Journal club 2016. 2. 26

PPARγ ameliorated LPS induced inflammation of HEK cell line expressing both human Toll-like receptor 4 (TLR4) and MD2.

Darehgazani R¹, Peymani M, Hashemi MS, Omrani MD, Movafagh A, Ghaedi K, Nasr-Esfahani MH.

¹Department of Medical Genetics, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Velenjak, 1985717443, Tehran, Iran.

Abstract

TLR4 is transmembrane pattern-recognition receptor that initiates signals in response to diverse pathogen-associated molecular patterns especially LPS. Recently, there have been an increasing number of studies about the role of TLRs in the pathogenesis of several disorders as well as the therapeutic potential of TLR intervention in such diseases. Peroxisome proliferator-activated receptor-gamma (PPARγ) is a ligand-activated transcription factor with numerous biological effects. PPARγ has been shown to exert a potential anti-inflammatory effect through suppression of TLR4-mediated inflammation. Therefore, PPARγ agonists may have a potential to combat inflammatory conditions in pathologic states. The current study aims to show the decrease of inflammation by overexpression of PPARγ in a cell reporter model. To reach this goal, recombinant pBudCE4.1 (+) containing encoding sequences of human TLR4 and MD2 was constructed and used to transfect HEK cells. Subsequently, inflammation was induced by LPS treatment as control group. In the treatment group, overexpression of PPARγ prior to inflammation was performed and the expression of inflammatory markers was assessed in this condition. The expression of inflammatory markers (TNFα and iNOS) was defined by quantitative real time PCR and the amount of phosphorylated NF-κB was measured by western blot. Data indicated expression of TNFα and iNOS increased in LPS induced inflammation of stably transformed HEK cells with MD2 and TLR4. In this cell reporter model overexpression of PPARγ dramatically prevented LPS-induced inflammation through the blocking of TLR4/NF-κB signaling. PPARγ was shown to negatively regulate TLR4 activity and therefore exerts its anti-inflammatory action against LPS induced inflammation.

PPARγ ameliorated LPS induced inflammation of HEK cell line expressing both human Toll-like receptor 4 (TLR4) and MD2

Journal club 2016-02-19

By Ramsha Afzal

Voltage-Gated Potassium Channels Involved in Regulation of Physiological Function in MrgprA3-Specific Itch Neurons.

Tang M¹, Wu G², Wang Z³, Yang N³, Shi H³, He Q⁴, Zhu C³, Yang Y³, Yu G³, Wang C³, Yuan X³, Liu Q⁵, Guan Y⁶, Dong X⁷, Tang Z⁸.

Abstract

Itch is described as an unpleasant or irritating skin sensation that elicits the desire or reflex to scratch. MrgprA3, one of members of the Mrgprs family, is specifically expressed in a subpopulation of dorsal root ganglion (DRG) in the peripheral nervous system (PNS). These MrgprA3-expressing DRG neurons have been identified as itch-specific neurons. They can be activated by the compound, chloroquine, which is used as a drug to treat malaria. In the present study, we labeled these itch-specific neurons using the method of molecular genetic markers, and then studied their electrophysiological properties. We also recorded the cutaneous MrgprA3^– neurons retrogradely labeled by Dil dye (MrgprA3^–-Dil). We first found that MrgprA3⁺ neurons have a lower excitability than MrgprA3^– neurons (MrgprA3^–-non-Dil and MrgprA3^–-Dil). The number of action potential (AP) was reduced more obviously in MrgprA3⁺ neurons than that of in MrgprA3^– neurons. In most cases, MrgprA3⁺ neurons only generated single AP; however, in MrgprA3^– neurons, the same stimulation could induce multiple AP firing due to the greater voltage-gated potassium (Kv) current existence in MrgprA3⁺ than in MrgprA3^– neurons. Thus, Kv current plays an important role in the regulation of excitability in itch-specific neurons.

KEYWORDS:

DRG; Itch; Kv current; MrgprA3

voltage gated K+ channel and Mrgpra3 specific itchneuron

Journal club 2016-02-12

By Babina Sanjel

TRPV1 and PLC Participate in Histamine H4 Receptor-Induced Itch

Tunyu Jian,¹ Niuniu Yang,¹ Yan Yang,¹ Chan Zhu,¹ Xiaolin Yuan,¹ Guang Yu,¹ Changming Wang,¹ Zhongli Wang,¹ Hao Shi,¹ Min Tang,¹ Qian He,¹ Lei Lan,² Guanyi Wu,^1,3 and Zongxiang Tang¹

¹College of Basic Medicine, Nanjing University of Chinese Medicine, 138 Xianlin Road, Nanjing 210023, China
²College of Life Science, Nanjing Normal University, Nanjing 210046, China
³College of Basic Medicine, Guangxi University of Chinese Medicine, 13 Wuhe Road, Nanning 530200, China

TRPV1 and PLC Participate in Histamine H4 Receptor-Induced Itch

Histamine H4 receptor has been confirmed to play a role in evoking peripheral pruritus. However, the ionic and intracellular signaling mechanism of activation of H4 receptor on the dorsal root ganglion (DRG) neurons is still unknown. By using cell culture and calcium imaging, we studied the underlying mechanism of activation of H4 receptor on the DRG neuron. Immepip dihydrobromide (immepip)—a histamine H4 receptor special agonist under cutaneous injection—obviously induced itch behavior of mice. Immepip-induced scratching behavior could be blocked by TRPV1 antagonist AMG9810 and PLC pathway inhibitor U73122. Application of immepip (8.3–50 μM) could also induce a dose-dependent increase in intracellular Ca²⁺ () of DRG neurons. We found that 77.8% of the immepip-sensitized DRG neurons respond to the TRPV1 selective agonist capsaicin. U73122 could inhibit immepip-induced Ca²⁺ responses. In addition, immepip-induced increase could be blocked by ruthenium red, capsazepine, and AMG9810; however it could not be blocked by TRPA1 antagonist HC-030031. These results indicate that TRPV1 but not TRPA1 is the important ion channel to induce the DRG neurons’ responses in the downstream signaling pathway of histamine H4 receptor and suggest that TRPV1 may be involved in the mechanism of histamine-induced itch response by H4 receptor activation.

Journal Club 2016.02.05.

By onlynice20

GROWTH FACTORS, CYTOKINES, AND CELL CYCLE MOLECULES
Histamine Released from Epidermal Keratinocytes Plays a Role in a-MelanocyteeStimulating Hormone-Induced Itching in Mice

Histamine Released from Epidermal Keratinocytes Plays a Role in a-MelanocyteeStimulating Hormone-Induced Itching in Mice

Kyoko Shimizu,* Tsugunobu Andoh,y Yoko Yoshihisa,* and Tadamichi Shimizu*
From the Departments of Dermatology* and Applied Pharmacology,y Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan

Sunburn, wound repair, and chronic renal failure with hemodialysis are usually accompanied by both pigmentation and itching. Proopiomelanocortin-derived a-melanocyteestimulating hormone (a-MSH) is produced in response to external stimuli, such as UV irradiation, and is involved in cutaneous pigmen- tation. However, it is unclear whether a-MSH is also involved in the itching. We therefore investigated whether a-MSH elicited itch-related responses in mice. We found that an intradermal injection of a-MSH induced hind-paw scratching, an itch-related response, in mice. The a-MSHeinduced scratching was inhibited by the m-opioid receptor antagonist naltrexone and the H1 histamine receptor antagonist terfenadine. In mast cell-deficient mice, a-MSH also elicited scratching, which was inhibited by terfe- nadine. The immunoreactivity for L-histidine decarboxylase, a key enzyme required for the production of histamine, histamine, and the melanocortin 1 and 5 receptors were shown in not only mast cells but also keratinocytes in murine skin. In addition to the expression of L-histidine decarboxylase and melanocortin 1 and 5 receptors, the mouse keratinocyte cell lines (Pam212) also showed immunoreactivity for L-histidine decarboxylase, histamine, and melanocortin 1 and 5 receptors. The application of a-MSH induced the release of histamine from Pam212 cells. These findings indicate that a-MSH may play an important role in the itching associated with pigmented cutaneous lesions and that the histamine released from keratinocytes is involved in this a-MSHeinduced itching. (Am J Pathol 2015, 185: 3003e3010; http://dx.doi.org/10.1016/j.ajpath.2015.07.015)