Myung-Gyu Kim

INTRODUCTION: Acute kidney injury (AKI) is a major risk factor in the development of chronic kidney disease (CKD). However, the mechanisms linking AKI to CKD remain unclear. We examined the alteration of macrophage phenotypes during an extended recovery period following ischemia/reperfusion injury (IRI) and determine their roles in the development of fibrosis. METHODS: The left renal pedicle of mice was clamped for 40 min. To deplete monocyte/macrophage, liposome clodronate was injected or CD11b-DTR and CD11c-DTR transgenic mice were used. RESULTS: Throughout the phase of IRI recovery, M2-phenotype macrophages made up the predominant macrophage subset. On day 28, renal fibrosis was clearly shown with increased type IV collagen and TGF-β. The depletion of macrophages induced by the liposome clodronate injection improved renal fibrosis with a reduction of kidney IL-6, type IV collagen, and TGF-β levels. Additionally, the adoptive transfer of the M2c macrophages partially reversed the beneficial effect of macrophage depletion, whereas the adoptive transfer of the M1 macrophages did not. M2 macrophages isolated from the kidneys during the recovery phase expressed 2.5 fold higher levels of TGF-β than the M1 macrophages. The injection of the diphtheria toxin into CD11b or CD11c-DTR transgenic mice resulted in lesser depletion or no change in M2 macrophages and had little impact on renal fibrosis. CONCLUSION: Although M2 macrophages are known to be indispensible for short-term recovery, they are thought to be main culprit in the development of renal fibrosis following IRI.

BACKGROUND: Emerging evidence suggests that intestinal dysbiosis is associated with diverse pathological processes. In this study we demonstrated intestinal barrier disruption and aberrant mucosal immunity in 5/6 nephrectomized mice and the effect of probiotics on chronic kidney disease (CKD). METHODS: CKD was induced in 6-week-old mice by 5/6 nephrectomy. They were fed a lactobacilli mixture for 8 weeks. Serum, urine and stool samples were collected for renal function assessments and gut microbiome analyses. Gut permeability, colon heat shock protein 70 (HSP70) and colon epithelial integrity were evaluated and cytokine levels in colon and kidney were measured. Colon leukocytes were analyzed by flow cytometry and bone marrow-derived cells were cocultured with lactobacilli mixture. RESULTS: In CKD mice, 'leaky gut' was accompanied by decreased colon HSP70 and claudin-1 expression, whereas it increased pore-forming claudin-2 expression and apoptosis. Although the percentage of regulatory T cells did not differ between CKD and control mice, cytokine expression and the ratio of CX3CR1intermediate:CX3CR1high pro-inflammatory/resident macrophages increased in the colon of CKD mice. Orally administered lactobacilli partially mitigated the CKD-induced 'leaky gut'; restored colon epithelial HSP70, claudin-1 and claudin-2 expression and decreased apoptosis. Probiotic treatment also restored the CX3CR1intermediate:CX3CR1high macrophage ratio and increased circular dichroism (CD)103+CD11c+ regulatory dendritic cells in the colon. These changes suppressed systemic inflammation and kidney fibrosis. CONCLUSIONS: Our results suggest that intestinal dysbiosis-associated gut barrier disruption and aberrant mucosal immunity are important for the systemic inflammation and progressive fibrosis of CKD. Targeting the intestine might provide novel therapeutic opportunities for CKD.

Regulatory T cells (Tregs) can suppress immunologic damage in renal ischemia-reperfusion injury (IRI), but the isolation and ex vivo expansion of these cells for clinical application remains challenging. Here, we investigated whether the IL-2/anti-IL-2 complex (IL-2C), a mediator of Treg expansion, can attenuate renal IRI in mice. IL-2C administered before bilateral renal IRI induced Treg expansion in both spleen and kidney, improved renal function, and attenuated histologic renal injury and apoptosis after IRI. Furthermore, IL-2C administration reduced the expression of inflammatory cytokines and attenuated the infiltration of neutrophils and macrophages in renal tissue. Depletion of Tregs with anti-CD25 antibodies abrogated the beneficial effects of IL-2C. However, IL-2C-mediated renal protection was not dependent on either IL-10 or TGF-β. Notably, IL-2C administered after IRI also enhanced Treg expansion in spleen and kidney, increased tubular cell proliferation, improved renal function, and reduced renal fibrosis. In conclusion, these results indicate that IL-2C-induced Treg expansion attenuates acute renal damage and improves renal recovery in vivo, suggesting that IL-2C may be a therapeutic strategy for renal IRI.

BACKGROUND: Although intraperitoneal surgery is a major operation associated with postoperative acute kidney injury (AKI), the incidence, risk factors, and long-term renal outcome are not well known. We aimed to determine the risk factors and 6 months renal outcome in patients with clinical or subclinical AKI after hepatobiliary surgery. We also assessed the validity of urine neutrophil gelatinase-associated lipocalin (NGAL) in the early detection of AKI or prediction of renal outcome. METHODS: This prospective observational study enrolled patients with normal renal function who underwent hepatobiliary surgeries. Urine and serum samples were collected for NGAL measurement. RESULTS: Among 131 patients, 10 (7.6%) developed postoperative AKI. Urine NGAL at 12 h postsurgery was the most predictive parameter for the diagnosis of AKI (cutoff, 92.85 ng/mL). With the cutoff value, subclinical AKI was diagnosed in 42 (32.1%) patients. Patients with clinical AKI and those with subclinical AKI were assigned to the AKI group. The AKI group had significantly higher model for end-stage liver disease and sodium (MELD-Na) score, lower albumin level, and longer hospital stay after surgery than the non-AKI group. Older age and higher MELD-Na score were independent risk factors for the development of postoperative AKI. At 6 months postsurgery, the estimated glomerular filtration rate (eGFR) in the AKI group was significantly lower than that in the non-AKI group, although the baseline eGFR was not different. In multiple linear regression analysis, the maximum urine NGAL level during 24 h postsurgery, intraoperative fluid balance, and having liver transplantation were significantly associated with a poor 6 months renal outcome. CONCLUSION: Urine NGAL was useful in the early diagnosis of postoperative AKI as well as in predicting the 6 months renal outcome after hepatobiliary surgery. A considerable proportion of patients developed subclinical AKI, and these patients showed worse renal outcome compared with the non-AKI group.