Delayed ischaemic preconditioning in the presence of galectin-9 protects against renal ischaemic injury through a regulatory T-cell dependent mechanism

Gal-9/Tim-3 signaling pathway activation suppresses the generation of Th17 cells and promotes the induction of Foxp3+ regulatory T cells in renal ischemia-reperfusion injury

CD4⁺ T cells mediate the pathogenesis of renal ischemia-reperfusion injury (IRI). Emerging research suggests that a Th17/regulatory T cell (Treg) imbalance plays a pivotal role in the development of renal IRI. A recently identified negative checkpoint protein, T cell immunoglobulin domain and mucin domain family 3 (Tim-3), inhibits the immune response by binding to its ligand, galectin-9 (Gal-9). However, the role of the Gal-9/Tim-3 signaling pathway in the regulation of CD4⁺ T cell subsets in renal IRI remains unclear. In this study, we investigated the effect of the Gal-9/Tim-3 signaling pathway on Th17/Treg subsets in renal IRI using a mouse model. Renal IRI induced the expression of Gal-9 in renal tubular epithelial cells and increased the proportion of Tim-3⁺ Th17 cells and Tim-3⁺ forkhead box P3 (Foxp3)⁺ Treg cells in the ischemia-reperfusion (IR) kidneys. Administration of rAAV9-Gal-9 suppressed kidney inflammation, reduced the mortality of mice with renal IRI, increased Foxp3⁺ Treg cells, and reduced Th17 cells. In contrast, the blockade of Tim-3 in vivo using an anti-Tim-3 monoclonal antibody aggravated renal inflammation, decreased Foxp3⁺ Treg cells, and promoted Th17 cells. Thus, Gal-9/Tim-3 signaling pathway activation may protect against renal IRI by inhibiting Th17 cell production and inducing Foxp3⁺ Treg cell expansion. Our study suggests that the Gal-9/Tim-3 signaling pathway may be targeted by immunotherapy in renal IRI.

Galectins as potential pharmacological targets in renal injuries of diverse etiology

Galectins are carbohydrate-binding proteins, and their importance in renal diseases of diverse etiology has been documented. Amongst different galectins, the role of galectin-3 in the pathophysiology of renal diseases has been well documented. There is an increase in galectin-3 in the circulation as well as on the kidneys in chronic kidney disease patients. The increase in galectin-3 is negatively correlated with a decrease in renal function and overall survival rate. The preclinical studies also correlate the increase in galectin-3 levels with renal dysfunction. Accordingly, scientists have exploited galectin-3 as a potential pharmacological target to improve renal functions in different preclinical models of renal injury. Apart from galectin-3, there have been few studies documenting the role of galectin-1, 8, and 9 in renal diseases. The role of galectin-1 is not clearly identified, and there have been conflicting reports regarding its role in renal diseases. Galectin-8 and 9 impart renoprotective effects as per clinical and preclinical studies, respectively. The present review discusses the role of different galectins in renal diseases of diverse etiology.

The Sweet-Side of Leukocytes: Galectins as Master Regulators of Neutrophil Function

Among responders to microbial invasion, neutrophils represent one of the earliest and perhaps most important factors that contribute to initial host defense. Effective neutrophil immunity requires their rapid mobilization to the site of infection, which requires efficient extravasation, activation, chemotaxis, phagocytosis, and eventual killing of potential microbial pathogens. Following pathogen elimination, neutrophils must be eliminated to prevent additional host injury and subsequent exacerbation of the inflammatory response. Galectins, expressed in nearly every tissue and regulated by unique sensitivity to oxidative and proteolytic inactivation, appear to influence nearly every aspect of neutrophil function. In this review, we will examine the impact of galectins on neutrophils, with a particular focus on the unique biochemical traits that allow galectin family members to spatially and temporally regulate neutrophil function.

Regulatory T cells in acute and chronic kidney diseases

Foxp3-expressing CD4+ regulatory T cells (Tregs) make up one subset of the helper T cells (Th) and are one of the major mechanisms of peripheral tolerance. Tregs prevent abnormal activation of the immune system throughout the lifespan, thus protecting from autoimmune and inflammatory diseases. Recent studies have elucidated the role of Tregs beyond autoimmunity. Tregs play important functions in controlling not only innate and adaptive immune cell activation, but also regulate nonimmune cell function during insults and injury. Inflammation contributes to a multitude of acute and chronic diseases affecting the kidneys. This review examines the role of Tregs in pathogenesis of renal inflammatory diseases and explores the approaches for enhancing Tregs for prevention and therapy of renal inflammation.

Superagonistic CD28 Protects against Renal Ischemic Injury by Expansion of Regulatory T-Cell

BACKGROUND

Regulatory T (Treg) cells are a highly suppressive subset of CD4+ lymphocytes and have recently been proved to be crucial to suppress the inflammatory responses of ischemic kidney injury. CD28 superagonists (CD28sa) are monoclonal antibodies that preferentially expand Treg cells without a T-cell receptor and a costimulatory signal. This study aims to test the protection and discover the mechanisms of CD28sa treatment against renal ischemia-reperfusion (IR) injury (IRI).

METHODS

Male C57BL/6N mice were treated with CD28sa via peritoneal injection (0.1 mg) 6 days before the induction of IRI, or with 18-min ischemic precondition (IPC). IRI was induced by bilateral clamping of renal pedicles for 35 min followed by reperfusion. The role of Treg expansion in renal protection conferred by CD28sa treatment was examined using anti-CD25 antibody.

RESULTS

CD28sa treatment alone significantly increased the percentage of Treg cells in the spleen (18.10 ± 2.00 vs. 6.64 ± 0.86%, p < 0.01), peripheral blood (16.43 ± 5.94 vs. 2.57 ± 1.09%, p < 0.01), and kidney (2.69 ± 0.90 vs. 0.53 ± 0.14%, p < 0.01) of C57BL/6N mice 6 days after the administration. Mice pretreated with CD28sa or IPC had less renal injury at 24 h after IRI with attenuation of renal tubular damage and lower serum creatinine compared with the mice that underwent renal IRI alone. The number of infiltrating macrophages in the kidney and IFN-γ secreting CD4+ T cells in peripheral blood were diminished in the CD28sa-IR group and the IPC-IR group. The renal protection bestowed by CD28sa or IPC was abolished by anti-CD25 antibody administration.

CONCLUSIONS

Treg expansion induced by CD28sa ameliorated renal IRI.