Kinetics of chemokines and their receptors in mercuric chloride-induced tubulointerstitial lesions in brown Norway rats

Mirabegron, dependent on β3-adrenergic receptor, alleviates mercuric chloride-induced kidney injury by reversing the impact on the inflammatory network, M1/M2 macrophages, and claudin-2

The β3-adrenergic receptor (β3-AR) agonism mirabegron is used to treat overactive urinary bladder syndrome; however, its role against acute kidney injury (AKI) is not unveiled, hence, we aim to repurpose mirabegron in the treatment of mercuric chloride (HgCl2)-induced AKI. Rats were allocated into normal, normal + mirabegron, HgCl2 untreated, HgCl2 + mirabegron, and HgCl2 + the β3-AR blocker SR59230A + mirabegron. The latter increased the mRNA of β3-AR and miR-127 besides downregulating NF-κB p65 protein expression and the contents of its downstream targets iNOS, IL-4, -13, and -17 but increased that of IL-10 to attest its anti-inflammatory capacity. Besides, mirabegron downregulated the protein expression of STAT-6, PI3K, and ERK1/2, the downstream targets of the above cytokines. Additionally, it enhanced the transcription factor PPAR-α but turned off the harmful hub HNF-4α/HNF-1α and the lipid peroxide marker MDA. Mirabegron also downregulated the CD-163 protein expression, which besides the inhibited correlated cytokines of M1 (NF-κB p65, iNOS, IL-17) and M2 (IL-4, IL-13, CD163, STAT6, ERK1/2), inactivated the macrophage phenotypes. The crosstalk between these parameters was echoed in the maintenance of claudin-2, kidney function-related early (cystatin-C, KIM-1, NGAL), and late (creatinine, BUN) injury markers, besides recovering the microscopic structures. Nonetheless, the pre-administration of SR59230A has nullified the beneficial effects of mirabegron on the aforementioned parameters. Here we verified that mirabegron can berepurposedto treat HgCl2-induced AKI by activating the β3-AR. Mirabegron signified its effect by inhibiting inflammation, oxidative stress, and the activated M1/M2 macrophages, events that preserved the proximal tubular tight junction claudin-2 via the intersection of several trajectories.

Dimethyl fumarate ameliorates cisplatin-induced renal tubulointerstitial lesions

Dimethyl fumarate (DMF) has an antioxidant effect by activating the nuclear factor erythroid 2-related transcription factor 2 (Nrf2). Cisplatin (CIS) has nephrotoxicity as a frequently associated side effect that is mainly mediated by oxidative stress. In this study, we investigated whether the DMF-mediated antioxidative mechanism activated by Nrf2 can ameliorate CIS-induced renal tubulointerstitial lesions in rats. In Experiments 1 and 2, 25 five-week-old male Wistar rats were divided into five groups: control, CIS, and 3 CIS+DMF groups (300, 1,500, and 7,500 ppm in Experiment 1; 2,000, 4,000, and 6,000 ppm in Experiment 2). Rats were fed their respective DMF-containing diet for 5 weeks. CIS was injected 1 week after starting DMF administration, and the same volume of saline was injected into the control group. CIS-induced severe tubular injury, such as necrosis and degeneration in the outer segment of the outer medulla, was inhibited in the 7,500 ppm DMF group and ameliorated in all DMF groups in Experiment 2. Increased interstitial mononuclear cell infiltration and increased Sirius red-positive areas were also observed in CIS-administered groups, and these increases tended to be dose-dependently inhibited by DMF co-administration in Experiments 1 and 2. The numbers of α-smooth muscle actin (SMA)-positive myofibroblasts, CD68-positive macrophages, and CD3-positive lymphocytes observed in the peritubular area also increased with CIS administration, and these increases were dose-dependently inhibited by DMF co-administration. Moreover, renal cortical mRNA expression of Nrf2-related genes such as NQO1 increased in DMF groups. This investigation showed that DMF ameliorates CIS-induced renal tubular injury via NQO1-mediated antioxidant mechanisms and reduces the consequent tubulointerstitial fibrosis.

Cardiac dysfunction in HgCl2-induced nephrotic syndrome

The experimental model of HgCl2 injection is characterized by a systemic autoimmune disease which leads to the development of nephrotic syndrome (NS). NS seems to be accompanied by cardiovascular alterations, since patients with NS present an increased incidence in cardiac disease. The aim of our work was to study the effects of HgCl2-induced NS on myocardial function and morphometry. Normotensive Brown–Norway rats were injected with HgCl2 (1 mg/kg, HgCl2 group; n = 6, subcutaneous) or the vehicle (control group; n = 6, subcutaneous) on days 0, 2, 4, 7, 9 and 11. The animals were placed in metabolic cages for evaluation of urinary excretion of noradrenaline, sodium, total proteins, albumin and creatinine. Fourteen and 21 days after the first HgCl2 injection, left ventricle (LV) hemodynamics was evaluated through pressure micromanometers in basal and isovolumetric heartbeats. The heart and gastrocnemius muscle weights and tibial length were also examined. In an additional group of animals cardiac dimensions and ejection fraction were assessed by echocardiography and LV apoptosis and fibrosis were studied. HgCl2-injected rats presented proteinuria, albuminuria, hyperlipidemia, anemia, sodium retention and ascites at day 14. These alterations were accompanied by LV hemodynamic changes only in isovolumetric heartbeats. Similarly, on day 21, HgCl2-injected rats presented proteinuria, albuminuria, hyperlipidemia, anemia, but no sodium retention or ascites. These animals presented LV systolic and diastolic dysfunction in both basal and isovolumetric heartbeats, as well as cardiac atrophy, LV fibrosis and an increase in myocyte apoptosis. In conclusion, HgCl2-induced NS is accompanied by LV dysfunction and can be a promising model for studying the link between NS and cardiac disease.

Noninvasive detection of renal allograft inflammation by measurements of mRNA for IP-10 and CXCR3 in urine

BACKGROUND

We explored the hypothesis that measurements of mRNA encoding interferon-inducible protein-10 (IP-10) or the chemokine receptor CXCR3 in urinary cells offer a noninvasive means of elucidating cellular traffic causing acute rejection of human renal allografts.

METHODS

We obtained 63 urine specimens from 58 renal allograft recipients who underwent 63 allograft biopsies to resolve the basis for graft dysfunction, and 27 additional urine samples from 24 other patients with stable allograft function. Twenty-seven of the 63 biopsies were classified as acute rejection, 20 as other, and 16 as chronic allograft nephropathy. We measured the levels of transcripts for IP-10 and CXCR3, and a constitutively expressed gene 18S rRNA in the urine specimens and correlated transcript levels with renal allograft diagnosis.

RESULTS

mRNA levels of IP-10 (P < 0.0001) or CXCR3 (P < 0.0001) but not the levels of 18S rRNA (P= 0.56) predicted intragraft cellular traffic causing acute rejection. Receiver-operating characteristic curve analysis demonstrated that acute rejection can be predicted with a sensitivity of 100% and a specificity of 78% using the (log-transformed) cutoff value of 9.11 copies of IP-10, and with a sensitivity of 63% and a specificity of 83% using the cutoff value of 11.59 copies of CXCR3. Immunohistologic analysis of allograft biopsies showed exuberant expression of IP-10 and CXCR3 during acute rejection whereas both were absent in grafts with stable function.

CONCLUSION

Our investigation demonstrates that intragraft cellular events associated with acute rejection of human renal allografts can be noninvasively identified by measurements of mRNA for IP-10 and CXCR3 in urinary cells.