The effects of splenectomy and splenic autotransplantation on plasma lipid levels

High-fat diet activates splenic NOD1 and enhances neutrophil recruitment and neutrophil extracellular traps release in the spleen of ApoE-deficient mice

In the course of atherogenesis, the spleen plays an important role in the regulation of extramedullary hematopoiesis, and in the control of circulating immune cells, which contributes to plaque progression. Here, we have investigated the role of splenic nucleotide-binding oligomerization domain 1 (NOD1) in the recruitment of circulating immune cells, as well as the involvement of this immune organ in extramedullary hematopoiesis in mice fed on a high-fat high-cholesterol diet (HFD). Under HFD conditions, the absence of NOD1 enhances the mobilization of immune cells, mainly neutrophils, from the bone marrow to the blood. To determine the effect of NOD1-dependent mobilization of immune cells under pro-atherogenic conditions, Apoe^−/− and Apoe^−/−Nod1^−/− mice fed on HFD for 4 weeks were used. Splenic NOD1 from Apoe^−/− mice was activated after feeding HFD as inferred by the phosphorylation of the NOD1 downstream targets RIPK2 and TAK1. Moreover, this activation was accompanied by the release of neutrophil extracellular traps (NETs), as determined by the increase in the expression of peptidyl arginine deiminase 4, and the identification of citrullinated histone H3 in this organ. This formation of NETs was significantly reduced in Apoe^−/−Nod1^−/− mice. Indeed, the presence of Ly6G⁺ cells and the lipidic content in the spleen of mice deficient in Apoe and Nod1 was reduced when compared to the Apoe^−/− counterparts, which suggests that the mobilization and activation of circulating immune cells are altered in the absence of NOD1. Furthermore, confirming previous studies, Apoe^−/−Nod1^−/− mice showed a reduced atherogenic disease, and diminished recruitment of neutrophils in the spleen, compared to Apoe^−/− mice. However, splenic artery ligation reduced the atherogenic burden in Apoe^−/− mice an effect that, unexpectedly was lost in Apoe^−/−Nod1^−/− mice. Together, these results suggest that neutrophil accumulation and activity in the spleen are driven in part by NOD1 activation in mice fed on HFD, contributing in this way to regulating atherogenic progression.

The impact of splenectomy on human lipid metabolism

BACKGROUND

Splenectomy impacts hematological, immunological, and metabolic functions of the patient. Since our understanding of its metabolic effects, in particular effects on lipid metabolism, is limited, this study aims to investigate the effects of splenectomy on lipid metabolism.

METHODS

The data from 316 patients undergoing splenectomy between 2009 and 2019 were retrospectively analyzed. Thirty-eight patients whose serum lipid values were measured both preoperatively and 1 year after surgery were included in this study.

RESULTS

Significantly higher levels of total cholesterol, low-density lipoprotein (LDL), and non-high-density lipoprotein (HDL) lipid profile were found in the postsplenectomy measurements. However, no significant differences were recorded in levels of triglyceride, HDL, or very-LDL.

CONCLUSION

We determined that splenectomy does impact lipid metabolism, and that the metabolic effects of splenectomy should further be investigated.

Contribution of Extramedullary Hematopoiesis to Atherosclerosis. The Spleen as a Neglected Hub of Inflammatory Cells

Cardiovascular diseases (CVDs) incidence is becoming higher. This fact is promoted by metabolic disorders such as obesity, and aging. Atherosclerosis is the underlying cause of most of these pathologies. It is a chronic inflammatory disease that begins with the progressive accumulation of lipids and fibrotic materials in the blood-vessel wall, which leads to massive leukocyte recruitment. Rupture of the fibrous cap of the atherogenic cusps is responsible for tissue ischemic events, among them myocardial infarction. Extramedullary hematopoiesis (EMH), or blood cell production outside the bone marrow (BM), occurs when the normal production of these cells is impaired (chronic hematological and genetic disorders, leukemia, etc.) or is altered by metabolic disorders, such as hypercholesterolemia, or after myocardial infarction. Recent studies indicate that the main EMH tissues (spleen, liver, adipose and lymph nodes) complement the hematopoietic function of the BM, producing circulating inflammatory cells that infiltrate into the atheroma. Indeed, the spleen, which is a secondary lymphopoietic organ with high metabolic activity, contains a reservoir of myeloid progenitors and monocytes, constituting an important source of inflammatory cells to the atherosclerotic lesion. Furthermore, the spleen also plays an important role in lipid homeostasis and immune-cell selection. Interestingly, clinical evidence from splenectomized subjects shows that they are more susceptible to developing pathologies, such as dyslipidemia and atherosclerosis due to the loss of immune selection. Although CVDs represent the leading cause of death worldwide, the mechanisms involving the spleen-atherosclerosis-heart axis cross-talk remain poorly characterized.

Systemic Amelioration via Curcumin in Rats following Splenectomy: Lipid Profile, Endothelial and Oxidative Damage

BACKGROUND

We investigated the postsurgical effects of splenectomy with additional curcumin therapy, as an antioxidant, anti-inflammatory substance among the lipid profile and histopathological changes.

MATERIALS AND METHODS

32 rats were randomly divided into four groups: control group (L): laparotomy, sham group: splenectomy (S), splenectomy group treated with curcumin (SC) and splenectomy group treated with corn oil (SCO) for 28 days. The primary outcomes; total cholesterol (TC), triglycerides (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), oxidized LDL (ox-LDL) very-low-density lipoprotein (VLDL) and lectin-type oxidized LDL receptor 1 (LOX-1), secondary outcomes: nuclear factor kappa B (NF-кB), malondialdehyde (MDA), glutathione peroxidase (GPx), superoxide dismutase (SOD) were measured. Histopathological changes were examined in vascular, intestinal and lung tissues. The analysis was performed by ANOVA.

RESULTS

TG, LDL, ox-LDL, and LOX-1 elevated in S group while reduced by curcumin compared with L group (p < 0.05). Serum and tissue levels of NF-кB and MDA were higher in S group and lower in SC group than L group (p < 0.05). Serum and intestinal levels of SOD and GPx increased in L group while reduced by curcumin (p < 0.05). Total histopathological scores of intestinal tissues were higher in S and SCO groups compared to L and SC groups (p < 0.05). No major changes in vascular and lung tissues were observed except the lymphoid follicles which was higher in S and SCO groups compared to L and SC groups (p < 0.05).

CONCLUSIONS

Curcumin partially improved the lipid profile dysfunction by modulating NF-кB, MDA, SOD, and GPx in splenectomized rats while less likely improving any vascular and alveolar regeneration.

The role of splenectomy in lipid metabolism and atherosclerosis (AS)

The extensive performance of splenectomy worldwide for patients suffered from splenic trauma has given rise to high risks of postoperative complications, which has been attracting increasing attention in recent years. Nowadays the spleen is regarded as a versatile organ of the human body, invested with various excellent properties. The spleen has been recognized to take a great part in lipid metabolism. While removal of the spleen intends to alter lipid values, especially with an elevated LDL, splenic autotransplantation is able to normalize these lipid alterations. What is more, conservative surgical procedures like subtotal or partial splenectomy, could as well, afford a correction of dyslipidemia. At the same time, clinically, splenectomy demonstrates a high rate of atherosclerosis (AS), whereas non-surgical treatment after splenic trauma shows unchanged propagation of AS. Based on the intimate relationship between serum lipids and AS, the lipid changes modulated by splenectomy are believed to be responsible for the development of AS. Therefore, a "splenic factor" is most likely present in the regulation of lipidation and AS. Several theories have been postulated to elucidate the possible mechanism involved, among which most are primarily based on its forceful natural immune function, that is to say, the mononuclear phagocytic system.However, the accurate mechanisms behind this mysterious phenomenon still remain unclear so far. Of importance, lipid fractions should be monitored consecutively in case of inevitable splenectomy.

Nonalcoholic fatty liver disease progression in rats is accelerated by splenic regulation of liver PTEN/AKT

BACKGROUND/AIM

The spleen has been reported to participate in the development of nonalcoholic fatty liver disease (NAFLD), but the mechanism has not been fully characterized. This study aims to elucidate how the spleen affects the development of NAFLD in a rat model.

MATERIALS AND METHODS

Following either splenectomy or sham operation, male Sprague-Dawley (SD) rats were fed a high-fat diet to drive the development of NAFLD; animals fed a normal diet were used as controls. Two months after surgery, livers and blood samples were collected. Serum lipids were measured; liver histology, phosphatase and tensin homologue deleted on chromosome 10 (PTEN) gene expression, and the ratio of pAkt/Akt were determined.

RESULTS

Splenectomy increased serum lipids, except triglyceride (TG) and high-density lipoprotein (HDL), in animals fed either a high-fat or normal diet. Furthermore, splenectomy significantly accelerated hepatic steatosis. Western blot analysis and real-time polymerase chain reaction showed splenectomy induced significant downregulation of PTEN expression and a high ratio of pAkt/Akt in the livers.

CONCLUSIONS

The spleen appears to play a role in the development of NAFLD, via a mechanism involving downregulation of hepatic PTEN expression.

Liver-spleen axis: Intersection between immunity, infections and metabolism

Spleen has been considered a neglected organ so far, even though is strictly linked to liver. The spleen plays an important role in the modulation of the immune system and in the maintenance of peripheral tolerance via the clearance of circulating apoptotic cells, the differentiation and activation of T and B cells and production of antibodies in the white pulp. Moreover, splenic macrophages are able to remove bacteria from the blood and protect from sepsis during systemic infections. We review the spleen function and its assessment in humans starting from the description of spleen diseases, ranging from the congenital asplenia to secondary hyposplenism. From the literature data it is clear that obesity in humans affects different compartments of immune system, even thought there are still few data available on the implicated mechamisms. The intent is to enable clinicians to evaluate the newly recognized role of metabolic and endocrine functions of the spleen with special emphasis to obesity and nonalcoholic fatty liver disease in the context of the available literature. Moreover, understanding the spleen function could be important to develop appropriate prevention strategies in order to counteract the pandemia of obesity. In this direction, we suggest spleen longitudinal diameter at ultrasonography, as simple, cheap and largely available tool, be used as new marker for assessing splenic function, in the context of the so-called liver-spleen axis.

Laparoscopy splenectomy for massive splenomegaly

OBJECTIVE

This study is aimed to evaluate the feasibility of laparoscopic splenectomy (LS) for massive splenomegaly in patients with hypersplenism secondary to portal hypertension and liver cirrhosis.

METHOD

A retrospective study of adult patients was conducted for splenectomy occurring from January 2006 to December 2010. We have performed the surgical procedures of splenectomy in 80 patients who were suffering from splenomegaly or hypersplenism secondary to portal hypertension and liver cirrhosis, among whom 40 patients underwent LS and another 40 patients received open surgery (OS).

RESULTS

Among the patients who had undergone LS, 2 patients were converted to OS and the other 38 patients underwent complete LS. The operation time, intraoperative blood loss, and the length of stay in LS group and OS group were 100-200 min (mean: 150 ± 30 min) vs. 120-210 min (mean: 100 ± 30 min), 50-1,000 ml (mean: 150 ± 110 ml) vs. 60-900 ml (mean: 140 ± 50 ml) and 4-9 days (mean: 6.1 ± 2.2 days) vs. 8-14 days (mean: 11.3 ± 2.3 days), respectively. No deaths occurred in the two groups, and there are no significant differences between the two groups in terms of estimated blood loss, complications, length of stay, and operating time.

CONCLUSION

LS for treatment of massive splenomegaly is a feasible, effective, and safe surgical technique. Hypersplenism secondary to portal hypertension and liver cirrhosis are not supposed to be considered absolute contraindications to LS.

Leukocyte ABCA1 remains atheroprotective in splenectomized LDL receptor knockout mice

Aim

ATP-binding cassette transporter A1 (ABCA1) is an important mediator of macrophage cholesterol efflux. It mediates the efflux of cellular cholesterol to lipid-poor apolipoprotein A-I. LDL receptor (LDLr) knockout (KO) mice deficient for leukocyte ABCA1 (ABCA1 KO→LDLr KO) show increased atherosclerosis and splenic lipid accumulation despite largely attenuated serum cholesterol levels. In the present study, we aimed to explore the importance of the spleen for the atheroprotective effects of leukocyte ABCA1.

Methods

LDLr KO mice were transplanted with bone marrow from ABCA1 KO mice or wild-type (WT) controls. After 8 weeks recovery, mice were either splenectomized (SP-x) or underwent a sham operation, and were subsequently challenged with a Western-type diet (WTD).

Results

In agreement with previous studies, the atherosclerotic lesion area in ABCA1 KO→LDLr KO sham animals (655±82×10³ µm²) was 1.4-fold (p = 0.03) larger compared to sham WT→LDLr KO mice (459±33×10³ µm²) after 8 weeks WTD feeding, despite 1.7-fold (p<0.001) lower serum cholesterol levels. Interestingly, deletion of ABCA1 in leukocytes led to 1.6-fold higher neutrophil content in the spleen in absence of differences in circulating neutrophils. Levels of KC, an important chemoattractant for neutrophils, in serum, however, were increased 2.9-fold (p = 0.07) in ABCA1 KO→LDLr KO mice. SP-x induced blood neutrophilia as compared to WT→LDLr KO mice (1.9-fold; p<0.05), but did not evoke differences in serum cholesterol and anti-oxLDL antibody levels. Atherosclerotic lesion development, however, was 1.3-fold induced both in the presence and absence of leukocyte ABCA1 (WT: 614±106×10³ µm², ABCA1 KO: 786±44×10³ µm²). Two-way ANOVA revealed independent effects on atherosclerosis for both leukocyte ABCA1 deficiency and SP-x (p<0.05).

Conclusions

The observed splenic alterations induced by leukocyte ABCA1 deficiency do not play a significant role in the anti-atherogenic effects of leukocyte ABCA1 on lesion development.

Long-term following-up of viability of spleen autotransplants in the Beagle canine model

PURPOSE

To examine the possible late complications of splenectomy or spleen autotransplantation in large laboratory animal model, in which we need non-invasive or minimal-invasive methods for long-term monitoring of the experimental animals.

METHODS

Experimental groups of beagle dogs were: non-operated control, sham-operated control, splenectomy, spleen autotransplantation with 5 or 10 spleen-chips taken into the greater omentum (Furka's technique). Prior to operations, on the 1(st) postoperative week, monthly till the 6(th) as well as in the 9(th) and 12(th) month, hemorheological examinations were performed. In postoperative 12(th) month colloid scintigraphy and diagnostic laparoscopy were carried out. At the end of the investigation comparative morphological examinations were performed, too.

RESULTS

From the 4(th)-5(th) postoperative month filtration function of spleen-autotransplants showed particular restoration compared to splenectomy group. However, the functional results did not reach the values of the control or sham-operated groups. Sham-operated control's scintigraphy nicely showed activity in the spleen. In spleen autotransplantation-groups scintigraphy indicated well the activity of spleen-chips. During diagnostic laparoscopy spleen-chips with their blood supply were found. Histologically, the structure of spleen-autotransplants was similar to normal splenic tissue.

CONCLUSIONS

The autotransplants are regenerated, their functions have been partly restored, and thus spleen autotransplantation may prevent the possible complications of splenectomy. These parameters and the presented investigative protocol are suitable for long-term following-up of viability of the spleen-autotransplants.

B1a B Lymphocytes Are Atheroprotective by Secreting Natural IgM That Increases IgM Deposits and Reduces Necrotic Cores in Atherosclerotic Lesions

Rationale:

Aggravated atherosclerosis in B lymphocyte-deficient chimeric mice and reduced atherosclerosis after transfer of unfractionated spleen B lymphocytes into splenectomized mice have led to the widely held notion that B lymphocytes are atheroprotective. However, B lymphocytes can be pathogenic, because their depletion by anti-CD20 antibody ameliorated atherosclerosis, and transfer of B2 lymphocytes aggravated atherosclerosis. These observations raise the question of the identity of the atheroprotective B-lymphocyte population.

Objective:

The purpose of the study was to identify an atheroprotective B-lymphocyte subset and mechanisms by which they confer atheroprotection.

Methods and Results:

Splenectomy of apolipoprotein E–deficient mice selectively reduced peritoneal B1a lymphocytes, plasma IgM, and oxidized low-density lipoprotein IgM levels and lesion IgM deposits. These reductions were accompanied by increased oil red O–stained atherosclerotic lesions and increased necrotic cores, oxidized low-density lipoproteins, and apoptotic cells in lesions. Plasma lipids, body weight, collagen, and smooth muscle content were unaffected. Transfer of B1a lymphocytes into splenectomized mice increased peritoneal B1a lymphocytes; restored plasma IgM, oxidized low-density lipoprotein IgM levels, and lesion IgM deposits; and potently attenuated atherosclerotic lesions, with reduced lesion necrotic cores, oxidized low-density lipoprotein, and apoptotic cells. In contrast, transfer of B1a lymphocytes that cannot secrete IgM failed to protect against atherosclerosis development in splenectomized mice despite reconstitution in the peritoneum.

Conclusions:

B1a lymphocytes are an atheroprotective B-lymphocyte population. Our data suggest that natural IgM secreted by these lymphocytes offers protection by depositing IgM in atherosclerotic lesions, which reduces the necrotic cores of lesions.

A new technique for spleen autotransplantation

PURPOSE

Although the efficacy of spleen autotransplantation is debated, this approach remains the only possibility for preserving splenic function after traumatic splenectomy. This report describes an alternative method for splenic autotransplantation in case of splenic trauma.

METHODS

After splenectomy, the organ was weighed and the undamaged part was cut transversely to prepare a segment of approximately 4 × 3 × 2 cm in size and of 35 g of weight to be transplanted. The greater omentum was pedunculated in its left lateral portion, and the previously prepared splenic tissue was implanted in a pouch created at the lower edge of the omentum. The omental peduncle containing the splenic tissue was fixed to the parietal peritoneum of posterior left upper quadrant of the abdomen where the native spleen was previously located.

RESULTS

This technique was performed in 4 patients after informed consent had been obtained. The functionality of the splenic implant was assessed after 3 months by abdominal computed tomography and scintigraphy. These exams showed the functioning of the trasplanted splenic tissue in all patients.

CONCLUSION

This new technique needs further evaluation, but it appears to be an easy and safe alternative for spleen autotransplantation.

Spleen: A new role for an old player?

The spleen could be considered a neglected organ. To date, it has been deemed an ancillary organ in portal hypertension or an organ localization in lymphoproliferative diseases, even though it has had significant attention in infectious diseases for some time. Now, it is thought to be central in regulating the immune system, a metabolic asset and involved in endocrine function with regard to nonalcoholic fatty liver disease. The main mechanisms involved in this complex network will be critically discussed in this article.