TNF-α-induced CXCL8 production by A549 cells: involvement of the non-neuronal cholinergic system

Potential antiproliferative and apoptotic effects of pilocarpine combined with TNF alpha in chronic myeloid leukemia cells

Pilocarpine is a selective M₁/M₃ agonist of muscarinic acetylcholine receptor subtypes. Muscarinic acetylcholine receptors are G protein-coupled receptors. These receptors are different drug targets. The aim of the present work was to investigate the effect of pilocarpine on the expression of M₃ muscarinic acetylcholine receptor, the AChE activity, IL-8 release response, and proliferation in K562 cells, via muscarinic receptor activation. Human chronic myeloid leukemic cell cultures were incubated with drugs. Proliferation assays were performed by BrdU assay. Expression of M₃ muscarinic acetylcholine receptor and apoptosis proteins such as bcl, bax, cyt C, and caspases was assessed with the semiquantitative Western blotting method. Pilocarpine inhibits chronic myeloid cell proliferation and M₃ muscarinic acetylcholine receptor protein expression. Pilocarpine increases caspase-8 and -9 expression levels, upregulating the proapoptotic protein Bax and downregulating the expression levels of the antiapoptotic protein Bcl-2. The apoptotic activity of pilocarpine is associated with an increase in AChE activity. M₃ muscarinic acetylcholine receptors can activate multiple signal transduction systems and mediate inhibitory effects on chronic myeloid K562 cell proliferation depending on the presence of 1% FBS conditions. This apoptotic effect of pilocarpine may be due to the concentration of pilocarpine and the increase in AChE level. Our results suggest that inhibition of cell proliferation by inducing apoptosis of pilocarpine in K562 cells may be one of the targets. M₃ selective agonist may have therapeutic potential in chronic myeloid leukemia.

Huperzine A lowers intraocular pressure via the M3 mAChR and provides retinal neuroprotection via the M1 mAChR: a promising agent for the treatment of glaucoma

BACKGROUND

Glaucoma is a neurodegenerative disease that shares similar pathological mechanisms with Alzheimer's disease (AD). Drug treatments for glaucoma increasingly rely upon both lowering of intraocular pressure (IOP) and optic nerve protection, as lowering of IOP alone has been unsatisfactory. Huperzine A (HupA) is an acetylcholinesterase inhibitor (AChEI) used for AD. This study investigated the potential of HupA as a treatment for glaucoma.

METHODS

The ability of HupA to lower IOP via causing pupil constriction was assessed using New Zealand rabbits. The retinal neuroprotective effects of HupA were assessed in vivo using rat retinas subjected to ischemia-reperfusion (I/R) and in vitro using primary retinal neurons (PRNs) suffering from oxygen-glucose deprivation (OGD).

RESULTS

HupA caused pupil constriction in a dose-time dependent manner which was reversed by the nonselective muscarinic acetylcholine receptor (mAChR) antagonist atropine and the selective M3 mAChR antagonist 4-DAMP. However, HupA had no effect on isolated iris muscle tension and calcium flow indicating an indirect M3 mAChR mediated effect. HupA exerted a neuroprotective effect against I/R and OGD to attenuate the retinal pathological lesion, improve retinal neuronal cell viability, reverse oxidative stress injury by increasing GSH levels and SOD activity, and decreasing MDA content and reduce the retinal neuronal apoptosis by decreasing Bax/Bcl-2 ratio and caspase-3 expression with no effect on the calcium flow tests. The effects were abolished by atropine and the selective M1 mAChR antagonist pirenzepine in OGD-induced PRNs suggesting an indirect M1 mAChR-mediated effect via inhibiting AChE activity to increase endogenous ACh level. Furthermore, HupA increased phosphorylated AKT level and decreased the levels of phosphorylated JNK, P38 MAPK and ERK via M1 mAChR antagonists indicating an involvement of activating the M1 mAChR and the downstream AKT/MAPK signaling pathway in the protective effects of HupA.

CONCLUSIONS

HupA could significantly decrease IOP via activating M3 mAChR indirectly and produce retinal neuroprotective effect through M1 mAChR/AKT/MAPK by increasing endogenous ACh level. These investigations demonstrated that HupA was an effective drug in glaucoma treatment and the clinical application of HupA and other AChEIs for glaucoma patients should be further investigated.

TNFα induces tolerant production of CXC chemokines in colorectal cancer HCT116 cells via A20 inhibition of ERK signaling

Ubiquitin editing enzyme A20 functions as a tumor suppressor in various cancer. However, the mechanism for A20 regulation of cancer progress is not fully understood. In this study, we found that in human colorectal cancer HCT116 cells, TNFα induced a tolerant production of CXC chemokines, including CXCL1, 2, and 8 in a dose and time dependent manner. TNFα pre-treatment of HCT116 cells down-regulated the chemokine production induced by TNFα re-treatment. TNFα induced the phosphorylation of MAPKs ERK, JNK, P38 and NF-κB P65, but only ERK inhibition decreased TNFα-induced chemokine production. Both RT-PCR and FACS results showed that TNFα treatment did not regulate the expression of TNF receptors. However, TNFα up-regulated the expression of A20 at both mRNA and protein levels significantly. TNFα pre-treatment inhibited the signal transduction of MAPKs induced by TNFα re-stimulation, and A20 over-expression decreased the signal transduction of ERK and P38. Meanwhile, A20 inhibition by RNA interference reversed chemokine down-regulation induced by TNFα re-stimulation after TNFα pre-treatment. Taken together, these results suggested that in human colorectal cancer cells, A20 may function to inhibit cancer progression via down-regulation of TNFα-induced chemokine production by suppression of ERK signaling.

Scavenging reactive oxygen species inhibits status epilepticus-induced neuroinflammation

Inflammation has been identified as an important mediator of seizures and epileptogenesis. Understanding the mechanisms underlying seizure-induced neuroinflammation could lead to the development of novel therapies for the epilepsies. Reactive oxygen species (ROS) are recognized as mediators of seizure-induced neuronal damage and are known to increase in models of epilepsies. ROS are also known to contribute to inflammation in several disease states. We hypothesized that ROS are key modulators of neuroinflammation i.e. pro-inflammatory cytokine production and microglial activation in acquired epilepsy. The role of ROS in modulating seizure-induced neuroinflammation was investigated in the pilocarpine model of temporal lobe epilepsy (TLE). Pilocarpine-induced status epilepticus (SE) resulted in a time-dependent increase in pro-inflammatory cytokine production in the hippocampus and piriform cortex. Scavenging ROS with a small-molecule catalytic antioxidant decreased SE-induced pro-inflammatory cytokine production and microglial activation, suggesting that ROS contribute to SE-induced neuroinflammation. Scavenging ROS also attenuated phosphorylation of ribosomal protein S6, the downstream target of the mammalian target of rapamycin (mTOR) pathway indicating that this pathway might provide one mechanistic link between SE-induced ROS production and inflammation. Together, these results demonstrate that ROS contribute to SE-induced cytokine production and antioxidant treatment may offer a novel approach to control neuroinflammation in epilepsy.

Combination of glycopyrronium and indacaterol inhibits carbachol-induced ERK5 signal in fibrotic processes

Background

Airway fibrosis is one of the pathological features of chronic obstructive pulmonary disease (COPD), and recent studies revealed that acetylcholine plays an important role in the development of airway remodeling by stimulating proliferation and collagen synthesis of lung fibroblasts. This study was designed to examine the effects of a long-acting muscarinic receptor antagonist (LAMA) glycopyrronium and a long-acting β2 adrenergic receptor agonist (LABA) indacaterol on acetylcholine-mediated fibrotic responses in lung fibroblasts.

Methods

After carbachol (CCh) or transforming growth factor-β1 (TGF-β1) exposure, the response to glycopyrronium and indacaterol was determined in vitro in fibroblasts isolated from mild-to-moderate COPD lung tissue. The ability of fibroblasts to mediate the contraction of collagen gels was assessed. The expression of α-smooth muscle actin (α-SMA) and the phosphorylation of extracellular-signal-regulated kinase 5 (ERK5) were determined by immunoblot. TGF-β1 was quantified by ELISA and acetylcholine was quantified by liquid chromatography tandem-mass spectrometry.

Results

CCh stimulated fibroblast-mediated collagen gel contraction and α-SMA expression and TGF-β1 release by fibroblasts. Blockade of autocrine TGF-β1 attenuated CCh-mediated fibrotic responses, while TGF-β1 did not stimulate acetylcholine release. Glycopyrronium plus indacaterol significantly attenuated CCh- and TGF-β1-mediated fibrotic responses through inhibition of ERK5 phosphorylation. Notably, the magnitudes of CCh- and TGF-β1-stimulated gel contraction, CCh-induced TGF-β1 release, and ERK5 phosphorylation were greater in fibroblasts isolated from COPD subjects than in those from non-smokers.

Conclusions

CCh induced TGF-β1 self-sustaining signaling loops by potentiating ERK5 signaling and promoted myofibroblast activity. This autocrine signaling mechanism may be an attractive therapeutic target to block the fibrotic response, which was modulated by the combination of glycopyrronium and indacaterol.

Carbocisteine attenuates TNF-α-induced inflammation in human alveolar epithelial cells in vitro through suppressing NF-κB and ERK1/2 MAPK signaling pathways

AIM

We previously proven that carbocisteine, a conventional mucolytic drug, remarkably reduced the rate of acute exacerbations and improved the quality of life in the patients with chronic obstructive pulmonary disease. In this study we investigated the mechanisms underlying the anti-inflammatory effects of carbocisteine in human alveolar epithelial cells in vitro.

METHODS

Human lung adenocarcinoma cell line A549 was treated with TNF-α (10 ng/mL). Carbocisteine was administered either 24 h prior to or after TNF-α exposure. The cytokine release and expression were measured using ELISA and qRT-PCR. Activation of NF-κB was analyzed with Western blotting, immunofluorescence assay and luciferase reporter gene assay. The expression of ERK1/2 MAPK signaling proteins was assessed with Western blotting.

RESULTS

Carbocisteine (10, 100, 1000 μmol/L), administered either before or after TNF-α exposure, dose-dependently suppressed TNF-α-induced inflammation in A549 cells, as evidenced by diminished release of IL-6 and IL-8, and diminished mRNA expression of IL-6, IL-8, TNF-α, MCP-1 and MIP-1β. Furthermore, pretreatment with carbocisteine significantly decreased TNF-α-induced phosphorylation of NF-κB p65 and ERK1/2 MAPK, and inhibited the nuclear translocation of p65 subunit in A549 cells. In an NF-κB luciferase reporter system, pretreatment with carbocisteine dose-dependently inhibited TNF-α-induced transcriptional activity of NF-κB.

CONCLUSION

Carbocisteine effectively suppresses TNF-α-induced inflammation in A549 cells via suppressing NF-κB and ERK1/2 MAPK signaling pathways.

The activation of M3 mAChR in airway epithelial cells promotes IL-8 and TGF-β1 secretion and airway smooth muscle cell migration

BACKGROUND

Muscarinic acetylcholine receptors (mAChRs) have been identified in airway epithelium, and epithelium-derived chemokines can initiate the migration of airway smooth muscle (ASM) cells. However, the mAChRs that are expressed in airway epithelium and the mechanism underlying the regulation of ASM cell migration are not clear. The aim of this study was to test whether the effects of the epithelium-derived chemokines on ASM cell migration could be modulated by mAChRs.

METHOD

Human epithelial cells (A549 cells) were stimulated with cigarette smoke extract (CSE) or the mAChRs agonist carbachol. IL-8 and TGF-β1 production were measured by ELISA, and human ASM cell migration was measured using the transwell migration assay and scratch assay. The mRNA levels of the mAChRs subtypes and the acetylcholine concentrations were measured using RT-PCR and LC-MS/MS, respectively.

RESULTS

ASM cell migration toward CSE-stimulated A549 cells was markedly reduced by Ac-RRWWCR-NH2 (IL-8 inhibitor) and SB431542 (TGF-β1 inhibitor). CSE-induced ASM cell migration was also suppressed by the mAChRs antagonist tiotropium. Interestingly, carbachol-stimulated A549 cells also induced ASM cell migration; this migration event was suppressed by tiotropium, Ac-RRWWCR-NH2 and SB431542. In addition, the effects of CSE on ASM cell migration were significantly and cooperatively enhanced by carbachol compared to CSE alone. Carbachol-induced ASM cell migration was reduced by selective inhibitors of PI3K/Akt (LY294002) and p38 (SB203580), suggesting that it occurred through p38 and Akt phosphorylation, which was inhibited by the M3 mAChR antagonist 4-DAMP.

CONCLUSIONS

These findings indicate that M3 mAChR may be important therapeutic target for obstructive airway diseases, as it regulates the effects of the epithelial-derived chemokines on ASM cell migration, which results in lung remodeling.

A20 regulates IL-1-induced tolerant production of CXC chemokines in human mesangial cells via inhibition of MAPK signaling

Chemokines and chemokine receptors are involved in the resolution or progression of renal diseases. Locally secreted chemokines mediated leukocyte recruitment during the initiation and amplification phase of renal inflammation. However, the regulation of chemokine induction is not fully understood. In this study, we found that IL-1 induced a significant up-regulation of CXC chemokines CXCL1, 2, and 8 at both mRNA and protein levels in human mesangial cells. The induction of chemokines was tolerant, as the pre-treatment of HMC with IL-1 down-regulated the induction of chemokines induced by IL-1 re-stimulation. IL-1 up-regulated the ubiquintin-editing enzyme A20. A20 over-expression down-regulated IL-1-induced up-regulation of chemokines, and A20 down-regulation reversed chemokine inhibition induced by IL-1 pre-treatment, suggested that A20 played important roles in the tolerant production of chemokines. Unexpectedly, A20 over- expression inhibited the activation of ERK, JNK, and P38, but did not inhibit the activation of NF-κB. In addition, both IL-1 treatment and A20 over-expression induced the degradation of IRAK1, an important adaptor for IL-1R1 signaling, and A20 inhibition by RNA interference partly reversed the degradation of IRAK1. Taken together, IL-1-induced A20 negatively regulated chemokine production, suggesting that A20 may be an important target for the prevention and control of kidney inflammation.

V0162 a new long-acting bronchodilator for treatment of chronic obstructive lung diseases: preclinical and clinical results

Background

Long acting bronchodilators are the standard of care in the management of chronic obstructive pulmonary disease (COPD). The aim of this study was to investigate the efficacy and safety of V0162, a novel anticholinergic agent with bronchodilator properties, in preclinical models and in patients with COPD.

Methods

Guinea pigs were used to evaluate the impact of V0162 on the acetylcholine or histamine-induced bronchoconstriction. V0162 was also investigated in an allergic asthma model on ovalbumin-sensitized guinea pig. For clinical investigations, healthy volunteers were included in a dose-escalation, randomized, placebo-controlled phase I study to determine the maximal tolerated dose, followed by a randomized, placebo-controlled, cross-over phase II study in patients with COPD. V0162 was given via inhalation route. The objectives of the phase I/II study were to assess the safety and efficacy of V0162, in terms of bronchodilation and reduction in hyperinflation.

Results

Preclinical results showed that V0162 was able to prevent bronchoconstriction induced either by acetylcholine or histamine. V0162 reversed the bronchoconstriction and airway inflammation caused by ovalbumin challenge in sensitized guinea pigs. In the healthy volunteers study, 88 subjects were enrolled: 66 received V0162 and 22 received placebo. No particular safety concerns were raised. The maximal tolerated dose was not reached and the dose escalation was stopped at 2400 μg. A total of 20 patients with COPD were then enrolled. All patients received a single-dose of V0162 1600 μg and of placebo in two alternating periods. In COPD patients, V0162 demonstrated a significant increase in FEV₁ compared with placebo (148 ± 137 ml vs. 36 ± 151 ml, p = 0.003). This bronchodilatory effect was corroborated by a reduction in hyperinflation. There was a trend toward dyspnea relief (change in visual analog scale at 22 h, −15.1 ± 26.0 mm vs.- 5.3 ± 28.8 mm with placebo, p = 0.054). No serious adverse events (AEs) were reported. Most common AEs were productive and non-productive cough, dyspnea and pruritus.

Conclusions

V0162 improved pulmonary function and tended to improve dyspnea in patients with COPD over more than 24 h. The slight plasmatic exposure observed might support the good safety profile.

Trial registration

ClinicalTrials.gov identifier: NCT01348555

The acetylcholine signaling network of corneal epithelium and its role in regulation of random and directional migration of corneal epithelial cells

PURPOSE

Because cholinergic drugs are used in ophthalmology and cholinergic stimulation has been shown to facilitate epithelialization of mucocutaneous wounds, we performed a systematic analysis of components of the cholinergic network of human and murine corneal epithelial cells (CECs) and determined the role of autocrine and paracrine acetylcholine (ACh) in regulation of CEC motility.

METHODS

We investigated the expression of ACh receptors at the mRNA and protein levels in human immortalized CECs, localization of cholinergic molecules in normal and wounded murine cornea, and the effects of cholinergic drugs on CEC directional and random migration in vitro, intercellular adhesion, and expression of integrin αV and E-cadherin.

RESULTS

We demonstrated that corneal epithelium expresses the ACh-synthesizing enzyme choline acetyltransferase, the ACh-degrading enzyme acetylcholinesterase, two muscarinic ACh receptors (mAChRs), M3 and M4, and several nicotinic ACh receptors (nAChRs), including both α7- and α9-made homomeric nAChRs and predominantly the α3β2±α5 subtype of heteromeric nAChRs. Wounding affected the expression patterns of cholinergic molecules in the murine corneal epithelium. Constant stimulation of CECs through both muscarinic and nicotinic signaling pathways was essential for CEC survival and both directional and random migration in vitro. Both α7 and non-α7 nAChRs elicited chemotaxis, with the α7 signaling exhibiting a stronger chemotactic effect. Cholinergic stimulation of CECs upregulated expression of the integrin and cadherin molecules involved in epithelialization. We found synergy between the proepithelialization signals elicited by different ACh receptors expressed in CECs.

CONCLUSIONS

Simultaneous stimulation of mAChRs and nAChRs by ACh may be required to synchronize and balance ionic and metabolic events in a single cell. Localization of these cholinergic enzymes and receptors in murine cornea indicated that the concentration of endogenous ACh and the mode of its signaling differ among corneal epithelial layers. Elucidation of the signaling events elicited upon agonist binding to corneal mAChRs and nAChRs will be crucial for understanding the mechanisms of ACh signaling in CECs, which has salient clinical implications.

Overexpression of muscarinic receptor 3 promotes metastasis and predicts poor prognosis in non-small-cell lung cancer

Introduction:

Chronic obstructive pulmonary disease (COPD) is an independent risk factor for lung cancer development, but the mechanism is not fully understood. Muscarinic receptor 3 (M3R) has been found to be involved in the progression of small-cell lung cancer and the pathological process of COPD. We hypothesized that M3R may contribute to lung cancer development, especially in patients with COPD.

Methods:

The correlation between M3R expression and clinical features of non–small-cell lung cancer (NSCLC) was evaluated in 148 paraffin-embedded archived NSCLC specimens with the use of immunohistochemistry. M3R agonist and siRNA treatments were used to study the role of M3R in NSCLC cell lines. Western blotting and zymography were used to examine the impact of M3R on the PI3K/Akt/matrix metalloproteinase 9 signaling pathway.

Results:

The expression of M3R in NSCLC was significantly increased and correlated with tumor metastasis and poor survival of NSCLC patients. NSCLC patients with COPD showed higher expression of M3R than those without COPD (p = 0.0014). Moreover, M3R expression was inversely related to percent forced expiratory volume in 1 second (r = 0.7017, p < 0.0001) and forced expiratory volume in 1 second /forced vital capacity (r = 0.5057, p < 0.0001), but positively related to smoking history. Down-regulation of M3R resulted in the inhibition of migration and invasion ability of NSCLC cell lines A549 and L78. Furthermore, M3R enhanced the expression and activity of matrix metalloproteinase 9 through PI3K/Akt, which promoted the migration and invasion of NSCLC cell lines.

Conclusion:

Our results suggest that overexpression of M3R in NSCLC promotes the progression of NSCLC, which could contribute to lung cancer development in COPD patients. M3R could be another pharmacological target in lung cancer, especially in COPD patients.

mAChRs activation induces epithelial-mesenchymal transition on lung epithelial cells

BACKGROUND

Epithelial-mesenchymal transition (EMT) has been proposed as a mechanism in the progression of airway diseases and cancer. Here, we explored the role of acetylcholine (ACh) and the pathway involved in the process of EMT, as well as the effects of mAChRs antagonist.

METHODS

Human lung epithelial cells were stimulated with carbachol, an analogue of ACh, and epithelial and mesenchymal marker proteins were evaluated using western blot and immunofluorescence analyses.

RESULTS

Decreased E-cadherin expression and increased vimentin and α-SMA expression induced by TGF-β1 in alveolar epithelial cell (A549) were significantly abrogated by the non-selective mAChR antagonist atropine and enhanced by the acetylcholinesterase inhibitor physostigmine. An EMT event also occurred in response to physostigmine alone. Furthermore, ChAT express and ACh release by A549 cells were enhanced by TGF-β1. Interestingly, ACh analogue carbachol also induced EMT in A549 cells as well as in bronchial epithelial cells (16HBE) in a time- and concentration-dependent manner, the induction of carbachol was abrogated by selective antagonist of M1 (pirenzepine) and M3 (4-DAMP) mAChRs, but not by M2 (methoctramine) antagonist. Moreover, carbachol induced TGF-β1 production from A549 cells concomitantly with the EMT process. Carbachol-induced EMT occurred through phosphorylation of Smad2/3 and ERK, which was inhibited by pirenzepine and 4-DAMP.

CONCLUSIONS

Our findings for the first time indicated that mAChR activation, perhaps via M1 and M3 mAChR, induced lung epithelial cells to undergo EMT and provided insights into novel therapeutic strategies for airway diseases in which lung remodeling occurs.

M3 muscarinic acetylcholine receptor dysfunction inhibits Rac1 activity and disrupts VE-cadherin/β-catenin and actin cytoskeleton interaction

The objective was to investigate whether M3 muscarinic acetylcholine receptor (mAChR) dysfunction disrupts the linkage between the vascular endothelial (VE)-cadherin in the adherens junctional complex and the actin-based cytoskeleton, increasing vascular permeability in atherosclerosis. Western blotting revealed that a selective M3 receptor antagonist, 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP), and M3 receptor siRNA decrease VE-cadherin and β-catenin in Triton X-100-insoluble fractions, indicating that M3 receptor inhibition weakens the linkage between the VE-cadherin/β-catenin complex and the actin cytoskeleton. Co-immunoprecipitation assays showed that M3 receptor inhibition reduces Rac1 activity and the association of IQ motif-containing GTPase-activating protein 1 (IQGAP1) with Ras-related C3 botulinum toxin substrate 1 (Rac1), while increasing the interaction between IQGAP1 and β-catenin. Using IQGAP1 siRNA, we found that IQGAP1 is required for stable interaction between VE-cadherin/β-catenin and the actin cytoskeleton in quiescent endothelial cells; IQGAP1 siRNA augments the M3 receptor inhibition-induced dissociation between them. Moreover, S-nitroso-N-acetylpenicillamine (SNAP), a nitric oxide (NO) donor, attenuates this disassociation and Rac1 activity inhibition. The M3 receptor facilitates interaction of the VE-cadherin-based adherens junctional complex and the actin-based cytoskeleton by maintaining Rac1 activity, which regulates the interaction between IQGAP1/Rac1 and IQGAP1/β-catenin, and may contribute to endothelial barrier function under physiological conditions.

Novel Aeruginosin-865 from Nostoc sp. as a potent anti-inflammatory agent

Aeruginosin-865 (Aer-865), isolated from terrestrial cyanobacterium Nostoc sp. Lukešová 30/93, is the first aeruginosin-type peptide containing both a fatty acid and a carbohydrate moiety, and is the first aeruginosin to be found in the genus Nostoc. Mass spectrometry, chemical and spectroscopic analysis as well as one- and two-dimensional NMR and chiral HPLC analysis of Marfey derivatives were applied to determine the peptidic sequence: D-Hpla, D-Leu, 5-OH-Choi, Agma, with hexanoic and mannopyranosyl uronic acid moieties linked to Choi. We used an AlphaLISA assay to measure the levels of proinflammatory mediators IL-8 and ICAM-1 in hTNF-α-stimulated HLMVECs. Aer-865 showed significant reduction of both: with EC50 values of (3.5±1.5) μg mL(-1) ((4.0±1.7) μM) and (50.0±13.4) μg mL(-1) ((57.8±15.5) μM), respectively. Confocal laser scanning microscopy revealed that the anti-inflammatory effect of Aer-865 was directly associated with inhibition of NF-κB translocation to the nucleus. Moreover, Aer-865 did not show any cytotoxic effect.