Pretreatment with obestatin inhibits the development of acetic acid-induced colitis in rats

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1 Experimentl reserch Pretretment with obesttin inhibits the development of cetic cid-induced colitis in rts Aleksndr Mtuszyk 1,2, Piotr Cernowicz 1, Zygmunt Wrzech 1, Jkub Cieszkowski 1, Krystyn Głązk 3, Jonn Bonior 4, Jolnt Jworek 4, Peter Christopher Konturek 5, Krzysztof Gil 6, Artur Dembiński 1 1 Deprtment of Physiology, Fculty of Medicine, Jgiellonin University Medicl College, Krkow, Polnd 2 Deprtment of Antomy, Fculty of Medicine, Jgiellonin University Medicl College, Krkow, Polnd 3 Deprtment of Pthomorphology, Fculty of Medicine, Jgiellonin University Medicl College, Krkow, Polnd 4 Deprtment of Medicl Physiology, Fculty of Helth Sciences, Jgiellonin University Medicl College, Krkow, Polnd 5 Deprtment of Internl Medicine II, Thuringi-Clinic Slfeld, Teching Hospitl of the University of Jen, Slfeld, Germny 6 Deprtment of Pthophysiology, Fculty of Medicine, Jgiellonin University Medicl College, Krkow, Polnd Corresponding uthor: Piotr Cernowicz MD, PhD Deprtment of Physiology Jgiellonin University Medicl College 16 Grzegórzeck St Krkow, Polnd Phone: Fx: E-mil: mpcerno@cyf-kr.edu.pl Submitted: 2 November 2015 Accepted: 22 Jnury 2016 Arch Med Sci 2018; 14, 4: DOI: Copyright 2016 Termedi & Bnch Abstrct Introduction: Obesttin is 23-mino cid peptide derived from proghrelin, common prohormone for ghrelin nd obesttin. Previous studies hve shown tht obesttin exhibits some protective nd therpeutic effects in the pncres nd stomch. The im of this study ws to exmine the effect of pretretment with obesttin on the development of cetic cid-induced colitis. Mteril nd methods: Studies were performed on Wistr rts. Before induction of colitis, rts were treted intrperitonelly with sline or obesttin, dministered twice t dose of 4, 8 or 16 nmol/kg/dose. The first dose of sline or obesttin ws dministered 8 h before the induction of colitis, the second one 7 h fter the first dose. Colitis ws induced by enem with 1 ml of 4% cetic cid solution. The severity of colitis ws ssessed 1 or 24 h fter dministrtion of enem. Results: Pretretment with obesttin dministered t dose of 8 or 16 nmol/ kg/dose significntly reduced the re of mucosl dmge evoked by enem with cetic cid (p < 0.05). This effect ws ccompnied by n improvement of mucosl blood flow nd DNA synthesis in the colon. Moreover, obesttin dministered t dose of 8 or 16 nmol/kg/dose significntly reduced mucosl concentrtion of IL-1β nd ctivity of myeloperoxidse (p < 0.05). Conclusions: Pretretment with obesttin exhibited protective effect in the colon, leding to reduction of colonic dmge in cetic cid-induced colitis. This effect ws ssocited with n improvement of mucosl blood flow, n increse in mucosl cell prolifertion, nd decrese in locl inflmmtion. Key words: cell prolifertion, blood flow, myeloperoxidse, interleukin-1β.

2 Pretretment with obesttin inhibits the development of cetic cid-induced colitis in rts Introduction Inflmmtory bowel disese (IBD), the min types of which re Cohn s disese nd ulcertive colitis, is group of chronic inflmmtions of the digestive trct [1]. They re chrcterized by phsic course, with lternte periods of excerbtion nd remission. According to epidemiologicl studies the incidence of IBD is constntly rising [1 4]. Although the etiology of IBD is still uncler, vilble studies suggest tht IBD results from n bnorml immunologicl response to microflor present in the digestive system, nd their pthogenesis is complex, requiring the co-existence of environmentl nd genetic fctors [1, 4, 5]. There re numerous methods to meliorte the signs nd symptoms of IBD, but there is no method to permnent cure this disese [1, 5, 6]. This leds to serch for new therpeutic strtegies. Obesttin is 23-mino cid peptide, discovered in rt stomch nd derived from preproghrelin, which is common prohormone for ghrelin nd obesttin [7, 8]. Secretion of obesttin is pulstile nd displys n ultrdin rhythmicity similr to ghrelin nd growth hormone [9]. Obesttin exhibits opposite effects to ghrelin on gstrointestinl motility nd energy metbolism. It hs been reported to be n norexic hormone, reducing food intke, gstric emptying time, jejunl motility, nd body weight gin [8 13]. Previous studies hve shown tht obesttin exhibits protective nd therpeutic effects in some orgns of the gut [8]. It hs been shown tht tretment with obesttin ccelertes the heling of cetic cid induced gstric ulcers [14]. The therpeutic effect of obesttin hs lso been found in experimentl colitis evoked by dextrn sodium sulfte [15]. In the pncres it hs been demonstrted tht preventive dministrtion of obesttin inhibits the development of cerulein- nd ischemi/reperfusion-induced cute pncretitis [16, 17] nd ccelertes the heling of experimentl pncretitis in rts [18, 19]. Also obesttin promotes survivl of pncretic islets, especilly β-cells [20]. Moreover, clinicl studies hve shown tht the obesttin/ghrelin rtio could serve s n index of IBD ctivity [21, 22]. The objective of the present study ws to determine the influence of pretretment with obesttin on the development of cetic cid-induced colitis in rts. Mteril nd methods Animls nd tretment The reserch ws performed on Wistr mle rts weighing g nd conducted following the experimentl protocol pproved by the First Locl Commission of Ethics for the Cre nd Use of Lbortory Animls in Crcow (Permit No. 2/2013). During the study, the nimls were kept in cges plced t room temperture nd 12- hour light-drkness cycle ws mintined. The nimls, prior to colitis induction with cetic cid solution, were fsted for 18 h with free ccess to wter. Before nd fter this period food nd tp wter were vilble d libitum. One hundred twenty-eight rts were rndomly divided into eight equl experimentl groups: (1) control rts treted intrperitonelly (i.p.) with sline without induction of colitis; (2 4) rts treted i.p. with obesttin given t dose of 4, 8 or 16 nmol/kg/dose without induction of colitis; (5) rts treted i.p. with sline before induction of colitis; (6 8) rts treted i.p. with obesttin dministered t dose of 4, 8 or 16 nmol/kg/dose before induction of colitis. The nimls from ech experimentl group were divided into two equl sub-groups. In the first sub-groups, the severity of colitis ws ssessed 1 h fter the cetic cid enem. In the second subgroups, the severity of colitis ws ssessed 24 h fter the cetic cid enem. The experiments were repeted to obtin 8 nimls in ech experimentl group nd ech time of observtion. Sline or rt obesttin (Ynihr Institute, Shizuok, Jpn) ws dministered intrperitonelly ccording to the group of nimls twice, 8 nd 1 h before the rectl dministrtion of sline or cetic cid solution. Obesttin ws used t the doses of 4, 8 nd 16 nmol/kg/dose, becuse previous studies showed tht these doses exhibited protective nd therpeutic effects in the pncres [16, 18] nd stomch [14]. Obesttin ws dissolved in sline nd then dministered in n mount which did not exceed 0.3 ml/dose. Before the induction of colitis, nimls were nesthetized with ketmine (50 mg/kg i.p., Bioketn, Vetoquinol Biowet, Gorzow Wielkopolski, Polnd). Colitis ws induced by intrrectl dministrtion of 1 ml of 4% cetic cid queous solution through polyethylene ctheter, which end ws inserted into the bowel 4.5 cm deep from the nus. The nimls without induction of colitis were treted with sline enem (shm opertion). Mesurement of colonic blood flow nd mucosl lesions One or 24 h fter enem, the rts were nesthetized gin with ketmine. After opening the bdominl cvity nd exposing the colon, the mesurement of colonic blood flow volume ws performed using lser Doppler flowmeter (Peri- Flux 4001 Mster monitor, Perimed AB, Jrfll, Sweden), in ccordnce with the methodology described before [23]. The blood flow mesurement Arch Med Sci 4, June /

3 A. Mtuszyk, P. Cernowicz, Z. Wrzech, J. Cieszkowski, K. Głązk, J. Bonior, J. Jworek, P.C. Konturek, K. Gil, A. Dembiński ws performed ech time in five different prts of the descending nd sigmoid colon nd the min vlue of five records ws expressed s the percentge of the vlue obtined in the nimls from the control group. After the mesurement of the colonic blood flow, the re of mucosl dmge ws mesured, using computerized plnimeter (Morphomt, Crl Zeiss, Berlin, Germny), in ccordnce with the method described erlier [24]. Biochemicl nlysis After the mesurement of the colonic blood flow nd re of lesions, biopsy smples of the colon were tken for determintion of mucosl DNA synthesis (n index of mucosl cell prolifertion), concentrtion of pro-inflmmtory interleukin-1β, ctivity of myeloperoxidse, nd for histologicl exmintion. Determintion of DNA synthesis in colonic mucos DNA synthesis ws determined by mesurement of [ 3 H]thymidine incorportion ([6-3H]-thymidine, Ci/mmol, Institute for Reserch, Production nd Appliction of Rdioisotopes, Prgue, Czech Republic) into the mucosl DNA s described previously [25]. The incorportion of lbeled thymidine into DNA ws determined by counting 0.5 ml of DNA-contining superntnt in liquid scintilltion system. The rte of DNA synthesis ws expressed s number of tritium disintegrtions per minute per μg of DNA (dpm/μg DNA). Determintion of interleukin-1β concentrtion in colonic mucos The smples of the colonic mucos were homogenized in ice-cold phosphte-buffered sline (PBS, 20 mm, ph 7.4). The homogente ws centrifuged t 1,500 g for 10 min t 4 C. The content of interleukin-1β in the superntnt ws mesured using the Rt IL-1β Pltinum Elis (Bender MedSystem GmbH, Vienn, Austri). The concentrtion of interleukin-1β in colonic mucos ws expressed s ng per g of tissue. Determintion of myeloperoxidse ctivity in colonic mucos The smples of colonic mucos were frozen in liquid nitrogen, nd, until the mesurement ws done, stored t 60 C. Myeloperoxidse ctivity ws ssessed using modifiction of the method described by Brdley et l. [26]. The mucos ws homogenized in 1 ml of 50 mm potssium phosphte buffer (ph 6.0) contining 0.5% of hexdecyltrimethyl mmonium bromide. Then the homogente ws freeze-thwed three times, subjected to soniction in n ice bth for 20 s nd centrifuged t 30,000 g for 15 min t 4 C. 100 µl of the superntnt ws tken nd 2.9 ml of 50 mm phosphte buffer ws dded, which contined 157 µg/ ml of o-dinisidine dihydrochloride nd % hydrogen peroxide. Hydrogen peroxide reduction through myeloperoxidse cuses oxidtion of o-dinisidine nd produces stined finl product. The intensity of stining ws mesured spectrophotometriclly with light wvelength of 460 nm. The obtined results were clculted in units per grm of tissue nd finlly expressed s the percentge of the vlue observed in the control group. Histologicl exmintion of the colon Smples of the colon were fixed in 10% buffered formldehyde nd embedded in prffin. Prffin sections were stined with hemtoxylin nd eosin. Slides were exmined by two experienced pthologists without knowledge of the tretment given. The histologicl grding of colonic dmge ws determined using scle previously presented by Vilsec et l. [27]. The histologicl grding of lesions ws mde using scle rnging from 0 to 2 (0 = no lesions; 1 = smll lesions < 3 mm; 2 = lrge lesions > 3 mm). Inflmmtory infiltrtion ws grded from 0 to 3 (0 = none; 1 smll; 2 = moderte; 3 = hevy), depth of the lesions ws grded from 0 to 3 (0 = no lesions; 1 = lesions reching submucos; 2 = lesions reching musculris propri; 3 = lesions reching seros). The presence of fibrosis ws grding from 0 to 2 (0 = none; 1 = mild; 2 = severe). Sttisticl nlysis The results were presented s the min vlue ± stndrd error (SEM). Sttisticl ssessment ws performed through one-wy nlysis of vrince followed by Tukey s multiple comprison test using GrphPd Prism (GrphPd Softwre, Sn Diego, CA, USA). Sttisticl nlysis ws performed seprtely for ech time of observtion. Differences were considered to be sttisticlly significnt if p ws less thn Results In the control sline-treted nimls without induction of colitis, no lesions of the colon were observed in mcroscopic or microscopic exmintion (Figures 1 nd 2; Tble I). Also dministrtion of obesttin ws without n effect on colonic morphology in rts without induction of colitis (Figure 1; Tble I). Rectl dministrtion of 4% solution of cetic cid led to induction of colitis in ll rts. In rts treted with sline, 1 h fter the induction of colitis, the mucosl dmge re ws 4.9 ±0.4 mm², wheres fter the next 23 h the re 922 Arch Med Sci 4, June / 2018

4 Pretretment with obesttin inhibits the development of cetic cid-induced colitis in rts Are of colonic lesions [mm 2 ] ,b,b,b,b Sline NCl (control) Without colitis Colitis 1 h 24 h Figure 1. Influence of pretretment with obesttin given intrperitonelly t dose of 4, 8 or 16 nmol/ kg/dose (O4, O8 or O16) on the re of colonic lesions observed 1 or 24 h fter induction of colitis Men ± stndrd error. N = 8 nimls in ech group. p < 0.05 compred to control t the sme time of observtion; b p < 0.05 compred to NCl + colitis t the sme time of observtion. A B C D E F Figures 2. A Representtive microscopic imge of colonic mucos observed 1 h fter enem with sline in sline-pretreted control rts. B Representtive microscopic imge of colonic mucos observed 1 h fter enem with cetic cid solution in sline-pretreted rts. C Representtive microscopic imge of colonic mucos observed 1 h fter enem with cetic cid solution in rts pretreted with obesttin given t dose of 8 nmol/kg/ dose. D Representtive microscopic imge of colonic mucos observed 24 h fter enem with sline in sline-pretreted control rts. E Representtive microscopic imge of colonic mucos observed 24 h fter enem with cetic cid solution in sline-pretreted rts. F Representtive microscopic imge of colonic mucos observed 24 h fter enem with cetic cid solution in rts pretreted with obesttin given t dose of 8 nmol/kg/dose. Hemtoxylin-eosin stin. Originl mgnifiction 400 Arch Med Sci 4, June /

5 A. Mtuszyk, P. Cernowicz, Z. Wrzech, J. Cieszkowski, K. Głązk, J. Bonior, J. Jworek, P.C. Konturek, K. Gil, A. Dembiński Tble I. Morphologicl signs of colonic dmge observed 1 or 24 h fter rectl dministrtion of sline or cetic cid solution (colitis) in rts pretreted with sline or obesttin given t dose of 4, 8 or 16 nmol/kg/dose (obesttin 4, obesttin 8 or obesttin 16) Vrible Morphologicl chnges Grding of colonic dmge (0 2) Inflmmtory infiltrtion (0 3) Depth of dmge (0 3) Fibrosis (0 3) 1 h: Sline (control) Obesttin Obesttin Obesttin Sline + colitis Obesttin 4 + colitis Obesttin 8 + colitis Obesttin 16 + colitis h: Sline (control) Obesttin Obesttin Obesttin Sline + colitis Obesttin 4 + colitis Obesttin 8 + colitis Obesttin 16 + colitis Numbers represent the predominnt histologicl grding in ech group. of colonic lesions enlrged to 32.3 ±2.5 mm² (Figure 1). In sline-treted nimls with colitis, histologicl exmintion performed 1 h fter cetic cid enem showed the presence of lrge lesions reching the level of the musculr membrne, with moderte inflmmtory infiltrtion (Tble I). Twenty-three hours lter, histologicl exmintion showed n increse in the severity of colonic dmge. There were lrge lesion ulcers, reching the musculr or serous membrne. These lesions were ccompnied by severe inflmmtory infiltrtion (Tble I, Figure 2). In rts with colitis, pretretment with obesttin reduced the development of colonic dmge. One hour fter induction of colitis, the re of colonic dmge ws reduced by 19%, 45% or 35% in rts pretreted with obesttin given t dose of 4, 8 or 16 nmol/kg/dose, respectively. Twenty-three hours lter, the re of the colonic lesion ws reduced by 11%, 38% or 44% depending on the dose of obesttin (Figure 1). The reduction in the re of colonic dmge evoked by obesttin given t dose of 8 nd 16 nmol/kg/dose ws sttisticlly significnt in both times of observtion, 1 nd 24 h fter induction of colitis. Pretretment with obesttin lso reduced histologicl mnifesttion of colonic dmge evoked by cetic cid (Tble I, Figure 2). One hour fter induction of colitis, the protective effect of pretretment with obesttin ws found s decrese in grding nd depth of lesions, s well s reduction in inflmmtory infiltrtion of the colonic wll. Twenty-three hours lter, the beneficil effect of pretretment with obesttin ws mnifested, prt from the effects mentioned bove, by inhibition of fibrosis development (Tble I, Figure 2). In the nimls from the control group, DNA synthesis in colonic mucos reched the vlue of 38.2 ±1.9 nd 37.5 ±2.8 dpm/µg DNA t the time of 1 nd 24 h fter the sline enem, respectively (Figure 3). Pretretment with obesttin, in the dosge used, did not exhibit sttisticlly significnt influence on the dynmics of DNA repliction in colonic mucos in nimls without induction of colitis. One nd 24 h fter the rectl dminis- 924 Arch Med Sci 4, June / 2018

6 Pretretment with obesttin inhibits the development of cetic cid-induced colitis in rts trtion of cetic cid solution, DNA synthesis ws significntly reduced by round 50% nd 62%, respectively. Prior dministrtion of obesttin prtilly reversed tht effect. Pretretment with obesttin given t dose of 8 or 16 nmol/kg/dose led to sttisticlly significnt, similr in the cse of both doses, improvement of DNA repliction in the colon mucous membrne, in the nimls with colitis. This effect ws observed t both times of observtion, 1 nd 24 h fter the induction of colitis (Figure 3). In contrst, pretretment with obesttin given t dose of 4 nmol/kg/dose ws without n effect on mucosl DNA synthesis in the colon of rts with cetic cid-induced colitis (Figure 3). In the groups of nimls without the induction of colitis, double intrperitonel dministrtion of obesttin in the doses used filed to ffect the mucosl blood flow in the colon (Figure 4). Induction of colitis led to sttisticlly significnt decrese in the blood flow through the colonic mucos by lmost 72% nd 77%, respectively fter 1 nd 24 h fter the enem with cetic cid solution (Figure 4). Prior double dministrtion of obesttin, given t dose of 8 or 16 nmol/kg/dose, significntly reversed the colitis-evoked decrese in the mucosl blood flow in the colon. This effect of obesttin ws found t both times of observtion, 1 nd 24 h fter the induction of colitis. The effect of obesttin dministered t dose of 4 nmol/kg/ dose on mucosl blood flow ws wek nd sttisticlly insignificnt (Figure 4). In the control rts, mucosl concentrtion of pro-inflmmtory IL-1β in the colon ws round 0.80 ng/g of tissue (Figure 5). Tretment with ny dose of obesttin ws without significnt effect on the mucosl IL-1β level in the rts without colitis. Administrtion of 4% solution of cetic cid incresed the mucosl IL-1β concentrtion by 50% nd 600% t 1 nd 24 h fter induction of colitis, respectively. Pretretment with obesttin t dose of 8 nd 16 nmol/kg/dose reduced the colitis-evoked increse in mucosl IL-1β concentrtion. This effect ws sttisticlly significnt t 1 nd 24 h fter induction of colitis in rts pretreted with obesttin given t dose of 16 nmol/ kg/dose. In the cse of nimls pretreted with obesttin given t dose of 8 nmol/kg/dose, significnt reduction in mucosl IL-1β concentrtion ws observed 24 h fter induction of colitis. One hour fter induction of colitis, pretretment with obesttin given t dose of 8 nmol/kg/dose reduced mucosl IL-1β concentrtion, but this effect ws sttisticlly insignificnt in comprison to the vlue observed in sline-treted nimls with colitis (Figure 5). Pretretment with obesttin dministered t dose of 4 nmol/kg/dose filed to ffect the mucosl concentrtion of IL-1β in the colon of nimls with colitis (Figure 5). Administrtion of obesttin given t the doses used filed to hve significnt effect on the mucosl myeloperoxidse (MPO) ctivity in the colon of rts without induction of colitis (Figure 6). One hour fter the enem with cetic cid, MPO ctivity in colonic mucos ws incresed lmost by 100%, wheres 23 h lter lmost 5-fold increse in MPO ctivity in colonic mucos ws observed. Pretretment with obesttin reduced the colitis-evoked increse in colonic ctivity of MPO. The effect of obesttin, dministered t dose of 4 nmol/kg/dose, ws sttisticlly insignificnt t both times of observtion. In contrst, obesttin given t dose of 8 or 16 nmol/kg/dose signifi- DNA synthesis [d.p.m./µg DNA] ,b,b,b Sline NCl (control) Without colitis Colitis 1 h 24 h,b Mucosl blood flow (% of control)120,b,b,b,b Sline NCl (control) Without colitis Colitis 1 h 24 h Figure 3. Influence of pretretment with obesttin given intrperitonelly t dose of 4, 8 or 16 nmol/ kg/dose (O4, O8 or O16) on DNA synthesis in colonic mucos observed 1 or 24 h fter induction of colitis Men ± stndrd error. N = 8 nimls in ech group. p < 0.05 compred to control t the sme time of observtion; b p < 0.05 compred to NCl + colitis t the sme time of observtion. Figure 4. Influence of pretretment with obesttin given intrperitonelly t dose of 4, 8 or 16 nmol/kg/dose (O4, O8 or O16) on mucosl blood flow in the colon observed 1 or 24 h fter induction of colitis Men ± stndrd error. N = 8 nimls in ech group. p < 0.05 compred to control t the sme time of observtion; b p < 0.05 compred to NCl + colitis t the sme time of observtion. Arch Med Sci 4, June /

7 A. Mtuszyk, P. Cernowicz, Z. Wrzech, J. Cieszkowski, K. Głązk, J. Bonior, J. Jworek, P.C. Konturek, K. Gil, A. Dembiński IL-1β [ng/g tissue] ,b Sline NCl (control) Without colitis Colitis 1 h 24 h b,b Myeloperoxidse [U/g tissue] ,b,b,b Sline NCl (control) Without colitis Colitis 1 h 24 h,b Figure 5. Influence of pretretment with obesttin given intrperitonelly t dose of 4, 8 or 16 nmol/ kg/dose (O4, O8 or O16) on interleukin-1β concentrtion in colonic mucos observed 1 or 24 h fter induction of colitis Men ± stndrd error. N = 8 nimls in ech group. p < 0.05 compred to control t the sme time of observtion; b p < 0.05 compred to NCl + colitis t the sme time of observtion. Figure 6. Influence of pretretment with obesttin given intrperitonelly t dose of 4, 8 or 16 nmol/ kg/dose (O4, O8 or O16) on myeloperoxidse ctivity in colonic mucos observed 1 or 24 h fter induction of colitis Men ± stndrd error. N = 8 nimls in ech group. p < 0.05 compred to control t the sme time of observtion; b p < 0.05 compred to NCl + colitis t the sme time of observtion. cntly inhibited the mucosl MPO ctivity in the colon of the nimls with colitis. This inhibitory effect ws similr for both bove doses of obesttin nd ws observed t both 1 nd 24 h fter the induction of colitis (Figure 6). Discussion This study provided importnt observtions showing tht obesttin ffects mintennce of the integrity of the mucous membrne in the colon. Pretretment with obesttin inhibited the development of cetic cid-induced colitis in rts, which ws found s decrese in the re of colonic dmge. This effect ws ssocited with the improvement of mucosl blood flow nd DNA synthesis, nd with reduction in the colitis-evoked increse in mucosl IL-1β concentrtion nd myeloperoxidse (MPO) ctivity. Preservtion of the integrity of gstrointestinl mucos is dependent on mintining dynmic blnce between dmging fctors cting on the mucous membrne nd mechnisms responsible for mucos protection. Adequte cell prolifertion plys n importnt role mong the mechnisms responsible for integrity of gstrointestinl mucos. Reduction in cell prolifertion, excessive poptosis nd incresed cell loss ply key role in the development of mucous membrne trophy nd ulcers [28, 29]. On the other hnd, incresed cell renewl leds to incresed mucosl protection in the gstrointestinl trct nd promotes heling of the dmge in the gut [30 33]. Mucosl cells re reconstructed by mitosis of stem nd progenitor cells. DNA synthesis occurs in the S phse during the cell cycle nd it is mndtory for cell division [33]. It cn be concluded tht DNA synthesis dynmics reflect the vitlity of cells, s well s cell prolifertion. As result of our present reserch, it ws demonstrted tht rectl dministrtion of cetic cid led to considerble decrese in DNA synthesis in the colonic mucous membrne. Tht decrese ws well correlted with the expnse of the re of inflmmtion. It indictes tht there is reltionship between cell prolifertion nd pthogenesis of cetic-cid-induced colitis. Our present study hs lso shown tht dministrtion of obesttin in the nimls without colitis induction hd no significnt influence on DNA synthesis in colonic mucos. This finding indictes tht dministrtion of obesttin t these doses does not induce cell hyperprolifertion nd mucosl hypertrophy in nimls with norml mucos. In contrst to tht, pretretment with obesttin before induction of colitis led to prtil, but significnt reversion of the colitis-evoked decrese in mucosl DNA synthesis. This observtion indictes tht improvement of cell vitlity nd prolifertion is involved in the protective effect of obesttin in the colon. Vsculr mechnisms ply key role in the processes of protection nd heling of mucos in the gut [34 36]. Experimentl studies hve demonstrted tht decrese in gstric blood flow increses the severity nd re of gstric ulcers fter exposure of gstric mucos to dmging fctors [34]. Similr effects of reduction in orgn blood flow on mucosl integrity hve been observed in other prts of the digestive trct such s the orl cvity [35], esophgus [36], duodenum [37] nd colon [38]. Our present results re in greement with those observtions. Rectl dministrtion 926 Arch Med Sci 4, June / 2018

8 Pretretment with obesttin inhibits the development of cetic cid-induced colitis in rts of cetic cid solution led to reduction in blood flow in the colon, nd this effect ws ssocited with the development of colonic wll dmge. Our present study lso showed tht dministrtion of obesttin prior to colitis induction cused the improvement of blood flow in colonic mucos, leding to decrese in the re nd severity of colonic mucos dmge. Tht observtion suggests tht the protective effect of obesttin on the colonic mucos is relted, t lest in prt, to improvement of blood flow in this membrne. In this study, we evluted the severity of colitis by mesurement of mucosl concentrtion of IL-1β nd MPO ctivity. IL-1β plys n essentil role in the development of locl nd systemic inflmmtion [39]. This pro-inflmmtory cytokine is minly produced by monocytes nd tissue mcrophges. Interleukin-1β is involved in mediting both cute nd chronic inflmmtion. It initites the inflmmtory cscde by ctivting the expression of further pro-inflmmtory cytokines, minly interleukin-6, TNF-α nd prostglndins [39, 40]. Interleukin-1β is synthesized in immture form, which is proteolyticlly processed to its ctive form by cspse-1 [41]. The interleukin-1 gene cluster hs been mpped to the long rm of chromosome 2 nd consists of three genes, IL-1α, IL-1β nd IL-1 receptor ntgonist genes, encoding IL-1α, IL-1β nd IL-1 receptor ntgonist proteins, respectively [42]. There re studies suggesting tht some kinds of polymorphisms in the IL1B gene re ssocited with n incresed risk of diseses such s chronic obstructive pulmonry disese [43] or chronic periodontitis [44]. In the experimentl nd clinicl reserch, it hs been demonstrted tht dministrtion of receptor ntgonist or immunoglobulins ginst IL-1β prevents the increse in IL-6 nd TNF-α in inflmmtion, s well s decresing the severity of inflmmtion [40, 45 48]. Our present study indicted tht cetic-cid-induced colitis leds to n increse in mucosl concentrtion of IL-1β in the colon. Prior dministrtion of obesttin prtly, lthough significntly, reversed tht effect. In contrst, dministrtion of obesttin in nimls without colitis did not ffect IL-1β concentrtion in colonic mucos. The grde of tissue infiltrtion by neutrophil grnulocytes is reflected by the level of MPO ctivity becuse it is n enzyme tht is present in grnulrities of these cells [49, 50]. During inflmmtion, MPO is relesed from neutrophils, leding to the cretion of hypochlorous cid nd other free rdicls, which hve strong bctericidl nd ntivirl properties. However, free rdicls which re creted in this process lso cuse dmge to host cells by destroying proteins, DNA nd lipids [50]. In the present reserch, enem with cetic cid solution led to significnt nd potent increse in myeloperoxidse ctivity in the colonic mucos. Prior dministrtion of obesttin, in nimls in which colitis ws induced, led to significnt reduction in the colitis-evoked increse in MPO ctivity in the colonic mucos. On the other hnd, dministrtion of obesttin filed to ffect MPO ctivity in the colonic mucos in nimls in which colitis ws not induced. The effects of obesttin on IL-1β concentrtion nd MPO ctivity in colonic mucos in rts with colitis suggest tht the protective effect of obesttin is relted to the inhibitory impct on the development of inflmmtion. The lck of effects of pretretment with obesttin on mucosl IL-1β nd MPO in nimls without colitis suggests tht this polypeptide hs no influence on the immune system ctivity, s well s migrtion, nd ctivity of leukocytes in the colon without inflmmtion. In conclusion, our present results indicte tht pretretment with obesttin protects the colonic mucos ginst cetic cid-induced dmge. This observtion suggests the potentil pplicbility of this peptide in mintennce of IBD ptients in remission. 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