TLR7 mediates increased vulnerability to ischemic acute kidney injury in diabetes

SUMMARY OBJECTIVE Diabetes is a risk factor for acute kidney injury (AKI). However, its mechanism of pathogenesis has not been elucidated. The aim of the study was to investigate the role of inflammation and the toll-like receptor 7 (TLR7) in ischemic AKI for diabetes. METHODS A high glucose hypoxia-reoxygenation model of human renal tubular epithelial (HK-2) cells was used to generate AKI induced by ischemia-reperfusion in diabetes. The activity of cells was measured by CCK-8 assay and LDH activity. Inflammatory cytokines were assessed by ELISA. TLR7, MyD88, and NF-κB expressions were examined by western blotting. Apoptosis was evaluated by flow cytometry. RESULTS The high glucose group and low glucose group were subjected to hypoxia-reoxygenation. The low glucose group developed only mild cell damage, apoptosis, and inflammatory response. In contrast, an equivalent hypoxia-reoxygenation injury provoked severe cell damage, apoptosis, and inflammatory response in the high glucose group. Expression of TLR7 and its related proteins were measured in the high glucose group before and after hypoxia-reoxygenation. The high glucose group exhibited more significant increases in TLR7 expression following hypoxia-reoxygenation than the low glucose group. In addition, the expression of TLR7 and its related proteins after hypoxia-reoxygenation were higher in the high glucose group than in the low glucose group. Inhibition of TLR7 provides significant protection against ischemic injury in diabetes. CONCLUSION Our results suggest that diabetes increases the vulnerability to ischemia-induced renal injury. This increased vulnerability originates from a heightened inflammatory response involving the TLR7 signal transduction pathway.

RESUMO OBJETIVO O diabetes é um fator de risco para a lesão renal aguda (LRA). No entanto, seu mecanismo de patogênese não foi elucidado. O objetivo do estudo foi investigar o papel da inflamação e do receptor Toll-like 7 (TLR7) na LRA isquêmica no diabetes. MÉTODOS Um modelo de hipóxia-reoxigenação de células epiteliais tubulares renais humanas (HK-2) na presença de concentrações altas de glicose foi utilizado para gerar LRA induzida por isquemia-reperfusão em diabetes. A atividade das células foi medida pelo ensaio Cell Counting Kit-8 (CCK-8) e pela atividade da lactato desidrogenase (LDH). As citocinas inflamatórias foram avaliadas por ensaio imunoenzimático (Elisa). A expressão de TLR7, do fator de diferenciação mieloide 88 (MyD88) e do fator de transcrição nuclear-κB (NF-κB) foi examinada por Western blotting. A apoptose foi avaliada por citometria de fluxo. RESULTADOS Os grupos glicose alta e glicose baixa foram submetidos à hipóxia-reoxigenação. O grupo de baixa glicose desenvolveu apenas danos celulares ligeiros, apoptose e uma resposta inflamatória. Em contraste, no grupo de alta glicose, uma lesão equivalente de hipóxia-reoxigenação provocou danos celulares graves, apoptose e uma resposta inflamatória. A expressão de TLR7 e suas proteínas relacionadas foi medida no grupo de alta glicose antes e após a hipóxia-reoxigenação. O grupo de alta glicose exibiu maiores aumentos na expressão de TLR7 após hipóxia-reoxigenação do que o grupo de baixa glicose. Além disso, a expressão de TLR7 e suas proteínas relacionadas após a hipóxia-reoxigenação foi maior no grupo com alto nível de glicose do que no grupo com baixo nível de glicose. A inibição do TLR7 fornece proteção significativa contra a lesão isquêmica no diabetes. CONCLUSÃO Nossos resultados sugerem que o diabetes aumenta a vulnerabilidade à lesão renal induzida por isquemia. Essa vulnerabilidade acrescida tem por origem uma resposta inflamatória aumentada envolvendo a via de transdução de sinal do TLR7.

Toll-like receptor 7 involves the injury in acute kidney ischemia/reperfusion of STZ-induced diabetic rats

ABSTRACT PURPOSE: To determine whether Toll-like receptor 7 (TLR7) is the potential targets of prevention or progression in the renal ischemia/reperfusion (I/R) injury of STZ-induced diabetic rats. METHODS: Thirty six Sprague-Dawley rats were randomly arranged to the nondiabetic (ND) or diabetic group (DM), with each group further divided into sham (no I/R injury), I/R (ischemia-reperfusion) and CD (given by Chloroquine) group. Preoperatively, Chloroquine (40 mg/kg, intraperitoneal injection.) was administrated 6 days for treatment group. I/R animals were subjected to 25 min of bilateral renal ischemia. Renal function, histology, apoptosis, cytokines, expression of TLR7, MyD88 and NF-κB were detected. RESULTS: The serum levels of blood urea nitrogen, creatinine, IL-6 and TNF-α, apoptotic tubular epithelial cells, expression of TLR7, MyD88 and NF-κB were significantly increased in DM+I/R group, compared with ND+I/R group (p<0.05). All these changes were further improved by TLR7 inhibition Chloroquine except Paller scores (p<0.05). CONCLUSION: Toll-like receptor 7 inhibition attenuates the acute renal ischemia/reperfusion injury of STZ-induced diabetic in SD rats.

Mast cells generate cysteinyl leukotrienes and interferon- as well as evince impaired IgE-dependent degranulation upon TLR7 engagement.

Mast cells are numerous at anatomical sites close to external environment, virtually at the portals of infection. A few data indicated that these cells express cytoplasmic Toll-like receptors (TLRs) recognizing virus-derived molecules. Accordingly, mast cells could participate in anti-viral defense or/and in viral-related diseases. However, data concerning the influence of viruses on mast cell activity are limited. Thus, the aim of our study was to determine mast cell response to TLR7 ligand, i.e. resiquimod (R848), a synthetic mimic of viral ssRNA. Since mast cells play a central role in allergic reactions the effect of TLR7 agonist was also investigated on FcεRI-dependent mast cell response. Experiments were carried out in vitro on freshly isolated fully mature rat peritoneal mast cells. Mast cells exhibit constitutive TLR7 molecule expression and its up-regulation after the agonist challenge. TLR7-mediated mast cell stimulation resulted in cysteinyl leukotriene (cysLT) and interferon (IFN)-β synthesis, whereas no histamine and CXCL8 secretion was stated. Moreover, mast cell priming with TLR7 ligand caused the reduction in anti-IgE-induced histamine release. The results suggest that ssRNA viruses could directly activate mast cells to alter their phenotype and to release of potent proinflammatory mediators or indirectly modulate IgE-dependent allergic processes.