Dopamine D2 receptor activator quinpirole protects against trypsinogen activation during acute pancreatitis via upregulating HSP70

HSP70 protects against acute pancreatitis-elicited intestinal barrier damage in rats

Acute pancreatitis (AP) is a frequent but severe abdominal emergency in general surgery with intestinal barrier dysfunction. Heat shock protein 70 (HSP70) is a ubiquitous molecular chaperone that has been proposed to exert favorable effects on AP. Nonetheless, the detailed impacts of HSP70 on the intestinal barrier function in AP are unknown, which will be investigated here. After the injection of sodium taurocholate into the biliopancreatic duct, the rat models of AP were established. After modeling, HSP70 expression was up-regulated through lentivirus infection. Western blot was used to detect HSP70 expression. H&E staining was used to examine the histological changes in the pancreatic and intestinal tissues. The levels of pancreatic biochemical markers and oxidative stress markers were detected using corresponding assay kits. ELISA was used to detect the levels of inflammatory cytokines and gastrointestinal function indicators. Immunofluorescence staining and Western blot were used to detect the expression of tight junction proteins. DCFH-DA probe and MitoSOX Red probe were used to detect total reactive oxygen species (ROS) and mitochondrial ROS (mtROS), respectively. TUNEL assay and Western blot were used to detect apoptosis. During the model construction, severe pancreatic and abnormal intestinal tissue abnormalities were observed, inflammatory response was activated and the intestinal barrier was disrupted. HSP70 expression was down-regulated in the intestinal tissues AP rat models. HSP70 ameliorated the morphological damage of pancreatic and intestinal tissues of AP rats. In addition, HSP70 significantly reduced intestinal barrier damage, inflammatory response, oxidative stress and apoptosis in the intestinal tissues of AP rat models. Collectively, HSP70 might attenuate AP through exerting anti-inflammatory, anti-oxidant, anti-apoptotic effects and inhibiting intestinal barrier disruption.

Polydopamine-loaded prunetin nanomaterials activate DRD2 to reduce UV-induced inflammation by stabilizing and promoting Nrf2 nuclear translocation

Skin damage caused by exposure to ultraviolet (UV) light has been well documented clinically and histologically. Dopamine receptor D2 (DRD2) possesses various biological functions. However, no study has reported the possible association of DRD2 with UV-induced skin damage. We established DRD2 conditional knockout and UV damage models in this work. The results showed that DRD2 played an important role in the treatment of UV-induced skin damage. The findings of the molecular mechanism study revealed that the internalization of DRD2 after activation can stabilize nuclear factor erythroid 2-related factor 2 (Nrf2). However, the entry of Nrf2 into the nucleus did not increase. We prepared and characterized hyaluronic acid (HA)-coated mesoporous polydopamine (MPDA) nanoparticles (H@P@M). HA facilitated skin epidermal penetration of the nanoparticles to reach the site of inflammation smoothly. Meanwhile, MPDA activated DRD2 internalization to stabilize Nrf2. The release of prunetin inhibited the interaction of Kelch-like ECH-associated protein 1 with Nrf2 and promoted the nuclear translocation of Nrf2. In summary, this study unveiled that in skin inflammation, H@P@M activated and internalized DRD2, which subsequently formed a protein complex with arrestin beta 1-ubiquitin specific protease 8 (USP8)-Nrf2. Deubiquitination was performed to stabilize Nrf2 while promoting the nuclear translocation of Nrf2 to exert anti-inflammatory and antioxidant functions. STATEMENT OF SIGNIFICANCE: Skin is the body's largest physical barrier, always protecting the body from the interference of the external environment. However, excessive exposure to ultraviolet rays in the sun can cause skin inflammation, leading to skin erythema, itching, edema and pain, which can be troublesome in our daily lives. The complex mechanism of skin inflammation caused by ultraviolet radiation has not been fully clarified. In this study, the role of DRD2 in UV-induced skin inflammation was explored, and nano-composite particles HA@Prunetin@MPDA, which act on multiple targets in the anti-inflammatory pathway of DRD2, were developed to maximize the effect of the drug. It provides a new way to treat skin inflammation caused by UV.

Anti-Inflammatory Effects of Peripheral Dopamine

Dopamine is synthesized in the nervous system where it acts as a neurotransmitter. Dopamine is also synthesized in a number of peripheral organs as well as in several types of cells and has organ-specific functions and, as demonstrated more recently, is involved in the regulation of the immune response and inflammatory reaction. In particular, the renal dopaminergic system is very important in the regulation of sodium transport and blood pressure and is particularly sensitive to stimuli that cause oxidative stress and inflammation. This review is focused on how dopamine is synthesized in organs and tissues and the mechanisms by which dopamine and its receptors exert their effects on the inflammatory response.

Correlation between the dopaminergic system and inflammation disease: a review

The dopaminergic system is inextricably linked with neurological diseases and addiction. In recent years, many studies have found that the dopaminergic system involves in inflammatory diseases, particularly neuroinflammatory diseases development; This review summarizes the studies of dopaminergic system in inflammatory diseases, and specifically highlights the mechanisms of how dopaminergic system regulates inflammation; In addition, we speculate that there are some cavities in current research, including mixed usage of inhibitors, agonists and lack of systematic controls; We expect this review would provide directions to future research of dopaminergic system and inflammatory diseases.

Dopamine D2 Receptor Signaling Attenuates Acinar Cell Necroptosis in Acute Pancreatitis through the Cathepsin B/TFAM/ROS Pathway

Acute pancreatitis (AP) is an inflammatory disease that is associated with trypsinogen activation, mitochondrial dysfunction, cell death, and inflammation. Dopamine D2 receptor (DRD2) plays an essential role in alleviating AP, while it is unclear whether it is involved in regulating acinar cell necroptosis. Here, we found that DRD2 agonist quinpirole alleviated acinar cell necroptosis via inhibiting cathepsin B (CTSB). Moreover, CTSB inhibition by CA-074Me ameliorated AP severity by reducing necroptosis. Notably, knockdown of TFAM reversed the therapeutic effect of either quinpirole or CA-074Me. We identified a new mechanism that DRD2 signaling inhibited CTSB and promoted the expression of mitochondrial transcription factor A(TFAM), leading to reduction of ROS production in AP, which attenuated acinar cell necroptosis ultimately. Collectively, our findings provide new evidence that DRD2 agonist could be a new potential therapeutic strategy for AP treatment.

Continuous Activation of Dopamine Receptors Alleviates LPS-Induced Liver Injury in Mice via β-arrestin2 Dependent Akt/NF-κB Pathway

Many studies showed that dopamine receptors (DRs) agonists have anti-inflammatory effects. Rotigotine, a non-ergot dopamine receptor agonist, mainly actives DRD2/DRD3/DRD1. Rotigotine extended-release microspheres (RoMS) are a sustained-release formulation that can release sustainably rotigotine for more than 7 days after a single dose of RoMS. This study aimed to investigate whether RoMS can attenuate the lipopolysaccharide (LPS)-induced liver injury of mice. The liver injury was evaluated by assaying serum transaminase and observing histopathological changes. The levels of pro-inflammatory cytokines in serum were also detected. Western blot was employed to assay the expression of proteins in the Akt/NF-κB pathway. The results showed that pre-administration with a single dose of RoMS could inhibit the increase of serum transaminase induced by LPS, alleviate the pathological damage of liver tissue, and decrease the levels of tumor necrosis factor-α and interleukin-6. In addition, RoMS decreased Toll-like receptor 4 protein expression in liver tissue. RoMS mitigated liver injury by activating DRs and negatively regulating the β-arrestin2-dependent Akt/NF-κB signaling pathway. The effects of RoMS could be weakened or abolished by the specific DRD2 antagonist, R121. In conclusion, activation of DRs inhibited the releases of pro-inflammatory cytokines and alleviated the immune-mediated liver injury induced by LPS in mice. The anti-inflammatory mechanism of RoMS may be related to the regulation of the β-arrestin2-dependent Akt/NF-κB signaling pathway.

Dopamine, a co-regulatory component, bridges the central nervous system and the immune system

Dopamine (DA) is a crucial neurotransmitter that plays an important role in maintaining physiological function in human body. In the past, most studies focused on the relationship between the dopaminergic system and neurological-related diseases. However, it has been found recently that DA is an immunomodulatory mediator and many immune cells express dopamine receptors (DRs). Some immune cells can synthesize and secrete DA and then participate in regulating immune function. DRs agonists or antagonists can improve the dysfunction of immune system through classical G protein signaling pathways or other non-receptor-dependent pathways. This article will discuss the relationship between the dopaminergic system and the immune system. It will also review the use of DRs agonists or antagonists to treat chronic and acute inflammatory diseases and corresponding immunomodulatory mechanisms.

Sodium butyrate alleviates cholesterol gallstones by regulating bile acid metabolism

Cholesterol overloading and bile acid metabolic disorders play an important role in the onset of cholesterol gallstone (CGS). Short-chain fatty acids (SCFAs) can regulate bile acid metabolism by modulating the gut microbiota. However, the role and mechanism by which sodium butyrate (NaB) targets bile acids to attenuate CGS are still unknown. In this study, continuous administration of 12 mg/day for 8 weeks was decreased the incidence of gallstones induced by lithogenic diet (LD) from 100% to 25%. NaB modulated SCFAs and improved the gut microbiota. The remodeling of the gut microbiota changed the bile acid compositions and decreased cecal tauro-α-muricholic acid (T-α-MCA) and tauro-β-muricholic acid (T-β-MCA) which are effective farnesoid X receptor (FXR) antagonists. The quantitative real-time PCR examination showed that NaB significantly increased levels of ileal Fxr, fibroblast growth factor-15 (Fgf-15) and small heterodimer partner (Shp) mRNA and subsequently inhibited bile acid synthesis. In addition, NaB enhanced bile acid excretion by increasing the levels of hepatic multidrug resistance protein 2 (Mdr2) and bile salt export pump (Bsep) mRNA, and it enhanced bile acid reabsorption in the intestine by increasing the levels of ileal bile acid transporter (Ibat) mRNA. In addition, NaB reduced the absorption of cholesterol in the intestine and inhibited the excretion of cholesterol in the liver, which reduced the cholesterol concentration in serum and bile. Furthermore, the protective effects of NaB administration were abolished by FXR antagonists. Taken together, our results suggest that NaB mitigates CGS by modulating the gut microbiota to regulate the FXR-FGF-15/SHP signaling pathway.