Liver diseases, including cirrhosis, viral hepatitis, and hepatocellular carcinoma, account for approximately two million annual deaths worldwide. They place a huge burden on the global healthcare systems, compelling researchers to find effective treatment for liver fibrosis-cirrhosis. Portacaval anastomosis (PCA) is a model of liver damage and fibrosis. Arginine vasopressin (AVP) has been implicated as a proinflammatory-profibrotic hormone. In rats, neurointermediate pituitary lobectomy (NIL) induces a permanent drop (80%) in AVP serum levels. We hypothesized that AVP deficiency (NIL-induced) may decrease liver damage and fibrosis in a rat PCA model. Male Wistar rats were divided into intact control (IC), NIL, PCA, and PCA+NIL groups. Liver function tests, liver gene relative expressions (IL-1, IL-10, TGF-β, COLL-I, MMP-9, and MMP-13), and histopathological assessments were performed. In comparison with those in the IC and PCA groups, bilirubin, protein serum, and liver glycogen levels were restored in the PCA+NIL group. NIL in the PCA animals also decreased the gene expression levels of IL-1 and COLL-I, while increasing those of IL-10, TGF-β, and MMP-13. Histopathology of this group also showed significantly decreased signs of liver damage with lower extent of collagen deposition and fibrosis. Low AVP serum levels were not enough to fully activate the AVP receptors resulting in the decreased activation of cell signaling pathways associated with proinflammatory-profibrotic responses, while activating cell molecular signaling pathways associated with an anti-inflammatory-fibrotic state. Thus, partial reversion of liver damage and fibrosis was observed. The study supports the crucial role of AVP in the inflammatory-fibrotic processes and maintenance of immune competence. The success of the AVP deficiency strategy suggests that blocking AVP receptors may be therapeutically useful to treat inflammatory-fibrotic liver diseases.

No abstract

Arginine vasopressin (AVP) is a naturally occurring hormone synthesized in the hypothalamus. AVP demonstrates pro-fibrotic effects as it stimulates hepatic stellate cells to secrete transforming growth factor-β (TGF-β) and collagen. Previous work in liver cirrhotic (CCL 4 -induced) hamsters demonstrated that AVP deficiency induced by neurointermediate pituitary lobectomy (NIL) can restore liver function. Therefore, we hypothesized that liver fibrosis would decrease in portocaval anastomosis (PCA) rats, which model chronic liver diseases, when they are treated with the V1a-V2 AVP receptor antagonist conivaptan (CV). In this study, changes in liver histology and gene expression were analysed in five experimental groups: control, PCA, NIL, PCA + NIL and PCA + CV, with NIL surgery or CV treatment administered 8 weeks after PCA surgery. Body weight gain was assessed on a weekly basis, and serum liver function, liver weight and liver glycogen content were assessed following euthanasia. Most PCA-induced phenotypes were reverted to normal levels following AVP-modelled deficiency, though hypoglycemia and ammonium levels remained elevated in the PCA + CV group. Liver histopathological findings showed a significant reversal in collagen content, less fibrosis in the triad and liver septa and increased regenerative nodules. Molecular analyses showed that the expression of fibrogenic genes (TGF-β and collagen type I) decreased in the PCA + CV group. Our findings strongly suggest that chronic NIL or CV treatment can induce a favourable microenvironment to decrease liver fibrosis and support CV as an alternative treatment for liver fibrosis.

Liver fibrosis is due to the over deposition of collagens on the extracellular matrix, causing fibrotic septa and liver failure. Portocaval anastomosis (PCA) is a model of liver disease. Fibrogenesis is stimulated by AVP. We have described the healthy effect of the AVP deficiency, induced by neurointermediate pituitary lobectomy (NIL), on liver functions and cirrhosis. We hypothesize that blocking the AVP receptors with the V1a‐V2 AVP receptor antagonist conivaptan (CV) will induce the same healthy effects of NIL on liver fibrosis. Male Wistar rats were divided in 6 groups (8‐10 each): Sham surgery (SHAM), PCA, NIL, PCA+NIL, CV and PCA+CV. SHAM, NIL and the 4 groups with PCA were operated at week 0, whereas NIL surgery in the PCA+NIL group was done at week 8. CV treatments (30 mg/day/im/8 weeks) in the CV group started at week 0, whereas in the PCA+CV group started at week 8. NIL and CV groups were sacrificed at week 8, whereas SHAM, PCA, PCA+NIL and PCA+CV groups were sacrificed at week 16. At sacrifice, serum levels of ALT, AST, bilirubin, NH4, urea, albumin and glucose were assessed. Livers were weighed and samples were processed for glycogen content and the other processed for light microscopy analysis (slide tissues stained with H‐E, Masson and Sirius red). Results are summarized in Table 1. Effects of Vasopressin (AVP) Deficiency and Conivaptan (an AVP Receptors Antagonist) on Liver Physiology and Fibrosis in Rats with Protracted Portacaval Anastomosis GROUPS SHAM PCA NIL PCA+NIL CV PCA+CV (Basal values)Body weight=↓ (‐29%)↓ (‐22%)(‐ ↓(‐29%)=↓ (23%)(g)NS vs SHAMNS vs SHAMNS vs SHAMNS vs SHAMLiver weight=↓ (‐54%)===↓ (‐22%)(g)p<0.05 vsSHAMNS vsSHAMALT(U/L)=↑↑↑↑↑↑===AST(U/L)=↑↑↑↑↑↑↑↑==Total bilirubin (mg/dL)=↑↑↑====Unconjugated bilirubin (mg/dL)=↑↑↑====Albumin(g/dL)======Glucose (mg/dL)=====↓↓↓NH4(µg/dL)=↑↑↑===↑↑↑Urea(mg/dL)=↓↓↓====Liver glycogen(mg/gr of tissue)=↓↓↓==== Liver histopathology. In the PCA group, mainly in the periportal areas, small inflammatory infiltrates and big deposits of collagen were developed. Compared with the PCA, PCA+NIL and PCA+CV groups showed less inflammatory areas and much less collagen deposits. Conclusions, all results showed that: 1) AVP deficiency restores to normality the liver physiology and histology in the protracted liver disease, 2) Except the alterations in glycemia and NH4 metabolism, similar restored effects in liver histophysiology were induced by CV, suggesting that similar cellular mechanisms are involved, 3) Results strongly support that AVP is an important role in the pathophysiology of the liver fibrosis and possibly other fibrotic diseases.

It is known that arginine vasopressin (AVP) participate in the regulation of the immune responses, including the scarring. However, the effect of how AVP regulates this process is not clear. Here we describe the impact of AVP deficiency induced by neurointermediate pituitary lobectomy (NIL) or blocking the V1a‐V2 AVP receptors with conivaptan (CON) on the kidney fibrosis (KF), induced by unilateral ureteral ligature (UUL). Groups of 5 Wistar male rats were prepared: Control Intact (CI), UUL, NIL, NIL+UUL, UUL+NIL and UUL+CON. The NIL group was operated 6 weeks before sacrifice. In the NIL+UUL group NIL was performed 3 weeks before UUL and sacrificed 3 weeks after. In the UUL+CON (3mg/kg/day/SC/3 weeks before sacrifice) the UUL was done 6 weeks before sacrifice. KF was evaluated in histological slides stained with H‐E, Masson and Sirius red. Results showed that UUL induced hydronephrosis, severe kidney fibrosis and loss of histological architecture, whose severity was related to each experimental condition: In the UUL severe fibrosis occurred in the ilium, pelvis, periglomerular, intraglomerular, intraluminal tubules and interstitial kidney areas. In comparison with the CI, NIL group showed normal kidney histology, whereas that, in comparison with the UUL the NIL+UUL group developed significant less histological alterations and less kidney fibrosis. In the UUL+NIL group (NIL surgery performed 3 weeks after UUL and sacrificed 3 weeks later), although histological changes and fibrosis were apparent, these were significantly less severe as compared with the UUL group. In comparison with the NIL+UUL group, the UUL+CON animals developed less severe fibrosis and less histopathological changes. Conclusions. Results showed that kidney fibrosis may be controlled by AVP deficiency or blocking the V1a‐V2 AVP receptors (CON) indicating a major role of AVP on the fibrotic process. Results also suggests that conivaptan may be used for kidney fibrosis treatment. Support or Funding Information Universidad Autónoma de Aguascalientes PIFF14‐1 and CONACYT 221262. México