Background: Septic kidney injury is one of the most common complications in critically ill patients with a high risk of developing chronic kidney disease (CKD). Emerging data indicate that mammalian target of rapamyci (mTOR) signaling plays a major role in septic inflammation by regulating the immune response of macrophage. This study was designed to evaluate the role of mTOR signaling in kidney macrophages during endotoxemia-induced chronic kidney injury and subsequent fibrogenesis. Methods: Male C57BL/6 mice were used for all animal studies (n = 9 for each group). Lipopolysaccharide (LPS) was injected intraperitoneally (1 mg/kg) every 2 days to induce persistent endotoxemia. Rapamycin (1 mg/kg·day) was administered to a subgroup of mice 1 day prior to LPS treatment and continued to termination of the experiment. In ex-vivo experiment, RAW264.7 cells were cultured and treated with LPS (2 µg/ml) for 48 h while a subgroup of cells were incubated in the presence of rapamycin (50 nmol) for 2 h. Results: Continuous administration of LPS resulted in progressive macrophage infiltration, tubular injury and collagen deposition in mice kidneys. Rapamycin markedly ameliorated LPS-induced kidney pathological changes. Expression of pS6K was rarely observed in normal kidney macrophages, but significantly increased with time by LPS treatment. In ex-vivo study, LPS induced prominent production of IL-1β and MCP-1 in cultured RAW264.7 cells, which was significantly suppressed by rapamycin. Conclusion: Taken together, our findings show that endotoxemia results in activation of mTOR signaling in macrophages, leading to progressive kidney inflammatory injuries and subsequent fibrosis. Our study may reveal a mechanism involved in the development of sepsis-associated CKD and kidney fibrosis.

Keywords:
Kidney fibrosis, Macrophage, Inflammation, mTOR, Endotoxemina
1.
Horkan CM, Purtle SW, Mendu ML, Moromizato T, Gibbons FK, Christopher KB: The association of acute kidney injury in the critically ill and postdischarge outcomes: a cohort study. Crit Care Med 2015;43:354-364.
2.
Coca SG, Singanamala S, Parikh CR: Chronic kidney disease after acute kidney injury: a systematic review and meta-analysis. Kidney Int 2012;81:442-448.
3.
Singbartl K, Kellum JA: AKI in the ICU: definition, epidemiology, risk stratification, and outcomes. Kidney Int 2012;81:819-825.
4.
Uchino S, Kellum JA, Bellomo R, Doig GS, Morimatsu H, Morgera S, Schetz M, Tan I, Bouman C, Macedo E, Gibney N, Tolwani A, Ronco C; Beginning and Ending Supportive Therapy for the Kidney (BEST Kidney) Investigators: Acute renal failure in critically ill patients: a multinational, multicenter study. JAMA 2005;294:813-818.
5.
Zarjou A, Agarwal A: Sepsis and acute kidney injury. J Am Soc Nephrol 2011;22:999-1006.
6.
Chang JW, Jeng MJ, Yang LY, Chen TJ, Chiang SC, Soong WJ, Wu KG, Lee YS, Wang HH, Yang CF, Tsai HL: The epidemiology and prognostic factors of mortality in critically ill children with acute kidney injury in Taiwan. Kidney Int 2015;87:632-639.
7.
Lameire NH, Bagga A, Cruz D, De Maeseneer J, Endre Z, Kellum JA, Liu KD, Mehta RL, Pannu N, Van Biesen W, Vanholder R: Acute kidney injury: an increasing global concern. Lancet 2013;382:170-179.
8.
Zeisberg M, Neilson EG: Mechanisms of tubulointerstitial fibrosis. J Am Soc Nephrol 2010;21:1819-1834.
9.
Duffield JS: Macrophages and immunologic inflammation of the kidney. Semin Nephrol 2010;30:234-254.
10.
Meng XM, Nikolic-Paterson DJ, Lan HY: Inflammatory processes in renal fibrosis. Nat Rev Nephrol 2014;10:493-503.
11.
Young BA, Burdmann EA, Johnson RJ, Alpers CE, Giachelli CM, Eng E, Andoh T, Bennett WM, Couser WG: Cellular proliferation and macrophage influx precede interstitial fibrosis in cyclosporine nephrotoxicity. Kidney Int 1995;48:439-448.
12.
Yang N, Isbel NM, Nikolic-Paterson DJ, Li Y, Ye R, Atkins RC, Lan HY: Local macrophage proliferation in human glomerulonephritis. Kidney Int 1998;54:143-151.
13.
Eardley KS, Kubal C, Zehnder D, Quinkler M, Lepenies J, Savage CO, Howie AJ, Kaur K, Cooper MS, Adu D, Cockwell P: The role of capillary density, macrophage infiltration and interstitial scarring in the pathogenesis of human chronic kidney disease. Kidney Int 2008;74:495-504.
14.
Chen G, Chen H, Wang C, Peng Y, Sun L, Liu H, Liu F: Rapamycin ameliorates kidney fibrosis by inhibiting the activation of mTOR signaling in interstitial macrophages and myofibroblasts. PLoS One 2012;7:e33626.
15.
Tian S, Zhang L, Tang J, Guo X, Dong K, Chen SY: HMGB1 exacerbates renal tubulointerstitial fibrosis through facilitating M1 macrophage phenotype at the early stage of obstructive injury. Am J Physiol Renal Physiol 2015;308:F69-F75.
16.
Ko GJ, Boo CS, Jo SK, Cho WY, Kim HK: Macrophages contribute to the development of renal fibrosis following ischaemia/reperfusion-induced acute kidney injury. Nephrol Dial Transplant 2008;23:842-852.
17.
Dessing MC, Tammaro A, Pulskens WP, Teske GJ, Butter LM, Claessen N, van Eijk M, van der Poll T, Vogl T, Roth J, Florquin S, Leemans JC: The calcium-binding protein complex S100A8/A9 has a crucial role in controlling macrophage-mediated renal repair following ischemia/reperfusion. Kidney Int 2015;87:85-94.
18.
Novitskaya T, McDermott L, Zhang KX, Chiba T, Paueksakon P, Hukriede NA, de Caestecker MP: A PTBA small molecule enhances recovery and reduces postinjury fibrosis after aristolochic acid-induced kidney injury. Am J Physiol Renal Physiol 2014;306:F496-F504.
19.
Han Y, Ma FY, Tesch GH, Manthey CL, Nikolic-Paterson DJ: Role of macrophages in the fibrotic phase of rat crescentic glomerulonephritis. Am J Physiol Renal Physiol 2013;304:F1043-F1053.
20.
Cao Q, Wang Y, Zheng D, Sun Y, Wang Y, Lee VW, Zheng G, Tan TK, Ince J, Alexander SI, Harris DC: IL-10/TGF-beta-modified macrophages induce regulatory T cells and protect against adriamycin nephrosis. J Am Soc Nephrol 2010;21:933-942.
21.
Doi K, Leelahavanichkul A, Yuen PS, Star RA: Animal models of sepsis and sepsis-induced kidney injury. J Clin Invest 2009;119:2868-2878.
22.
Vaidya VS, Ozer JS, Dieterle F, Collings FB, Ramirez V, Troth S, Muniappa N, Thudium D, Gerhold D, Holder DJ, Bobadilla NA, Marrer E, Perentes E, Cordier A, Vonderscher J, Maurer G, Goering PL, Sistare FD, Bonventre JV: Kidney injury molecule-1 outperforms traditional biomarkers of kidney injury in preclinical biomarker qualification studies. Nat Biotechnol 2010;28:478-485.
23.
Lieberthal W, Fuhro R, Andry C, Patel V, Levine JS: Rapamycin delays but does not prevent recovery from acute renal failure: role of acquired tubular resistance. Transplantation 2006;82:17-22.
24.
Humphreys BD, Xu F, Sabbisetti V, Grgic I, Movahedi Naini S, Wang N, Chen G, Xiao S, Patel D, Henderson JM, Ichimura T, Mou S, Soeung S, McMahon AP, Kuchroo VK, Bonventre JV: Chronic epithelial kidney injury molecule-1 expression causes murine kidney fibrosis. J Clin Invest 2013;123:4023-4035.
25.
Bode JG, Ehlting C, Häussinger D: The macrophage response towards LPS and its control through the p38(MAPK)-STAT3 axis. Cell Signal 2012;24:1185-1194.
26.
Chawla LS, Kimmel PL: Acute kidney injury and chronic kidney disease: an integrated clinical syndrome. Kidney Int 2012;82:516-524.
27.
Susnik N, Sörensen-Zender I, Rong S, von Vietinghoff S, Lu X, Rubera I, Tauc M, Falk CS, Alexander WS, Melk A, Haller H, Schmitt R: Ablation of proximal tubular suppressor of cytokine signaling 3 enhances tubular cell cycling and modifies macrophage phenotype during acute kidney injury. Kidney Int 2014;85:1357-1368.
28.
Huen SC, Huynh L, Marlier A, Lee Y, Moeckel GW, Cantley LG: GM-CSF promotes macrophage alternative activation after renal ischemia/reperfusion injury. J Am Soc Nephrol 2015;26:1334-1345.
29.
Anders HJ, Ryu M: Renal microenvironments and macrophage phenotypes determine progression or resolution of renal inflammation and fibrosis. Kidney Int 2011;80:915-925.
30.
Karasawa K, Asano K, Moriyama S, Ushiki M, Monya M, Iida M, Kuboki E, Yagita H, Uchida K, Nitta K, Tanaka M: Vascular-resident cd169-positive monocytes and macrophages control neutrophil accumulation in the kidney with ischemia-reperfusion injury. J Am Soc Nephrol 2015;26:896-906.
31.
Lee S, Huen S, Nishio H, Nishio S, Lee HK, Choi BS, Ruhrberg C, Cantley LG: Distinct macrophage phenotypes contribute to kidney injury and repair. J Am Soc Nephrol 2011;22:317-326.
32.
Lu J, Cao Q, Zheng D, Sun Y, Wang C, Yu X, Wang Y, Lee VW, Zheng G, Tan TK, Wang X, Alexander SI, Harris DC, et al: Discrete functions of M2a and M2c macrophage subsets determine their relative efficacy in treating chronic kidney disease. Kidney Int 2013;84:745-755.
33.
Ferenbach DA, Sheldrake TA, Dhaliwal K, Kipari TM, Marson LP, Kluth DC, Hughes J: Macrophage/monocyte depletion by clodronate, but not diphtheria toxin, improves renal ischemia/reperfusion injury in mice. Kidney Int 2012;82:928-933.
34.
Dessing MC, Tammaro A, Pulskens WP, Teske GJ, Butter LM, Claessen N, van Eijk M, van der Poll T, Vogl T, Roth J, Florquin S, Leemans JC: The calcium-binding protein complex S100A8/A9 has a crucial role in controlling macrophage-mediated renal repair following ischemia/reperfusion. Kidney Int 2015;87:85-94.
35.
Ma FY, Ikezumi Y, Nikolic-Paterson DJ: Macrophage signaling pathways: a novel target in renal disease. Semin Nephrol 2010;30:334-344.
36.
Lin HY, Chang KT, Hung CC, Kuo CH, Hwang SJ, Chen HC, Hung CH, Lin SF: Effects of the mTOR inhibitor rapamycin on monocyte-secreted chemokines. BMC Immunol 2014;15:37.
37.
Dos Santos S, Delattre AI, De Longueville F, Bult H, Raes M: Gene expression profiling of LPS-stimulated murine macrophages and role of the NF-kappaB and PI3K/mTOR signaling pathways. Ann N Y Acad Sci 2007;1096:70-77.
38.
Lloberas N, Cruzado JM, Franquesa M, Herrero-Fresneda I, Torras J, Alperovich G, Rama I, Vidal A, Grinyó JM: Mammalian target of rapamycin pathway blockade slows progression of diabetic kidney disease in rats. J Am Soc Nephrol 2006;17:1395-1404.
39.
Braun WE, Schold JD, Stephany BR, Spirko RA, Herts BR: Low-dose rapamycin (sirolimus) effects in autosomal dominant polycystic kidney disease: an open-label randomized controlled pilot study. Clin J Am Soc Nephrol 2014;9:881-888.
40.
Dong G, Liu Y, Zhang L, Huang S, Ding HF, Dong Z: mTOR contributes to ER stress and associated apoptosis in renal tubular cells. Am J Physiol Renal Physiol 2015;308:F267-F274.
41.
Howell GM, Gomez H, Collage RD, Loughran P, Zhang X, Escobar DA, Billiar TR, Zuckerbraun BS, Rosengart MR: Augmenting autophagy to treat acute kidney injury during endotoxemia in mice. PLoS One 2013;8:e69520.
42.
Nazio F, Strappazzon F, Antonioli M, Bielli P, Cianfanelli V, Bordi M, Gretzmeier C, Dengjel J, Piacentini M, Fimia GM, Cecconi F: mTOR inhibits autophagy by controlling ULK1 ubiquitylation, self-association and function through AMBRA1 and TRAF6. Nat Cell Biol 2013;15:406-416.
43.
Huber TB, Edelstein CL, Hartleben B, Inoki K, Jiang M, Koya D, Kume S, Lieberthal W, Pallet N, Quiroga A, Ravichandran K, Susztak K, Yoshida S, Dong Z: Emerging role of autophagy in kidney function, diseases and aging. Autophagy 2012;8:1009-1031.
44.
Harris J, Hartman M, Roche C, Zeng SG, O'Shea A, Sharp FA, Lambe EM, Creagh EM, Golenbock DT, Tschopp J, Kornfeld H, Fitzgerald KA, Lavelle EC: Autophagy controls IL-1beta secretion by targeting pro-IL-1beta for degradation. J Biol Chem 2011;286:9587-9597.
45.
Giegerich AK, Kuchler L, Sha LK, Knape T, Heide H, Wittig I, Behrends C, Brüne B, von Knethen A: Autophagy-dependent PELI3 degradation inhibits proinflammatory IL1B expression. Autophagy 2014;10:1937-1952.
46.
Shi CS, Shenderov K, Huang NN, Kabat J, Abu-Asab M, Fitzgerald KA, Sher A, Kehrl JH: Activation of autophagy by inflammatory signals limits IL-1β production by targeting ubiquitinated inflammasomes for destruction. Nat Immunol 2012;13:255-263.
47.
Linkermann A, Green DR: Necroptosis. N Engl J Med 2014;370:455-465.
48.
Linkermann A, Stockwell BR, Krautwald S, Anders HJ: Regulated cell death and inflammation: an auto-amplification loop causes organ failure. Nat Rev Immunol 2014;14:759-767.
49.
Mulay SR, Linkermann A, Anders HJ: Necroinflammation in kidney disease. J Am Soc Nephrol 2015; pii:ASN.2015040405.
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