Hydrogen Sulfide Contributes to Uterine Quiescence Through Inhibition of NLRP3 Inflammasome Activation by Suppressing the TLR4/NF-κB Signalling Pathway

A hydrogen sulphide-releasing non-steroidal anti-inflammatory, ATB-346, significantly attenuates human myometrial contractions

BACKGROUND

Spontaneous preterm birth is the leading cause of perinatal morbidity and mortality. Tocolytics are drugs used to inhibit uterine contractions in cases of imminent preterm birth, however, few are effective in stopping labour once initiated and all have side effects. Combination approaches involving drugs that target multiple signalling pathways that regulate contractions may increase efficacy, reduce dosage and improve tolerability. Both non-steroidal anti-inflammatory drugs (NSAIDs) and hydrogen sulphide (H2S)-releasing compounds can reduce myometrial contractions. In a novel approach we evaluated the tocolytic properties of ATB-346-a H2S-releasing derivative of the NSAID naproxen, shown clinically to reduce pain and inflammation in arthritis.

METHODS

Using organ baths, paired strips of human myometrium were exposed to increasing concentrations of ATB-346, or equimolar concentrations (10µM and 30µM) of the parent drug, naproxen, or the H2S-releasing moiety, 4-hydroxy-thiobenzamide (TBZ), alone. The ability of ATB-346 versus the individual components of ATB-346 to decrease ex vivo spontaneous contractions was investigated, and the potency was compared to a known H2S donor, Na2S.

RESULTS

Acute application of Na2S produced a concentration-dependent decrease in force amplitude and force integral (area under the curve) of contraction. ATB-346 produced a more profound decrease in contraction compared to equimolar concentrations of naproxen or TZB alone and was more potent than the equivalent concentration of Na2S.

CONCLUSIONS

ATB-346 exhibits potent tocolytic properties in human myometrium. These exciting results call for further exploration of ATB-346, with a view to repurposing this or similar drugs as novel therapies for delaying preterm labour.

Rac1 promotes the lipopolysaccharide-induced inflammatory response and contraction-associated proteins (CAPs) expression in mouse uterine smooth muscle cells

Activation of the maternal immune system leads to a downstream cascade of proinflammatory events that culminate in the activation of spontaneous uterine contractions, which is associated with preterm birth. Ras-related C3 botulinum toxin substrate 1 (Rac1) is a crucial protein related to cell contraction and inflammation. The main purpose of this study was to explore the role and function of Rac1's regulation of inflammation through in- vivo and in-vitro experiments. Rac1 inhibitor was used in animal model of preterm birth and cells isolated from the uterine tissues of pregnant mice on gestational day 16 were transfected with adenovirus to knockdown or overexpress Rac1 and treated with the Calcium-calmodulin-dependent protein kinase II (CaMKII) inhibitor KN93. The expression of Rac1, uterine contraction-associated proteins (CAPs) (COX-2 and Connexin43), and inflammatory cytokines, were assessed by Western blotting and RTPCR. LPS upregulated Rac1, COX-2 and Connexin43 expression in uterine smooth muscle cells (USMCs). The expression of inflammatory cytokines, COX-2, and Connexin43 was significantly decreased in shRac1-transfected cells compared with cells stimulated with LPS only. Rac1 overexpression led to an increase in the expression of inflammatory cytokines, COX-2, and Connexin43. Furthermore, after Rac1 overexpression, KN93 reduced the expression of uterine contraction-associated proteins and inflammatory cytokines. It is thought that the effect of Rac1 on inflammatory cytokine and contraction-associated protein expression in USMCs is mediated by CaMKII. Rac1 can modulate the expression of contraction-associated proteins and inflammatory cytokines through the CaMKII pathway. Rac1 could be an effective therapeutic target for improving the outcome of preterm birth.

Pretreatment with Indole-3-Propionic Acid Attenuates Lipopolysaccharide-Induced Cardiac Dysfunction and Inflammation Through the AhR/NF-κB/NLRP3 Pathway

Background

Patients with sepsis frequently develop septic cardiomyopathy, which is known to be closely related to excessive inflammatory responses. Indole-3-propionic acid (IPA) is a tryptophan metabolite with anti-inflammatory properties that have been demonstrated in various studies. In this study, we investigated the underlying mechanisms and therapeutic role of IPA in septic cardiomyopathy.

Methods

To investigate the role of IPA in septic cardiomyopathy, we constructed a lipopolysaccharide (LPS)-induced rat model of septic cardiomyopathy, and treated rats with IPA. Inflammatory factors and the NF-κB/NLRP3 pathway were evaluated in myocardial tissues and cells after IPA treatment using RT-qPCR, ELISA, Western blotting, and immunohistochemistry. To further elucidate the role of the aryl hydrocarbon receptor (AhR), we detected changes in inflammatory mediators and the NF-κB/NLRP3 pathway in in vivo and in vitro models of septic cardiomyopathy, which were treated with the AhR antagonist CH-223191 and/or AhR agonist FICZ.

Results

IPA supplementation improved cardiac dysfunction in rats with septic cardiomyopathy. IPA reduced inflammatory cytokine release and inhibited NF-κB/NLRP3 signaling pathway in myocardial tissue and in H9c2 cells. CH-223191 impaired the anti-inflammatory effect of IPA in LPS-treated cells, whereas FICZ exerted the same effect as IPA. IPA also exhibited anti-inflammatory activity by binding to the AhR. Our results indicated that IPA attenuated septic cardiomyopathy in rats via AhR/NF-κB/NLRP3 signaling.

Conclusion

Our study revealed that IPA improved left heart dysfunction and myocardial inflammation caused by sepsis via AhR/NF-κB/NLRP3 signaling, suggesting that IPA is a potential therapy for septic cardiomyopathy.

Hydrogen sulfide and its role in female reproduction

Hydrogen sulfide (H2S) is a gaseous signaling molecule produced in the body by three enzymes: cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST). H2S is crucial in various physiological processes associated with female mammalian reproduction. These include estrus cycle, oocyte maturation, oocyte aging, ovulation, embryo transport and early embryo development, the development of the placenta and fetal membranes, pregnancy, and the initiation of labor. Despite the confirmed presence of H2S-producing enzymes in all female reproductive tissues, as described in this review, the exact mechanisms of H2S action in these tissues remain in most cases unclear. Therefore, this review aims to summarize the knowledge about the presence and effects of H2S in these tissues and outline possible signaling pathways that mediate these effects. Understanding these pathways may lead to the development of new therapeutic strategies in the field of women's health and perinatal medicine.

The association between pregnancy levels of blood lipids and the risk of preterm birth

Preterm labor, a condition associated with various risk factors such as a history of prior preterm birth (PTB) and multiple pregnancies, has recently seen an increasing focus on its potential link with dyslipidemia. This study aims to investigate the relationship between dyslipidemia in expectant mothers and the risks of PTB. We studied 6963 mothers who gave birth at the International Peace Maternal and Child Health Hospital of Shanghai Jiaotong University School of Medicine in 2020, among which, 437 women had PTB. We extracted clinical and lipid data from electronic records, using multivariable logistic regression and restricted cubic spline models to explore the link between lipid concentrations (by quartiles) in pregnancy stages and PTB risk. The PTB rate was 6.3%. Early pregnancy in the PTB group showed elevated ApoA, ApoB, CHOL, LDL, and TG levels compared to controls (all P < 0.05). Late pregnancy showed no notable lipid differences. Multivariable analysis revealed elevated ApoA, TG, higher age, BMI ≥ 28 kg/m2, hypertension, assisted reproductive technology and gestational diabetes as PTB risk factors (all P < 0.05). After adjustments, higher ApoA, ApoB, CHOL and TG levels correlated with increased PTB risk. Using the lowest quartile, the adjusted ORs for early pregnancy's highest quartile of ApoA, ApoB, CHOL and TG were 1.348, 1.442, 1.442 and 2.156, respectively. Our findings indicate that dyslipemia in early pregnancy, including elevated levels of ApoA, ApoB, CHOL and TG, are associated with PTB. Managing lipid abnormalities during pregnancy may help reduce the risk of PTB.

In need of a specific antibody against the oxytocin receptor for neuropsychiatric research: A KO validation study

Antibodies are one of the most utilized tools in biomedical research. However, few of them are rigorously evaluated, as there are no accepted guidelines or standardized methods for determining their validity before commercialization. Often, an antibody is considered validated if it detects a band by Western blot of the expected molecular weight and, in some cases, if blocking peptides result in loss of staining. Neither of these approaches are unquestionable proof of target specificity. Since the oxytocin receptor has recently become a popular target in neuropsychiatric research, the need for specific antibodies to be used in brain has arisen. In this work, we have tested the specificity of six commercially available oxytocin receptor antibodies, indicated by the manufacturers to be suitable for Western blot and with an available image showing the correct size band (45-55 KDa). Antibodies were first tested by Western blot in brain lysates of wild-type and oxytocin receptor knockout mice. Uterus tissue was also tested as control for putative differential tissue specificity. In brain, the six tested antibodies lacked target specificity, as both wild-type and receptor knockout samples resulted in a similar staining pattern, including the expected 45-55 KDa band. Five of the six antibodies detected a selective band in uterus (which disappeared in knockout tissue). These five specific antibodies were also tested for immunohistochemistry in uterus, where only one was specific. However, when the uterine-specific antibody was tested in brain tissue, it lacked specificity. In conclusion, none of the six tested commercial antibodies are suitable to detect oxytocin receptor in brain by either Western blot or immunohistochemistry, although some do specifically detect it in uterus. The present work highlights the need to develop standardized antibody validation methods, including a proper negative control, in order to grant quality and reproducibility of the generated data.

Therapeutic Potential of Hydrogen Sulfide in Reproductive System Disorders

Hydrogen sulfide (H2S), previously regarded as a toxic exhaust and atmospheric pollutant, has emerged as the third gaseous signaling molecule following nitric oxide (NO) and carbon monoxide (CO). Recent research has revealed significant biological effects of H2S in a variety of systems, such as the nervous, cardiovascular, and digestive systems. Additionally, H2S has been found to impact reproductive system function and may have therapeutic implications for reproductive disorders. This paper explores the relationship between H2S and male reproductive disorders, specifically erectile dysfunction, prostate cancer, male infertility, and testicular damage. Additionally, it examines the impact of H2S regulation on the pathophysiology of the female reproductive system, including improvements in preterm birth, endometriosis, pre-eclampsia, fetal growth restriction, unexplained recurrent spontaneous abortion, placental oxidative damage, embryo implantation, recovery of myometrium post-delivery, and ovulation. The study delves into the regulatory functions of H2S within the reproductive systems of both genders, including its impact on the NO/cGMP pathway, the activation of K+ channels, and the relaxation mechanism of the spongy smooth muscle through the ROCK pathway, aiming to broaden the scope of potential therapeutic strategies for treating reproductive system disorders in clinical settings.

BKCa channels are involved in spontaneous and lipopolysaccharide-stimulated uterine contraction in late gestation mice†

The large-conductance, voltage-gated, calcium (Ca2+)-activated potassium channel (BKCa) is one of the most abundant potassium channels in the myometrium. Previous work conducted by our group has identified a link between inflammation, BKCa channels and excitability of myometrial smooth muscle cells. Here, we investigate the role of BKCa channels in spontaneous and lipopolysaccharide (LPS)-stimulated uterine contraction to gain a better understanding of the relationship between the BKCa channel and uterine contraction in basal and inflammatory states. Uteri of C57BL/6 J mice on gestational day 18.5 (GD18.5) were obtained and either fixed in formalin or used immediately for tension recording or isolation of primary myocytes for patch-clamp. Paraffin sections were used for immunofluorescenctdetection of BKCa and Toll-like receptor (TLR4). For tension recordings, LPS was administered to determine its effect on uterine contractions. Paxilline, a BKCa inhibitor, was used to dissect the role of BKCa in uterine contraction in basal and inflammatory states. Finally, patch-clamp recordings were performed to investigate the relationship between LPS, the BKCa channel and membrane currents in mouse myometrial smooth muscle cells (mMSMCs). We confirmed the expression of BKCa and TLR4 in the myometrium of GD18.5 mice and found that inhibiting BKCa channels with paxilline suppressed both spontaneous and LPS-stimulated uterine contractions. Furthermore, application of BKCa inhibitors (paxilline or iberiotoxin) after LPS inhibited BKCa channel activity in mMSMCs. Moreover, pretreatment with BKCa inhibitor or the TLR4 inhibitor suppressed LPS-activated BKCa currents. Our study demonstrates that BKCa channels are involved in both basal and LPS-stimulated uterine contraction in pregnant mice.

Regulatory effects of hydrogen sulfide on the female reproductive system

Hydrogen sulfide (H2S), a colorless exhaust gas, has been traditionally considered an air pollutant. However, recent studies have revealed that H2S functions as a novel gas signaling molecule, exerting diverse biological effects on various systems, including the cardiovascular, digestive, and nervous systems. Thus, H2S is involved in various pathophysiological processes. As H2S affects reproductive function, it has potential therapeutic implications in reproductive system diseases. This review examined the role of H2S in various female reproductive organs, including the ovary, fallopian tube, vagina, uterus, and placenta. Additionally, the regulatory function of H2S in the female reproductive system has been discussed to provide useful insights for developing clinical therapeutic strategies for reproductive diseases.

Hydrogen sulfide inhibits the rupture of fetal membranes throngh anti-aging pathways

INTRODUCTION

To investigate the relationship between hydrogen sulfide(H2S) and the senescence level of the fetal membranes, and to elucidate how H2S affects the integrity of the fetal membranes.

METHODS

The H2S and the senescence levels of fetal membranes, and the expressions of H2S synthase CBS and CSE were detected in the preterm (PT) group and the preterm premature ruptured membranes (pPROM) group. The effects of H2S donors and knockdown of CBS on the senescence level of amniotic epithelial cells, and the expression level of matrix metalloproteinases (MMPs) and epithelial-mesenchymal translation (EMT) were observed.

RESULTS

The level of H2S in the fetal membranes in the pPROM group is significantly lower than that in the PT group matched for gestational age. The level of H2S is negatively correlated with the senescence level of fetal membranes. Treatment with H2S donors reduced cell senescence and MMPs expression, but did not affect EMT. CBS siRNA transfection accelerated the senescence of amniotic epithelial cells, and promoted the expression of MMPs and EMT occurrence, but l-cysteine could reverse these effects.

DISCUSSION

Our study suggests that H2S, through its anti-aging effect, can influence the expression of MMPs and EMT, thereby contributing to the maintenance of fetal membrane integrity.

Elevated expression of Toll-like receptor 4 and cytokines in both serum and myometrium at term may serve as promising biomarkers for uterine activation preceding labor

Objective

Increased inflammation and cytokine levels are considered risk factors and promoters of preterm birth (PTB). However, the regulatory mechanism of pregnancy-related inflammation remains unclear. Toll-like receptor 4 (TLR4) plays a critical role in inflammatory responses in various diseases. Therefore, our study aimed to investigate whether TLR4 is involved in the inflammatory responses during uterine activation for labor, with the goal of identifying potential biomarkers for uterine activation at term.

Materials and methods

We used flow cytometry to detect TLR4 expression on CD14+ maternal blood monocytes in the first, second, and third trimesters. ELISA was employed to measure TLR4 and cytokines levels in the maternal serum of term non-labor (TNL), term labor (TL) women and LPS induced preterm labor and PBS injected controls. TLR4siRNA was transfected into the human myometrial smooth muscle cells (HMSMCs), which were subsequently treated with IL-1β. The mRNA and protein levels of TLR4, uterine contraction-related protein connexin 43 (CX43), oxytocin receptor (OTR), MAPK/NF-κB signaling pathway, and cytokines were analyzed using qRT-PCR, western blotting, and immunohistochemistry.

Results

The study revealed TLR4 expression on CD14+ maternal blood monocytes was higher in the third trimester group compared to the first and second trimester groups (p<0.001). Maternal serum concentrations of TLR4 and cytokines were significantly higher in the TL group than the TNL group (p<0.001). TLR4, OTR, CX43, activated MAPK/NF-κB expression, and cytokines levels were upregulated in TL group, and similarly significantly higher in the LPS-induced preterm group than in the control group. Using the HMSMCs we demonstrated that TLR4siRNA transfection suppressed contractility. Interfering with TLR4 expression reduced the expression of OTR, CX43, cytokines, and MAPK/NF-κB activation. There was a significant positive relationship between TLR4 expression and the inflammatory status in the myometrium. ROC analysis indicated that TLR4 and cytokines may serve as potential biomarkers for predicting uterine activation for labor.

Conclusion

Our data suggest that TLR4 and cytokines can act as stimulators of uterine activation for labor at term. Furthermore, the MAPK/NF-κB pathway appears to be one of the potential signaling pathways mediating TLR4's regulation of parturition initiation.

Deficiency of hydrogen sulfide production and pregnancy rate in an experimental model: Association with preterm delivery

PROBLEM

Pro-inflammatory phenomena drive preterm delivery (PTD). Hydrogen sulfide is a gasotransmitter with anti-inflammatory properties produced through the activity of the enzyme cystathionine-γ-lyase (CSE), and its impact was studied in models of normal delivery and PTD in mice.

METHOD OF STUDY

Female CSE+/+ and CSE-/- mice were mated with male CSE+/+ mice; mating was done with drinking water unsupplemented and supplemented with cysteine. The pregnancy rate was monitored. PTD was induced by the intraperitoneal injection of bacterial lipopolysaccharide (LPS) on day 14.5 of pregnancy. Mice were sacrificed for tissue collection and splenocyte isolation after 6 and 12 h. Isolated splenocytes were stimulated for the production of tumor necrosis factor-alpha (TNFα), interleukin (IL)-10 and interferon-gamma (IFNγ); TNFα and vascular endothelial growth factor (VEGF) were measured in the fetuses and the placenta.

RESULTS

The successful pregnancy rate was lower in CSE-/- mice and it was restored with cysteine supplementation. CSE deficiency was associated with higher tissue concentrations of TNFα in the fetuses, attenuated IL-10 responses and higher IFNγ production from splenocytes. CSE deficiency was not associated with PTD. Following PTD induction, CSE-/- mice did not show attenuated IL-10 responses but the production of TNFα and IFNγ was lowered over-time; placental VEGF was also increased over-time.

CONCLUSIONS

CSE deficiency has an unfavorable impact on pregnancy. H2 S deficiency through CSE does not drive PTD but mediates pro-inflammatory phenomena in fetuses.

Plasma hydrogen sulfide, nitric oxide, and thiocyanate levels are lower during pregnancy compared to postpartum in a cohort of women from the Pacific northwest of the United States

AIMS

Pregnancy alters multiple physiological processes including angiogenesis, vasodilation, inflammation, and cellular redox, which are partially modulated by the gasotransmitters hydrogen sulfide (H2S) and nitric oxide (NO). In this study, we sought to determine how plasma levels of H2S, NO, and the H2S-related metabolites thiocyanate (SCN-), and methanethiol (CH3SH) change during pregnancy progression.

MATERIALS AND METHODS

Plasma was collected from 45 women at three points: 25-28 weeks gestation, 28-32 week gestation, and at ≥3 months postpartum. Plasma levels of H2S, SCN-, and CH3SH were measured following derivatization using monobromobimane followed by LC-MS/MS. Plasma NO was measured indirectly using the Griess reagent.

KEY FINDINGS

NO and SCN- were significantly lower in women at 25-28 weeks gestation and 28-32 weeks gestation than postpartum while plasma H2S levels were significantly lower at 28-32 weeks gestation than postpartum. No significant differences were observed in CH3SH.

SIGNIFICANCE

Previous reports demonstrated that the production of H2S and NO are stimulated during pregnancy, but we observed lower levels during pregnancy compared to postpartum. Previous reports on NO have been mixed, but given the related effects of H2S and NO, it is expected that their levels would be higher during pregnancy vs. postpartum. Future studies determining the mechanism for decreased H2S and NO during pregnancy will elucidate the role of these gasotransmitters during normal and pathological progression of pregnancy.

Epidural-related maternal fever: incidence, pathophysiology, outcomes, and management

Epidural-related maternal fever affects 15% to 25% of patients who receive a labor epidural. Two meta-analyses demonstrated that epidural-related maternal fever is a clinical phenomenon, which is unlikely to be caused by selection bias. All commonly used neuraxial techniques, local anesthetics with or without opioids, and maintenance regimens are associated with epidural-related maternal fever, however, the impact of each component is unknown. Two major theories surrounding epidural-related maternal fever development have been proposed. First, labor epidural analgesia may lead to the development of hyperthermia through a sterile (noninfectious) inflammatory process. This process may involve reduced activation of caspase-1 (a protease involved in cell apoptosis and activation of proinflammatory pathways) secondary to bupivacaine, which impairs the release of the antipyrogenic cytokine, interleukin-1-receptor antagonist, from circulating leucocytes. Detailed mechanistic processes of epidural-related maternal fever remain to be determined. Second, thermoregulatory mechanisms secondary to neuraxial blockade have been proposed, which may also contribute to epidural-related maternal fever development. Currently, there is no prophylactic strategy that can safely prevent epidural-related maternal fever from occurring nor can it easily be distinguished clinically from other causes of intrapartum fever, such as chorioamnionitis. Because intrapartum fever (of any etiology) is associated with adverse outcomes for both the mother and baby, it is important that all parturients who develop intrapartum fever are investigated and treated appropriately, irrespective of labor epidural utilization. Institution of treatment with appropriate antimicrobial therapy is recommended if an infectious cause of fever is suspected. There is currently insufficient evidence to warrant a change in recommendations regarding provision of labor epidural analgesia and the benefits of good quality labor analgesia must continue to be reiterated to expectant mothers.

Is human labor at term an inflammatory condition?†

Parturition at term in normal pregnancy follows a predictable sequence of events. There is some evidence that a state of inflammation prevails in the reproductive tissues during labor at term, but it is uncertain whether this phenomenon is the initiating signal for parturition. The absence of a clear temporal sequence of inflammatory events prior to labor casts doubt on the concept that normal human labor at term is primarily the result of an inflammatory cascade. This review examines evidence linking parturition and inflammation in order to address whether inflammation is a cause of labor, a consequence of labor, or a separate but related phenomenon. Finally, we identify and suggest ways to reconcile inconsistencies regarding definitions of labor onset in published research, which may contribute to the variability in conclusions regarding the genesis and maintenance of parturition. A more thorough understanding of the processes underlying normal parturition at term may lead to novel insights regarding abnormal labor, including spontaneous preterm labor, preterm premature rupture of the fetal membranes, and dysfunctional labor, and the role of inflammation in each.

Physiological roles of hydrogen sulfide in mammalian cells, tissues and organs

H2S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H2S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H2S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H2S and oxidative posttranscriptional modification of proteins, the effect of H2S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H2S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H2S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H2S in various cell types and organ systems are overviewed. Finally, the role of H2S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H2S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H2S in the physiological regulation of all organ functions emerges from this review.

The Anti-Inflammation and Anti-Nociception Effect of Ketoprofen in Rats Could Be Strengthened Through Co-Delivery of a H2S Donor, S-Propargyl-Cysteine

PURPOSE

Ketoprofen (KETO) is a traditional non-steroidal anti-inflammatory drug (NSAIDs) with good analgesic and antipyretic effects. However, as NASIDs, the toxicity of KETO towards gastrointestinal (GI) system might limit its clinical use. S-propargyl-cysteine (SPRC) is an excellent endogenous H2S donor showed wide application in the field of anti-inflammation, anti-oxidative stress, or even the protection of cardiovascular system through the elevation of endogenous H2S concentration. As recently studies reported, co-administration of H2S donor might potentially mitigate the GI toxicity and relevant side effects induced by series of NSAIDs.

METHODS

In this study, we established a SPRC and KETO co-encapsulated poly (lactic-co-glycolic acid) microsphere (SK@MS), and its particle size, morphology, storage stability and in vitro release profile were firstly investigated. The elevation of endogenous H2S level of SK@MS was then calculated, and the pharmacodynamic study (anti-inflammation and analgesic effects) of SK@MS, SPRC, and KETO towards adjuvant induced arthritis (AIA) in rats were also studied. Finally, to test the potential side effect, the heart, liver, spleen, lung, kidney, stomach, small intestine, and large intestine were resected from rats and examined by H&E staining.

RESULTS

A monodispersed SK@MS could be observed under the SEM, and particle size was calculated around 25.12 μm. The loading efficiency (LE) for SPRC and KETO were 6.67% and 2.64%, respectively, while the encapsulation efficiency (EE) for SPRC and KETO were 37.20% and 68.28%, respectively. SK@MS showed a sustained release of SPRC and KETO in vitro, which was up-to 15 days. SK@MS could achieve a long-term elevation of the H2S concentration in vivo, while SPRC showed an instant H2S elevation and metabolize within 6 h. Interestingly, the KETO did not show any influence on the H2S concentration in vivo. After establishment of AIA model, neither SPRC nor KETO showed scarcely anti-inflammation and anti-nociception effect, while conversely, SK@MS showed an obvious mitigation towards paw edema and pain in AIA rats, which indicated an improved anti-inflammation and anti-nociception effect when co-delivery of SRC and KETO. Besides, low stimulation towards major organs in rats observed in any experimental group.

CONCLUSION

A monodispersed was successfully prepared in this study, and SK@MS showed a sustained SPRC and KETO release in vitro and H2S release in vivo. In the pharmacodynamics study, SK@MS not only exhibited an excellent anti-inflammation and analgesic effects in AIA rats but also showed low stimulation towards rats.