PPARγ in Ischemia-Reperfusion Injury: Overview of the Biology and Therapy

An Overview of the Role of Peroxisome Proliferator-activated Receptors in Liver Diseases

Peroxisome proliferator-activated receptors (PPARs) are a superfamily of nuclear transcription receptors, consisting of PPARα, PPARγ, and PPARβ/δ, which are highly expressed in the liver. They control and modulate the expression of a large number of genes involved in metabolism and energy homeostasis, oxidative stress, inflammation, and even apoptosis in the liver. Therefore, they have critical roles in the pathophysiology of hepatic diseases. This review provides a general insight into the role of PPARs in liver diseases and some of their agonists in the clinic.

Pretreatment with a modified St. Thomas' solution in patients with severe upper limb injuries: Four case reports

BACKGROUND

This study aims to describe the application of a modified St. Thomas' solution in patients with severe limb injuries.

CASE SUMMARY

Four patients who sustained a high-energy trauma and underwent complete upper limb amputation were pretreated with a modified St. Thomas' solution before upper limb replantation. After the perfusion solution stopped flowing from the blood vessel, the amputated upper limb amputation was replanted. The patients were instructed to perform functional rehabilitation training after the operation. All 4 patients were followed up for 5 years. All the severed upper limbs survived. Routine re-examination after the operation showed that the function of the affected limb was restored. All the patients were satisfied with the sensory and functional recovery of the affected limb.

CONCLUSION

The modified St. Thomas' solution can effectively improve the success rate of limb salvage surgery and the recovery of limb function in patients with a severe limb injury.

Pretreatment with a modified St. Thomas' solution in patients with severe upper limb injuries: Four case reports

BACKGROUND

This study aims to describe the application of a modified St. Thomas' solution in patients with severe limb injuries.

CASE SUMMARY

Four patients who sustained a high-energy trauma and underwent complete upper limb amputation were pretreated with a modified St. Thomas' solution before upper limb replantation. After the perfusion solution stopped flowing from the blood vessel, the amputated upper limb amputation was replanted. The patients were instructed to perform functional rehabilitation training after the operation. All 4 patients were followed up for 5 years. All the severed upper limbs survived. Routine re-examination after the operation showed that the function of the affected limb was restored. All the patients were satisfied with the sensory and functional recovery of the affected limb.

CONCLUSION

The modified St. Thomas' solution can effectively improve the success rate of limb salvage surgery and the recovery of limb function in patients with a severe limb injury.

Human Umbilical Cord Mesenchymal Stem Cells Attenuate Severe Burn-Induced Multiple Organ Injury via Potentiating IGF-1 and BCL-2/BAX Pathway

Background

Early multiple organ injuries induced by severe burn predict a high mortality. Mesenchymal stem cells (MSCs) are able to repair and reconstruct the injured tissues and organs induced by trauma and diseases. However, potential protective effect and mechanism of MSCs on multiorgan injury induced by severe burn at early stage remain to be not clarified. Therefore, this study was to explore the effect and mechanism of human umbilical cord-derived MSCs (hUCMSCs) against severe burn-induced early organ injuries in rats.

Methods

Adult male Wistar rats were randomly divided into sham, burn, and burn+hUCMSCsgroups. GFP-labeled hUCMSCs or PBS was intravenous injected into respective groups. Migration and distribution patterns of GFP-labeled hUCMSCs were observed by inverted fluorescence microscope. The structures and cell apoptosis of the heart, kidney, and liver were measured by immunohistochemistry. Biochemical parameters in serum were assayed by standard Roche-Hitachi methodology. Western blotting was performed on these organs of rats in the three groups to explore the underlying mechanisms.

Results

At 24 hours after hUCMSCs transplantation, we found that GFP-labeled hUCMSCs mainly localized in the blood vessel of the heart, kidney, and liver and a very few cells migrated into tissues of these organs. Compared with the sham group, structure damages and cell apoptosis of these organs were induced by severe burn, and systematic administrations of hUCMSCs significantly improved the damaged structures, cell apoptosis rates, and biochemical parameters of these organs. Furthermore, IGF-1 (insulin-like growth factor 1) level in burn+hUCMSCs group was significantly higher than that in the sham and burn groups. Meanwhile, severe burn induced BCL-2/BAX significantly decreased compared to the sham group, and it was markedly increased by hUCMSCs administration.

Conclusion

The hUCMSCs transplantation can attenuate severe burn-induced early organ injuries and protect multiorgan functions by encouraging migration of hUCMSCs with blood circulation and increasing protective cytokine IGF-1 level and regulating BCL-2/BAX pathway of these vital organs. Furthermore, these data might provide the theoretical foundation for further clinical applications of hUCMSCs in burn areas.

Possible Implication of Nrf2, PPAR-γ and MAPKs Signaling in the Protective Role of Mangiferin against Renal Ischemia/Reperfusion in Rats

Mangiferin (Mang) is a known glucosylxanthone that has proven its shielding effect against ischemia/reperfusion (Is/R). However, its full underlying mechanistic perspective against renal Is/R induced lesions is not fully revealed. Consequently, the purpose of this study is to track further non-investigated modulatory signals of Mang against the renal Is/R model involving nuclear factor erythroid 2-related factor (Nrf)2/heme oxygenase (HO)-1, peroxisome proliferator-activated receptor (PPAR)-γ/nuclear factor (NF)-κB, p38 mitogen-activated protein kinase (MAPK), and c-Jun N-terminal kinase (JNK) signaling. To ratify our aim, Mang was administrated (20 mg/kg, i.p for seven days) before the induction of bilateral Is/R. Mechanistic maneuver revealed that Mang balanced oxidative state via increasing the expression of the antioxidant Nrf2/HO-1 cue with subsequent enhancement of GSH besides MDA lessening. Additionally, Mang enhanced PPAR-γ mRNA expression and declined p-p38 MAPK and p-JNK expression with concomitant NF-κB downsizing leading to iNOS/NOx and TNF-α rebating. Furthermore, the Mang anti-apoptotic trait was affirmed by enriching Bcl-2 expression as well as decreasing Bax and caspase-3 expression. All these potentials were in the line with the molecular docking results and the improved histopathological findings and renal function biomarkers. Consequently, Mang provided plausible protective mechanisms against renal Is/R-related events, possibly by amending oxidative status, inflammatory mediators, and apoptotic cell death through the involvement of Nrf2, PPAR-γ, MAPK, JNK, and NF-κB signaling.

Cardioprotective Effects and Mechanisms of Saponins on Cardiovascular Disease

Cardiovascular disease (CVD), a leading cause of morbidity and mortality, is among the most prevalent health problems worldwide and effective strategies for its prevention and treatment are urgently required. In this regard, increasing research has demonstrated that natural drugs offer antihypertensive, antiatherosclerotic, and cardioprotective activities, and many are applied widely for the treatment of CVD and its manifestations such as myocardial infarction, peripheral vascular diseases, and coronary heart disease. Natural drugs have significant advantages in the treatment of CVD due to their efficacy and safety profiles. Saponins are an important class of active components of plant natural products and play an important role in the treatment of CVD. This review covers the most up-to-date information on saponins concerning their cardioprotective effects and mechanisms of action.

Protective Effects of PPARγ on Renal Ischemia-Reperfusion Injury by Regulating miR-21

Renal ischemia-reperfusion injury (RIRI) is a common pathological process that causes kidney injury. Previous studies have indicated that both peroxisome proliferator-activated receptor γ (PPARγ) and microRNA-21 (miR-21) exert protective effects against RIRI. However, their relationship is not well understood. In the present study, we investigated the role of the PPARγ/miR-21/programmed cell death 4 (PDCD4) axis in IRI, both in vivo and in vitro. In vitro cell hypoxia/reoxygenation (H/R) and in vivo RIRI models were established, and cell viability, cell apoptosis, and key molecule expression profiles were analyzed. Our results showed that both PPARγ and miR-21 had protective effects against RIRI to varying degrees, and there was an interaction between PPARγ and miR-21. PPARγ could promote the expression of miR-21 and partially protect against RIRI by reducing the level of the miR-21 target protein (PDCD4). Our findings underscore the potential utility of future clinical investigations of PPARγ activation and targeting of the underlying miR-21/PDCD4/caspase-3 pathway, which may participate in the pathogenesis of human IRI.

A Novel Polysaccharide From Chuanminshen violaceum and Its Protective Effect Against Myocardial Injury

We isolated and purified a novel polysaccharide from the root of Chuanminshen violaceum, namely, Chuanminshen violaceumis polysaccharide (CVP) and confirmed its structure and molecular weight. Furthermore, in vivo experiment, CVP’s protective effect against myocardial ischemia-reperfusion (I/R) injury in mice was evidenced by significantly reducing I/R-induced myocardial infarction (MI) size, decreasing the secretion of heart damage biomarkers, and improving cardiac function. Then, the myocardial anoxia/reoxygenation (A/R) injury model was established to mimic reperfusion injury. Noticeably, ferroptosis was the major death manner for A/R-damaged H9c2 cells. Meanwhile, CVP significantly inhibited ferroptosis by decreasing intracellular Fe²⁺ level, enhancing GPX4 expression, and suppressing lipid peroxidation to confront A/R injury. In conclusion, CVP, with a clear structure, ameliorated I/R injury by inhibiting ferroptosis.

Prussian Blue Nanozyme Promotes the Survival Rate of Skin Flaps by Maintaining a Normal Microenvironment

Ischemia-reperfusion (I/R) injury leads to a low success rate of skin flap transplantation in reconstruction surgery, thus requiring development of new treatments. Necroptosis and apoptosis pathways, along with overexpression of reactive oxygen species and pro-inflammatory factors in skin flap transplantation, are deemed as potential therapeutic targets. This study provides a paradigm for nanozyme-mediated microenvironment maintenance to improve the survival rate of the transplanted skin flap. Prussian blue nanozyme (PBzyme) with multiple intrinsic biological activities was constructed and selected for this proof-of-concept study. The prepared PBzyme shows anti-inflammatory, antiapoptotic, antinecroptotic, and antioxidant activities in both in vitro and in vivo models of I/R injured skin flaps. The multiple inhibitory effects of PBzyme maintained a normal microenvironment and thus significantly promoted the survival rate of the I/R injured skin flap (from 37.21 ± 8.205% to 79.61 ± 7.5%). Of note, PBzyme regulated the expression of the characteristic signal molecules of necroptosis, including Rip 1, Rip 3, and pMLKL, indicating that PBzyme may be a therapeutic agent for necroptosis-related diseases. This study shows great prospects for clinical application of PBzyme in the treatment of skin flaps via local administration.

PPARγ Mediates Protective Effect against Hepatic Ischemia/Reperfusion Injury via NF-κB Pathway

BACKGROUND

Hepatic ischemia/reperfusion injury (HIRI) is an unavoidable complication in liver surgery, however its pathological process is still unclear. Therefore, in this study, the role and mechanism of peroxisome proliferator-activated receptor gamma (PPARγ) was investigated in HIRI.

MATERIALS AND METHODS

We constructed mice models with HIRI and L02 cell models insulted hypoxia/re-oxygenation (H/R). PPARγ agonist rosiglitazone was administered prior to HIRI in mice and PPARγ-siRNA was to H/R treatment in L02 cells. Liver injury was measured by serum ALT, AST and LDH levels and performing H&E staining; the inflammatory injury was reflected by inflammatory markers IL-1β, IL-6 and TNF-α, which were assayed by Real-time PCR and Western blotting, MPO activity was determined using commercial kits; oxidative stress injury was evaluated by iNOS, MDA, SOD and GSH-PX levels; apoptosis was detected by cleaved-Caspase-3, TUNEL staining and flow cytometry; NF-κB signaling activation was reflected by phosphorylation of IκBα (p-IκBα) and nuclear translocation of NF-κB p65.

RESULTS

The level of PPARγ expression was obviously down-regulated both in mice liver subjected to IRI and in L02 cells to H/R. Overexpression of PPARγ presented protective effect on HIRI by reducing serum levels of aminotransferase and hepatic necrosis, inhibiting inflammation and apoptosis and alleviating oxidative stress in vivo. But PPARγ-siRNA aggravate H/R insult by promoting inflammation and apoptosis in vitro. Mechanistically, the NF-κB pathway activity was increased with PPARγ down-regulation by PPARγ-siRNA. Importantly, inhibition of NF-κB signaling abolished PPARγ knockdown-mediated hepatic injury.

CONCLUSIONS

PPARγ present protective effects on HIRI by attenuating liver injury, inflammatory response, oxidative stress and apoptosis in vivo and in vitro, and its mechanism may be related to down-regulation of NF-κB signaling.

PPARγ Mediates the Cardioprotective Roles of Danlou Tablet After Acute Myocardial Ischemia-Reperfusion Injury

Ischemic heart disease is one of the biggest threats to human life in the world. Reperfusion therapy is an effective strategy to reduce infarct size and ischemic injury. However, reperfusion process may cause secondary myocardial injury which is defined as ischemia-reperfusion injury (IRI). Exploring potential therapeutic strategy to attenuate IRI is extremely important. Danlou tablet (Dan), a Chinese herbal compound consisting of ten herbs, has been identified to be protective for the heart. However, the mechanism of Dan-induced cardioprotection after acute reperfusion was unelucidated. In this study, to investigate the role and mechanism of Dan in myocardial IRI, we performed acute IRI modeling in mice and oxygen-glucose deprivation–reperfusion (OGD/R)-induced apoptosis in primary neonatal rat cardiomyocytes (NRCMs). We found that Dan had protective effect against acute IRI in mice, as evidenced by reduced infarct size, TUNEL-positive cardiomyocytes (CMs), and Bax/Bcl2 ratio and cleaved-caspase 3/caspase 3 ratio in vivo. Meanwhile, Dan inhibited OGD/R-induced apoptosis of NRCMs in vitro. Mechanistically, Dan could activate proliferator-activated receptor gamma (PPARγ) in both IRI hearts and OGD/R-stressed NRCMs, while inhibition of PPARγ attenuated the protective effect of Dan against IRI in vivo and OGD/R-induced CM apoptosis in vitro. These data reveal that Dan attenuates acute myocardial IRI and CM apoptosis through activating PPARγ. Our findings may extend the knowledge of Chinese medicine and provide potential strategy for the precise treatment of ischemic heart diseases.

BRCC36 promotes intestinal mucosal barrier injury caused by BMP2 after ischemia-reperfusion via inhibiting PPARγ signaling

As one of the most common pathological changes in trauma and surgery practice, intestinal ischemia-reperfusion (I/R) injury is regarded as a major precipitating factor in the occurrence and development of fatal diseases. BRCA1-BRCA2-containing complex subunit 36 (BRCC36), a deubiquitinase, has been proved important in a variety of pathophysiological processes such as DNA repair, cell cycle regulation, tumorigenesis and inflammatory response. However, the effect of BRCC36 on intestinal mucosal barrier injury after I/R has not been fully elucidated. Our research found that BRCC36 aggravated intestinal mucosal barrier injury caused by BMP2 (Bone morphogenetic protein 2) after I/R by downregulating PPARγ (Peroxisome proliferator-activated receptor-γ) signaling. These results suggested that BRCC36/PPARγ axis might serve as a potential therapeutic target for preventing intestinal mucosal barrier injury after I/R.

Two steps, one ligand: How PPARγ binds small-molecule agonists

In this issue of Structure,Shang and Kojetin (2021) present insights into the binding mechanism of artificial agonists to the PPARγ nuclear receptor. These data support a two-step model with induced fit and conformational selection aspects. This mechanism may exist in related receptors, providing new opportunities for drug development.

Pioglitazone Ameliorates Renal Ischemia-Reperfusion Injury via Inhibition of NF-κB Activation and Inflammation in Rats

Renal ischemia-reperfusion injury (IRI) is considered as a major cause of acute kidney injury. In this study, we investigated the role of the NF-κB signaling pathway and inflammation in the amelioration of renal IRI using pioglitazone. Sprague–Dawley (SD) rats were subjected to bilateral renal artery clamping for 45 min followed by perfusion restoration for establishing a simulated renal IRI model. At 24 h post-operatively, we assessed the serum levels of creatinine and urea nitrogen, expression levels of peroxisome proliferator-activated receptor gamma (PPAR-γ) and NF-κB-related (p-IKK-β and IκB-α) proteins, and mRNA expression levels of the inflammatory cytokines, including TNF-α and MCP-1, in the renal tissue of various study groups. The histopathological evaluation of renal tissue was also conducted. In rat renal tissue, pioglitazone treatment decreased the serum levels of post-renal IRI creatinine and urea nitrogen, as well as necrosis. Furthermore, it elevated the expression of PPAR-γ protein and decreased the expression of NF-κB-related proteins. Pioglitazone also decreased the mRNA expression of TNF-α and MCP-1 in the renal tissue. Thus, pioglitazone ameliorates renal IRI by inhibiting the NF-κB signaling pathway and inflammatory response in rats.