Evaluation of renal ischemia–reperfusion injury in rabbits using microbubbles targeted to activated neutrophils

Phospholipids, the Masters in the Shadows during Healing after Acute Myocardial Infarction

Phospholipids are major components of cell membranes with complex structures, high heterogeneity and critical biological functions and have been used since ancient times to treat cardiovascular disease. Their importance and role were shadowed by the difficulty or incomplete available research methodology to study their biological presence and functionality. This review focuses on the current knowledge about the roles of phospholipids in the pathophysiology and therapy of cardiovascular diseases, which have been increasingly recognized. Used in singular formulation or in inclusive combinations with current drugs, phospholipids proved their positive and valuable effects not only in the protection of myocardial tissue, inflammation and fibrosis but also in angiogenesis, coagulation or cardiac regeneration more frequently in animal models as well as in human pathology. Thus, while mainly neglected by the scientific community, phospholipids present negligible side effects and could represent an ideal target for future therapeutic strategies in healing myocardial infarction. Acknowledging and understanding their mechanisms of action could offer a new perspective into novel therapeutic strategies for patients suffering an acute myocardial infarction, reducing the burden and improving the general social and economic outcome.

Can R2 ' mapping evaluate hypoxia in renal ischemia reperfusion injury quantitatively? An experimental study

PURPOSE

To explore if R₂ ' mapping can assess renal hypoxia in rabbits with ischemia reperfusion injury (IRI).

METHODS

Forty rabbits were randomly divided into 4 groups according to the clipping time: the sham group and 45 min, 60 min, and 75 min for the mild, moderate, and severe groups (with n = 10 each group), respectively. Intravenous furosemide (FU) was administered 24 h after IRI. All rabbits were performed 5 times (IRI_pre , IRI_24h , FU_5min , FU_12min , and FU_24min ) with a 3.0 Tesla MR. The R₂ ' values and the hypoxic scores were then recorded. The repeated measurement analysis of variance and Spearman correlation analysis was used for statistical analysis.

RESULTS

Compared to the baseline, the medullary R₂ ' values increased significantly 24 h after the IRI (baseline 19.31 ± 1.21 s^-1 , mild group 20.05 ± 1.26 s^-1 , moderate group 25.38 ± 1.38 s^-1 , and severe group 25.79 ± 1.10 s^-1 ; each P < .001). FU led to a significant decrease in the medullary R₂ ' value (sham group 11.17 ± 4.33 s^-1 , mild group 7.80 ± 0.74 s^-1 , moderate group 3.92 ± 0.28 s^-1 , and severe group 3.82 ± 0.23 s^-1 ; each P < .05). Quantitative hypoxic scores revealed significant differences among the 4 groups in the outer medulla (P < .001 each). The medullary R₂ ' differences (before and after intravenous FU) were significantly correlated with the hypoxic scores, respectively (P < .001).

CONCLUSION

R₂ ' mapping can evaluate the renal hypoxia in the procession of IRI in rabbits and might serve as a quantitative biomarker for IRI.

Quantitative evaluation of dexamethasone treatment effects in renal ischemia-reperfusion injury using contrast enhanced ultrasonography in rats

BACKGROUND

Renal ischemia-reperfusion (I/R) injury often occurs in various clinical events, and its incidence and mortality have been increasing.

OBJECTIVE

To investigate the value of contrast enhanced ultrasonography (CEUS) in the monitoring of dexamethasone in the improvement of renal I/R injury in rats.

METHODS

Eighteen healthy male Sprague-Dawley rats were randomly divided into sham-operated, I/R, and I/R surgery plus dexamethasone treatment (Dexa) groups. In the I/R group 45-minute renal ischemia with 24 h reperfusion period was monitored. Time-intensity curve (TIC)-derived parameters, which included peak value, time to peak (TP), area under the curve (AUC), and mean transit time (MTT) were compared to the blood creatinine, urea, Caspase-1, and NLRP3 levels.

RESULTS

The I/R group showed an increased peak value, prolonged TP and MTT, and greater AUC (P < 0.05). The Dexa group showed shorter TP and MTT, and smaller AUC (P < 0.05). Results show that the associations between (i) TP, AUC, and MTT and (ii) creatinine, urea, Caspase-1, and NLRP3 levels were significant (P < 0.05).

CONCLUSION

Dexamethasone can alleviate renal I/R injury in rats, which may be related to the inhibition of NLRP3 and caspase-1. CEUS can quantitatively measure this change, in which the changes in TP, AUC and MMT values have considerable reference values.

Inflammasome/NF-κB translocation inhibition via PPARγ agonist mitigates inorganic mercury induced nephrotoxicity

Mercury (Hg) pollution poses global human health and environmental risks. However, still knowledge gaps exist on both exposures and health effects. Here, we combined transcriptome sequencing technique to further investigate the specific mechanisms of inorganic Hg toxicity in the kidney. Strikingly, transcriptomic analysis revealed that 4174 unigenes (including 2646 upregulated and 1528 downregulated unigenes) were differentially expressed under acute HgCl₂ (5 mg/kg) exposure in the kidney. Additionally, we observed that HgCl₂ selectively induced tumor necrosis factor superfamily (TNFSF) to participate in renal damage, which was consistent with the high-throughput sequencing data. The phenomenon is accompanied by NLRP3 inflammasome and NF-κB signal activation in the kidney. Simultaneously, ELISA results shown that TNF-α, IL-1β and IL-6 concentrations in the kidney were significant increased. KEGG enrichment analysis showed that peroxisome proliferators-activated receptors (PPAR) signaling pathway might be vital toxic mechanism of Hg in the kidney. Then, our data showed that PPARγ agonist (GW 1929) attenuated HgCl₂ (15 μg/ml)-induced apoptosis and NLRP3 inflammasome activation via decreasing translocation of NF-κB and increasing Bcl2 levels in vitro. Along with this, we demonstrated that PPARγ antagonists (GW9662) effectively aggravated HgCl₂-induced nephrotoxicity. Overall, our results suggested that PPARγ signaling pathway is considered to be a protective mechanism to combat against HgCl₂-triggered NLRP3 inflammasome activation and apoptosis.

Recent advances in renal imaging

Kidney diseases can be caused by a wide range of genetic, hemodynamic, toxic, infectious, and autoimmune factors. The diagnosis of kidney disease usually involves the biochemical analysis of serum and blood, but these tests are often insufficiently sensitive or specific to make a definitive diagnosis. Although radiologic imaging currently has a limited role in the evaluation of most kidney diseases, several new imaging methods hold great promise for improving our ability to non-invasively detect structural, functional, and molecular changes within the kidney. New methods, such as dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and blood oxygen level-dependent (BOLD) MRI, allow functional imaging of the kidney. The use of novel contrast agents, such as microbubbles and nanoparticles, allows the detection of specific molecules in the kidney. These methods could greatly advance our ability to diagnose disease and also to safely monitor patients over time. This could improve the care of individual patients, and it could also facilitate the evaluation of new treatment strategies.

New Ultrasound Techniques Promise Further Advances in AKI and CKD

AKI and CKD are important clinical problems because they affect many patients and the associated diagnostic and treatment paradigms are imperfect. Ultrasound is a cost-effective, noninvasive, and simple imaging modality that offers a multitude of means to improve the diagnosis, monitoring, and treatment of both AKI and CKD, especially considering recent advances in this technique. Ultrasound alone can attenuate AKI and prevent CKD by stimulating the splenic cholinergic anti-inflammatory pathway. Additionally, microbubble contrast agents are improving the sensitivity and specificity of ultrasound for diagnosing kidney disease, especially when these agents are conjugated to ligand-specific mAbs or peptides, which make the dynamic assessment of disease progression and response to treatment possible. More recently, drug-loaded microbubbles have been developed and the load release by ultrasound exposure has been shown to be a highly specific treatment modality, making the potential applications of ultrasound even more promising. This review focuses on the multiple strategies for using ultrasound with and without microbubble technology for enhancing our understanding of the pathophysiology of AKI and CKD.

Niclosamide attenuates inflammatory cytokines via the autophagy pathway leading to improved outcomes in renal ischemia/reperfusion injury

Renal ischemia/reperfusion (I/R) injury is a debilitating condition that leads to loss renal function and damage to kidney tissue in the majority of patients with acute kidney disease. Previous studies have indicated that autophagy serves a protective function in renal I/R injury. In the present study, the effect of the anthelmintic niclosamide in the regulation of inflammatory responses in kidney I/R was investigated. A total of 40 Sprague-Dawley rats were randomly divided into the following 5 groups (n=8 in each group): Sham group; renal I/R injury; renal I/R injury plus 3-methyladenine (3-MA) treatment (15 mg/kg); renal I/R injury plus niclosamide (25 mg/kg); and renal I/R injury plus rapamycin (10 mg/kg). The expression levels of autophagy-associated proteins in kidney samples obtained from rats with I/R injury were examined using reverse transcription-quantitative polymerase chain reaction and western blotting techniques. In addition, histopathological alterations, the expression of cytokines and renal function were evaluated. Treatment with niclosamide was associated with induction of autophagy and an overall improvement in renal function. There was an increased expression of autophagosome-associated proteins, suggesting a strong correlation between autophagy and improvement of renal function. The increased levels of anti-inflammatory cytokines and decreased levels of pro-inflammatory cytokines provided additional evidence that niclosamide may be effective for the treatment of renal I/R injury. Clinical studies are required to further validate the results of the present study.

Major Ozonated Autohemotherapy Preconditioning Ameliorates Kidney Ischemia-Reperfusion Injury

Medical ozone has therapeutic properties as an antimicrobial, anti-inflammatory, modulator of antioxidant defense system. Major ozonated autohemotherapy (MOA) is a new therapeutic approach that is widely used in the treatment of many diseases. The objective of the present study was to determine whether preischemic application of MOA would attenuate renal ischemia-reperfusion injury (IRI) in rabbits. Twenty-four male New Zealand white rabbits were divided into four groups, each including six animals: (1) Sham-operated group, (2) Ozone group (the MOA group without IRI), (3) IR group (60 min ischemia followed by 24 h reperfusion), and (4) IR + MOA group (MOA group). The effects of MOA were examined by use of hematologic and biochemical parameters consisting of neutrophil to lymphocyte ratio (NLR), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), ischemia-modified albumin (IMA), total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI). In addition, the histopathological changes including the tubular brush border loss (TBBL), tubular cast (TC), tubular necrosis (TN), intertubular hemorrhage and congestion (IHC), dilatation of bowman space (DBS), and interstitial inflammatory cells infiltration (IECI) were evaluated. In the IR group, compared to the Sham group, biochemical parameters indicating oxidative stress, NLR, IL-6, TNF-α, IMA, TOS, and OSI have increased. MOA reduced inflammation and oxidative stress parameters. Although TAS values have decreased in the IR group and increased in the MOA-pretreated group, no significant changes in TAS values were detected between the IR and MOA groups. The total score was obtained by summing all the scores from morphological kidney damage markers. The total score has increased with IR damage when compared with the Sham group (13.83 ± 4.30 vs 1.51 ± 1.71; p = 0.002). But, the total score has decreased significantly after application of MOA (5.01 ± 1.49; p = 0.002; compared with the IR group). MOA preconditioning is effective in reducing tissue damage induced in kidney ischemia-reperfusion injury. The protective effect of MOA is mediated via reducing inflammatory response and regulating of reactive oxygen species (ROS). Renal histology also showed convincing evidence regarding MOA's protective nature against kidney injury induced renal ischemia-reperfusion. Consequently, MOA might be helpful in protecting the kidneys from IR-induced damage in humans, probably through the anti-inflammatory effect and reducing the total oxidant status.

Glycyrrhizin protects mice against renal ischemia-reperfusion injury through inhibition of apoptosis and inflammation by downregulating p38 mitogen-activated protein kinase signaling

Ischemia-reperfusion (I/R) often leads to acute kidney injury, chronic renal failure and kidney transplantation failure. Glycyrrhizin is extracted from Glycyrrhiza glabra roots and is the predominant active component, which exhibits anti-inflammatory effects. However, to the best of our knowledge, the effect of glycyrrhizin on I/R-induced renal injury has not been investigated. In the present study, glycyrrhizin was demonstrated to attenuate renal I/R injury in mice via administration of glycyrrhizin, which suppressed the serum levels of creatinine and blood urea nitrogen 6 h following reperfusion; furthermore, the superoxide anions as well as the activity of superoxide dismutase within renal tissues was reduced by glycyrrhizin pretreatment. Moreover, the protein level of cleaved caspase-3, as well as its activity in renal tissue, was suppressed as a result of the glycyrrhizin pretreatment, indicating that glycyrrhizin inhibits I/R-induced renal cell apoptosis. In addition, glycyrrhizin pretreatment appeared to ameliorate I/R-induced renal injury via inhibition of inflammatory cell infiltration, as well as the production of pro-inflammatory cytokines, including tumor necrosis factor-α, interferon-γ, interleukin (IL)-1β and IL-6. The underlying molecular mechanism was investigated and it was shown that the activity of p38 mitogen-activated protein kinase signaling was downregulated as a result of glycyrrhizin administration. In conclusion, the present study indicated that glycyrrhizin provided significant protection against I/R-induced renal injury in mice by inhibiting inflammatory responses and renal cell apoptosis. Therefore, glycyrrhizin may be used in abdominal surgery and kidney transplantation for the prevention of renal I/R damage.

Contrast ultrasound and targeted microbubbles: diagnostic and therapeutic applications in progressive diabetic nephropathy

Diabetic nephropathy remains one of the most common causes for end-stage renal disease worldwide. Although therapies aimed at optimizing glycemic control and systemic blood pressure have benefit, the reduction in progressive nephropathy remains modest at best. Thus, research continues to focus on newer therapies to address the unmet needs for additional renal protective strategies. The ability to noninvasively image the molecular and cellular processes that underlie diabetic nephropathy would be useful in risk stratifying patients with diabetes, and more importantly would aid in the evaluation of novel therapies to prevent and treat nephropathy. In addition, the development of ultrasound technologies that allow targeted gene delivery using high-power ultrasound and DNA-bearing microbubbles may have applicability for gene therapy to prevent diabetic nephropathy. This review highlights contrast-enhanced ultrasound imaging techniques for the evaluation of renal pathologies, including perfusion and molecular imaging techniques, and ultrasound-mediated gene delivery for therapeutic applications in diabetic nephropathy, that have potential for translation to clinical practice.

"Smart" liposomal nanocontainers in biology and medicine

The perspectives of using liposomes for delivery of drugs to desired parts of the human body have been intensively investigated for more than 30 years. During this time many inventions have been suggested and different kinds of liposomal devices developed, and a number of them have reached the stages of preclinical or clinical trials. The latest techniques can be used to develop biocompatible nano-sized liposomal containers having some abilities of artificial intellect, such as the presence of sensory and responsive units. However, only a few have been clinically approved. Further improvements in this area depend on our knowledge of the interactions of drugs with the lipid bilayer of liposomes. Further studies on liposomal transport through the human body, their targeting of cells requiring therapeutic treatment, and finally, the development of techniques for controlled drug delivery to desired acceptors on cell surfaces or in cytoplasm are still required.

Molecular sonography with targeted microbubbles: current investigations and potential applications

Sonography using targeted microbubbles affords a variety of diagnostic and potentially therapeutic clinical applications. It provides a whole new world of functional information at the cellular and molecular level. This information can then be used to diagnose and possibly prevent diseases at early stages as well as devise therapeutic strategies at the molecular level. It is also useful in monitoring tumor response to therapy and devising treatment timing and plans based on the molecular state of an individual's health. Moreover, targeted microbubble-enhanced sonography has several advantages over other imaging modalities, including widespread availability, low cost, fast acquisition times, and lack of radiation risk. These traits are likely to advance it as one of the imaging methods of choice in future clinical trials examining the impact of molecular imaging on treatment outcome. This review describes the fundamental concepts of targeted microbubble-enhanced sonography as well as its potential clinical applications.