The TIM-1:TIM-4 pathway enhances renal ischemia-reperfusion injury

Kidney Injury in a Murine Hemorrhagic Shock/Resuscitation Model Is Alleviated by sulforaphane's Anti-Inflammatory and Antioxidant Action

Hemorrhagic shock/resuscitation (HS/R) can lead to acute kidney injury, mainly manifested as oxidative stress and inflammatory injury in the renal tubular epithelial cells, as well as abnormal autophagy and apoptosis. Sulforaphane (SFN), an agonist of the nuclear factor-erythroid factor 2-related factor 2 (Nrf2) signaling pathway, is involved in multiple biological activities, such as anti-inflammatory, antioxidant, autophagy, and apoptosis regulation. This study investigated the effect of SFN on acute kidney injury after HS/R in mice. Hemorrhagic shock was induced in mice by controlling the arterial blood pressure at a range of 35-45 mmHg for 90 min within arterial blood withdrawal. Fluid resuscitation was carried out by reintroducing withdrawn blood and 0.9% NaCl. We found that SFN suppressed the elevation of urea nitrogen and serum creatinine levels in the blood induced by HS/R. SFN mitigated pathological alterations including swollen renal tubules and renal casts in kidney tissue of HS/R mice. Inflammation levels and oxidative stress were significantly downregulated in mouse kidney tissue after SFN administration. In addition, the kidney tissue of HS/R mice showed high levels of autophagosomes as observed by electron microscopy. However, SFN can further enhance the formation of autophagosomes in the HS/R + SFN group. SFN also increased autophagy-related proteins Beclin1 expression and suppressed P62 expression, while increasing the ratio of microtubule-associated protein 1 light chain 3 (LC3)-II and LC3-I (LC3-II/LC3-I). SFN also effectively decreased cleaved caspase-3 level and enhanced the ratio of anti-apoptotic protein B cell lymphoma 2 and Bcl2-associated X protein (Bcl2/Bax). Collectively, SFN effectively inhibited inflammation and oxidative stress, enhanced autophagy, thereby reducing HS/R-induced kidney injury and apoptosis levels in mouse kidneys.

TIM proteins and microRNAs: distinct impact and promising interactions on transplantation immunity

Achieving sustained activity and tolerance in of allogeneic grafts after post-transplantation remains a substantial challenge. The response of the immune system to "non-self" MHC-antigenic peptides initiates a crucial phase, wherein blocking positive co-stimulatory signals becomes imperative to ensure graft survival and tolerance. MicroRNAs (miRNAs) inhibit mRNA translation or promote mRNA degradation by complementary binding of mRNA seed sequences, which ultimately affects protein synthesis. These miRNAs exhibit substantial promise as diagnostic, prognostic, and therapeutic candidates for within the realm of solid organ transplantations. Current research has highlighted three members of the T cell immunoglobulin and mucin domain (TIM) family as a novel therapeutic avenue in transplantation medicine and alloimmunization. The interplay between miRNAs and TIM proteins has been extensively explored in viral infections, inflammatory responses, and post-transplantation ischemia-reperfusion injuries. This review aims to elucidate the distinct roles of miRNAs and TIM in transplantation immunity and delineate their interdependent relationships in terms of targeted regulation. Specifically, this investigation sought seeks to uncover the potential of miRNA interaction with TIM, aiming to induce immune tolerance and bolster allograft survival after transplantation. This innovative strategy holds substantial promise in for the future of transplantation science and practice.

Quantitative proteomics analysis reveals the protective role of S14G-humanin in septic acute kidney injury using 4D-label-free and PRM Approaches

Mitochondrial dysfunction contributes to septic acute kidney injury (S-AKI), making mitochondrial protection a potential therapeutic strategy. This study investigates the effects of S14G-humanin (HNG) in S-AKI, utilizing 4D-label-free and parallel reaction monitoring (PRM) techniques for proteomic analysis. An S-AKI model was created in male C57BL/6 mice using lipopolysaccharide (LPS) injection, followed by HNG administration. After 24 h, kidney tissues were analyzed for histology, biochemistry, mitochondrial function, and proteomics. HNG treatment improved renal function, reduced tubular injury, and decreased pro-inflammatory cytokines and oxidative stress markers. Proteomic analysis identified 5900 proteins, with 5111 quantifiable. HNG altered the expression of 132 proteins, with 18 selected for PRM validation. Ten of these proteins were linked to key pathways, including fatty acid degradation and PPAR signaling. This study is the first to show HNG's protective effects in S-AKI, providing insights into its mechanisms through advanced proteomic techniques.

Extreme Heat Exposure Induced Acute Kidney Injury through NLRP3 Inflammasome Activation in Mice

Climate change has resulted in a marked increase in heat extremes that carry a severe risk for morbidity and mortality. Kidney is sensitive to heat stimulation, and acute kidney injury (AKI) is the early event. In this study, we investigated the adverse effects of heat extremes and their underlying mechanism. A total of 16 wild-type C57BL/6N mice were randomly divided into groups of control (exposed to 22 ± 0.5 °C) and heat (exposed to 39.5 ± 0.5 °C until the core body temperature reached the maximum). First, extreme heat exposure induced AKI evidenced by kidney dysfunction and morphological impairment. In addition, heat exposure suppressed expression of molecules for mitochondrial energetics and fatty acid beta-oxidation and disturbed the balance of oxidative stress in the kidney. Moreover, heat exposure enhanced the protein levels in the upstream signaling pathway for NLRP3 inflammasome formation, followed by NLRP3 inflammasome activation and inflammatory cytokine production. These findings demonstrated that acute extreme heat exposure may induce AKI through the NLRP3 inflammasome formation and activation.

Aurantio-obtusin exerts an anti-inflammatory effect on acute kidney injury by inhibiting NF-κB pathway

Acute kidney injury (AKI) is one of the major complications of sepsis. Aurantio-obtusin (AO) is an anthraquinone compound with antioxidant and anti-inflammatory activities. This study was developed to concentrate on the role and mechanism of AO in sepsis-induced AKI. Lipopolysaccharide (LPS)-stimulated human renal proximal tubular epithelial cells (HK-2) and BALB/c mice receiving cecal ligation and puncture (CLP) surgery were used to establish in vitro cell model and in vivo mouse model. HK-2 cell viability was measured using MTT assays. Histological alterations of mouse renal tissues were analyzed via hematoxylin and eosin staining. Renal function of mice was assessed by measuring the levels of serum creatinine (SCr) and blood urea nitrogen (BUN). The concentrations of pro-inflammatory cytokines in HK-2 cells and serum samples of mice were detected using corresponding ELISA kits. Protein levels of factors associated with nuclear factor kappa-B (NF-κB) pathway were measured in HK-2 cells and renal tissues by Western blotting. AO exerted no cytotoxic effect on HK-2 cells and AO dose-dependently rescued LPS-induced decrease in HK-2 cell viability. The concentrations of pro-inflammatory cytokines were increased in response to LPS or CLP treatment, and the alterations were reversed by AO treatment. For in vivo experiments, AO markedly ameliorated renal injury and reduced high levels of SCr and BUN in mice underwent CLP operation. In addition, AO administration inhibited the activation of NF-κB signaling pathway in vitro and in vivo. In conclusion, AO alleviates septic AKI by suppressing inflammatory responses through inhibiting the NF-κB pathway.

Biotherapy of experimental acute kidney injury: emerging novel therapeutic strategies

Acute kidney injury (AKI) is a complex and heterogeneous disease with high incidence and mortality, posing a serious threat to human life and health. Usually, in clinical practice, AKI is caused by crush injury, nephrotoxin exposure, ischemia-reperfusion injury, or sepsis. Therefore, most AKI models for pharmacological experimentation are based on this. The current research promises to develop new biological therapies, including antibody therapy, non-antibody protein therapy, cell therapy, and RNA therapy, that could help mitigate the development of AKI. These approaches can promote renal repair and improve systemic hemodynamics after renal injury by reducing oxidative stress, inflammatory response, organelles damage, and cell death, or activating cytoprotective mechanisms. However, no candidate drugs for AKI prevention or treatment have been successfully translated from bench to bedside. This article summarizes the latest progress in AKI biotherapy, focusing on potential clinical targets and novel treatment strategies that merit further investigation in future pre-clinical and clinical studies.

Immune surveillance and humoral immune responses in kidney transplantation - A look back at T follicular helper cells

T follicular helper cells comprise a specialized, heterogeneous subset of immune-competent T helper cells capable of influencing B cell responses in lymphoid tissues. In physiology, for example in response to microbial challenges or vaccination, this interaction chiefly results in the production of protecting antibodies and humoral memory. In the context of kidney transplantation, however, immune surveillance provided by T follicular helper cells can take a life of its own despite matching of human leukocyte antigens and employing the latest immunosuppressive regiments. This puts kidney transplant recipients at risk of subclinical and clinical rejection episodes with a potential risk for allograft loss. In this review, the current understanding of immune surveillance provided by T follicular helper cells is briefly described in physiological responses to contrast those pathological responses observed after kidney transplantation. Sensitization of T follicular helper cells with the subsequent emergence of detectable donor-specific human leukocyte antigen antibodies, non-human leukocyte antigen antibodies their implication for kidney transplantation and lessons learnt from other transplantation "settings" with special attention to antibody-mediated rejection will be addressed.

A model of porcine polymicrobial septic shock

BACKGROUND

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Mortality of patients with sepsis is high and largely unchanged throughout the past decades. Animal models have been widely used for the study of sepsis and septic shock, but translation into effective treatment regimes in the clinic have mostly failed. Pigs are considered as suitable research models for human diseases due to their high comparability and similarity to human anatomy, genetics, and the immune system. We here evaluated the previously reported models of septic shock in pigs and established a novel model of polymicrobial sepsis that meets the clinical criteria of septic shock in pigs.

MATERIALS AND METHODS

The literature search was performed using the keywords "pig", "sepsis" and "septic shock". For the establishment of septic shock in n = 10 German landrace pigs, mechanical ventilation was initiated, central venous and arterial lines and invasive hemodynamic monitoring via pulse contour cardiac output measurement (PiCCO) established. Peritoneal polymicrobial faecal sepsis was induced by application of 3 g/kg body weight faeces into the abdominal cavity. Septic shock was defined according to the third international consensus definitions (Sepsis-3). Upon shock, pigs underwent the 1-h bundle for the treatment of human sepsis. Cytokine levels were measured by ELISA.

RESULTS

Published porcine sepsis models exhibited high methodological variability and did not meet the clinical criteria of septic shock. In our model, septic shock developed after an average of 4.8 ± 0.29 h and was associated with a reproducible drop in blood pressure (mean arterial pressure 54 ± 1 mmHg) and significant hyperlactatemia (3.76 ± 0.65 mmol/L). Septic shock was associated with elevated levels of interleukin-6 (IL6) and initial cardiac depression followed by a hyperdynamic phase with significant loss of systemic vascular resistance index after initial resuscitation. In addition, organ dysfunction (acute kidney injury) occurred.

CONCLUSIONS

We here established a model of septic shock in pigs that meets the clinical criteria of septic shock utilized in human patients. Our model may thus serve as a reference for clinically relevant sepsis research in pigs.

FFAR4 improves the senescence of tubular epithelial cells by AMPK/SirT3 signaling in acute kidney injury

Acute kidney injury (AKI) is a serious clinical complication with high morbidity and mortality rates. Despite substantial progress in understanding the mechanism of AKI, no effective therapy is available for treatment or prevention. We previously found that G protein-coupled receptor (GPCR) family member free fatty acid receptor 4 (FFAR4) agonist TUG891 alleviated kidney dysfunction and tubular injury in AKI mice. However, the versatile role of FFAR4 in kidney has not been well characterized. In the study, the expression of FFAR4 was abnormally decreased in tubular epithelial cells (TECs) of cisplatin, cecal ligation/perforation and ischemia/reperfusion injury-induced AKI mice, respectively. Systemic and conditional TEC-specific knockout of FFAR4 aggravated renal function and pathological damage, whereas FFAR4 activation by TUG-891 alleviated the severity of disease in cisplatin-induced AKI mice. Notably, FFAR4, as a key determinant, was firstly explored to regulate cellular senescence both in injured kidneys of AKI mice and TECs, which was indicated by senescence-associated β-galactosidase (SA-β-gal) activity, marker protein p53, p21, Lamin B1, phospho-histone H2A.X, phospho-Rb expression, and secretory phenotype IL-6 level. Mechanistically, pharmacological activation and overexpression of FFAR4 reversed the decrease of aging-related SirT3 protein, where FFAR4 regulated SirT3 expression to exhibit anti-senescent effect via Gq subunit-mediated CaMKKβ/AMPK signaling in cisplatin-induced mice and TECs. These findings highlight the original role of tubular FFAR4 in cellular senescence via AMPK/SirT3 signaling and identify FFAR4 as a potential drug target against AKI.

Immune response associated with ischemia and reperfusion injury during organ transplantation

Background

Ischemia and reperfusion injury (IRI) is an ineluctable immune-related pathophysiological process during organ transplantation, which not only causes a shortage of donor organs, but also has long-term and short-term negative consequences on patients. Severe IRI-induced cell death leads to the release of endogenous substances, which bind specifically to receptors on immune cells to initiate an immune response. Although innate and adaptive immunity have been discovered to play essential roles in IRI in the context of organ transplantation, the pathway and precise involvement of the immune response at various stages has not yet to be elucidated.

Methods

We combined “IRI” and “organ transplantation” with keywords, respectively such as immune cells, danger signal molecules, macrophages, neutrophils, natural killer cells, complement cascade, T cells or B cells in PubMed and the Web of Science to search for relevant literatures.

Conclusion

Comprehension of the immune mechanisms involved in organ transplantation is promising for the treatment of IRI, this review summarizes the similarities and differences in both innate and adaptive immunity and advancements in the immune response associated with IRI during diverse organ transplantation.

T-Cell Immunoglobulin and Mucin Domain-Containing Protein-4 Is Critical for Kupffer Cell Homeostatic Function in the Activation and Resolution of Liver Ischemia Reperfusion Injury

BACKGROUND AND AIMS

Liver ischemia reperfusion injury (IRI) remains an unresolved clinical problem. This study dissected roles of liver-resident macrophage Kupffer cells (KCs), with a functional focus on efferocytosis receptor T-cell immunoglobulin and mucin domain-containing protein-4 (TIM-4), in both the activation and resolution of IRI in a murine liver partial warm ischemia model.

APPROACH AND RESULTS

Fluorescence-activated cell sorting results showed that TIM-4 was expressed exclusively by KCs, but not infiltrating macrophages (iMФs), in IR livers. Anti-TIM-4 antibody depleted TIM-4⁺ macrophages in vivo, resulting in either alleviation or deterioration of liver IRI, which was determined by the repopulation kinetics of the KC niche with CD11b⁺ macrophages. To determine the KC-specific function of TIM-4, we reconstituted clodronate-liposome-treated mice with exogenous wild-type or TIM-4-deficient KCs at either 0 hour or 24 hours postreperfusion. TIM-4 deficiency in KCs resulted in not only increases in the severity of liver IRI (at 6 hours postreperfusion), but also impairment of the inflammation resolution (at 7 days postreperfusion). In vitro analysis revealed that TIM-4 promoted KC efferocytosis to regulate their Toll-like receptor response by up-regulating IL-10 and down-regulating TNF-α productions.

CONCLUSIONS

TIM-4 is critical for KC homeostatic function in both the activation and resolution of liver IRI by efferocytosis.

Kidney injury molecule-1 is a potential receptor for SARS-CoV-2

COVID-19 patients present high incidence of kidney abnormalities, which are associated with poor prognosis and mortality. The identification of SARS-CoV-2 in the kidney of COVID-19 patients suggests renal tropism of SARS-CoV-2. However, whether there is a specific target of SARS-CoV-2 in the kidney remains unclear. Herein, by using in silico simulation, coimmunoprecipitation, fluorescence resonance energy transfer, fluorescein isothiocyanate labeling, and rational design of antagonist peptides, we demonstrate that kidney injury molecule-1 (KIM1), a molecule dramatically upregulated upon kidney injury, binds with the receptor-binding domain (RBD) of SARS-CoV-2 and facilitates its attachment to cell membrane, with the immunoglobulin variable Ig-like (Ig V) domain of KIM1 playing a key role in this recognition. The interaction between SARS-CoV-2 RBD and KIM1 is potently blockaded by a rationally designed KIM1-derived polypeptide AP2. In addition, our results also suggest interactions between KIM1 Ig V domain and the RBDs of SARS-CoV and MERS-CoV, pathogens of two severe infectious respiratory diseases. Together, these findings suggest KIM1 as a novel receptor for SARS-CoV-2 and other coronaviruses. We propose that KIM1 may thus mediate and exacerbate the renal infection of SARS-CoV-2 in a ‘vicious cycle’, and KIM1 could be further explored as a therapeutic target.

Expression of 4-Hydroxynonenal (4-HNE) and Heme Oxygenase-1 (HO-1) in the Kidneys of Plasmodium berghei-Infected Mice

Acute kidney injury (AKI) is one of the most serious complications of severe Plasmodium falciparum malaria, but the exact pathogenic mechanisms of AKI in P. falciparum infection have not been clearly elucidated. We hypothesized that oxidative stress is a potential mediator of acute tubular necrosis in P. falciparum-infected kidneys. Therefore, this study aimed to investigate the histopathological changes and markers of oxidative stress in kidney tissues from mice with experimental malaria. DBA/2 mice were divided into two groups: the mice in the malaria-infected group (n = 10) were intraperitoneally injected with 1 × 10⁶P. berghei ANKA-infected red blood cells, and the mice in the control group (n = 10) were intraperitoneally injected with a single dose of 0.85% normal saline. Kidney sections were collected and used for histopathological examination and the investigation of 4-hydroxynonenal (4-HNE) and heme oxygenase-1 (HO-1) expression through immunohistochemistry staining. The histopathology study revealed that the P. berghei-infected kidneys exhibited a greater area of tubular necrosis than those of the control group (p < 0.05). The positive staining scores for 4-HNE and HO-1 expression in tubular epithelial cells of the P. berghei-infected group were significantly higher than those found for the control group (p < 0.05). In addition, significant positive correlations were found between the tubular necrosis score and the positive staining scores for 4-HNE and HO-1 in the kidneys from the P. berghei-infected group. In conclusion, this finding demonstrates that increased expression of 4-HNE and HO-1 might be involved in the pathogenesis of acute tubular damage in the kidneys during malaria infection. Our results provide new insights into the pathogenesis of malaria-associated AKI and might provide guidelines for the future development of a therapeutic intervention for malaria.

Histone Methylation Inhibitor DZNep Ameliorated the Renal Ischemia-Reperfusion Injury via Inhibiting TIM-1 Mediated T Cell Activation

Renal ischemia-reperfusion injury (IRI) after renal transplantation often leads to the loss of kidney graft function. However, there is still a lack of efficient regimens to prevent or alleviate renal IRI. Our study focused on the renoprotective effect of 3-Deazaneplanocin A (DZNep), which is a histone methylation inhibitor. We found that DZNep significantly alleviated renal IRI by suppressing nuclear factor kappa-B (NF-κB), thus inhibiting the expression of inflammatory factors in renal tubular epithelial cells in vivo or in vitro. After treatment with DZNep, T cell activation was impaired in the spleen and kidney, which correlated with the downregulated expression of T-cell immunoglobulin mucin (TIM)-1 on T cells and TIM-4 in macrophages. In addition, pretreatment with DZNep was not sufficient to protect the kidney, while administration of DZNep from before to after surgery significantly ameliorated IRI. Our findings suggest that DZNep can be a novel strategy for preventing renal IRI following kidney transplantation.

Modification of an aggressive model of Alport Syndrome reveals early differences in disease pathogenesis due to genetic background

The link between mutations in collagen genes and the development of Alport Syndrome has been clearly established and a number of animal models, including knock-out mouse lines, have been developed that mirror disease observed in patients. However, it is clear from both patients and animal models that the progression of disease can vary greatly and can be modified genetically. We have identified a point mutation in Col4a4 in mice where disease is modified by strain background, providing further evidence of the genetic modification of disease symptoms. Our results indicate that C57BL/6J is a protective background and postpones end stage renal failure from 7 weeks, as seen on a C3H background, to several months. We have identified early differences in disease progression, including expression of podocyte-specific genes and podocyte morphology. In C57BL/6J mice podocyte effacement is delayed, prolonging normal renal function. The slower disease progression has allowed us to begin dissecting the pathogenesis of murine Alport Syndrome in detail. We find that there is evidence of differential gene expression during disease on the two genetic backgrounds, and that disease diverges by 4 weeks of age. We also show that an inflammatory response with increasing MCP-1 and KIM-1 levels precedes loss of renal function.

Costimulation Blockade in Transplantation

T cells play a pivotal role in orchestrating immune responses directed against a foreign (allogeneic) graft. For T cells to become fully activated, the T-cell receptor (TCR) must interact with the major histocompatibility complex (MHC) plus peptide complex on antigen-presenting cells (APCs), followed by a second "positive" costimulatory signal. In the absence of this second signal, T cells become anergic or undergo deletion. By blocking positive costimulatory signaling, T-cell allo-responses can be aborted, thus preventing graft rejection and promoting long-term allograft survival and possibly tolerance (Alegre ML, Najafian N, Curr Mol Med 6:843-857, 2006; Li XC, Rothstein DM, Sayegh MH, Immunol Rev 229:271-293, 2009). In addition, costimulatory molecules can provide negative "coinhibitory" signals that inhibit T-cell activation and terminate immune responses; strategies to promote these pathways can also lead to graft tolerance (Boenisch O, Sayegh MH, Najafian N, Curr Opin Organ Transplant 13:373-378, 2008). However, T-cell costimulation involves an incredibly complex array of interactions that may act simultaneously or at different times in the immune response and whose relative importance varies depending on the different T-cell subsets and activation status. In transplantation, the presence of foreign alloantigen incites not only destructive T effector cells but also protective regulatory T cells, the balance of which ultimately determines the fate of the allograft (Lechler RI, Garden OA, Turka LA, Nat Rev Immunol 3:147-158, 2003). Since the processes of alloantigen-specific rejection and regulation both require activation of T cells, costimulatory interactions may have opposing or synergistic roles depending on the cell being targeted. Such complexities present both challenges and opportunities in targeting T-cell costimulatory pathways for therapeutic purposes. In this chapter, we summarize our current knowledge of the various costimulatory pathways in transplantation and review the current state and challenges of harnessing these pathways to promote graft tolerance (summarized in Table 10.1).

Inhibition of TIM-4 protects against cerebral ischaemia-reperfusion injury

TIM‐4 plays an important role in ischaemia‐reperfusion injury of liver and kidney; however, the effects of TIM‐4 on cerebral ischaemia‐reperfusion injury (IRI) are unknown. The purpose of the present study was to investigate the potential role of TIM‐4 in experimental brain ischaemia‐reperfusion injury. In this study, cerebral ischaemia reperfusion was induced by transient middle cerebral artery occlusion (MCAO) for 1 hour in C57/BL6 mice. The TIM‐4 expression was detected in vivo or vitro by real‐time quantitative polymerase chain reaction, Western blot and flow cytometric analysis. In vivo, the administration of anti‐TIM‐4 antibodies significantly suppressed apoptosis, inhibited inflammatory cells and enhanced anti‐inflammatory responses. In vitro, activated microglia exhibited reduced cellular proliferation and induced IRI injury when co‐cultured with neurons; these effects were inhibited by anti‐TIM‐4 antibody treatment. Similarly, microglia transfected with TIM‐4 siRNA and stimulated by LPS + IFN‐γ alleviated the TIM‐4‐mediated damage to neurons. Collectively, our data indicate that the inhibition of TIM‐4 can improve the inflammatory response and exerts a protective effect in cerebral ischaemia‐reperfusion injury.

Anti-CD45RB Antibody Therapy Attenuates Renal Ischemia-Reperfusion Injury by Inducing Regulatory B Cells

BACKGROUND

Regulatory B cells are a newly discovered B cell subset that suppresses immune responses. Recent studies found that both anti-CD45RB and anti-Tim-1 treatments regulate immune responses by inducing regulatory B cells; however, the role of these cells in renal ischemia-reperfusion injury (IRI) is unknown.

METHODS

Using mouse models, including T cell-deficient (RAG1 knockout and TCRα knockout) mice and B cell-deficient (μMT) mice, we investigated the effects of regulatory B cells and anti-CD45RB on IRI and the mechanisms underlying these effects.

RESULTS

Adoptive transfer of regulatory B cells before or after IRI attenuated renal IRI. Anti-CD45RB treatment with or without anti-Tim-1 before IRI increased renal infiltration of CD19⁺Tim-1⁺ regulatory B and regulatory T cells. Anti-CD45RB decreased serum creatinine levels, pathologic injury score, tubular apoptosis, and proinflammatory cytokines levels, whereas IL-10 levels increased. Following IRI, anti-CD45RB with or without anti-Tim-1 also induced regulatory B cells, improving renal function and tubular regeneration. In RAG1 knockout mice with B cell transfer, TCRα knockout mice, and wild-type mice with T cell depletion, anti-CD45RB increased regulatory B cells and attenuated IRI. However, anti-CD45RB did not attenuate IRI in RAG1 knockout mice with T cell transfer or μMT mice and induced only mild improvement in wild-type mice with B cell depletion. Furthermore, B cell-deficient mice receiving B cells from IL-10 knockout mice (but not from wild-type mice) did not show renal protection against IRI when treated with anti-CD45RB.

CONCLUSIONS

Anti-CD45RB treatment attenuated acute renal injury and facilitated renal recovery after IRI through induction of IL-10⁺ regulatory B cells, pointing to anti-CD45RB as a potential therapeutic strategy in renal IRI.

TIM‑4 blockade of KCs combined with exogenous TGF‑β injection helps to reverse acute rejection and prolong the survival rate of mice receiving liver allografts

An acute reaction response (AR) following liver transplantation (LT) is caused by immune responses that are primarily mediated by T lymphocytes. Kupffer cells (KCs) are the largest antigen presenting cell (APC) group in vivo and are the primary modulators of the inflammatory or tolerogenic immune response in liver tissues. T cell immunoglobulin-domain and mucin-domain-4 (TIM-4), the only TIM protein not expressed on T cells, is expressed on APCs; suggesting that it mediates the various immune responses. However, to the best of our knowledge, the role of TIM-4 expressed by KCs in LT injury remains unknown. The present study aimed to explore whether and how TIM-4 expressed by KCs is involved in the AR of liver allografts. Orthotopic liver transplantation (OLT) was performed in mice to establish a model of AR and results demonstrated that LT may lead to the augmented expression of TIM-4 in activated KCs. It was also revealed that TIM-4 blockade markedly attenuated AR injury in vivo via the nuclear factor-κB (NF-κB) and p38 mitogen-activated protein kinase (p38 MAPK) signaling pathways. In addition, levels of transforming growth factor-β (TGF-β) were increased following TIM-4 blockade. Furthermore, in a KC/cluster of differentiation (CD)4⁺ T cell co-culture system, blocking TIM-4 inhibited T helper 2 (Th2) differentiation, stimulated the conversion of naive (CD)4⁺ T cells into CD4⁺CD25⁺Forkhead box protein p3⁺ T regulatory cells and suppressed interleukin-4/signal transducer and activator of transcription 6/transcription factor gata3 signaling. These effects were enhanced following the addition of TGF-β. It was also demonstrated that LT mouse models treated with TIM-4 blockade in combination with exogenous TGF-β injections, increased the survival times of mice and enhanced the amelioration of AR in LT. These results indicate that blocking the expression of TIM-4 by KCs via exogenous TGF-β injection may be an effective therapeutic strategy to inhibit the AR of liver allografts.

Soluble Tim-3 and Gal-9 are associated with renal allograft dysfunction in kidney transplant recipients: A cross-sectional study

BACKGROUND

T cell immunoglobulin mucin-3 (Tim-3) has been reported to participate in the regulation of immune response and the induction of allograft tolerance. However, the association between Tim-3 and renal allograft dysfunction is unclear. We studied the expression of cellular and soluble Tim-3 (sTim-3), soluble galectin-9 (sGal-9) and carcinoembryonic antigen-related cell adhesion molecule-1 (sCEACAM-1) in kidney transplantation recipients (KTRs) to explore their roles in allograft dysfunction.

METHODS

96 KTRs (53 with stable graft and 43 with graft dysfunction) and 30 healthy controls (HC) were enrolled. Among the KTRs, 55 used Tacrolimus (TAC) and 41 used Sirolimus (SRL). In the dysfunction group, 29 recipients have undergone graft biopsy and 14 were classified as biopsy-proven rejection (BPR). Cellular Tim-3 was determined by flow cytometry. sTim-3 was determined by ELISA. sGal-9 and sCEACAM-1 were determined by Bio-Plex® suspension array system.

RESULTS

KTRs with renal dysfunction showed significantly higher levels of sTim-3 and sGal-9 but similar levels of cellular Tim-3 and sCEACAM-1 compared with stable recipients. Correlation analysis revealed that estimated glomerular filtration rate (eGFR) was negatively associated with sTim-3 and sGal-9. Both BPR and non-BPR groups showed comparable levels of Tim-3, Gal-9 and CEACAM-1. Moreover, SRL group showed significantly higher levels of sCEACAM-1 than TAC and HC groups.

CONCLUSIONS

sTim-3 and sGal-9 were promising biomarkers for allograft dysfunction, but unable to differentiate allograft rejection from other causes of renal dysfunction in KTRs. Moreover, long-term administration of sirolimus would up-regulate sCEACAM-1 level, while exert similar regulatory effects on Tim-3 and Gal-9 compared to tacrolimus.

Pharmacological inhibition of fatty acid-binding protein 4 (FABP4) protects against renal ischemia-reperfusion injury

Fatty acid-binding protein 4 (FABP4) is a key mediator of endoplasmic reticulum (ER) stress and apoptosis in diabetes and atherosclerosis. Studies also confirmed that circulating FABP4 depended on renal function in chronic kidney disease (CKD) and acute kidney injury (AKI) patients. However, the function of FABP4 in AKI remains poorly understood and the aim of this study was to investigate the role of FABP4 in ischemia-reperfusion (I/R)-induced AKI. In the present study, renal I/R injury triggered the high expression of the FABP4 gene and protein in the nucleus and cytoplasm of tubular cells of mouse kidney tissue compared to that of Sham. Pretreatment with BMS309403, a highly selective inhibitor of FABP4 at a dose of 20 mg kg⁻¹ d⁻¹ for 4 d, significantly reduced serum creatinine levels to improve acute renal dysfunction and attenuated renal tubular damage in injured kidneys. Pharmacological inhibition of FABP4 also decreased the number of TdT-mediated dUTP nick-end labeling (TUNEL) positive apoptotic tubular cells, accompanied by the down-regulation of cleaved-caspase-3 expression. Furthermore, oral administration of FABP4 inhibitor resulted in a significant attenuation of ER stress indicated by its maker proteins expression of glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), and caspase-12 in I/R injured kidneys. In vitro, the increased expression of FABP4 in the human renal proximal tubule cell line (HK-2 cell) was induced by hypoxia followed by reoxygenation (HR) and the FABP4 inhibitor resulted in a significant attenuation of cell apoptosis and ER stress in HR-induced HK-2 cells. In summary, these findings indicated that FABP4 contributed to the pathogenesis of I/R-induced AKI and suggested that the inhibition of FABP4 might be a promising therapeutic strategy for AKI treatment.

FABP4 inhibition might attenuate I/R-induced AKI through reducing ER stress and apoptosis.

Anti-Inflammatory Pyranochalcone Derivative Attenuates LPS-Induced Acute Kidney Injury via Inhibiting TLR4/NF-κB Pathway

Treatment of septic acute kidney injury (AKI) has still been beyond satisfaction, although anti-inflammatory therapy is beneficial for sepsis-induced AKI. Compound 5b was derived from natural pyranochalcones and exhibited potent anti-inflammatory activity in adjuvant-induced arthritis. In this study, we aimed to investigate the renoprotective effects and potential mechanism of 5b against lipopolysaccharide (LPS)-induced AKI. C57BL/6 mice and human renal proximal tubule cell line (HK-2 cell) were treated with LPS, respectively. Compound 5b was orally administrated at a dose of 25 mg/kg/day for 5 days before LPS (10 mg/kg) intraperitoneal injection. Cells were pretreated with 25 μg/mL 5b for 30 min before LPS (1 μg/mL) treatment. Pretreatment with 5b markedly alleviated tubular injury and renal dysfunction in LPS-induced AKI. The expression of IL-1β, IL-6, and TNF-α both in renal tissue of AKI mice and in the LPS-stimulated HK-2 cell culture medium were reduced by 5b treatment (p < 0.05). The results of immunohistochemistry staining showed that 5b reduced the expression of NF-κB p65 in kidneys. Similarly, 5b decreased the LPS-induced levels of NF-κB p65 and TLR4 proteins in kidneys and HK-2 cells. These data demonstrated that a potent pyranochalcone derivative, 5b, exhibited renoprotective effect against LPS-induced AKI, which was associated with anti-inflammatory activity by inhibiting the TLR4/NF-κB pathway.

Promoter polymorphisms of the TIM-4 gene are correlated with disease activity in patients with systemic lupus erythematosus

Although the TIM gene family plays important roles in immune responses, little is known about TIM regulation in the development of systemic lupus erythematosus (SLE). This study aimed to investigate the association of two TIM-4 single nucleotide polymorphisms (SNPs) rs6874202 (-1419G>A) and rs62382402 (-1609G>A) with SLE susceptibility in a Chinese Han population. The results showed no significant differences between patients with SLE and control group for rs6874202 and rs62382402 (p = .72, .53 respectively). However, the anti-dsDNA levels in serum from SLE patients with GG genotype of TIM-4 gene at -1419 site were significantly higher than those with GA and AA genotype (p = .0335), and C3 levels of SLE patients with GG and GA genotype were much lower than those with AA genotypes (p = .0187). Moreover, the apoptotic cell levels of SLE patients with AA and GG genotypes were significantly higher than those with GA genotypes in patients with SLE (p = .0393). In addition, the C3 concentration of SLE patients with the GG genotype of TIM-4 gene at -1609 site was found to be significantly higher than those with the GA genotype (p = .0129). The results imply that GG genotype of the TIM-4 gene at -1419 site might be associated with the disease activity of SLE.

σ1-Receptor Agonism Protects against Renal Ischemia-Reperfusion Injury

Mechanisms of renal ischemia-reperfusion injury remain unresolved, and effective therapies are lacking. We previously showed that dehydroepiandrosterone protects against renal ischemia-reperfusion injury in male rats. Here, we investigated the potential role of σ1-receptor activation in mediating this protection. In rats, pretreatment with either dehydroepiandrosterone or fluvoxamine, a high-affinity σ1-receptor agonist, improved survival, renal function and structure, and the inflammatory response after sublethal renal ischemia-reperfusion injury. In human proximal tubular epithelial cells, stimulation by fluvoxamine or oxidative stress caused the σ1-receptor to translocate from the endoplasmic reticulum to the cytosol and nucleus. Fluvoxamine stimulation in these cells also activated nitric oxide production that was blocked by σ1-receptor knockdown or Akt inhibition. Similarly, in the postischemic rat kidney, σ1-receptor activation by fluvoxamine triggered the Akt-nitric oxide synthase signaling pathway, resulting in time- and isoform-specific endothelial and neuronal nitric oxide synthase activation and nitric oxide production. Concurrently, intravital two-photon imaging revealed prompt peritubular vasodilation after fluvoxamine treatment, which was blocked by the σ1-receptor antagonist or various nitric oxide synthase blockers. In conclusion, in this rat model of ischemia-reperfusion injury, σ1-receptor agonists improved postischemic survival and renal function via activation of Akt-mediated nitric oxide signaling in the kidney. Thus, σ1-receptor activation might provide a therapeutic option for renoprotective therapy.

Lymphocyte-specific deletion of IKK2 or NEMO mediates an increase in intrarenal Th17 cells and accelerates renal damage in an ischemia-reperfusion injury mouse model

Acute kidney injury (AKI) is associated with poor patient outcome and a global burden for end-stage renal disease. Ischemia-reperfusion injury (IRI) is one of the major causes of AKI, and experimental work has revealed many details of the inflammatory response in the kidney, such as activation of the NF-κB pathway. Here, we investigated whether deletion of the NF-κB kinases IKK2 or NEMO in lymphocytes or systemic inhibition of IKK2 would cause different kidney inflammatory responses after IRI induction. Serum creatinine, blood urea nitrogen (BUN) level, and renal tubular injury score were significantly increased in CD4^creIKK2^f/f (CD4xIKK2^Δ) and CD4^creNEMO^f/f (CD4xNEMO^Δ) mice compared with CD4cre mice after IRI induction. The frequency of Th17 cells infiltrating the kidneys of CD4xIKK2^Δ or CD4xNEMO^Δ mice was also significantly increased at all time points. CCL20, an important chemokine in Th17 cell recruitment, was significantly increased at early time points after the induction of IRI. IL-1β, TNF-α, and CCL2 were also significantly increased in different patterns. A specific IKK2 inhibitor, KINK-1, reduced BUN and serum creatinine compared with nontreated mice after IRI induction, but the frequency of kidney Th17 cells was also significantly increased. In conclusion, although systemic IKK2 inhibition improved kidney function, lymphocyte-specific deletion of IKK2 or NEMO aggravated kidney injury after IRI, and, in both conditions, the percentage of Th17 cells was increased. Our findings demonstrate the critical role of the NF-κB pathway in Th17 activation, which advises caution when using systemic IKK2 inhibitors in patients with kidney injury, since they might impair the T cell response and aggravate renal disease.

Immune Regulation and Antitumor Effect of TIM-1

T cells play an important role in antitumor immunity, and the T cell immunoglobulin domain and the mucin domain protein-1 (TIM-1) on its surface, as a costimulatory molecule, has a strong regulatory effect on T cells. TIM-1 can regulate and enhance type 1 immune response of tumor association. Therefore, TIM-1 costimulatory pathways may be a promising therapeutic target in future tumor immunotherapy. This review describes the immune regulation and antitumor effect of TIM-1.

Negative CD4 + TIM-3 signaling confers resistance against cold preservation damage in mouse liver transplantation

Ischemia-reperfusion injury (IRI), an innate immunity-driven local inflammation, remains the major problem in clinical organ transplantation. T cell immunoglobulin and mucin domain (TIM-3)-Galectin-9 (Gal-9) signaling regulates CD4+ Th1 immune responses. Here, we explored TIM-3-Gal-9 function in a clinically relevant murine model of hepatic cold storage and orthotopic liver transplantation (OLT). C57BL/6 livers, preserved for 20 h at 4°C in UW solution, were transplanted to syngeneic mouse recipients. Up-regulation of TIM-3 on OLT-infiltrating activated CD4+ T cells was observed in the early IRI phase (1 h). By 6 h of reperfusion, OLTs in recipients treated with a blocking anti-TIM-3 Ab were characterized by: (1) enhanced hepatocellular damage (sALT levels, liver Suzuki's histological score); (2) polarized cell infiltrate towards Th1/Th17-type phenotype; (3) depressed T cell exhaustion markers (PD-1, LAG3); and (4) elevated neutrophil and macrophage infiltration/activation. In parallel studies, adoptive transfer of CD4+ T cells from naïve WT, but not from TIM-3 Tg donors, readily recreated OLT damage in otherwise IR-resistant RAG(-/-) test recipients. Furthermore, pre-treatment of mice with rGal-9 promoted hepatoprotection against preservation-association liver damage, accompanied by enhanced TIM-3 expression in OLTs. Thus, CD4+ T cell-dependent "negative" TIM-3 costimulation is essential for hepatic homeostasis and resistance against IR stress in OLTs.

KIM-1-mediated phagocytosis reduces acute injury to the kidney

Kidney injury molecule 1 (KIM-1, also known as TIM-1) is markedly upregulated in the proximal tubule after injury and is maladaptive when chronically expressed. Here, we determined that early in the injury process, however, KIM-1 expression is antiinflammatory due to its mediation of phagocytic processes in tubule cells. Using various models of acute kidney injury (AKI) and mice expressing mutant forms of KIM-1, we demonstrated a mucin domain-dependent protective effect of epithelial KIM-1 expression that involves downregulation of innate immunity. Deletion of the mucin domain markedly impaired KIM-1-mediated phagocytic function, resulting in increased proinflammatory cytokine production, decreased antiinflammatory growth factor secretion by proximal epithelial cells, and a subsequent increase in tissue macrophages. Mice expressing KIM-1Δmucin had greater functional impairment, inflammatory responses, and mortality in response to ischemia- and cisplatin-induced AKI. Compared with primary renal proximal tubule cells isolated from KIM-1Δmucin mice, those from WT mice had reduced proinflammatory cytokine secretion and impaired macrophage activation. The antiinflammatory effect of KIM-1 expression was due to the interaction of KIM-1 with p85 and subsequent PI3K-dependent downmodulation of NF-κB. Hence, KIM-1-mediated epithelial cell phagocytosis of apoptotic cells protects the kidney after acute injury by downregulating innate immunity and inflammation.

Endogenous Tim-1 promotes severe systemic autoimmunity and renal disease MRL-Faslpr mice

The T-cell immunoglobulin mucin 1, also known as kidney injury molecule-1, modulates CD4+ T-cell responses and is also expressed by damaged proximal tubules within the kidney. Both Th subset imbalance (Th1/Th2/Th17) and regulatory T-cell and B-cell alterations contribute to the pathogenesis of autoimmune disease. This study investigated the effects of an inhibitory anti-T-cell immunoglobulin mucin 1 antibody (RMT1–10) in lupus-prone MRL- Fas lpr mice. MRL- Fas lpr mice were treated with RMT1–10 or a control antibody intraperitoneally twice weekly from 3 mo of age for 16 wk. RMT1–10 treatment significantly improved survival, limited the development of lymphadenopathy and skin lesions, preserved renal function and decreased proteinuria, reduced serum anti-DNA antibody levels, and attenuated renal leukocyte accumulation. Th1 and Th17 cellular responses systemically and intrarenally were reduced, but regulatory T and B cells were increased. RMT1–10 treatment also reduced glomerular immunoglobulin and C3 deposition and suppressed cellular proliferation and apoptosis. Urinary excretion and renal expression of kidney injury molecule-1 was reduced, reflecting diminished interstitial injury. As RMT1–10 attenuated established lupus nephritis, manipulating immune system T-cell immunoglobulin mucin 1 may represent a therapeutic strategy in autoimmune diseases affecting the kidney.

Expanding role of T cells in acute kidney injury

PURPOSE OF REVIEW

Recent advances in T cell biology have shed light on the role of T cell subsets in the pathogenesis of acute kidney injury (AKI). The purpose of this review is to harness our understanding of recent advances in T cell biology in tissue injury and repair and provide a mechanistic insight into the role of T cells in the inflammation of AKI.

RECENT FINDINGS

New specific reagents and genetic animal models have led to advances in our understanding of the role of T cell subsets involved in renal injury. Whereas some T cells promote innate renal inflammation and injury, other T cells promote protection and repair. Recent studies illuminated the pathogenic mechanisms of invariant natural killer T (NKT) cells and T helper1-type responses, and the beneficial functions of regulatory T cells and NKT cells are just beginning to be explored. Pharmacologic and cell-based therapies that influence T cell responses to experimental AKI suggest that this is a promising approach to preserve renal function.

SUMMARY

The recent insights gained into how T cells modulate renal injury suggest that strategies targeting specific types of T cells, to either inhibit or enhance their activity, may ameliorate renal injury in patients.

A bioinformatics approach identifies signal transducer and activator of transcription-3 and checkpoint kinase 1 as upstream regulators of kidney injury molecule-1 after kidney injury

Kidney injury molecule-1 (KIM-1)/T cell Ig and mucin domain-containing protein-1 (TIM-1) is upregulated more than other proteins after AKI, and it is highly expressed in renal damage of various etiologies. In this capacity, KIM-1/TIM-1 acts as a phosphatidylserine receptor on the surface of injured proximal tubular epithelial cells, mediating phagocytosis of apoptotic cells, and it may also act as a costimulatory molecule for immune cells. Despite recognition of KIM-1 as an important therapeutic target for kidney disease, the regulators of KIM-1 transcription in the kidney remain unknown. Using a bioinformatics approach, we identified upstream regulators of KIM-1 after AKI. In response to tubular injury in rat and human kidneys or oxidant stress in human proximal tubular epithelial cells (HPTECs), KIM-1 expression increased significantly in a manner that corresponded temporally and regionally with increased phosphorylation of checkpoint kinase 1 (Chk1) and STAT3. Both ischemic and oxidant stress resulted in a dramatic increase in reactive oxygen species that phosphorylated and activated Chk1, which subsequently bound to STAT3, phosphorylating it at S727. Furthermore, STAT3 bound to the KIM-1 promoter after ischemic and oxidant stress, and pharmacological or genetic induction of STAT3 in HPTECs increased KIM-1 mRNA and protein levels. Conversely, inhibition of STAT3 using siRNAs or dominant negative mutants reduced KIM-1 expression in a kidney cancer cell line (769-P) that expresses high basal levels of KIM-1. These observations highlight Chk1 and STAT3 as critical upstream regulators of KIM-1 expression after AKI and may suggest novel approaches for therapeutic intervention.

The innate immune system and transplantation

The sensitive and broadly reactive character of the innate immune system makes it liable to activation by stress factors other than infection. Thermal and metabolic stresses experienced during the transplantation procedure are sufficient to trigger the innate immune response and also augment adaptive immunity in the presence of foreign antigen on the donor organ. The resulting inflammatory and immune reactions combine to form a potent effector response that can lead to graft rejection. Here we examine the evidence that the complement and toll-like receptor systems are central to these pathways of injury and present a formidable barrier to transplantation. We review extensive information about the effector mechanisms that are mediated by these pathways, and bring together what is known about the damage-associated molecular patterns that initiate this sequence of events. Finally, we refer to two ongoing therapeutic trials that are evaluating the validity of these concepts in man.

Kidney injury molecule-1: more than just an injury marker of tubular epithelial cells?

Regardless of the original causes and etiology, the progression to renal function declines follows a final common pathway associated with tubulointerstitial injury, in which the proximal tubular epithelial cells (PTEC) are instrumental. Kidney injury molecule-1 (KIM-1) is an emerging biomarker, and its expression and release are induced in PTEC upon injury. KIM-1 plays the role as a double-edged sword and implicates in the process of kidney injury and healing. Expression of KIM-1 is also associated with tubulointerstitial inflammation and fibrosis. More importantly, KIM-1 expressing PTEC play the role as the residential phagocytes, contribute to the removal of apoptotic cells and facilitate the regeneration of injured tubules. The precise mechanism of KIM-1 and its sheded ectodomain on restoration of tubular integrity after injury is not fully understood. Other than PTEC, macrophages (Mø) also implicate in tubular repair. Understanding the crosstalk between Mø and the injured PTEC is essential for designing appropriate methods for controlling the sophisticated machinery in tubular regeneration and healing. This article will review the current findings of KIM-1, beginning with its basic structure, utility as a biomarker, and possible functions, with focus on the role of KIM-1 in regeneration and healing of injured PTEC.

Delayed graft function after kidney transplantation: the clinical perspective

Delayed graft function continues to pose a significant challenge to clinicians in the context of kidney transplantation. With the present disparity between supply and demand for organs, transplantation is proceeding with more marginal kidneys and therefore the problem of delayed graft function is likely to increase in the future. Although our understanding of the mechanism and risk factors for delayed graft function has improved, translation of this understanding into targeted clinical therapy to attenuate or manage established delayed graft function has been elusive. Based on current trends, the use of kidneys from expanded criteria or cardiac death donors will continue to expand, which will increase the prevalence of delayed graft function in the immediate postoperative setting. The aim of this article is to discuss and critique the available clinical evidence for targeted intervention in the prevention and management of delayed graft function and review emerging and experimental therapies.

Ischaemia-reperfusion injury in liver transplantation--from bench to bedside

Ischaemia-reperfusion injury (IRI) in the liver, a major complication of haemorrhagic shock, resection and transplantation, is a dynamic process that involves the two interrelated phases of local ischaemic insult and inflammation-mediated reperfusion injury. This Review highlights the latest mechanistic insights into innate-adaptive immune crosstalk and cell activation cascades that lead to inflammation-mediated injury in livers stressed by ischaemia-reperfusion, discusses progress in large animal experiments and examines efforts to minimize liver IRI in patients who have received a liver transplant. The interlinked signalling pathways in multiple hepatic cell types, the IRI kinetics and positive versus negative regulatory loops at the innate-adaptive immune interface are discussed. The current gaps in our knowledge and the pathophysiology aspects of IRI in which basic and translational research is still required are stressed. An improved appreciation of cellular immune events that trigger and sustain local inflammatory responses, which are ultimately responsible for organ injury, is fundamental to developing innovative strategies for treating patients who have received a liver transplant and developed ischaemia-reperfusion inflammation and organ dysfunction.

Targeting TIM-1 on CD4 T cells depresses macrophage activation and overcomes ischemia-reperfusion injury in mouse orthotopic liver transplantation

Hepatic injury due to cold storage followed by reperfusion remains a major cause of morbidity and mortality after orthotopic liver transplantation (OLT). CD4 T cell TIM-1 signaling costimulates a variety of immune responses in allograft recipients. This study analyzes mechanisms by which TIM-1 affects liver ischemia-reperfusion injury (IRI) in a murine model of prolonged cold storage followed by OLT. Livers from C57BL/6 mice, preserved at 4°C in the UW solution for 20 h, were transplanted to syngeneic recipients. There was an early (1 h) increased accumulation of TIM-1+ activated CD4 T cells in the ischemic OLTs. Disruption of TIM-1 signaling with a blocking mAb (RMT1-10) ameliorated liver damage, evidenced by reduced sALT levels and well-preserved architecture. Unlike in controls, TIM-1 blockade diminished OLT expression of Tbet/IFN-γ, but amplified IL-4/IL-10/IL-22; abolished neutrophil and macrophage infiltration/activation and inhibited NF-κB while enhancing Bcl-2/Bcl-xl. Although adoptive transfer of CD4 T cells triggered liver damage in otherwise IR-resistant RAG(-/-) mice, adjunctive TIM-1 blockade reduced Tbet transcription and abolished macrophage activation, restoring homeostasis in IR-stressed livers. Further, transfer of TIM-1(Hi) CD4+, but not TIM-1(Lo) CD4+ T cells, recreated liver IRI in RAG(-/-) mice. Thus, TIM-1 expressing CD4 T cells are required in the mechanism of innate immune-mediated hepatic IRI in OLTs.

Mouse model of ischemic acute kidney injury: technical notes and tricks

Renal ischemia-reperfusion leads to acute kidney injury (AKI), a major kidney disease associated with an increasing prevalence and high mortality rates. A variety of experimental models, both in vitro and in vivo, have been used to study the pathogenic mechanisms of ischemic AKI and to test renoprotective strategies. Among them, the mouse model of renal clamping is popular, mainly due to the availability of transgenic models and the relatively small animal size for drug testing. However, the mouse model is generally less stable, resulting in notable variations in results. Here, we describe a detailed protocol of the mouse model of bilateral renal ischemia-reperfusion. We share the lessons and experiences gained from our laboratory in the past decade. We further discuss the technical issues that account for the variability of this model and offer relevant solutions, which may help other investigators to establish a well-controlled, reliable animal model of ischemic AKI.

Kim-1/Tim-1 and immune cells: shifting sands

Kim-1/Tim-1 is an apoptotic-cell phagocytosis and scavenger receptor that is most highly upregulated in proximal tubular epithelium in acute and chronic kidney injury. While Kim-1/Tim-1 has been proposed to be a costimulatory molecule for immune cells, its potential immunological role has been controversial. In the presence of very high epithelial cell expression, understanding the influence of immune cell Kim-1/Tim-1 expression in kidney injury relies on a better definition of its functional significance in immune cells and better characterization of antibodies used to probe function.

Endogenous Tim-1 (Kim-1) promotes T-cell responses and cell-mediated injury in experimental crescentic glomerulonephritis

The T-cell immunoglobulin mucin 1 (Tim-1) modulates CD4(+) T-cell responses and is also expressed by damaged proximal tubules in the kidney where it is known as kidney injury molecule-1 (Kim-1). We sought to define the role of endogenous Tim-1 in experimental T-cell-mediated glomerulonephritis induced by sheep anti-mouse glomerular basement membrane globulin acting as a planted foreign antigen. Tim-1 is expressed by infiltrating activated CD4(+) cells in this model, and we studied the effects of an inhibitory anti-Tim-1 antibody (RMT1-10) on immune responses and glomerular disease. Crescentic glomerulonephritis, proliferative injury, and leukocyte accumulation were attenuated following treatment with anti-Tim-1 antibodies, but interstitial foxp3(+) cell accumulation and interleukin-10 mRNA were increased. T-cell proliferation and apoptosis decreased in the immune system along with a selective reduction in Th1 and Th17 cellular responses both in the immune system and within the kidney. The urinary excretion and renal expression of Kim-1 was reduced by anti-Tim-1 antibodies reflecting diminished interstitial injury. The effects of anti-Tim-1 antibodies were not apparent in the early phase of renal injury, when the immune response to sheep globulin was developing. Thus, endogenous Tim-1 promotes Th1 and Th17 nephritogenic immune responses and its neutralization reduces renal injury while limiting inflammation in cell-mediated glomerulonephritis.

Role of TIM-4 in innate or adaptive immune response

Human being living in constant contact with microbes and pathogen and in the process has developed a recognition pattern of pathogenic structure in the immune cells. The gut lumen has high density of microbes thus the immune response is slightly tolerable to certain microbes, known as commensal flora. These microbes along with other innocuous agents do not cause any inflammation response normally, and are considered as harmless by the immune cells. In immune hypersensitivity condition, such as colitis or food allergy, this mechanism is disturbed. T cell immunoglobulin and mucin domain (TIM)-4 is a phosphatidylserine receptor expressed in mature antigen presenting cells. It is shown that TIM-4 and its ligand TIM-1 are associated in intestinal immune response. However the characteristic of TIM-4 sometimes seems to be two-faced and there is a possibility that TIM-4 also bind to other ligands.