Bv8, the amphibian homologue of the mammalian prokineticins, induces a proinflammatory phenotype of mouse macrophages

The Prokineticin System in Inflammatory Bowel Diseases: A Clinical and Preclinical Overview

Inflammatory bowel disease (IBD) includes Crohn's disease (CD) and ulcerative colitis (UC), which are characterized by chronic inflammation of the gastrointestinal (GI) tract. IBDs clinical manifestations are heterogeneous and characterized by a chronic relapsing-remitting course. Typical gastrointestinal signs and symptoms include diarrhea, GI bleeding, weight loss, and abdominal pain. Moreover, the presence of pain often manifests in the remitting disease phase. As a result, patients report a further reduction in life quality. Despite the scientific advances implemented in the last two decades and the therapies aimed at inducing or maintaining IBDs in a remissive condition, to date, their pathophysiology still remains unknown. In this scenario, the importance of identifying a common and effective therapeutic target for both digestive symptoms and pain remains a priority. Recent clinical and preclinical studies have reported the prokineticin system (PKS) as an emerging therapeutic target for IBDs. PKS alterations are likely to play a role in IBDs at multiple levels, such as in intestinal motility, local inflammation, ulceration processes, localized abdominal and visceral pain, as well as central nervous system sensitization, leading to the development of chronic and widespread pain. This narrative review summarized the evidence about the involvement of the PKS in IBD and discussed its potential as a druggable target.

Therapeutic Potential of Targeting Prokineticin Receptors in Diseases

The prokineticins (PKs) were discovered approximately 20 years ago as small peptides inducing gut contractility. Today, they are established as angiogenic, anorectic, and proinflammatory cytokines, chemokines, hormones, and neuropeptides involved in variety of physiologic and pathophysiological pathways. Their altered expression or mutations implicated in several diseases make them a potential biomarker. Their G-protein coupled receptors, PKR1 and PKR2, have divergent roles that can be therapeutic target for treatment of cardiovascular, metabolic, and neural diseases as well as pain and cancer. This article reviews and summarizes our current knowledge of PK family functions from development of heart and brain to regulation of homeostasis in health and diseases. Finally, the review summarizes the established roles of the endogenous peptides, synthetic peptides and the selective ligands of PKR1 and PKR2, and nonpeptide orthostatic and allosteric modulator of the receptors in preclinical disease models. The present review emphasizes the ambiguous aspects and gaps in our knowledge of functions of PKR ligands and elucidates future perspectives for PK research. SIGNIFICANCE STATEMENT: This review provides an in-depth view of the prokineticin family and PK receptors that can be active without their endogenous ligand and exhibits "constitutive" activity in diseases. Their non- peptide ligands display promising effects in several preclinical disease models. PKs can be the diagnostic biomarker of several diseases. A thorough understanding of the role of prokineticin family and their receptor types in health and diseases is critical to develop novel therapeutic strategies with safety concerns.

Prokineticin 2 as a potential biomarker for the diagnosis of Kawasaki disease

Kawasaki disease is a pressing acute self-limiting inflammatory disorder disease which lack of specific biomarkers. Our research aims to investigate the serum expression of a novel immune regulator PK2 in children with Kawasaki disease and to evaluate the ability of PK2 to predict Kawasaki disease. A total of 70 children with Kawasaki disease in the Children's Hospital of Chongqing Medical University who were first diagnosed, 20 children with common fever admitted to hospital due to bacterial infection during the same period, and 31 children underwent physical examination were included in this study. Venous blood was collected for complete blood count, CRP, ESR, PCT, and PK2 before clinical intervention. The predictive potential of PK2 as a biomarker for the diagnosis of Kawasaki disease was judged by correlation analysis, the receiver operating characteristic (ROC) and combined score. Compared with healthy children and children with common fever, children diagnosed with Kawasaki disease had significantly lower serum PK2 concentrations (median 28,503.7208 ng/ml, 26,242.5484 ng/ml, and 16,890.2452 ng/ml, respectively, Kruskal-Wallis test: p < 0.0001). Analysis of the existing indicators in other laboratories showed that WBC (Kruskal-Wallis test: p < 0.0001), PLT (Kruskal-Wallis test: p = 0.0018), CRP (Mann-Whitney U: p < 0.0001), ESR (Mann-Whitney U: p = 0.0092), NLR (Kruskal-Wallis test: p < 0.0001), and other indicators were significantly increased compared with healthy children and children with common fever, RBC (Kruskal-Wallis test: p < 0.0001), and Hg (Kruskal-Wallis test: p < 0.0001) were significantly decreased in children with Kawasaki disease conversely. In the analysis of the Spearman correlation, it was found that serum PK2 concentration and NLR ratio were significantly negatively correlated in children with Kawasaki disease (rs = -0.2613, p = 0.0301). In the analysis of the ROC curves, it was found that the area under the PK2 curve was 0.782 (95% confidence interval 0.683-0.862; p < 0.0001), the ESR was 0.697 (95% confidence interval 0.582-0.796; p = 0.0120), the CRP was 0.601 (95% confidence interval 0.683-0.862; p = 0.1805), and the NLR was 0.735 (95% confidence interval 0.631-0.823; p = 0.0026). PK2 can significantly predict Kawasaki disease independently of CRP and ESR (p < 0.0001). The combined score of PK2 and ESR can significantly improve the diagnostic performance of PK2 (AUC = 0.827, 95% CI 0.724-0.903, p < 0.0001). The sensitivity was 87.50%, the sensitivity was 75.81%, the positive likelihood ratio was 6.0648, and the Youden index was 0.6331. PK2 has the potential to be a biomarker for early diagnosis of Kawasaki disease, and the combined use of ESR can further improve its diagnostic performance. Our study identifies PK2 as an important biomarker for Kawasaki disease and provides a potential new diagnostic strategy for Kawasaki disease.

Characterization of prokineticin system in Crohn's disease pathophysiology and pain, and its modulation by alcohol abuse: A preclinical study

BACKGROUND

Crohn's disease-(CD) pathogenesis is still unknown and chronic pain is a frequent symptom in CD-patients. Identifying novel therapeutic targets and predisposing factors is a primary goal. In this regard, prokineticin system-(PKS) appears a promising target.

AIMS AND METHODS

TNBS-model was used. DAI, abdominal and visceral pain, and muscle strength were monitored. CD-mice were sacrificed at two times (day 7 and 14 after TNBS) in order to identify PKS involvement in CD pathophysiology and pain. PKS characterization was performed in mesenteric lymph nodes-(MLN), colon, myenteric plexus-(MP), dorsal root ganglia-(DRGs) and spinal cord-(SC). Inflammation/neuroinflammation was also assessed in the same tissues. In order to evaluate alcohol abuse as a possible trigger for CD and its effect on PKS activation, naïve mice were administered (oral-gavage) with ethanol for 10 consecutive days. PKS as well as inflammation/neuroinflammation were evaluated in MLN, colon and MP.

RESULTS

TNBS treated-mice showed a rapid increase in DAI, abdominal/visceral hypersensitivity and a progressive strength loss. In all tissue analysed of CD-mice, a quick and significant increase of mRNA of PKs and PKRs was observed, associated with an increase of pro-inflammatory cytokines (IL-1β, IL-6 and TNFα) and macrophage/glia markers (iba1, CD11b and GFAP) levels. In alcohol abuse model, ethanol induced in colon and MP a significant PKS activation accompanied by inflammation/neuroinflammation.

CONCLUSIONS

We can assume that PKS may be involved in CD development and pain. Furthermore, alcohol appears to activate PKS and may be a trigger factor for CD.

Bv8 mediates myeloid cell migration and enhances malignancy of colorectal cancer

Colorectal cancer (CRC) is the third most predominant malignancy in the world. Although the importance of immune system in cancer development has been well established, the underlying mechanisms remain to be investigated further. Here we studied a novel protein prokineticin 2 (Prok2, also known as Bv8) as a key pro-tumoral factor in CRC progression in in vitro and ex vivo settings. Human colorectal tumor tissues, myeloid cell lines (U937 cells and HL60 cells) and colorectal cancer cell line (Caco-2 cells) were used for various studies. Myeloid cell infiltration (especially neutrophils) and Bv8 accumulation were detected in human colorectal tumor tissue with immunostaining. The chemotactic effects of Bv8 on myeloid cells were presented in the transwell assay and chemotaxis assy. Cultured CRC cells treated with myeloid cells or Bv8 produced reactive oxygen species (ROS) and vascular endothelial growth factor (VEGF). Furthermore, ROS and VEGF acted as pro-angiogenesis buffer in myeloid cell-infiltrated CRC microenvironment. Moreover, myeloid cells or Bv8 enhanced energy consumption of glycolysis ATP and mitochondria ATP of CRC cells. Interestingly, myeloid cells increased CRC cell viability, but CRC cells decreased the viability of myeloid cells. ERK signalling pathway in CRC cells was activated in the presence of Bv8 or co-cultured myeloid cells. In conclusion, our data indicated the vital roles of Bv8 in myeloid cell infiltration and CRC development, suggesting that Bv8 may be a potential therapeutic target for colorectal cancer-related immunotherapy.

Blocking prokineticin receptors attenuates synovitis and joint destruction in collagen-induced arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease mediated by an interdependent network of proinflammatory molecules such as chemokines. Prokineticin 2 (PK2) is a chemokine-like peptide that modulates nociceptive threshold and immuno-inflammatory processes via two G-protein-linked receptors, prokineticin receptor 1 and 2 (PKR1 and PKR2). In the present study, we investigated the effects of the prokineticin receptor antagonist PC1 on arthritic pain and the inflammatory response in type II collagen-induced arthritis (CIA) in mice. We demonstrated that PC1, administered subcutaneously from day 25 to day 35 after CIA, improved clinical signs of arthritis such as paw edema, pain, and impaired locomotor activity. In CIA mice, PC1 was also able to lower plasma malondialdehyde (MDA) levels, suggesting a role in reducing oxidative damage, as well as joint expression levels of PK2, PKRs, TNFα, IL-1β, CD4, CD8, and NF-kB. These results suggest that blocking PKRs may be a successful strategy to control arthritic pain and pathology development. KEY MESSAGES: PK2/PKRs expression levels strongly increase in the synovium of RA mice. PC1 treatment shows anti-arthritic activity and reduces arthritis-induced pain. PC1 treatment significantly lowers synovial PK2/PKRs levels. PC1 treatment lowers plasma MDA levels and synovial levels of TNFα and IL -1β PC1 treatment is a viable therapeutic option for RA.

The Regulation of Neutrophil Migration in Patients with Sepsis: The Complexity of the Molecular Mechanisms and Their Modulation in Sepsis and the Heterogeneity of Sepsis Patients

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Common causes include gram-negative and gram-positive bacteria as well as fungi. Neutrophils are among the first cells to arrive at an infection site where they function as important effector cells of the innate immune system and as regulators of the host immune response. The regulation of neutrophil migration is therefore important both for the infection-directed host response and for the development of organ dysfunctions in sepsis. Downregulation of CXCR4/CXCL12 stimulates neutrophil migration from the bone marrow. This is followed by transmigration/extravasation across the endothelial cell barrier at the infection site; this process is directed by adhesion molecules and various chemotactic gradients created by chemotactic cytokines, lipid mediators, bacterial peptides, and peptides from damaged cells. These mechanisms of neutrophil migration are modulated by sepsis, leading to reduced neutrophil migration and even reversed migration that contributes to distant organ failure. The sepsis-induced modulation seems to differ between neutrophil subsets. Furthermore, sepsis patients should be regarded as heterogeneous because neutrophil migration will possibly be further modulated by the infecting microorganisms, antimicrobial treatment, patient age/frailty/sex, other diseases (e.g., hematological malignancies and stem cell transplantation), and the metabolic status. The present review describes molecular mechanisms involved in the regulation of neutrophil migration; how these mechanisms are altered during sepsis; and how bacteria/fungi, antimicrobial treatment, and aging/frailty/comorbidity influence the regulation of neutrophil migration.

PK2/PKRs pathway is involved in the protective effect of artemisinin against trimethyltin chloride-induced hippocampal injury

Neuroinflammation is one of the important mechanisms of trimethyltin chloride (TMT) central neurotoxicity. Artemisinin (ARS) is a well-known antimalarial drug that also has significant anti-inflammatory effects. Prokineticin 2 (PK2) is a small molecule secreted protein that is widely expressed in the nervous system and plays a key role in the development of neuroinflammation. However, it remains unclear whether ARS can ameliorate neuroinflammation caused by TMT and whether PK2/PKRs signaling pathway plays a part in it. In this research, male Balb/c mice were administered TMT (2.8 mg/kg, i.p.) followed by immunohistochemistry to assess the expression of PK2, PKR1, and PKR2 proteins in the hippocampus. Network pharmacology was used to predict the intersection targets of ARS, central nervous system(CNS) injury and TMT. The neurobehavior of mice was evaluated by behavioral scores. Histopathological damage of the hippocampus was evaluated by HE, Nissl and Electron microscopy. Western blotting was used to identify the expression of synapse-related proteins (PSD95, SYN1, Synaptophysin), PK system-related proteins (PK2, PKR1, PKR2), and inflammation-related proteins (TNF-α, NF-κB p65). Immunohistochemistry showed that TMT resulted in elevated PK2 and PKR2 protein expression in the CA2 and CA3 regions of the hippocampus in mice, while PKR1 protein was not significantly altered. Network pharmacology showed that PK2 could interact with the intersectional targets of ARS, CNS injury, and TMT. ARS remarkably attenuated TMT-induced seizures and hippocampal histological damage. Further studies demonstrated that ARS treatment attenuated TMT-induced hippocampal ultrastructural damage, possibly by increasing the number of rough endoplasmic reticulum and mitochondria as well as upregulating the levels of synapse-associated proteins (PSD95, SYN1, Synaptophysin). Western blotting results revealed that ARS downregulated TMT-induced TNF-α and NF-κB p65 protein levels. In addition, ARS also decreased TMT-induced protein expression of PK2 and PKR2 in the mouse hippocampus, but had no significant effect on PKR1 protein expression. Our results suggested that ARS ameliorated TMT-induced abnormal neural behavior and hippocampal injury, which may be achieved by regulating PK2/PKRs inflammatory pathway and ameliorating synaptic injury. Therefore, we suggest that PK2/PKRs pathway may be involved in TMT neurotoxicity and ARS may be a promising drug that can relieve TMT neurotoxicity.

Integrated multiple microarray studies by robust rank aggregation to identify immune-associated biomarkers in Crohn's disease based on three machine learning methods

Crohn's disease (CD) is a complex autoimmune disorder presumed to be driven by complex interactions of genetic, immune, microbial and even environmental factors. Intrinsic molecular mechanisms in CD, however, remain poorly understood. The identification of novel biomarkers in CD cases based on larger samples through machine learning approaches may inform the diagnosis and treatment of diseases. A comprehensive analysis was conducted on all CD datasets of Gene Expression Omnibus (GEO); our team then used the robust rank aggregation (RRA) method to identify differentially expressed genes (DEGs) between controls and CD patients. PPI (protein‒protein interaction) network and functional enrichment analyses were performed to investigate the potential functions of the DEGs, with molecular complex detection (MCODE) identifying some important functional modules from the PPI network. Three machine learning algorithms, support vector machine-recursive feature elimination (SVM-RFE), random forest (RF), and least absolute shrinkage and selection operator (LASSO), were applied to determine characteristic genes, which were verified by ROC curve analysis and immunohistochemistry (IHC) using clinical samples. Univariable and multivariable logistic regression were used to establish a machine learning score for diagnosis. Single-sample GSEA (ssGSEA) was performed to examine the correlation between immune infiltration and biomarkers. In total, 5 datasets met the inclusion criteria: GSE75214, GSE95095, GSE126124, GSE179285, and GSE186582. Based on RRA integrated analysis, 203 significant DEGs were identified (120 upregulated genes and 83 downregulated genes), and MCODE revealed some important functional modules in the PPI network. Machine learning identified LCN2, REG1A, AQP9, CCL2, GIP, PROK2, DEFA5, CXCL9, and NAMPT; AQP9, PROK2, LCN2, and NAMPT were further verified by ROC curves and IHC in the external cohort. The final machine learning score was defined as [Expression level of AQP9 × (2.644)] + [Expression level of LCN2 × (0.958)] + [Expression level of NAMPT × (1.115)]. ssGSEA showed markedly elevated levels of dendritic cells and innate immune cells, such as macrophages and NK cells, in CD, consistent with the gene enrichment results that the DEGs are mainly involved in the IL-17 signaling pathway and humoral immune response. The selected biomarkers analyzed by the RRA method and machine learning are highly reliable. These findings improve our understanding of the molecular mechanisms of CD pathogenesis.

Blood transcriptomic biomarkers of alcohol consumption and cardiovascular disease risk factors: the Framingham Heart Study

BACKGROUND

The relations of alcohol consumption and gene expression remain to be elucidated.

MATERIALS AND METHODS

We examined cross-sectional associations between alcohol consumption and whole blood derived gene expression levels and between alcohol-associated genes and obesity, hypertension, and diabetes in 5531 Framingham Heart Study (FHS) participants.

RESULTS

We identified 25 alcohol-associated genes. We further showed cross-sectional associations of 16 alcohol-associated genes with obesity, nine genes with hypertension, and eight genes with diabetes at P < 0.002. For example, we observed decreased expression of PROK2 (β = -0.0018; 95%CI: -0.0021, -0.0007; P = 6.5e - 5) and PAX5 (β = -0.0014; 95%CI: -0.0021, -0.0007; P = 6.5e - 5) per 1 g/day increase in alcohol consumption. Consistent with our previous observation on the inverse association of alcohol consumption with obesity and positive association of alcohol consumption with hypertension, we found that PROK2 was positively associated with obesity (OR = 1.42; 95%CI: 1.17, 1.72; P = 4.5e - 4) and PAX5 was negatively associated with hypertension (OR = 0.73; 95%CI: 0.59, 0.89; P = 1.6e - 3). We also observed that alcohol consumption was positively associated with expression of ABCA13 (β = 0.0012; 95%CI: 0.0007, 0.0017; P = 1.3e - 6) and ABCA13 was positively associated with diabetes (OR = 2.57; 95%CI: 1.73, 3.84; P = 3.5e - 06); this finding, however, was inconsistent with our observation of an inverse association between alcohol consumption and diabetes.

CONCLUSIONS

We showed strong cross-sectional associations between alcohol consumption and expression levels of 25 genes in FHS participants. Nonetheless, complex relationships exist between alcohol-associated genes and CVD risk factors.

Prokineticin 2 promotes macrophages-mediated antibacterial host defense against bacterial pneumonia

OBJECTIVES

Bacterial pneumonia is a common serious infectious disease with high morbidity and mortality. Prokineticin 2 (PK2) has recently been identified as a novel immunomodulator in a variety of diseases; however, its role in bacterial pneumonia remains unclear.

METHODS

The levels of PK2 were measured and analyzed in patients with pneumonia and healthy controls. The effects of PK2 on the host response to pneumonia were evaluated by in vivo animal experiments and in vitro cell experiments.

RESULTS

PK2 levels dramatically decreased in patients with pneumonia compared with healthy controls, and PK2 levels were lower in patients with severe pneumonia than in pneumonia. In a mouse model of bacterial pneumonia, transtracheal administration of recombinant PK2 significantly alleviated lung injury and improved the survival, which was associated with increased host's bacterial clearance capacity, as manifested by decreased pulmonary bacterial loads. PK2 enhanced the chemotaxis, phagocytosis, and killing ability of macrophages, whereas the protective efficacy of PK2 was abolished after macrophage depletion.

CONCLUSION

Impaired alveolar macrophage function caused by decreased PK2 is a new endogenous cause of the occurrence and development of bacterial pneumonia. The administration of recombinant PK2 may be a potential adjuvant therapy for bacterial pneumonia.

Identifying Prokineticin2 as a Novel Immunomodulatory Factor in Diagnosis and Treatment of Sepsis

OBJECTIVES

Sepsis remains a highly lethal disease, whereas the precise reasons for death remain poorly understood. Prokineticin2 is a secreted protein that regulates diverse biological processes. Whether prokineticin2 is beneficial or deleterious to sepsis and the underlying mechanisms remain unknown.

DESIGN

Prospective randomized animal investigation and in vitro studies.

SETTING

Research laboratory at a medical university hospital.

SUBJECTS

Prokineticin2 deficiency and wild-type C57BL/6 mice were used for in vivo studies; sepsis patients by Sepsis-3 definitions, patient controls, and healthy controls were used to obtain blood for in vitro studies.

INTERVENTIONS

Prokineticin2 concentrations were measured and analyzed in human septic patients, patient controls, and healthy individuals. The effects of prokineticin2 on sepsis-related survival, bacterial burden, organ injury, and inflammation were assessed in an animal model of cecal ligation and puncture-induced polymicrobial sepsis. In vitro cell models were also used to study the role of prokineticin2 on antibacterial response of macrophages.

MEASUREMENTS AND MAIN RESULTS

Prokineticin2 concentration is dramatically decreased in the patients with sepsis and septic shock compared with those of patient controls and healthy controls. Furthermore, the prokineticin2 concentration in these patients died of sepsis or septic shock is significantly lower than those survival patients with sepsis or septic shock, indicating the potential value of prokineticin2 in the diagnosis of sepsis and septic shock, as well as the potential value in predicting mortality in adult patients with sepsis and septic shock. In animal model, recombinant prokineticin2 administration protected against sepsis-related deaths in both heterozygous prokineticin2 deficient mice and wild-type mice and alleviated sepsis-induced multiple organ damage. In in vitro cell models, prokineticin2 enhanced the phagocytic and bactericidal functions of macrophage through signal transducers and activators of transcription 3 pathway which could be abolished by signal transducers and activators of transcription 3 inhibitors S3I-201. Depletion of macrophages reversed prokineticin2-mediated protection against polymicrobial sepsis.

CONCLUSIONS

This study elucidated a previously unrecognized role of prokineticin2 in clinical diagnosis and treatment of sepsis. The proof-of-concept study determined a central role of prokineticin2 in alleviating sepsis-induced death by regulation of macrophage function, which presents a new strategy for sepsis immunotherapy.

Matrine alleviates spatial learning and memory impairment in diabetic mice by inhibiting endoplasmic reticulum stress and through modulation of PK2/PKRs pathway

Clinical and epidemiological studies indicate that diabetic cognitive impairment often occurs in diabetes mellitus patients. Matrine (Mat), an active component of Sophora flavescens Ait root extracts, has widely pharmacological activities including anti-tumor, anti-diabetes, cardioprotective and neuroprotective effects. The present study was designed to elucidate the possibly neuroprotective effects of Mat against diabetic spatial learning and memory impairment caused by high-fat diet and streptozotocin injection in mice. The results showed that Mat treatment significantly ameliorated fasting blood glucose level, impaired glucose tolerance, and lipid metabolism disorder in diabetic mice. In addition, diabetic mice exhibited spatial learning and memory impairment in the Morris water maze test, which could be attenuated by Mat treatment. Moreover, administration of Mat remarkably alleviated histological damage in diabetic hippocampus. Also, further investigations showed that Mat treatment abated endoplasmic reticulum stress induced hippocampal ultra-structure injury as evidenced by increasing the numbers of rough endoplasmic reticulum and mitochondria, as well as down-regulating endoplasmic reticulum stress related protein levels (GRP78, CHOP, ATF6 and Caspase-12). Furthermore, administration of Mat enhanced hippocampal protein expressions of PK2, PKR1 and PKR2, which decreased significantly in diabetic mice. Collectively, these findings suggested that Mat could ameliorate diabetes-induced spatial learning and memory impairment, possibly by alleviating ER stress, and partly through modulation of PK2/PKRs pathway.

Versatile Role of Prokineticins and Prokineticin Receptors in Neuroinflammation

Prokineticins are a new class of chemokine-like peptides involved in a wide range of biological and pathological activities. In particular, prokineticin 2 (PK2), prokineticin receptor 1 (PKR1) and prokineticin receptor 2 (PKR2) play a central role in modulating neuroinflammatory processes. PK2 and PKRs, which are physiologically expressed at very low levels, are strongly upregulated during inflammation and regulate neuronal-glial interaction. PKR2 is mainly overexpressed in neurons, whereas PKR1 and PK2 are mainly overexpressed in astrocytes. Once PK2 is released in inflamed tissue, it is involved in both innate and adaptive responses: it triggers macrophage recruitment, production of pro-inflammatory cytokines, and reduction of anti-inflammatory cytokines. Moreover, it modulates the function of T cells through the activation of PKR1 and directs them towards a pro-inflammatory Th1 phenotype. Since the prokineticin system appears to be upregulated following a series of pathological insults leading to neuroinflammation, we will focus here on the involvement of PK2 and PKRs in those pathologies that have a strong underlying inflammatory component, such as: inflammatory and neuropathic pain, Alzheimer's disease, Parkinson's disease, multiple sclerosis, stroke, obesity, diabetes, and gastrointestinal inflammation.

Interplay between Prokineticins and Histone Demethylase KDM6A in a Murine Model of Bortezomib-Induced Neuropathy

Chemotherapy-induced neuropathy (CIN) is a major adverse effect associated with many chemotherapeutics, including bortezomib (BTZ). Several mechanisms are involved in CIN, and recently a role has been proposed for prokineticins (PKs), a chemokine family that induces proinflammatory/pro-algogen mediator release and drives the epigenetic control of genes involved in cellular differentiation. The present study evaluated the relationships between epigenetic mechanisms and PKs in a mice model of BTZ-induced painful neuropathy. To this end, spinal cord alterations of histone demethylase KDM6A, nuclear receptors PPARα/PPARγ, PK2, and pro-inflammatory cytokines IL-6 and IL-1β were assessed in neuropathic mice treated with the PK receptors (PKRs) antagonist PC1. BTZ treatment promoted a precocious upregulation of KDM6A, PPARs, and IL-6, and a delayed increase of PK2 and IL-1β. PC1 counteracted allodynia and prevented the increase of PK2 and of IL-1β in BTZ neuropathic mice. The blockade of PKRs signaling also opposed to KDM6A increase and induced an upregulation of PPAR gene transcription. These data showed the involvement of epigenetic modulatory enzymes in spinal tissue phenomena associated with BTZ painful neuropathy and underline a role of PKs in sustaining the increase of proinflammatory cytokines and in exerting an inhibitory control on the expression of PPARs through the regulation of KDM6A gene expression in the spinal cord.

Differential inflammation-mediated function of prokineticin 2 in the synovial fibroblasts of patients with rheumatoid arthritis compared with osteoarthritis

Prokineticin 2 (PK2) is a secreted protein involved in several pathological and physiological processes, including the regulation of inflammation, sickness behaviors, and circadian rhythms. Recently, it was reported that PK2 is associated with the pathogenesis of collagen-induced arthritis in mice. However, the role of PK2 in the pathogenesis of rheumatoid arthritis (RA) or osteoarthritis (OA) remains unknown. In this study, we collected synovial tissue, plasma, synovial fluid, and synovial fibroblasts (SF) from RA and OA patients to analyze the function of PK2 using immunohistochemistry, enzyme-linked immunosorbent assays, and tissue superfusion studies. PK2 and its receptors prokineticin receptor (PKR) 1 and 2 were expressed in RA and OA synovial tissues. PKR1 expression was downregulated in RA synovial tissue compared with OA synovial tissue. The PK2 concentration was higher in RA synovial fluid than in OA synovial fluid but similar between RA and OA plasma. PK2 suppressed the production of IL-6 from TNFα-prestimulated OA-SF, and this effect was attenuated in TNFα-prestimulated RA-SF. This phenomenon was accompanied by the upregulation of PKR1 in OA-SF. This study provides a new model to explain some aspects underlying the chronicity of inflammation in RA.

Prokineticin 2 overexpression induces spermatocyte apoptosis in varicocele in rats

Varicocele is one of the most important causes of male infertility, as this condition leads to a decline in sperm quality. It is generally believed that the presence of varicocele induces an increase in reactive oxygen species levels, leading to oxidative stress and sperm apoptosis; however, the specific pathogenic mechanisms affecting spermatogenesis remain elusive. Prokineticin 2 (PK2), a secretory protein, is associated with multiple biological processes, including cell migration, proliferation, and apoptosis. In the testis, PK2 is expressed in spermatocytes under normal physiological conditions. To investigate the role of PK2 in varicocele, a rat varicocele model was established to locate and quantify the expression of PK2 and its receptor, prokineticin receptor 1 (PKR1), by immunohistochemistry and quantitative real-time PCR assays (qPCR). Moreover, H₂O₂ was applied to mimic the oxidative stress state of varicocele through coculturing with a spermatocyte-derived cell line (GC-2) in vitro, and the apoptosis rate was detected by flow cytometry. Here, we illustrated that the expression levels of PK2 and PKR1 were upregulated in the spermatocytes of the rat model. Administration of H₂O₂ stimulated the overexpression of PK2 in GC-2. Transfection of recombinant pCMV-HA-PK2 into GC-2 cells promoted apoptosis by upregulating cleaved-caspase-3, caspase-8, and B cell lymphoma 2-associated X; downregulating B cell lymphoma 2; and promoting the accumulation of intracellular calcium. Overall, we revealed that the varicocele-induced oxidative stress stimulated the overexpression of PK2, leading to apoptosis of spermatocytes. Our study provides new insight into the mechanisms underlying oxidative stress-associated male infertility and suggests a novel therapeutic target for male infertility.

Prokineticin receptors interact unselectively with several G protein subtypes but bind selectively to β-arrestin 2

Prokineticin 1 (pk1) and prokineticin 2 (pk2) interact with two structurally related G-protein coupled receptors, prokineticin receptor 1 (PKR1) and prokineticin receptor 2 (PKR2). Cellular signalling studies show that the activated receptors can evoke Ca²⁺-mobilization, pertussis toxin-sensitive ERK phosphorylation, and intracellular cAMP accumulation, which suggests the partecipation of several G protein subtypes, such as G_q/11, G_i/o and G_s. However, direct interactions with these transduction proteins have not been studied yet. Here we measured by bioluminescence resonance energy transfer (BRET) the association of PKR1 and PKR2 with different heterotrimeric Gα proteins in response to pk1 and pk2 activation. Using host-cell lines carrying gene deletions of Gα_q/11 or Gα_s, and pertussis toxin treatment to abolish the receptor interactions with Gα_i/o, we determined that both receptors could couple with comparable efficiency to G_q/11 and G_i/o, but far less efficiently to G_s or other pertussis toxin-insensitive G proteins. We also used BRET methodology to assess the association of prokineticin receptors with β-arrestin isoforms. Fluorescent versions of the isoforms were transfected both in HEK293 cells and in double KO β-arrestin 1/2 mouse fibroblasts, to study receptor interaction with the reconstituted individual β-arrestins without background expression of the endogenous genes. Both receptors formed stable BRET-emitting complexes with β-arrestin 2 but not with β-arrestin 1, indicating strong selectivity for the former. In all the studied transducer interactions and in both receptors, pk2 was more potent than pk1 in promoting receptor binding to transduction proteins.

The effects of metformin on autophagy

Metformin is the first-line option for treating newly diagnosed diabetic patients and also involved in other pharmacological actions, including antitumor effect, anti-aging effect, polycystic ovarian syndrome prevention, cardiovascular action, and neuroprotective effect, etc. However, the mechanisms of metformin actions were not fully illuminated. Recently, increasing researches showed that autophagy is a vital medium of metformin playing pharmacological actions. Nevertheless, results on the effects of metformin on autophagy were inconsistent. Apart from few clinical evidences, more data focused on kinds of no-clinical models. First, many studies showed that metformin could induce autophagy via a number of signaling pathways, including AMPK-related signaling pathways (e.g. AMPK/mTOR, AMPK/CEBPD, MiTF/TFE, AMPK/ULK1, and AMPK/miR-221), Redd1/mTOR, STAT, SIRT, Na⁺/H⁺ exchangers, MAPK/ERK, PK2/PKR/AKT/ GSK3β, and TRIB3. Secondly, some signaling pathways were involved in the process of metformin inhibiting autophagy, such as AMPK-related signaling pathways (AMPK/NF-κB and other undetermined AMPK-related signaling pathways), Hedgehog, miR-570-3p, miR-142-3p, and MiR-3127-5p. Thirdly, two types of signaling pathways including PI3K/AKT/mTOR and endoplasmic reticulum (ER) stress could bidirectionally impact the effectiveness of metformin on autophagy. Finally, multiple signal pathways were reviewed collectively in terms of affecting the effectiveness of metformin on autophagy. The pharmacological effects of metformin combining its actions on autophagy were also discussed. It would help better apply metformin to treat diseases in term of mediating autophagy.

Circulating Prokineticin 2 Levels Are Increased in Children with Obesity and Correlated with Insulin Resistance

OBJECTIVE

Prokineticin 2 (PK2) has been shown to regulate food intake, fat production, and the inflammation process, which play vital roles in the pathogenesis of obesity. The first aim of this study was to investigate serum PK2 levels in children with obesity and normal-weight children. The second aim was to compare the levels of PK2 between children with obesity, with and without nonalcoholic fatty liver disease (NAFLD).

METHODS

Seventy normal-weight children and 91 children with obesity (22 with NAFLD) were recruited. Circulating PK2, IL-6, and TNF-α were measured by enzyme-linked immunosorbent assays. Anthropometric and biochemical measurements related to adiposity, lipid profile, and insulin resistance were examined for all participants.

RESULTS

Serum PK2 was significantly higher in children with obesity than in the normal-weight controls. Circulating PK2 levels were not different between the patients with and without NAFLD. Circulating PK2 was positively correlated with BMI, BMI z-score, insulin, glucose, HOMA-IR, total cholesterol, low-density lipoprotein cholesterol, alanine aminotransferase, and gamma-glutamyl transpeptidase. Binary logistic regression revealed that the odds ratios for obesity were significantly elevated with increasing PK2.

CONCLUSIONS

PK2 was strongly associated with obesity, and it may also be related to metabolic disorders and insulin resistance. This trial is registered with ChiCTR2000038838.

Evaluation of Murine Macrophage Cytokine Production After In Vivo Morphine Treatment

The discovery of opioid receptor expression on immune cells has originated a large research activity on the possible modulation by opioid drugs of immune system responses. In this chapter we describe an easy methodology useful to obtain information about the potential immunomodulatory activity of opioid drugs. An in vivo treatment schedule is used, and macrophages are studied for their ability to release different cytokines.

Prokineticin Receptor Inhibition With PC1 Protects Mouse Primary Sensory Neurons From Neurotoxic Effects of Chemotherapeutic Drugs in vitro

Neurotoxicity is a common side effect of chemotherapeutics that often leads to the development of chemotherapy-induced peripheral neuropathy (CIPN). The peptide Prokineticin 2 (PK2) has a key role in experimental models of CIPN and can be considered an insult-inducible endangering mediator. Since primary afferent sensory neurons are highly sensitive to anticancer drugs, giving rise to dysesthesias, the aim of our study was to evaluate the alterations induced by vincristine (VCR) and bortezomib (BTZ) exposure in sensory neuron cultures and the possible preventive effect of blocking PK2 signaling. Both VCR and BTZ induced a concentration-dependent reduction of total neurite length that was prevented by the PK receptor antagonist PC1. Antagonizing the PK system also reduced the upregulation of PK2, PK-R1, TLR4, IL-6, and IL-10 expression induced by chemotherapeutic drugs. In conclusion, inhibition of PK signaling with PC1 prevented the neurotoxic effects of chemotherapeutics, suggesting a promising strategy for neuroprotective therapies against the sensory neuron damage induced by exposure to these drugs.

Methane Ameliorates Lipopolysaccharide-Induced Acute Orchitis by Anti-inflammatory, Antioxidative, and Antiapoptotic Effects via Regulation of the PK2/PKR1 Pathway

Objective

The present study is aimed at investigating the anti-inflammatory, antioxidative, and antiapoptotic effects of methane on lipopolysaccharide- (LPS-) induced acute orchitis and its potential mechanisms.

Methods

Adult male rats were intraperitoneally (i.p.) injected with methane-rich saline (MS, 20 mL/kg) following LPS (5 mg/kg, i.p.). The survival rate was assessed every 12 h until 72 h after LPS induction, and surviving rats were sacrificed for further detection. The wet/dry (W/D) ratio was determined, and testicular damage was histologically assessed. Inflammatory cytokines in the testes and serum, including interleukin-1β (IL-1β), IL-6, IL-10, and tumor necrosis factor-α (TNF-α), were measured using ELISA and RT-qPCR. Oxidative stress was evaluated by the level of superoxide dismutase (SOD) and malondialdehyde (MDA). Testicular apoptosis was detected via TUNEL staining. The expression of prokineticin 2 (PK2)/prokineticin receptor 1 (PKR1) was also analyzed using RT-qPCR, western blotting, and immunohistochemistry.

Results

It was found that methane significantly prolonged rat survival, decreased the W/D ratio, alleviated LPS-induced histological changes, and reduced apoptotic cells in the testes. Additionally, methane suppressed and promoted the production of pro- and anti-inflammatory cytokines, respectively. Furthermore, methane significantly increased SOD levels, decreased MDA levels, and decreased testicular expression of PK2 and PKR1. Therefore, methane exerts therapeutic effects on acute orchitis and might be a new and convenient strategy for the treatment of inflammation-related testicular diseases.

Neutralization of Bombina variegata peptide 8 suppresses retinal neovascularization in two different murine models: The oxygen-induced retinopathy model and the rhodopsin promoter/VEGF transgenic mouse model

Bombina variegata 8 (Bv8), also known as prokineticin-2 (PK-2), is a potent pro-angiogenic factor. However, its role in retinal neovascularization (RNV) remains unknown. In this study, we explored the role of Bv8 in the pathogenesis of RNV. We found that the expression of Bv8 was significantly increased in two different models of retinal neovascularization: the oxygen-induced retinopathy (OIR) mouse model and the rhodopsin promoter (rho)/VEGF transgenic mouse model. Neutralization of Bv8 by intravitreal injections of its antibody, not only inhibited retinal and subretinal neovascularization but also decreased the mRNA and protein levels of several pro-angiogenic factors. Our in vitro assay showed that recombinant human Bv8 (RhBv8) protein promoted human retinal microvascular endothelial cells (HRECs) tube-formation, cell proliferation and vascular endothelial growth factor receptor 1 (VEGFR1) and receptor 2 (VEGFR2) expression. Our findings suggest that Bv8 could be used as a novel target for the treatment of RNV-related ocular diseases.

Prokineticin 2 promotes and sustains neuroinflammation in vincristine treated mice: Focus on pain and emotional like behavior

Vincristine (VCR) treatment is often associated to painful neuropathy. Its development is independent from antitumoral mechanism and involves neuroinflammation. We investigated the role of the chemokine prokineticin (PK)2 in a mouse model of VCR induced neuropathy using a PK-receptors (PK-R) antagonist to counteract its development. We also evaluated emotional like deficits in VCR mice. VCR (0,1 mg/kg) was i.p. injected in C57BL/6J male mice once a day for 14 consecutive days. Pain, anxiety and depressive like behaviors were assessed in animals. PK2, PK-Rs, cytokines, neuroinflammatory markers (CD68, CD11b, GFAP, TLR4) and ATF3 were evaluated in DRG, spinal cord, prefrontal cortex and hippocampus. The PK-Rs antagonist PC1, was s.c. injected (150 μg/kg) twice a day from day 7 (hypersensitivity state) until day 14. Its effect on pain and neuroinflammation was evaluated. VCR mice developed neuropathic pain but not mood alterations. After 7 days of VCR treatment we observed a neuroinflammatory condition in DRG with high levels of PK-Rs, TLR4, CD68, ATF3 and IL-1β without relevant alterations in spinal cord. At day 14, an upregulation of PK system and a marked neuroinflammation was evident also in spinal cord. Moreover, at the same time, we observed initial alterations in supraspinal brain areas. PC1 treatment significantly counteracted neuropathic pain and blunted neuroinflammation.

Activation of the NLRP3 Inflammasome Pathway by Prokineticin 2 in Testicular Macrophages of Uropathogenic Escherichia coli- Induced Orchitis

Infections of the reproductive tract are known to contribute to testicular inflammatory impairment, leading to an increase of pro-inflammatory cytokines such as IL-1β, and a decline in sperm quality. Prokineticin 2 (PK2), a secretory protein, is closely associated with the secretion of pro-inflammatory cytokines in inflamed tissue. It was reported that increased PK2 is related to the upregulation of IL-1β, but the underlying mechanism remains elusive. Here, we illustrated that PK2 was upregulated in testicular macrophages (TM) in a rat model of uropathogenic Escherichia coli (UPEC) infection, which induced the activation of the NLRP3 inflammasome pathway to boost IL-1β secretion. Administration of PK2 inhibitor alleviated the inflammatory damage and suppressed IL-1β secretion. Moreover, PK2 promoted NLRP3 expression and the release of cleaved IL-1β from TM to the supernatants after the challenge with UPEC in vitro. IL-1β in the supernatants affected Leydig cells by suppressing the expression of genes encoding for the enzymes P450scc and P450c17, which are involved in testosterone production. Overall, we revealed that increased PK2 levels in TM in UPEC-induced orchitis may impair testosterone synthesis via the activation of the NLRP3 pathway. Our study provides a new insight into the mechanisms underlying inflammation-associated male infertility and suggests an anti-inflammatory therapeutic target for male infertility.

Targeting prokineticin system counteracts hypersensitivity, neuroinflammation, and tissue damage in a mouse model of bortezomib-induced peripheral neuropathy

BACKGROUND

Neuropathy is a dose-limiting side effect of many chemotherapeutics, including bortezomib. The mechanisms underlying this condition are not fully elucidated even if a contribution of neuroinflammation was suggested. Here, we investigated the role of a chemokine family, the prokineticins (PKs), in the development of bortezomib-induced peripheral neuropathy (BIPN), and we used a PK receptor antagonist to counteract the development and progression of the pathology.

METHODS

Neuropathy was induced in male C57BL/6J mice by using a protocol capable to induce a detectable neuropathic phenotype limiting systemic side effects. The presence of allodynia (both mechanical and thermal) and thermal hyperalgesia was monitored over time. Mice were sacrificed at two different time points: 14 and 28 days after the first bortezomib (BTZ) injection. At these times, PK system activation (PK2 and PK-Rs), macrophage and glial activation markers, and cytokine production were evaluated in the main station involved in pain transmission (sciatic nerve, DRG, and spinal cord), and the effect of a PK receptors antagonist (PC1) on the same behavioral and biochemical parameters was assessed. Structural damage of DRG during BTZ treatment and an eventual protective effect of PC1 were also evaluated.

RESULTS

BTZ induces in mice a dose-related allodynia and hyperalgesia and a progressive structural damage to the DRG. We observed a precocious increase of macrophage activation markers and unbalance of pro- and anti-inflammatory cytokines in sciatic nerve and DRG together with an upregulation of GFAP in the spinal cord. At higher BTZ cumulative dose PK2 and PK receptors are upregulated in the PNS and in the spinal cord. The therapeutic treatment with the PK-R antagonist PC1 counteracts the development of allodynia and hyperalgesia, ameliorates the structural damage in the PNS, decreases the levels of activated macrophage markers, and prevents full neuroimmune activation in the spinal cord.

CONCLUSIONS

PK system may be a strategical pharmacological target to counteract BTZ-induced peripheral neuropathy. Blocking PK2 activity reduces progressive BTZ toxicity in the DRG, reducing neuroinflammation and structural damage to DRG, and it may prevent spinal cord sensitization.

The Prokineticins: Neuromodulators and Mediators of Inflammation and Myeloid Cell-Dependent Angiogenesis

The mammalian prokineticins family comprises two conserved proteins, EG-VEGF/PROK1 and Bv8/PROK2, and their two highly related G protein-coupled receptors, PKR1 and PKR2. This signaling system has been linked to several important biological functions, including gastrointestinal tract motility, regulation of circadian rhythms, neurogenesis, angiogenesis and cancer progression, hematopoiesis, and nociception. Mutations in PKR2 or Bv8/PROK2 have been associated with Kallmann syndrome, a developmental disorder characterized by defective olfactory bulb neurogenesis, impaired development of gonadotropin-releasing hormone neurons, and infertility. Also, Bv8/PROK2 is strongly upregulated in neutrophils and other inflammatory cells in response to granulocyte-colony stimulating factor or other myeloid growth factors and functions as a pronociceptive mediator in inflamed tissues as well as a regulator of myeloid cell-dependent tumor angiogenesis. Bv8/PROK2 has been also implicated in neuropathic pain. Anti-Bv8/PROK2 antibodies or small molecule PKR inhibitors ameliorate pain arising from tissue injury and inhibit angiogenesis and inflammation associated with tumors or some autoimmune disorders.

PK2β ligand, a splice variant of prokineticin 2, is able to modulate and drive signaling through PKR1 receptor

Prokineticin-2 (PK2) is a secreted bioactive peptide that signals through two GPCRs, the prokineticin receptors (PKRs), and regulates a variety of biological processes including angiogenesis, immunity and nociception. The PK2 primary transcript has two alternative splice variants, PK2 and PK2L (a Long form) which is cleaved in an active peptide, named PK2β that preferentially binds to PKR1 receptor. The aim of this study was to characterize the PK2β. Using different Saccharomyces cerevisiae strains, we examined the specificity of PKR1 and PKR2 G-protein coupling following PK2β binding. Data obtained in yeast confirmed that PK2 binds both receptors, inducing a comparable response throughout a promiscuous coupling of G protein subtypes. Conversely, we demonstrated, for the first time, that PK2β preferentially binding to PKR1, activates a signaling cascade that not depends on Gα_i/o coupling. The binding specificity of PK2β for PKR1 was evaluated by the analysis of PKR mutant in yeast and GST pull-down experiments, suggesting an important role of PKR1 amino-terminal region. We also evaluated the ability of PK2β to differentially activate PKR1 and/or PKR2 by in vivo nociceptive experiments and we showed that PK2β induces intense sensitization of peripheral nociceptors to painful stimuli through the activation of PKR1. To analyze PK2β-induced signal transduction, we demonstrated the inability of PK2β to induce STAT3 protein phosphorylation in organotypic primary explants from mice Dorsal Root Ganglion (DRG), an important pain station. The control of the concentration ratio between PK2β and PK2 could be one of the keys to allow the specificity of the cell response of prokineticin signaling pathway.

Prokineticin-2 promotes chemotaxis and alternative A2 reactivity of astrocytes

Astrocyte reactivity is disease- and stimulus-dependent, adopting either a proinflammatory A1 phenotype or a protective, anti-inflammatory A2 phenotype. Recently, we demonstrated, using cell culture, animal models and human brain samples, that dopaminergic neurons produce and secrete higher levels of the chemokine-like signaling protein Prokineticin-2 (PK2) as a compensatory protective response against neurotoxic stress. As astrocytes express a high level of PK2 receptors, herein, we systematically characterize the role of PK2 in astrocyte structural and functional properties. PK2 treatment greatly induced astrocyte migration, which was accompanied by a shift in mitochondrial energy metabolism, a reduction in proinflammatory factors, and an increase in the antioxidant genes Arginase-1 and Nrf2. Overexpression of PK2 in primary astrocytes or in the in vivo mouse brain induced the A2 astrocytic phenotype with upregulation of key protective genes and A2 reactivity markers including Arginase-1 and Nrf2, PTX3, SPHK1, and TM4SF1. A small-molecule PK2 agonist, IS20, not only mimicked the protective effect of PK2 in primary cultures, but also increased glutamate uptake by upregulating GLAST. Notably, IS20 blocked not only MPTP-induced reductions in the A2 phenotypic markers SPHK1 and SCL10a6 but also elevation of the of A1 marker GBP2. Collectively, our results reveal that PK2 regulates a novel neuron-astrocyte signaling mechanism by promoting an alternative A2 protective phenotype in astrocytes, which could be exploited for development of novel therapeutic strategies for PD and other related chronic neurodegenerative diseases. PK2 signals through its receptors on astrocytes and promotes directed chemotaxis. PK2-induced astrocyte reactivity leads to an increase in antioxidant and anti-inflammatory proteins while increasing glutamate uptake, along with decreased inflammatory factors. © 2018 Wiley Periodicals, Inc.

Prokineticin 2 expression as a novel prognostic biomarker for human colorectal cancer

Molecular tumor biomarkers hold considerable promise for accurately predicting colorectal cancer (CRC) recurrence and progression. Prokineticin 2 (PROK2) may be associated with angiogenesis and tumor formation in some malignant tumors. However, its prognostic value remains unknown. We focused on the association between PROK2 expression and clinical characteristics of CRC to assess value of PROK2 as a potential biomarker for stage I–III CRC patients prognosis.

Between 1992 and 2006, 436 consecutive patients with stage I–III CRC treated with curative resection were included. PROK2 expression in primary tumors was investigated using immunohistochemistry. An animal model of liver metastasis was used to assess the role of PROK2.

Positive PROK2 expression in primary tumors was found in 222 of 436 (50.9%) human CRC specimens and was significantly associated with lymphatic invasion, lymph node metastasis, clinical stage, and postoperative liver recurrence rate. Recurrence-free survival was significantly shorter in patients with positive PROK2 expression than in those with negative PROK2 expression. PROK2 expression was an independent unfavorable prognostic indicator for CRC [hazards ratio, 2.119; 95% confidence interval, 1.315–3.415; p = 0.002]. PROK2 overexpression promoted liver metastasis in vivo.

We suggest that positive PROK2 expression is observed in CRC primary tissues; thus, PROK2 may be a useful predictor for liver recurrence and prognosis in CRC.

Astakines in arthropods-phylogeny and gene structure

Astakine1 was isolated as a hematopoietic cytokine in the freshwater crayfish Pacifastacus leniusculus. In this study we detect and compare 79 sequences in GenBank, which we consider to be possible astakine orthologs, among which eleven are crustacean, sixteen are chelicerate and 52 are from insect species. Available arthropod genomes are searched for astakines, and in conclusion all astakine sequences in the current study have a similar exon containing CCXX(X), thus potentially indicating that they are homologous genes with the structure of this exon highly conserved. Two motifs, RYS and YP(N), are also conserved among the arthropod astakines. A phylogenetic analysis reveals that astakine1 and astakine2 from P. leniusculus and Procambarus clarkii are distantly related, and may have been derived from a gene duplication occurring early in crustacean evolution. Moreover, a structural comparison using the Mamba intestinal toxin (MIT1) from Dendroaspis polylepis as template indicates that the overall folds are similar in all crustacean astakines investigated.

Effects of prokineticin 2 on testicular inflammation in rats

PROBLEM

Prokineticin 2 (PK2), a pro-inflammatory peptide, is highly expressed in primary spermatocytes. However, systematic research on PK2 and testicular inflammation is lacking to date.

METHOD OF STUDY

An experimental autoimmune orchitis (EAO) model was established to detect the expression of PK2 and its receptor (prokineticin receptor 1, PKR1) 50 and 80 days after immunization. PK2 siRNA sequence was injected into the rat rete testis to downregulate the expression of PK2. PK2 was over-expressed in the testis by injecting PK2 protein through the rat rete testis at different concentrations. Testicular morphology and expression of inducible nitric oxide synthase (iNOS) were detected after the intervention.

RESULTS

Results showed that PK2 and PKR1 were upregulated in EAO at 50 days and downregulated at 80 days. PK2 over-expression contributed to the apoptosis of spermatogenic epithelial cells and increased infiltration of the inflammatory cells, whereas PK2 under-expression showed no change. Furthermore, iNOS expression was increased significantly when PK2 was over-expressed.

CONCLUSION

This finding demonstrated that the PK2/PKR1 signals may have an essential role in the regulation of testicular inflammation through iNOS. PK2 interference may represent a novel and promising therapeutic strategy for the clinical management of orchitis.

The prokineticin system: an interface between neural inflammation and pain

Prokineticins (PK) 1 and 2 belong to a new family of chemokines capable to interact with two different G coupled receptors: Prokineticin receptor (PKR)1 and 2. Both prokineticins and their receptors are widely distributed in different tissues and regulate several biological functions. In particular, a role of the PK system in inflammation and nociception has been established. PKRs are expressed in regions of the nervous system associated with pain and in primary sensitive neurons they colocalize with transient potential receptor vanilloid-TRPV1 providing an anatomical interaction in nociceptor sensitization. Moreover, PKs are strongly upregulated in immune and glial cells and sustain a proinflammatory loop in inflamed tissues. Recent evidences indicate that the block of the PK system represents a promising strategy to contrast inflammation and pain.

Mendelian Disease Associations Reveal Novel Insights into Inflammatory Bowel Disease

Background

Monogenic diseases have been shown to contribute to complex disease risk and may hold new insights into the underlying biological mechanism of Inflammatory Bowel Disease (IBD).

Methods

We analyzed Mendelian disease associations with IBD using over 55 million patients from the Optum's deidentified electronic health records dataset database. Using the significant Mendelian diseases, we performed pathway enrichment analysis and constructed a model using gene expression datasets to differentiate Crohn's disease (CD), ulcerative colitis (UC), and healthy patient samples.

Results

We found 50 Mendelian diseases were significantly associated with IBD, with 40 being significantly associated with both CD and UC. Our results for CD replicated those from previous studies. Pathways that were enriched consisted of mainly immune and metabolic processes with a focus on tolerance and oxidative stress. Our 3-way classifier for UC, CD, and healthy samples yielded an accuracy of 72%.

Conclusions

Mendelian diseases that are significantly associated with IBD may reveal novel insights into the genetic architecture of IBD.

Prokineticin Is a New Linker between Obesity and Cardiovascular Diseases

Obesity is a fast growing epidemic event worldwide. Fatness is associated with a number of comorbidities, including cardiovascular diseases (CVDs). Although obesity can be heredity in 30–70% cases, the environmental contributions also play an important role in the increasing prevalence of obesity. The relationship between development of obesity and CVD is poorly characterized. Obesity and CVD can also be resulted from a common mechanism such as metabolic, inflammatory, and neurohormonal changes. Prokineticins are defined as cytokines (immunoregulatory proteins), adipokines (adipocyte-secreted hormone), angiogenic (increasing vessel formation), or aneroxic (lowering food intake) hormones. Prokineticin-mediated signaling plays a key role in the development of obesity and CVD. Two forms of prokineticins exist in circulation and in various tissues including the brain, heart, kidney, and adipose. Prokineticins act on the two G protein-coupled receptors, namely, PKR1 and PKR2. Prokineticin-2 (PK2) via PKR1 receptor controls food intake and prevents adipose tissue expansion. The anti-adipocyte effect of PKR1 signaling is due to suppression of preadipocyte proliferation and differentiation capacity into adipocytes. PK2/PKR1 signaling promotes transcapillary passages of insulin and increases insulin sensitivity. It also plays an important role in the heart and kidney development and functions. Here, we discuss PK2 as a new adipocytokine in the association between obesity and CVD. We also highlight targeting PKR1 can be a new approach to treat obesity and CVD.

Involvement of Prokineticin 2 and Prokineticin Receptor 1 in Lipopolysaccharide-Induced Testitis in Rats

Prokineticin 2, a newly discovered proinflammatory peptide, has been amply evidenced to be involved in the occurrence and progress of local and systematical inflammation. Although the presence of Prokineticn 2 in mammal testis has been documented clearly, research targeting the involvement of prokineticin 2 in testicular pathology, especially testitis, is rather scarce. Employing a lipopolysaccharide-induced testitis rat model, we for the first time demonstrated the expression and upregulation of prokineticin 2 in orchitis at several levels. Our effort also addressed the differential expression patterns of prokineticin 2 and interleukin-1β, a key inflammation indicator, during testitis suggesting Prokineticn 2 serves more than a proinflammatory factor in the context of testitis. Given one of the cognate receptors of prokineticin 2, prokineticin receptor 1 (PKR1) was also significantly upregulated in orchitis as discussed in the current study, it is very likely that PK2/PKR1 signaling contribute to the development of inflammation-related testicular diseases.

Synthesis and evaluation of new 5-aminolevulinic acid derivatives as prodrugs of protoporphyrin for photodynamic therapy

Upon light activation, 13a can induce the production of PpIX in vivo which produces ROS and other reactive oxygen species to lead to the apoptosis of S180 cell tumors.

Prokineticin 2 Plays a Pivotal Role in Psoriasis

Psoriasis is histologically characterized by keratinocytes (KC) hyperproliferation, inflammation, and increased angiogenesis, but the pathological factor responsible for these symptoms is unknown. Here, a neuroendocrine peptide (prokineticin 2, PK2), is highly expressed in human and mouse psoriatic skins but no significant change in other autoimmune diseases, suggesting that PK2 is a psoriasis-specific factor. Bacterial products significantly up-regulated PK2, implying that infection induces PK2 over-expression. PK2 promoted KC and macrophage to produce interleukin-1 (IL-1), the central player of inflammation and psoriasis, which acts on adjacent fibroblast to induce inflammatory cascades and KC hyperproliferation. IL-1 feeds back on macrophages to induce PK2 production to perpetuate PK2-IL-1 positive feedback loop. PK2 also promoted angiogenesis, another psoriatic symptom. In mouse models, PK2 over-expression aggravated psoriasis while its knock-down inhibited pathological development. The results indicate that PK2 over-production perpetuates psoriatic symptoms by creating PK-2-IL-1 vicious loop. PK2 is a central player in psoriasis and a promising psoriasis-specific target.

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High level of PK2 is found in psoriasis but not in other autoimmunity diseases.

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Bacterial products induce PK2 over-expression to promote IL-1 signal.

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IL-1 induces PK2 secretion to create a PK2-IL-1 circle to perpetuate symptoms.

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PK2 is a central player in psoriasis and may be a psoriasis-specific target.

Psoriasis is a common autoimmune disease whose pathogenesis remains poorly understood. We found that PK2 was highly expressed in psoriasis but not in other autoimmune diseases. To investigate the role of PK2 in psoriasis, the effect of PK2 on keratinocyte proliferation, inflammation and angiogenesis were analyzed. PK2 expression mediated by virus in psoriasis was applied. The results demonstrated that PK2 promoted psoriasis development. PK2 over-expression in mouse model aggravates psoriasis while knock-down of PK2 improves the disease. PK2 plays a pivotal role in psoriasis.

Prokineticin 2 antagonist, PKRA7 suppresses arthritis in mice with collagen-induced arthritis

BACKGROUND

Prokineticin 2 (PK2) expression is upregulated in mice with collagen-induced arthritis (CIA), an animal model of rheumatoid arthritis. The purpose of our study was to investigate the effects of PK2 inhibition on CIA.

METHODS

PK2, prokineticin receptor (PKR) 1, and PKR2 mRNA transcripts in the joints of CIA mice were measured by real-time PCR on Days 21, 28, and 35 (n = 15/day). Localization of PKR1 and PKR2 proteins was examined immunohistochemically. PKRA7, a PK2 antagonist, was administered intraperitoneally for 2 weeks to CIA mice, and the severity of arthritis was compared between treated (n = 12) and untreated (n = 12) mice. The gene expression levels of inflammatory cytokines IL-1β, IL-6, TNF-α, and VEGF were also measured by real-time PCR and compared between treated (n = 6) and untreated (n = 6) CIA mice. The data was statistically analyzed, and P values of less than 0.05 were considered significant.

RESULTS

In the thickened synovial membrane, PKR1 protein was expressed in infiltrating neutrophils, while PKR2 expression was found in macrophage-like mononuclear cells. PK2 gene expression was significantly more pronounced on Days 28 and 35 than on Day 21 (2.15 and 2.03 versus 1.00, P = 0.0311 and 0.0247; Dunn's multiple comparison). PKR2 gene expression levels were significantly higher on Days 28 and 35 compared to Day 21 (25.4 and 39.3 versus 1.0, P = 0.002 and < 0.0001; Dunn's multiple comparison). Administration of PKRA7 suppressed the severity of arthritis (P < 0.001; two-way analysis of variance). A gene expression analysis of inflammatory cytokines revealed significantly reduced IL-1β and lL-6 expression in the joints of PKRA7-treated mice compared to untreated mice (0.1 versus 1.0, P = 0.0043 and 0.04 versus 1.0, P = 0.0022, respectively; Mann-Whitney test).

CONCLUSIONS

PK2 inhibition suppressed arthritis in mice with CIA.

Prokineticins are neuroprotective in models of cerebral ischemia and ischemic tolerance in vitro

Bv8/prokineticin 2 (PK2) is a member of a bioactive family of peptides that regulate multiple functions in the CNS including hyperalgesia, neurogenesis, neuronal survival and inflammation. Recent studies have associated PK2 and prokineticin receptors (PKR) with human diseases, but because their role in neuropathology is still debated we examined whether prokineticins exert a protective or deleterious role in models of cerebral ischemia and ischemic tolerance in vitro. In order to mimic cerebral ischemia, we exposed primary murine cortical cell cultures or rat organotypic hippocampal slices to appropriate periods of oxygen-glucose deprivation (OGD), which leads to neuronal damage 24 h later. Ischemic tolerance was induced by exposing hippocampal slices to a preconditioning subtoxic pharmacological stimulus (3 μM NMDA for 1 h) 24 h before the exposure to OGD. Bv8 (10-100 nM) attenuated OGD injury in cortical cultures and hippocampal slices, and the effect was prevented by the PKR antagonist PC7. The development of OGD tolerance was associated with an increase in the expression of PK2, PKR1 and PKR2 mRNA and proteins and was prevented by addition of the antagonist PC7 into the medium during preconditioning. Both Bv8 at protective concentrations and the NMDA preconditioning stimulus promoted the phosphorylation of ERK1/2 and Akt. These findings indicate that the prokineticin system can be up-regulated by a defensive preconditioning subtoxic NMDA stimulus and that PK2 may act as an endogenous neuroprotective factor through the activation of the ERK1/2 and Akt transduction pathways.

Antagonism of the Prokineticin System Prevents and Reverses Allodynia and Inflammation in a Mouse Model of Diabetes

Neuropathic pain is a severe diabetes complication and its treatment is not satisfactory. It is associated with neuroinflammation-related events that participate in pain generation and chronicization. Prokineticins are a new family of chemokines that has emerged as critical players in immune system, inflammation and pain. We investigated the role of prokineticins and their receptors as modulators of neuropathic pain and inflammatory responses in experimental diabetes. In streptozotocin-induced-diabetes in mice, the time course expression of prokineticin and its receptors was evaluated in spinal cord and sciatic nerves, and correlated with mechanical allodynia. Spinal cord and sciatic nerve pro- and anti-inflammatory cytokines were measured as protein and mRNA, and spinal cord GluR subunits expression studied. The effect of preventive and therapeutic treatment with the prokineticin receptor antagonist PC1 on behavioural and biochemical parameters was evaluated. Peripheral immune activation was assessed measuring macrophage and T-helper cytokine production. An up-regulation of the Prokineticin system was present in spinal cord and nerves of diabetic mice, and correlated with allodynia. Therapeutic PC1 reversed allodynia while preventive treatment blocked its development. PC1 normalized prokineticin levels and prevented the up-regulation of GluN2B subunits in the spinal cord. The antagonist restored the pro-/anti-inflammatory cytokine balance altered in spinal cord and nerves and also reduced peripheral immune system activation in diabetic mice, decreasing macrophage proinflammatory cytokines and the T-helper 1 phenotype. The prokineticin system contributes to altered sensitivity in diabetic neuropathy and its inhibition blocked both allodynia and inflammatory events underlying disease.

Prokineticin-2 is associated with metabolic syndrome in a middle-aged and elderly Chinese population

Background

Prokineticin-2 is confirmed to be involved in the inflammatory process. Inflammation plays an important role in the pathogenesis of metabolic syndrome (MS). However, whether prokineticin-2 is associated with MS or not remains unknown. Thus, we present this study to explore the association between prokineticin-2 and MS in a Chinese population.

Methods

This study included 162 middle-aged and elderly Chinese patients with cardiovascular risk factors. The relationship between serum prokineticin-2 levels and various cardiometabolic risk factors, and MS were evaluated.

Results

The participants with serum prokineticin-2 levels >6.32 ng/ml had increased waist circumference, body mass index (BMI), plasma triglyceride, diastolic blood pressure (DBP), blood glucose, and serum uric acid, but decreased age, plasma high-density lipoprotein cholesterol (HDL-C), and HDL-C/total cholesterol (TC) (all P < 0.05). A higher percentage of them had history of lipid disorders (19.3 vs 2.5 %, P = 0.001) and MS (77.1 vs 48.1 %, P < 0.001). Prokineticin-2 was positively correlated with TC (partial correlation coefficient: 0.233, P = 0.011), triglyceride (partial correlation coefficient: 0.504, P < 0.001), fasting plasma glucose (partial correlation coefficient: 0.336, P < 0.001), HbA1c (partial correlation coefficient: 0.285, P = 0.002), and uric acid (partial correlation coefficient: 0.234, P = 0.011) respectively, but was negatively correlated with HDL-C/TC (partial correlation coefficient: −0.269, P = 0.003) with adjustment for age, man, and BMI. Prokineticin-2 was significantly elevated in participants with MS (7.72 ± 3.34 vs 5.56 ± 2.39 ng/ml, P < 0.001). Furthermore, prokineticin-2 was significantly elevated in participants with increased numbers of MS components (5.17 ± 2.29 vs 5.94 ± 2.47 vs 7.13 ± 3.33 vs 8.32 ± 2.81 vs 9.82 ± 4.37 ng/ml, P for trend <0.001). Multiple logistic regression analysis indicated that prokineticin-2 was independently associated with MS (OR: 1.307, 95 % confidence interval: 1.127–1.515, P < 0.001) with adjustment for other potential confounders. If serum prokineticin-2 value can be considered as an indicator to discriminate MS, receiver operating characteristic curve analysis exhibited the area under the curve as 0.701.

Conclusions

Prokineticin-2 is correlated with various cardiometabolic risk factors including blood lipid, blood glucose, blood pressure, BMI, and uric acid. And furthermore, the increased prokineticin-2 is independently associated with MS.

PK2/PKR1 Signaling Regulates Bladder Function and Sensation in Rats with Cyclophosphamide-Induced Cystitis

Prokineticin 2 (PK2) is a novel chemokine-like peptide with multiple proinflammatory and nociception-related activities. This study aimed to explore the potential role of PK2 in modulating bladder activity and sensation in rats with cyclophosphamide- (CYP-) induced cystitis. Changes of PK2 and prokineticin receptors (PKRs) in normal and inflamed urinary bladders were determined at several time points (4 h, 48 h, and 8 d) after CYP treatment. Combining a nonselective antagonist of prokineticin receptors (PKRA), we further evaluated the regulatory role of PK2 in modulating bladder function and visceral pain sensation via conscious cystometry and pain behavioral scoring. PK2 and prokineticin receptor 1 (PKR1), but not prokineticin receptor 2, were detected in normal and upregulated in CYP-treated rat bladders at several levels. Immunohistochemistry staining localized PKR1 primarily in the urothelium. Blocking PKRs with PKRA showed no effect on micturition reflex activity and bladder sensation in control rats while it increased the voiding volume, prolonged voiding interval, and ameliorated visceral hyperalgesia in rats suffering from CYP-induced cystitis. In conclusion, PK2/PKR1 signaling pathway contributes to the modulation of inflammation-mediated voiding dysfunction and spontaneous visceral pain. Local blockade of PKRs may represent a novel and promising therapeutic strategy for the clinical management of inflammation-related bladder diseases.

Can prokineticin prevent obesity and insulin resistance?

PURPOSE OF REVIEW

Because of its increasing prevalence and morbi-mortality, obesity is a major health problem. Obesity etiology includes a combination of excess dietary calories and decreased physical activity, coupled with either predisposing genetic factors or metabolic disorders such as insulin resistance. Adipose tissue secretes several metabolically important proteins known as 'adipokines' that play a major role in obesity and insulin resistance. High levels of a newly identified group of adipokines, called prokineticins, have been found in obese adipose tissues. Prokineticins are peptide hormones released principally from macrophages and reproductive organs. They act on the G protein-coupled receptors PKR1 and PKR2. This review aims to provide an overview of current knowledge of the role of prokineticins and their receptors in the development of obesity and insulin resistance.

RECENT FINDINGS

The principal biological effect of prokineticins in the central nervous system is the control of food intake. Nevertheless, peripheral biological effects of prokineticin are associated with increasing insulin sensitivity and suppressing the adipose tissue expansion.

SUMMARY

We outline the biological significance of the central and peripheral effects of prokineticins, and the potential of their receptors as targets for the treatment of obesity and insulin resistance.

Evaluation of murine macrophage cytokine production after in vivo morphine treatment

The discovery of opioid receptors expression on immune cells has originated a large research activity on the possible modulation by opioid drugs of immune system responses. In the present chapter we describe an easy methodology useful to obtain information about the potential immunomodulatory activity of opioid drugs. An in vivo treatment schedule is used, and macrophages are studied for their ability to release different cytokines.

Critical role for prokineticin 2 in CNS autoimmunity

Objective:

To investigate the potential role of prokineticin 2 (PK2), a bioactive peptide involved in multiple biological functions including immune modulation, in CNS autoimmune demyelinating disease.

Methods:

We investigated the expression of PK2 in mice with experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis (MS), and in patients with relapsing-remitting MS. We evaluated the biological effects of PK2 on expression of EAE and on development of T-cell response against myelin by blocking PK2 in vivo with PK2 receptor antagonists. We treated with PK2 immune cells activated against myelin antigen to explore the immune-modulating effects of this peptide in vitro.

Results:

Pk2 messenger RNA was upregulated in spinal cord and lymph node cells (LNCs) of mice with EAE. PK2 protein was expressed in EAE inflammatory infiltrates and was increased in sera during EAE. In patients with relapsing-remitting MS, transcripts for PK2 were significantly increased in peripheral blood mononuclear cells compared with healthy controls, and PK2 serum concentrations were significantly higher. A PK2 receptor antagonist prevented or attenuated established EAE in chronic and relapsing-remitting models, reduced CNS inflammation and demyelination, and decreased the production of interferon (IFN)-γ and interleukin (IL)-17A cytokines in LNCs while increasing IL-10. PK2 in vitro increased IFN-γ and IL-17A and reduced IL-10 in splenocytes activated against myelin antigen.

Conclusion:

These data suggest that PK2 is a critical immune regulator in CNS autoimmune demyelination and may represent a new target for therapy.

Prokineticin 2 upregulation in the peripheral nervous system has a major role in triggering and maintaining neuropathic pain in the chronic constriction injury model

The new chemokine Prokineticin 2 (PROK2) and its receptors (PKR₁ and PKR₂) have a role in inflammatory pain and immunomodulation. Here we identified PROK2 as a critical mediator of neuropathic pain in the chronic constriction injury (CCI) of the sciatic nerve in mice and demonstrated that blocking the prokineticin receptors with two PKR₁-preferring antagonists (PC1 and PC7) reduces pain and nerve damage. PROK2 mRNA expression was upregulated in the injured nerve since day 3 post injury (dpi) and in the ipsilateral DRG since 6 dpi. PROK2 protein overexpression was evident in Schwann Cells, infiltrating macrophages and axons in the peripheral nerve and in the neuronal bodies and some satellite cells in the DRG. Therapeutic treatment of neuropathic mice with the PKR-antagonist, PC1, impaired the PROK2 upregulation and signalling. This fact, besides alleviating pain, brought down the burden of proinflammatory cytokines in the damaged nerve and prompted an anti-inflammatory repair program. Such a treatment also reduced intraneural oedema and axon degeneration as demonstrated by the physiological skin innervation and thickness conserved in CCI-PC1 mice. These findings suggest that PROK2 plays a crucial role in neuropathic pain and might represent a novel target of treatment for this disease.