelled cells and staining intensity in the upper dermis decreased contralateral to the burn, as did nerve fibre density in the deep dermis. These findings suggest that inflammatory mediators and/or growth factors at the site of a burn trigger the synthesis of α1-adrenoceptors on resident epidermal cells and nerve fibres, and an influx of α1-adrenoceptor labelled cells. The heightened expression of α1-adrenoceptors in injured tissue could shape inflammatory and wound healing responses.

RhoA Kinase (Rock) and p90 Ribosomal S6 Kinase (p90Rsk) phosphorylation of the sodium hydrogen exchanger (NHE1) is required for lysophosphatidic acid-induced transport, cytoskeletal organization and migration

The sodium hydrogen exchanger isoform one (NHE1) plays a critical role coordinating asymmetric events at the leading edge of migrating cells and is regulated by a number of phosphorylation events influencing both the ion transport and cytoskeletal anchoring required for directed migration. Lysophosphatidic acid (LPA) activation of RhoA kinase (Rock) and the Ras-ERK growth factor pathway induces cytoskeletal reorganization, activates NHE1 and induces an increase in cell motility. We report that both Rock I and II stoichiometrically phosphorylate NHE1 at threonine 653 in vitro using mass spectrometry and reconstituted kinase assays. In fibroblasts expressing NHE1 alanine mutants for either Rock (T653A) or ribosomal S6 kinase (Rsk; S703A) we show that each site is partially responsible for the LPA-induced increase in transport activity while NHE1 phosphorylation by either Rock or Rsk at their respective site is sufficient for LPA stimulated stress fiber formation and migration. Furthermore, mutation of either T653 or S703 leads to a higher basal pH level and a significantly higher proliferation rate. Our results identify the direct phosphorylation of NHE1 by Rock and suggest that both RhoA and Ras pathways mediate NHE1-dependent ion transport and migration in fibroblasts.

Neuronal changes resulting in up-regulation of alpha-1 adrenoceptors after peripheral nerve injury

Under normal conditions, the sympathetic neurotransmitter noradrenaline inhibits the production and release of pro-inflammatory cytokines. However, after peripheral nerve and tissue injury, pro-inflammatory cytokines appear to induce the expression of the alpha1A-adrenoceptor subtype on immune cells and perhaps also on other cells in the injured tissue. In turn, noradrenaline may act on up-regulated alpha1-adrenoceptors to increase the production of the pro-inflammatory cytokine interleukin-6. In addition, the release of inflammatory mediators and nerve growth factor from keratinocytes and other cells may augment the expression of alpha1-adrenoceptors on peripheral nerve fibers. Consequently, nociceptive afferents acquire an abnormal excitability to adrenergic agents, and inflammatory processes build. These mechanisms could contribute to the development of sympathetically maintained pain in conditions such as post-herpetic neuralgia, cutaneous neuromas, amputation stump pain and complex regional pain syndrome.

Cellular and physiological roles for phospholipase D1 in cancer

Phospholipase D enzymes have long been proposed to play multiple cell biological roles in cancer. With the generation of phospholipase D1 (PLD1)-deficient mice and the development of small molecule PLD-specific inhibitors, in vivo roles for PLD1 in cancer are now being defined, both in the tumor cells and in the tumor environment. We review here tools now used to explore in vivo roles for PLD1 in cancer and summarize recent findings regarding functions in angiogenesis and metastasis.

Inside out: targeting NHE1 as an intracellular and extracellular regulator of cancer progression

The sodium hydrogen exchanger isoform one is a critical regulator of intracellular pH, serves as an anchor for the formation of cytoplasmic signaling complexes, and modulates cytoskeletal organization. There is a growing interest in the potential for sodium hydrogen exchanger isoform one as a therapeutic target against cancer. Sodium hydrogen exchanger isoform one transport drives formation of membrane protrusions essential for cell migration and contributes to the establishment of a tumor microenvironment that leads to the rearrangement of the extracellular matrix further supporting tumor progression. Here, we focus on the potential impact that an inexpensive, $100 genome would have in identifying prospective therapeutic targets to treat tumors based upon changes in gene expression and variation of sodium hydrogen exchanger isoform one regulators. In particular, we will focus on the ezrin, radixin, moesin family proteins, calcineurin B homologous proteins, Ras/Raf/MEK/ERK signaling, and phosphoinositide signaling as they relate to the regulation of sodium hydrogen exchanger isoform one in cancer progression.

Urokinase plasminogen activator receptor induced non-small cell lung cancer invasion and metastasis requires NHE1 transporter expression and transport activity

BACKGROUND: Non-small cell lung cancers (NSLC) are aggressive cancers that are insensitive to chemotherapies and accounts for nearly 33% of all cancer deaths in the United States. Two hallmarks of cancer that allow cells to invade and metastasize are sustained proliferation and enhanced motility. In this study we investigate the relationship between urokinase plasminogen activator (uPA)/uPA receptor (uPAR) signaling and Na(+)/H(+) exchanger isoform 1 (NHE1) expression and activity. METHODS AND RESULTS: The addition of 10nM uPA increased the carcinogenic potential of three NSCLC cell lines, NCI-H358, NCI-H460, and NCI-H1299. This included an increase in the rate of cell proliferation 1.6 to 1.9 fold; an increase in the percentage of cells displaying stress fibers 3.05 to 3.17 fold; and an increase in anchorage-independent growth from 1.64 to 2.0 fold. In each of these cases the increase was blocked when the experiments were performed with NHE1 inhibited by 10 μM EIPA (ethylisopropyl amiloride). To further evaluate the role of uPA/uPAR and NHE1 in tumor progression we assessed signaling events using full-length uPA compared to the uPA amino terminal fragment (ATF). Comparing uPA and ATF signaling in H460 cells, we found that both uPA and ATF increased stress fiber formation approximately 2 fold, while uPA increased matrix metalloproteinase 9 (MMP9) activity 5.44 fold compared to 2.81 fold for ATF. To expand this signaling study, two new cell lines were generated, one with reduced NHE1 expression (H460 NHE1 K/D) and one with reduced uPAR expression (H460 uPAR K/D). Using the K/D cell lines we found that neither uPA nor ATF could stimulate stress fiber formation or MMP9 activity in cells with dramatically decreased NHE1 or uPAR expression. Finally, using in vivo tumor formation studies in athymic mice we found that when mice were injected with H460 cells 80% of mice formed tumors with an average volume of 390 mm(3). This was compared to 20% of H460 uPAR K/D injected mice forming tumors with an average volume of 15 mm(3) and 10% of H460 NHE1 K/D injected mice forming tumors with an average volume of 5 mm(3). CONCLUSION: Taken together, these data demonstrate that uPA/uPAR-mediated tumor progression and metastasis requires NHE1 in NSCLC cells and suggests a potential therapeutic approach to blocking cancer progression.