- Research article
- Open Access
Effect of L-arginine on HSP70 expression in liver in weanling piglets
- Xin Wu1, 2,
- Chunyan Xie†1,
- Yulong Yin†1, 2, 3Email author,
- Fengna Li1,
- Tiejun Li1,
- Ruilin Huang1,
- Zheng Ruan2 and
- Zeyuan Deng2
© Wu et al.; licensee BioMed Central Ltd. 2013
- Received: 26 November 2012
- Accepted: 27 March 2013
- Published: 4 April 2013
This study was conducted to evaluate the effects of L-arginine (Arg) on photomicrographs and HSP70 expression in the liver of weanling piglets. Twelve healthy Landrace × Yorkshire piglets that had been weaned at 21 d (average body weight 5.56 ± 0.51 kg) were randomly divided into a control group and an Arg group (6 g/kg feed). At age 28 d, all of the piglets were slaughtered to obtain liver samples to determine HSP70 expression by real-time PCR, western blot and immunohistochemistry.
The results showed that, compared to control piglets, treatment with Arg decreased inflammatory reactions caused by weaning. The immunohistochemical localization of HSP70 in liver revealed strong expression in the Arg group. Arg increased HSP70 mRNA and HSP70 expression in the liver (P < 0.05).
These findings suggest that dietary supplementation with Arg could maintain liver health by inducing HSP70 expression in weanling piglets.
- Weanling piglets
As the largest internal organ, the liver is responsible for about 500 vital bodily functions, and plays important roles in digestion and metabolism by regulating the production, storage, and release of sugar, fats, and cholesterol. The liver produces a variety of important proteins, including enzymes, hormones, blood proteins, clotting factors, and immune factors. As the main site of detoxification and the primary defense barrier, the liver is liable to be injured by weaning stress . Weaning stress in piglets is often associated with reduced food consumption as well as temporary reductions in weight gain, which can result in postweaning lag, a period of decreased feed intake and increased diarrhea, disease, intestinal dysfunction and atrophy, and mortality in piglets [2–6]. A healthy liver can produce approximately 80 percent of the body’s required amino acids, among which L-arginine (Arg) is essential; when Arg turnover increases, as in growth, inflammation, or tissue repair, the dietary supply can become rate-limiting for Arg-metabolizing pathways [7–10]. Arg deficiency can result in hyperammonemia, and intestinal and immunological dysfunction [11, 12]. The administration of Arg reduces damage to liver tissue after ischaemia injury . Urea synthesis from primary hepatocytes seems to be a valid viability indicator, since mitochondrial transmembrane transport of the urea cycle intermediates ornithine and citrulline is involved in the urea cycle .
Heat shock protein 70 (HSP70) is a member of a highly conserved family that possess a variety of functions, but are best known for chaperoning and re-folding partially denatured protein [15–17]. The hepatic response to stress may involve the synthesis and accumulation of HSP70s [18, 19]. Experimental evidence suggests that some amino acids such as glutamine and arginine regulate HSP expression, which is essential for preventing organ dysfunction . The aim of the present study was to investigate the effects of Arg on photomicrographs and HSP70 expression in the liver under weaning stress in piglets.
Animals, housing and treatments
Composition of the basal diet for weanling pigs (as-fed basis)
Corn (8% CP; < 13% H2O)
Soybean expanded (43% CP)
Fish meal (CP 65%)
Cream powder (50% fat)
L-Lysine · HCl
Nutrient levels 2
Crude protein (%)
Available phosphorus (%)
Arg was obtained from Ajinomoto (Tokyo, Japan).
The experiment was carried out in accordance with the Chinese Guidelines for Animal Welfare and approved by the Animal Welfare Committee of the Institute of Subtropical Agriculture, the Chinese Academy of Sciences.
At age 28 d, blood samples were obtained for the analysis of serum indices. All of the experimental piglets were anaesthetised with an i.v injection of sodium pentobarbital (50 mg/kg BW) and bled by exsanguination. Liver samples were rapidly frozen in liquid nitrogen and stored at −80 for real-time PCR and Western blotting analysis. Additional liver samples from the same location were fixed in 4% paraformaldehyde for two hours at 4, transferred to PBS overnight and 30% sucrose for 2 hours at 4, and then embedded in paraffin, sectioned, and stained with hematoxylin and eosin for histologic studies. The histological activity index (HAI) were evaluated according to Ishak and colleagues .
Serum biochemical indices
An Automated Biochemistry Analyzer (Synchron CX Pro, Beckman Coulter, Fullerton, CA, USA) was used to determine the concentrations of serum glucose, glutamic-oxalacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT), lactic acid (LAC), lactate dehydrogenase (LDH), and alkaline phosphatase (ALP) activities, according to commercial kits and the manufacturer’s instructions. All kits were purchased from Beijing Chemlin Biotech Co., Ltd (Beijing, China).
Serum cortisol (COR) was determined by radioimmunoassay according to the instructions of the manufacturer of the corresponding reagent kit (China Institute of Atomic Energy, Beijing, China).
Immunohistochemistry for HSP70
Paraffin-embedded liver tissue samples were processed using an immunohistochemical technique with specific anti-HSP70 (SPA-810 Stressgen Bioreagents, British Columbia, Canada) diluted 1:400 using PBS buffer. Samples were subjected to antigen retrieval and the reduction of non-specific binding. The tissue sections were incubated with primary antibody in a humidified chamber at 4°C. After the tissue sections were rinsed with Tris buffered saline (TBS), pH 7.4, they were incubated at room temperature for 30 min for the detection of HSP70. The BCIP-NBT substrate system (Sigma, St. Louis, MO) was used to detect alkaline phosphatase conjugate activity. The sections were then counterstained with haematoxylin for 5 s, and then rinsed, dried and mounted with coverslips. The sections were examined by light microscopy and images were captured with a digital camera.
Real-time PCR for HSP70
Total RNA was extracted from liver tissue by a guanidinium isothiocyanate method using TrizolTM reagent (Gibco BRL, Berlin, Germany) and treated with DNase according to the manufacturer’s instructions. The mRNA of HSP70 was determined by a standard real-time polymerase chain reaction (PCR) method as previously described . The following primer pairs were used: GAPDH: (Fwd—5’-GTCGGTGTGAACGGATTT-3’; Rev—5’-ACTCCACGACGTACTCAGC-3’) and HSP70 (Fwd—5’-GCCCTGAATCCGCAGAATA-3’; Rev—5’-TCCCCACGGTAGGAAACG-3’) based on the following conditions: 30 s of denaturation at 94, 30 s of annealing at 56, and 30 s of extension at 72 for 30 cycles.
Western blot for HSP70
To confirm the results of immunohistochemistry, the expression of HSP70 in the liver was detected by Western blot assay. Western blot analysis was performed as described previously , with GAPDH as a loading control. One hundred-microgram samples were homogenized in 6 volumes of buffer A (20 mM HEPES, pH 7.4, 100 mM KCl, 0.2 mM EDTA, 2 mM EGTA, 1 mM DTT, 50 mM NaF, 50 mM β-glycerolphosphate, 0.1 mM PMSF, 1 mM benzamidine, 0.5 mM sodium vanadate, and 1 μM microcystin LR) and centrifuged at 10,000 g for 10 min at 4. The pellet was discarded and the supernatant was aliquoted into microcentrifuge tubes. The protein content was quantified using a detergent-compatible protein assay kit (Bio-Rad), and aliquots of 10 μg were taken individually from each sample, mixed with a one-fifth volume of the sample buffer [0.35 M Tris-Cl, pH 6.8, 10% SDS, 30% glycerol, 9.3% dithiothreitol (DTT), and 0.175 mM bromophenol blue], and then heat-denatured by boiling for 5 min. Separated proteins were transferred to polyvinylidene difluoride membranes (Immobilon-P, Millipore, Bedford, MA) overnight at 4, and then incubated with a blocking solution (0.05% Tween 20, 50 mM Tris, pH 8.0, 150 mM NaCl, and 5% powdered non-fat milk) for 1 h. Membranes were then incubated in a 1:500 dilution of monoclonal antibody raised against HSP70 diluted 1:3000 for two hours at room temperature. Similar treatment of the same blot sheet was performed using rabbit polyclonal anti-GAPDH antibody diluted 1:5000 (CSA-400 Stressgen Bioreagents, British Columbia, Canada) after the first antibody treatment had been stripped off. The membrane was incubated with appropriate peroxidase-labeled secondary antibody prepared in PBS-Tween 20. Membranes were then washed and incubated in the goat anti-rabbit secondary antibody (horseradish peroxidase-conjugated goat anti-mouse, Zhongsan Golden Bridge, China) at a 1:5000 dilution at room temperature for 2 h. Primary antibody binding was visualized using an enhanced chemiluminescence kit (Pierce, Rockford, IL) and Hyperfilm-MP (Amersham International, Buckinghamshire, UK).
Immunohistochemical staining was performed on an Alpha Innotech (San Leandro, CA) 8800 image station with FLUORCHEM software using enhanced chemiluminescence (ECL) as the chromagen. The relative intensities of the Western blot membranes were compared using Alpha Ease software.
The data were analyzed by Student’s T-test, with the significance level set at 0.05. A P-value of P > 0.05 but P < 0.1 was taken to indicate a trend. Data are presented as the mean ± standard error.
Effect of Arg on liver weight and serum biochemical indices
Effects of Arg on pathological findings
Effects of Arg on liver weight and serum biochemical indices in weanling piglets (n = 6)
Initial body weight (kg)
5.9 ± 0.4
5.9 ± 0.4
Final body weight (kg)
6.1 ± 0.3 a
6.6 ± 0.3 b
Feed intake daily (g)
158.3 ± 20.9a
180.6 ± 29.3b
Liver weight (kg)
140.9 ± 5.0
143.9 ± 5.2
Liver weight/Body weight (%)
2.3 ± 0.1
2.18 ± 0.1
7.7 ± 1.0
6.9 ± 0.6
Glutamic-oxalacetic transaminase (mmol/L)
46.3 ± 10.5a
34.5 ± 6.2b
Glutamic pyruvic transaminase (mmol/L)
43.0 ± 5.8
45.2 ± 4.9
Alkaline phosphatase (mmol/L)
166.8 ± 50.5a
224.2 ± 36.6b
Lactic acid (mmol/L)
69.8 ± 12.9a
41.2 ± 11.1b
Lactate dehydrogenase (U/L)
597.8 ± 69.0
546.5 ± 86.3
88.7 ± 26.1a
69.6 ± 22.7b
Immunohistochemistry, real-time PCR, and Western blot for HSP70 in liver
In rodents and humans, Arg is essential when Arg turnover increases, as in growth, inflammation, or tissue repair, and the dietary supply can become rate-limiting for Arg-metabolizing pathways [7, 27]. Indeed, low Arg levels have been documented in weaning-age piglets . It has been reported that, compared to that in newborn pigs, the intestinal synthesis of citrulline and Arg from glutamine and glutamate decreases by 70-73% in 7-d-old suckling pigs, and declines further in 14- to 21-d-old pigs .
In the present study, the significant increase in serum COR and the marked decrease in ALP in the control group indicated that weaning caused stress in piglets, and the elevation of AST in serum may indicate that the liver was damaged. Accordingly, the present results indicated that Arg decreased damage to liver tissue after weaning, in comparison to the control group. This is consistent with the results of other studies. For example, the administration of Arg reduces damage to liver tissue after ischaemia injury . In addition, it has been reported that Arg could protect rats with liver cirrhosis from acute ammonia intoxication .
HSPs are intracellular chaperones that play a key role in the recovery from stress and are involved in nearly all intracellular compartments. Stress-induced HSP70s function to promote refolding and prevent the aggregation of partially-denatured proteins, as well as tag irreversibly-damaged proteins for proteolysis . Arg deprivation decreases HSP expression, and enhances the cellular susceptibility to apoptosis . HSP70 could be used as a marker for assessing the biological behavior under stress in vivo . It has been reported that the overexpression of liver HSP70, particularly during the summer, may confer differential effects on cell survival by protecting against changes induced by oxidative stress . Our results suggest that Arg increased HSP70 mRNA and protein in the liver. Accordingly, immunohistochemistry studies showed differences in HSP70 expression. Our study demonstrated that the expression of HSP70 in the liver was negatively correlated with an increase in the aggressiveness of the histological type. It has also been reported that HSP70 levels in the liver were significantly increased in heat-stressed mice that had been administered Arg compared with a heat-stress-only group . If we consider the role of HSP70 in RNA-DNA proliferation, these increases may be explained by an increase in cell proliferation and protein synthesis promoted by supplementation with Arg [33, 34].
In summary, the present results indicated that pretreatment with Arg could increase the expression of HSP70 in the liver, which might be able to reduce liver injury and enhance liver health in piglets during weaning.
This study was jointly supported by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (2012BAD39B00), National Basic Research Project (2012CB124704), the NSFC (31101730, 31110103909, 30901040, 30901041), Chinese Academy of Sciences and Knowledge Innovation Project (2012B091100259, 2012B091100210, CXJQ120113), and China Postdoctoral Science Foundation Funded Project (2012 T50592; 20110491493).
- Chen T, Zamora R, Zuckerbraun B, Billiar TR: Role of nitric oxide in liver injury. Curmol med. 2003, 3 (6): 519-526.Google Scholar
- Lalles JP, Bosi P, Smidt H, Stokes CR: Weaning - A challenge to gut physiologists. Livest Sci. 2007, 108 (1–3): 82-93.View ArticleGoogle Scholar
- Castillo M, Martin-Orue SM, Nofrarias M, Manzanilla EG, Gasa J: Changes in caecal microbiota and mucosal morphology of weaned pigs. Vet Microbiol. 2007, 124 (3–4): 239-247.PubMedView ArticleGoogle Scholar
- Boudry G, Peron V, Le Huerou-Luron I, Lalles JP, Seve B: Weaning induces both transient and long-lasting modifications of absorptive, secretory, and barrier properties of piglet intestine. J Nutr. 2004, 134 (9): 2256-2262.PubMedGoogle Scholar
- Gu X, Li D, She R: Effect of weaning on small intestinal structure and function in the piglet. Arch Tierernahr. 2002, 56 (4): 275-286. 10.1080/00039420214345.PubMedView ArticleGoogle Scholar
- Hampson DJ: Alterations in piglet small intestinal structure at weaning. Res Vet Sci. 1986, 40 (1): 32-40.PubMedGoogle Scholar
- Wu G, Knabe DA, Kim SW: Arginine nutrition in neonatal pigs. J Nutr. 2004, 134 (10): 2783S-2790S. discussion 2796S-2797S.PubMedGoogle Scholar
- Liu XD, Wu X, Yin YL, Liu YQ, Geng MM, Yang HS, Francois B, Wu GY: Effects of dietary L-arginineor N-carbamylglutamate supplementation during late gestation of sows on the miR-15b/16, miR-221/222, VEGFA and eNOS expression in umbilicalvein. Amino Acids. 2012, 42: 2111-2119. 10.1007/s00726-011-0948-5.PubMedPubMed CentralView ArticleGoogle Scholar
- Ren WK, Luo W, Wu MM, Liu G, Yu XL, Fang J, Li TJ, Yin YL, Wu GY: Dietary L-glutamine supplementation improves pregnancy outcome in mice infected with type-2 porcine circovirus. Amino Acids. 10.1007/s00726-011-1134-5.Google Scholar
- Ren WK, Yin YL, Liu G, Yu XL, Li YH, Yang G, Li TJ, Wu GY: Effect of dietary arginine supplementation on reproductive performance of mice with porcine circovirus type 2 (PCV2) infection. Amino Acids. 2012, 42: 2089-2094. 10.1007/s00726-011-0942-y.PubMedPubMed CentralView ArticleGoogle Scholar
- Tong BC, Barbul A: Cellular and physiological effects of arginine. Mini Rev Med Chem. 2004, 4 (8): 823-832. 10.2174/1389557043403305.PubMedView ArticleGoogle Scholar
- Wu G, Jaeger LA, Bazer FW, Rhoads JM: Arginine deficiency in preterm infants: biochemical mechanisms and nutritional implications. J Nutr Biochem. 2004, 15 (8): 442-451. 10.1016/j.jnutbio.2003.11.010.PubMedView ArticleGoogle Scholar
- Calabrese F, Valente M, Pettenazzo E, Ferraresso M, Burra P, Cadrobbi R, Cardin R, Bacelle L, Parnigotto A, Rigotti P: The protective effects of L-arginine after liver ischaemia/reperfusion injury in a pig model. J Pathol. 1997, 183 (4): 477-485. 10.1002/(SICI)1096-9896(199712)183:4<477::AID-PATH955>3.0.CO;2-E.PubMedView ArticleGoogle Scholar
- Satrustegui J, Pardo B, Del Arco A: Mitochondrial transporters as novel targets for intracellular calcium signaling. Physiolrev. 2007, 87 (1): 29-67.Google Scholar
- Beckmann RP, Mizzen LE, Welch WJ: Interaction of Hsp 70 with newly synthesized proteins: implications for protein folding and assembly. Science. 1990, 248 (4957): 850-854. 10.1126/science.2188360.PubMedView ArticleGoogle Scholar
- Johnson JL, Craig EA: Protein folding in vivo: unraveling complex pathways. Cell. 1997, 90 (2): 201-204. 10.1016/S0092-8674(00)80327-X.PubMedView ArticleGoogle Scholar
- Samali A, Orrenius S: Heat shock proteins: regulators of stress response and apoptosis. Cell Stress Chaperones. 1998, 3 (4): 228-236. 10.1379/1466-1268(1998)003<0228:HSPROS>2.3.CO;2.PubMedPubMed CentralView ArticleGoogle Scholar
- Gonzalez B, Manso R: Induction, modification and accumulation of HSP70s in the rat liver after acute exercise: early and late responses. J Physiol. 2004, 556 (Pt 2): 369-385.PubMedPubMed CentralView ArticleGoogle Scholar
- Boeri D, Dondero F, Storace D, Maiello M, Pasqualini M, Pellicci R: Heat-shock protein 70 favours human liver recovery from ischaemia-reperfusion. Euro J clin invest. 2003, 33 (6): 500-504. 10.1046/j.1365-2362.2003.01157.x.View ArticleGoogle Scholar
- Chatterjee S, Premachandran S, Sharma D, Bagewadikar RS, Poduval TB: Therapeutic treatment with L-arginine rescues mice from heat stroke-induced death: physiological and molecular mechanisms. Shock. 2005, 24 (4): 341-347. 10.1097/01.shk.0000180983.55623.2b.PubMedView ArticleGoogle Scholar
- Kim SW, Wu G: Dietary arginine supplementation enhances the growth of milk-fed young pigs. J Nutr. 2004, 134 (3): 625-630.PubMedGoogle Scholar
- NRC: Nutrient Requirements of Swine. 10th edition. Washington, DC, USA: National Academy Press; 1998.Google Scholar
- Wu X, Ruan Z, Gao Y, Yin Y, Zhou X, Wang L, Geng M, Hou Y, Wu G: Dietary supplementation with L-arginine or N-carbamylglutamate enhances intestinal growth and heat shock protein-70 expression in weanling pigs fed a corn- and soybean meal-based diet. Amino Acids. 2010, 39 (3): 831-839. 10.1007/s00726-010-0538-y.PubMedView ArticleGoogle Scholar
- Ishak K, Baptista A, Bianchi L, Callea F, De Groote J, Gudat F, Denk H, Desmet V, Korb G, MacSween RN: Histological Grading and Staging of Chronic Hepatitis. J Hepatol. 1995, 22 (6): 696-699. 10.1016/0168-8278(95)80226-6.PubMedView ArticleGoogle Scholar
- Yu H, Bao ED, Zhao RQ, Lv QX: Effect of transportation stress on heat shock protein 70 concentration and mRNA expression in heart and kidney tissues and serum enzyme activities and hormone concentrations of pigs. Am J Vet Res. 2007, 68 (11): 1145-1150. 10.2460/ajvr.68.11.1145.PubMedView ArticleGoogle Scholar
- Yao K, Yin YL, Chu W, Liu Z, Deng D, Li T, Huang R, Zhang J, Tan B, Wang W: Dietary arginine supplementation increases mTOR signaling activity in skeletal muscle of neonatal pigs. J Nutr. 2008, 138 (5): 867-872.PubMedGoogle Scholar
- Flynn NE, Meininger CJ, Haynes TE, Wu G: The metabolic basis of arginine nutrition and pharmacotherapy. Biomed Pharmacother. 2002, 56 (9): 427-438. 10.1016/S0753-3322(02)00273-1.PubMedView ArticleGoogle Scholar
- Kim W, Park H, Yun C, Cho H, Kim S, Paik W, Jeon S, Lee J: Mixture of N-carbamoyl-L-glutamate plus L-arginine can protect rats with liver cirrhosis from acute ammonia intoxication. J Hepat. 2001, 35 (6): 719-725. 10.1016/S0168-8278(01)00199-4.View ArticleGoogle Scholar
- Wu X, Zhang Y, Yin Y, Ruan Z, Yu H, Wu Z, Wu G: Roles of heat-shock protein 70 in protecting against intestinal mucosal damage. Front Biosci. 2013, 18: 356-365. 10.2741/4106.View ArticleGoogle Scholar
- Lenaerts K, Renes J, Bouwman FG, Noben JP, Robben J, Smit E, Mariman EC: Arginine deficiency in preconfluent intestinal Caco-2 cells modulates expression of proteins involved in proliferation, apoptosis, and heat shock response. Proteomics. 2007, 7 (4): 565-577. 10.1002/pmic.200600715.PubMedView ArticleGoogle Scholar
- Sepponen K, Poso AR: The inducible form of heat shock protein 70 in the serum, colon and small intestine of the pig: comparison to conventional stress markers. Vet J. 2006, 171 (3): 519-524. 10.1016/j.tvjl.2005.01.005.PubMedView ArticleGoogle Scholar
- Padmini E, Vijaya Geetha B: Impact of season on liver mitochondrial oxidative stress and the expression of HSP70 in grey mullets from contaminated estuary. Ecotox (London, England). 2009, 18 (3): 304-311. 10.1007/s10646-008-0282-1.View ArticleGoogle Scholar
- Tan BE, Yin YL, Liu ZQ, Li XG, Xu HJ, Kong XF, Huang RL, Tang WJ, Shinzato I, Smith SB, Wu GY: Dietary L-arginine supplementation increases muscle gain and reduces body fat mass in growing-finishing pigs. Amino Acids. 2009, 37: 169-175. 10.1007/s00726-008-0148-0.PubMedView ArticleGoogle Scholar
- Kong XF, Tan BE, Yin YL, Li XL, Jaeger LA, Bazer FW, Wu GY: Arginine stimulates the mTOR signaling pathway and protein synthesis in porcine trophectoderm cells. J Nutr Biochem. 2012, 23 (9): 1178-1183. 10.1016/j.jnutbio.2011.06.012.PubMedView ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.