Leptin attenuates lipopolysaccharide-induced apoptosis of thymocytes partially via down-regulation of cPLA2 and p38 MAPK activation

Epigallocatechin-3-gallate ameliorates lipopolysaccharide-induced acute thymus involution in mice via AMPK/Sirt1 pathway

The thymus, a site to culture the naïve T lymphocytes, is susceptible to atrophy or involution due to aging, inflammation, and oxidation. Epigallocatechin-3-gallate (EGCG) has been proven to possess anti-inflammatory, antioxidant, and antitumor activity. Here, we investigate the effects of EGCG on thymic involution induced by lipopolysaccharide (LPS), an endotoxin derived from Gram-negative bacteria. The methodology included an in vivo experiment on female Kunming mice exposed to LPS and EGCG. Morphological assessment of thymic involution, immunohistochemical detection, and thymocyte subsets analysis by flow cytometry were further carried out to evaluate the potential role of EGCG on the thymus. As a result, we found that EGCG alleviated LPS-induced thymic atrophy, increased mitochondrial membrane potential and superoxide dismutase levels, and decreased malondialdehyde and reactive oxygen species levels. In addition, EGCG pre-supplement restored the ratio of thymocyte subsets, the expression of autoimmune regulator, sex-determining region Y-box 2, and Nanog homebox, and reduced the number of senescent cells and collagen fiber deposition. Western blotting results indicated that EGCG treatment elevated LPS-induced decrease in pAMPK, Sirt1 protein expression. Collectively, EGCG relieved thymus architecture and function damaged by LPS via regulation of AMPK/Sirt1 signaling pathway. Our findings may provide a new strategy on protection of thymus from involution caused by LPS by using EGCG. And EGCG might be considered as a potential agent for the prevention and treatment of thymic involution.

Primary and secondary defects of the thymus

The thymus is the primary site of T-cell development, enabling generation, and selection of a diverse repertoire of T cells that recognize non-self, whilst remaining tolerant to self- antigens. Severe congenital disorders of thymic development (athymia) can be fatal if left untreated due to infections, and thymic tissue implantation is the only cure. While newborn screening for severe combined immune deficiency has allowed improved detection at birth of congenital athymia, thymic disorders acquired later in life are still underrecognized and assessing the quality of thymic function in such conditions remains a challenge. The thymus is sensitive to injury elicited from a variety of endogenous and exogenous factors, and its self-renewal capacity decreases with age. Secondary and age-related forms of thymic dysfunction may lead to an increased risk of infections, malignancy, and autoimmunity. Promising results have been obtained in preclinical models and clinical trials upon administration of soluble factors promoting thymic regeneration, but to date no therapy is approved for clinical use. In this review we provide a background on thymus development, function, and age-related involution. We discuss disease mechanisms, diagnostic, and therapeutic approaches for primary and secondary thymic defects.

Leptin mediates the suppressive effect of partial fat removal on cellular and humoral immunity in striped hamsters

Leptin secreted mainly by white adipose tissues (WAT) plays an important role in immune responses. To understand the role of energy status and leptin in immunity, bilateral perigonadal fat pads were removed or sham-removed in male striped hamsters (Cricetulus barabensis). Half of these hamsters were injected with sterile saline, and another half were administrated with exogenous leptin each day, which lasted for 20 days. Fat removal reduced total body fat mass and leptin titers significantly, leptin administration increased leptin levels in the fat removed hamsters to the control levels, but did not affect total body fat mass. Body mass and gross energy intake were not affected by fat removal, leptin supplement or their interaction. Fat removal decreased thymus mass, phytohaemagglutinin (PHA) response at 12 h, and the levels of immunoglobin (Ig) G 5, IgG10, IgM5, IgM10, IL-2, IL-4, and TNF-α, indicating a reduction in fat mass suppressed cellular and humoral immunity and the production of cytokines. However, fat removal had no effect on spleen mass, bacteria killing activity and IFN-γ titers. Leptin supplement increased PHA response at 6 h and 12 h, and the levels of IgG5, IgG10, IL-4, and IFN-γ to the control levels, implying its boosting effects on these parameters. In addition, leptin level was positively correlated with body fat mass, PHA 6 h, 12 h, Ig G10, Ig M5, Ig M10, IL-2, IL-4, and TNF-α. Collectively, these findings implied leptin was a link between energy status and immunity, and leptin mediated the suppressive effects of reduced energy storage on cellular and humoral immunity.

Infection-Associated Thymic Atrophy

The thymus is a vital organ of the immune system that plays an essential role in thymocyte development and maturation. Thymic atrophy occurs with age (physiological thymic atrophy) or as a result of viral, bacterial, parasitic or fungal infection (pathological thymic atrophy). Thymic atrophy directly results in loss of thymocytes and/or destruction of the thymic architecture, and indirectly leads to a decrease in naïve T cells and limited T cell receptor diversity. Thus, it is important to recognize the causes and mechanisms that induce thymic atrophy. In this review, we highlight current progress in infection-associated pathogenic thymic atrophy and discuss its possible mechanisms. In addition, we discuss whether extracellular vesicles/exosomes could be potential carriers of pathogenic substances to the thymus, and potential drugs for the treatment of thymic atrophy. Having acknowledged that most current research is limited to serological aspects, we look forward to the possibility of extending future work regarding the impact of neural modulation on thymic atrophy.

Leptin is upregulated in epididymitis and promotes apoptosis and IL-1β production in epididymal epithelial cells by activating the NLRP3 inflammasome

Epididymitis, one of the most common urological disease, is a significant cause of male infertility. Leptin is capable of modulating both reproduction and immune response. We analyzed the serum and seminal plasma levels of leptin in infertile patients with or without chronic epididymitis. Experimental epididymitis models were generated by administrating 200 μg Lipopolysaccharide (LPS) to Sprague-Dawley rats. The expression of leptin in epididymis were detected using qPCR, Western blots 6-72 h after injection, and using immunohistochemistry 72 h after injection. Besides, rat epididymal epithelial cells were isolated as an in vitro model and were treated with leptin (5-40 ng/ml, 6-48 h), LPS (1ug/ml, 6 h), and NLRP3 inflammasome inhibitor MCC950 (10 μM, 2 h). Cell Counting Kits-8 assay and Annexin V/PE assay were used to evaluate cell viability and apoptosis. Quantitive PCR and ELISA assay were used to detected inflammatory cytokines interleukin-1beta (IL-1β) production. Western Blots were used to detect molecular related to cell apoptosis, IL-1β maturation, and NLRP3 inflammasome. We found that patients with chronic epididymitis presented a significantly higher level of seminal plasma leptin and correlated declined sperm progressive motility. Leptin and leptin receptor expression in epididymis was significantly upregulated 24 h after LPS administration both in mRNA and protein level, and highly expressed in the epididymis epithelium 72 h after LPS administration. In epididymal epithelial cells, leptin reduced cell viability and promoted apoptosis in a concentration-dependent manner via cleavage of caspase-9, caspase-3, and PARP. Leptin enhanced the LPS-induced production of IL-1β, which was associated with increased IL-1β maturation and caspase-1 activation. Furthermore, NLRP3 inhibitor MCC950 attenuated the effects of leptin or co-treatment with LPS on NLRP3, ASC expression, IL-1β maturation, and caspase-1 activation, which indicated that leptin promotes IL-1β production via activating the NLRP3 inflammasome. These data suggested that leptin may act as a potential evaluation and treatment target for epididymitis and male subfertility.

Casein glycomacropeptide hydrolysates inhibit PGE2 production and COX2 expression in LPS-stimulated RAW 264.7 macrophage cells via Akt mediated NF-κB and MAPK pathways

A casein glycomacropeptide hydrolysate (GMPH) was found to possess inhibitory activity against lipopolysaccharide (LPS)-induced inflammatory response in our previous study. In the current study, the inhibitory effect and the underlying molecular mechanism of GMPH on inflammatory response in LPS-stimulated RAW264.7 macrophages were further investigated. Results showed that GMPH significantly suppressed LPS-induced intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) production. GMPH reduced the production of prostaglandin E2 (PEG2) and the expression of cyclooxygenase-2 (COX-2) and cytosolic phospholipase A2 (cPLA2) in LPS-stimulated macrophages. GMPH also attenuated LPS-induced phosphorylation of MAPK (c-Jun NH2-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and p38) and protein kinase B (Akt). Furthermore, GMPH inhibited nuclear transcription factor kappa-B (NF-κB) activation by suppressing the nuclear translocation of NF-κB p65, which was markedly reversed by LY294002, an Akt inhibitor. These results demonstrated that GMPH exerts anti-inflammatory functions through the inactivation of MAPK and Akt in LPS-stimulated RAW264.7 macrophages, therefore may hold potential to ameliorate inflammation-related metabolic disorders.

Thymic Atrophy: Experimental Studies and Therapeutic Interventions

The thymus is essential for T cell development and maturation. It is extremely sensitive to atrophy, wherein loss in cellularity of the thymus and/or disruption of the thymic architecture occur. This may lead to lower naïve T cell output and limited TCR diversity. Thymic atrophy is often associated with ageing. What is less appreciated is that proper functioning of the thymus is critical for reduction in morbidity and mortality associated with various clinical conditions including infections and transplantation. Therefore, therapeutic interventions which possess thymopoietic potential and lower thymic atrophy are required. These treatments enhance thymic output, which is a vital factor in generating favourable outcomes in clinical conditions. In this review, experimental studies on thymic atrophy in rodents and clinical cases where the thymus atrophies are discussed. In addition, mechanisms leading to thymic atrophy during ageing as well as during various stress conditions are reviewed. Therapies such as zinc supplementation, IL7 administration, leptin treatment, keratinocyte growth factor administration and sex steroid ablation during thymic atrophy involving experiments in animals and various clinical scenarios are reviewed. Interventions that have been used across different scenarios to reduce the extent of thymic atrophy and enhance its output are discussed. This review aims to speculate on the roles of combination therapies, which by acting additively or synergistically may further alleviate thymic atrophy and boost its function, thereby strengthening cellular T cell responses.

The clinical analysis of acute pancreatitis in colorectal cancer patients undergoing chemotherapy after operation

Acute pancreatitis is a rare complication in postoperative colorectal cancer patients after FOLFOX6 (oxaliplatin + calcium folinate +5-FU [5-fluorouracil]) chemotherapy. In this paper, a total of 62 patients with gastrointestinal cancer were observed after the burst of acute pancreatitis. Surgery of the 62 cases of colorectal cancer patients was completed successfully. But when they underwent FOLFOX6 chemotherapy, five patients got acute pancreatitis (8.06%), four (6.45%) had mild acute pancreatitis, and one (1.61%) had severe acute pancreatitis, of which two were males (3.23%) and three females (4.84%). No patients (0.00%) had acute pancreatitis on the 1st day after chemotherapy; one patient (1.61%) got it in the first 2 and 3 days after chemotherapy; and three others (4.83%) got it in the first 4 days after chemotherapy. In the 62 patients with malignant tumors, the body mass index (BMI) was less than 18 (underweight) in six of them, with two cases of acute pancreatitis (33.33%); the BMI was 18–25 (normal weight) in 34 cases, with one case (2.94%) of acute pancreatitis; the BMI was 25–30 (overweight) in 13 cases, with 0 cases (0.00%) of acute pancreatitis; and the BMI was ≥30 (obese) in nine patients, with two cases of acute pancreatitis (22.22%). After symptomatic treatment, four patients were cured and one died; the mortality rate was 1.61%. Most of them appeared in the first 4 days after chemotherapy; the probability of this complication is significantly higher in slim and obese patients than in normal weight patients. Postoperative colorectal cancer patients after FOLFOX6 chemotherapy have a sudden onset of acute pancreatitis occult, especially in patients with severe acute pancreatitis; the symptoms are difficult to control, there is high mortality and it is worthy of clinician’s attention.

Leptin downregulates aggrecan through the p38-ADAMST pathway in human nucleus pulposus cells

The mechanistic basis of obesity-associated intervertebral disc degeneration (IDD) is unclear. Aberrant expression of aggrecan and its degrading enzymes ADAMTS-4 and ADAMTS-5 is implicated in the development of IDD. Here, we investigated the effect of leptin, a hormone with increased circulating levels in obesity, on the expression of aggrecan and ADAMTSs in primary human nucleus pulposus (NP) cells. Real-time PCR and Western blots showed that leptin increased the mRNA and protein expression of ADAMTS-4 and ADAMTS-5 and reduced the level of aggrecan in NP cells, accompanied by a prominent induction of p38 phosphorylation. Treatment of NP cells with SB203580 (a p38 inhibitor) abolished the regulation of aggrecan and ADAMTSs by leptin. Knockdown of ADAMTS-4 and ADAMTS-5 by siRNAs also attenuated the degradation of aggrecan in leptin-stimulated NP cells. To conclude, we demonstrated that leptin induces p38 to upregulate ADAMTSs and thereby promoting aggrecan degradation in human NP cells. These results provide a novel mechanistic insight into the molecular pathogenesis of obesity-associated IDD.