The role of senescence of bone marrow cells in acute kidney injury

BACKGROUND: The prevalence of acute kidney injury (AKI) in elderly patients has grown considerably. Age-associated changes in the immune system can be one of the critical factors determining AKI outcomes. This study aimed to investigate the role of senescence of bone marrow (BM)-derived cells in the development of AKI, focusing on the immune response. METHODS: Female 7-week-old C57BL/6 mice were irradiated and treated with BM cells from either 48-week-old or 8-week-old male mice. Ischemia-reperfusion injury (IRI) was induced, and their functional deterioration, histological tubular damage, and inflammatory responses were compared. For the in-vitro study, lipopolysaccharide (LPS)-stimulated cytokine production by BM cells from old and young mice were examined. RESULTS: At 24 hours after IRI, there was no significant difference in the number of circulating immune cells between the mice transplanted with old or young BM cells. However, the mice with old BM cells showed less functional deterioration and histological tubular injury than those with young BM cells. Moreover, macrophage infiltration and renal cytokine interleukin (IL)-12 levels were lower in the mice with old BM cells at 24 hours post-IRI. Consistently, the in vitro study showed that LPS-induced production of cytokines interferon-γ, monocyte chemoattractant protein-1, and IL-10 was attenuated in cultured old BM cells, suggesting that age-related functional changes in these cells may lead to reduced inflammation in IRI. CONCLUSION: Immunosenescence could affect the susceptibility and response to renal IRI. Further studies specifically addressing age-related alterations can help in the development of treatment strategies for elderly patients with AKI.

Blocking junctional adhesion molecule C promotes the recovery of cisplatin-induced acute kidney injury

BACKGROUND/AIMS: Recent findings have demonstrated the occurrence of neutrophil transendothelial migration in the reverse direction (reverse TEM) and that endothelial junctional adhesion molecule C (JAM-C) is a negative regulator of reverse TEM. In this study, we tested the effects of a JAM-C blocking antibody on the resolution of kidney injuries and inflammation in a mouse model of cisplatin-induced acute kidney injury (AKI). METHODS: Cisplatin was administered via intraperitoneal injection. A JAM-C blocking antibody or a control immunoglobulin G was administered intraperitoneal at 1.5 mg/kg, with the injection being delayed until day 4 following cisplatin administration to restrict the effect of antibodies on recovery. RESULTS: After cisplatin injection, serum creatinine and histologic injuries peaked on day 4. Treatment with a JAM-C blocking antibody on days 4 and 5 promoted the functional and histologic recovery of cisplatin-induced AKI on days 5 and 6. Facilitating recovery with a JAM-C blocking antibody correlated with significantly increased circulating intercellular adhesion molecule 1+ Tamm-Horsfall protein+ neutrophils and significantly decreased renal neutrophil infiltration, indicating that facilitating reverse the TEM of neutrophils from the kidney to the peripheral circulation partially mediated the resolution of inflammation and recovery. CONCLUSIONS: These results demonstrated that reverse TEM is involved in the resolution of neutrophilic inflammation in cisplatin-induced AKI and that JAM-C is an important regulator of this process.

Fate of Neutrophils during the Recovery Phase of Ischemia/Reperfusion Induced Acute Kidney Injury

Effective clearance of inflammatory cells is required for resolution of inflammation. Here, we show in vivo evidence that apoptosis and reverse transendothelial migration (rTEM) are important mechanisms in eliminating neutrophils and facilitating recovery following ischemia/reperfusion injury (IRI) of the kidney. The clearance of neutrophils was delayed in the Bax knockout (KO)BM → wild-type (WT) chimera in which bone marrow derived cells are partially resistant to apoptosis, compared to WTBM → WT mice. These mice also showed delayed functional, histological recovery, increased tissue cytokines, and accelerated fibrosis. The circulating intercellular adhesion molecule-1 (ICAM-1)+ Gr-1+ neutrophils displaying rTEM phenotype increased during the recovery phase and blockade of junctional adhesion molecule-C (JAM-C), a negative regulator of rTEM, resulted in an increase in circulating ICAM-1+ neutrophils, faster resolution of inflammation and recovery. The presence of Tamm-Horsfall protein (THP) in circulating ICAM-1+ neutrophils could suggest that they are derived from injured kidneys. In conclusion, we suggest that apoptosis and rTEM are critically involved in the clearance mechanisms of neutrophils during the recovery phase of IRI.

Requirement of ERK Activation in Hypoxia Induced Caspase Activation and Apoptosis of Cultured Tubular Cells / 대한신장학회잡지

BACKGOUND: Renal tubular epithelial cells are primary target for hypoxic injury. Hypoxia induced tubular cell apoptosis has been reported previously and thought to be important mechanism of renal dysfunction in ischemic ARF, but precise signaling mechanisms need to be defined. The aim of this study is to clarify intracellular signaling mechanism mediating apoptosis by hypoxic stimuli in cultured tubular cells. METHODS: HK-2 cells were placed in hypoxic chamber (O2<1%) for 24 hrs in minimal essential medium. DNA fragmentation was detected by Hoechst 33342 stain and FACS. The activation of caspase was measured by fluorometry and activations of p-38, ERK, and JNK were examined by western blot analysis. RESULTS: Hypoxia induced caspase 3 activation and apoptosis at 24 hrs and this was accompanied by increased phosphorylation of p-38, ERK1/2, and JNK. Pretreatment of p-38 inhibitor (SB 203280) and JNK inhibitor (SP600125) did not afftect the activation of caspase 3 and apoptosis but inhibition of ERK1/2 by PD98059 resulted in partial inhibition of caspase 3 and apoptosis induced by hypoxia. CONCLUSION: ERK 1/2 activation can be an upstream signal in hypoxia induced caspase 3 activation and apoptosis in tubular cells.

The Reversible Y-Suture Lens Opacity Formation in Endotoxin Induced Uveitis Model

The present study was undertaken to find out the role of NO on cataractogenesis in the experimenally-induced uveitis(EIU) model. Nitrite and nitrate, stable oxidative products of nitric oxide(NO), were measured in the aqueous humor and the progression of inflammations and lens opacities were evaluated with slit lamp biomicroscope. Immunoperoxidase staining and immunofluorescent staining for inducible NO synthase(iNOS) and peroxynitrite were performed to confirm the site of production of NO and peroxynitrite. The grades of inflammation were peaked at 24 hours inflammation was gradually decreased after 48 hours and lens opacity after 72 hours. These changes returned to the baseline level by one week after LPS injection. Similarly, NO concentration in aqueous humor was peaked at 24 hours. And it was then decreased after 48 hours and returned to the baseline level by one week. These inflammatory signs and lens opacities were significantly decreased in NG-nitro-L-arginine methyl ester(L-NAME) administrated group. Inflammatory cells in anterior chamber, iris, and ciliary body expressed highly iNOS which was coincide with peroxynitrite immunolocalization. Therefore, these results suggest that cataract formation in EIU is related to the NO production in aqueous humor. Furthermore, lipid peroxidation by peroxynitrite is possibly related with cataractogenesis in EIU. But, we need a further evaluation to seek the relationship between cataractogenesis and increased nitric oxide concentration, combined with studies of other biochemical changes in anterior chamber and lens.