Localisation and role of activin receptor-interacting protein 1 in mouse brain

Neuroadaptations in the dorsal hippocampus underlie cocaine seeking during prolonged abstinence

Relapse vulnerability in substance use disorder is attributed to persistent cue-induced drug seeking that intensifies (or "incubates") during drug abstinence. Incubated cocaine seeking has been observed in both humans with cocaine use disorder and in preclinical relapse models. This persistent relapse vulnerability is mediated by neuroadaptations in brain regions involved in reward and motivation. The dorsal hippocampus (DH) is involved in context-induced reinstatement of cocaine seeking but the role of the DH in cocaine seeking during prolonged abstinence has not been investigated. Here we found that transforming growth factor-β (TGF-β) superfamily member activin A is increased in the DH on abstinence day (AD) 30 but not AD1 following extended-access cocaine self-administration compared to saline controls. Moreover, activin A does not affect cocaine seeking on AD1 but regulates cocaine seeking on AD30 in a bidirectional manner. Next, we found that activin A regulates phosphorylation of NMDA receptor (NMDAR) subunit GluN2B and that GluN2B-containing NMDARs also regulate expression of cocaine seeking on AD30. Activin A and GluN2B-containing NMDARs have both previously been implicated in hippocampal synaptic plasticity. Therefore, we examined synaptic strength in the DH during prolonged abstinence and observed an increase in moderate long-term potentiation (LTP) in cocaine-treated rats compared to saline controls. Lastly, we examined the role of DH projections to the lateral septum (LS), a brain region implicated in cocaine seeking and found that DH projections to the LS govern cocaine seeking on AD30. Taken together, this study demonstrates a role for the DH in relapse behavior following prolonged abstinence from cocaine self-administration.

Perspectives of small molecule inhibitors of activin receptor‑like kinase in anti‑tumor treatment and stem cell differentiation (Review)

Activin receptor‑like kinases (ALKs), members of the type I activin receptor family, belong to the serine/threonine kinase receptors of the transforming growth factor‑β (TGF‑β) superfamily. ALKs mediate the roles of activin/TGF‑β in a wide variety of physiological and pathological processes, ranging from cell differentiation and proliferation to apoptosis. For example, the activities of ALKs are associated with an advanced tumor stage in prostate cancer and the chondrogenic differentiation of mesenchymal stem cells. Therefore, potent and selective small molecule inhibitors of ALKs would not only aid in investigating the function of activin/TGF‑β, but also in developing treatments for these diseases via the disruption of activin/TGF‑β. In recent studies, several ALK inhibitors, including LY‑2157299, SB‑431542 and A‑83‑01, have been identified and have been confirmed to affect stem cell differentiation and tumor progression in animal models. This review discusses the therapeutic perspective of small molecule inhibitors of ALKs as drug targets in tumor and stem cells.

Research Progress on the Role and Mechanism of Action of Activin A in Brain Injury

Activin A belongs to the transforming growth factor superfamily and has a variety of biological functions. Studies have revealed that activin A can regulate the body's immune and inflammatory responses and participate in the regulation of cell death. In addition, activin A also has neurotrophic function and plays an important role in the repair of brain damage. This article summarizes recent advances in understanding the role and mechanism of action of activin A in brain injury and provides new hints into the application of activin A in the treatment of brain injury.

Activin A increases arterial pressure in the hypothalamic paraventricular nucleus in rats by angiotension II

Activin A, a member of the transforming growth factor β superfamily, plays an important role in the central nervous system as a neurotrophic and neuroprotective factor. The hypothalamic paraventricular nucleus (PVN) in the central nervous system is characterized as an important integrative site to regulate arterial pressure (AP). However, whether activin A in the PVN is involved in the regulation of AP is not well characterized. This study aimed to determine the effect of activin A on AP in the PVN in rats. The results showed that activin βA, activin type IIA and IIB receptors (ActRIIA and ActRIIB), and Smad2 and Smad3 mRNA expressions were detectable in the PVN of WKY rats by reverse-transcription PCR, and the expression of ActRIIA protein in the PVN was further confirmed by immunohistochemical staining. A microinjection of angiotensin II (AngII) (0.1 nmol/100 nl) or activin A (2 ng/100 nl) into the PVN increased AP significantly in WKY rats (P<0.05). Moreover, activin A (5 ng/ml) promoted AngII release from the primary cultured PVN neurons that can increase AP and upregulated the expressions of ActRIIA and Smad3 mRNA in the primary cultured PVN neurons (P<0.05). These data suggest that activin A can regulate AP in the PVN in an autocrine or a paracrine manner, which is related to AngII release and the ActRIIA-Smad3 signal pathway.

Activin A induces apoptosis of mouse myeloma cells via the mitochondrial pathway

Activin A is a pleiotropic cytokine belonging to the transforming growth factor β superfamily. Abnormal expression of activin A is associated with tumorigenesis. Multiple myeloma is characterized by the development of osteolytic disease, which ultimately leads to cachexia. However, the involvement of activin A in myeloma cell viability and apoptosis remains to be fully elucidated. For this purpose, mouse myeloma NS-1 cells were treated with activin A, and subsequently subjected to 5-bromo-2'-deoxyuridine analysis, Hoechst 33342 staining, flow cytometry and western blot analysis. The results revealed that activin A significantly suppressed NS-1 cell viability, and induced NS-1 cell apoptosis. In addition, activin A-induced promotion of NS-1 cell apoptosis was accompanied by upregulated expression of BCL2 associated X, apoptosis regulator (Bax), but downregulated expression of B cell lymphoma-2 (Bcl-2), resulting in an increase of the Bax/Bcl-2 ratio. Furthermore, cytochrome c and caspase-3 protein expression also increased following treatment with activin A. These data suggest that activin A induces apoptosis in mouse myeloma NS-1 cells via the mitochondrial pathway, providing a novel insight into multiple myeloma treatment.

Role of activin A in carbon tetrachloride-induced acute liver injury

AIM: To investigate the expression and role of activin A in a mouse model of acute chemical liver injury.

METHODS: Acute liver injury in C57BL/6 male mice was induced by intraperitoneal injection with carbon tetrachloride (CCl₄) (0.5 mL/kg, body weight) dissolved in olive oil (1:19 v/v). Mice were sacrificed 1, 3, 5 and 7 d after the treatment. The levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum were examined and pathological changes of liver observed by hematoxylin and eosin staining to evaluate the liver injury. Activin A protein levels in serum and hepatic tissue homogenate of mice were detected by enzyme-linked immunosorbent assay, and the expression pattern of activin A protein in livers of mice was examined by immunohistochemistry. Activin type IIA receptor (ActRIIA) and Smad3 expressions in the liver were analyzed by real-time quantitative reverse transcription-polymerase chain reaction. In order to further investigate the role of activin A, we also utilized activin A blocking experiment by anti-activin A antibody (500 μg/kg, body weight) injection into mouse tail vein.

RESULTS: In CCl₄-treated mice, serum ALT and AST levels were significantly increased, compared with that in control mice (P < 0.01). Furthermore, the serious necrosis was observed around hepatic portal areas in CCl₄-treated mice. Simultaneously, activin A levels in serum and hepatic tissue homogenate of mice treated with CCl₄ for 1, 3 and 5 d increased significantly, compared with that in control mice (P < 0.01). Activin A protein expression in hepatocytes not within the necrotic area was also upregulated in mice following CCl₄ treatment. Not only activin A, but also ActRIIA and activin signaling molecule Smad3 mRNA expressions in injury liver induced by CCl₄ were significantly higher than that in control liver. In addition, levels of serum ALT and AST in CCl₄-treated mice were significantly decreased by injection of anti-activin A antibody to block endogenous activin A action, compared with that in CCl₄-treated mice by injection of immunoglobulin G instead of anti-activin A antibody (P < 0.01), and the severity of liver injury was also reduced remarkably.

CONCLUSION: These data show that activin A is involved in CCl₄-induced acute liver injury. Blocking activin A actions may be a therapeutic approach for acute liver injury.