Serum activity of prolyl endopeptidase, but not of dipeptidyl peptidase IV, is decreased by immunotherapy with IFN-alpha in high-risk melanoma patients

Prolyl endopeptidase and dipeptidyl peptidase IV are associated with externalizing and aggressive behaviors in normal and autistic adolescents

AIMS

Peptides and a dysregulated immune system play a role in the pathophysiology of autism. Dysfunctions in prolyl endopeptidase (PEP) and dipeptidyl peptidase IV (DPP-IV) may underpin both the peptidergic and immune alterations in autism. The aims of this study are to: (i) delineate serum PEP and DPP-IV enzyme activities in autism, and (ii) examine the associations between both peptidases and behavioral characteristics or immune variables.

MAIN METHODS

We included 18 autistic patients and 22 healthy controls and measured the Child Behavior Checklist (CBCL), serum PEP and DPP-IV and immune biomarkers, i.e. the serum protein fractions α1, α2 and γ, and immunoglobulins, i.e. IgG1, IgG2, IgG3 and IgG4. Results were adjusted for possible effects of age and body mass index (BMI).

KEY FINDINGS

There were no significant differences in PEP or DPP-IV between the autistic patients and controls. DPP-IV was significantly and positively associated with the CBCL attention problems, aggressive and externalizing behavior subscales. PEP was significantly and positively associated with the CBCL delinquent, aggressive, externalizing and internalizing behavior subscales. There was a negative correlation between both peptidases and age and Tanner stage. DPP-IV was associated with α2-globulin (positively) and IgG3 (inversely) levels, while PEP activity was correlated with IgG2 levels (inversely). BMI was significantly associated with aggressive and externalizing behaviors.

SIGNIFICANCE

These findings demonstrate an association between peptidases and aggressive and externalizing behaviors, which may be explained by effects of these peptidases cleaving behavioral neuropeptides. Both peptidases are associated with immune biomarkers suggesting multiple bidirectional effects.

Perioperative care and cancer recurrence: Is there a connection?

Cancer is the second most common cause of death in the United States. Metastatic disease is a more important cause of cancer-related death relative to primary tumor progression. Surgical excision is the primary treatment for most malignant tumors. However, surgery itself can inhibit important host defenses and promote the development of metastases. An altered balance between the metastatic potential of the tumor and the anti-metastatic host defenses, including cell-mediated immunity and natural killer cell function, is a plausible mechanism of increased cancer metastasis. This article reviews the increasingly recognized concept of anesthetic technique along with perioperative factors and their potential to affect long-term outcome after cancer surgery. The potential effect of intravenous anesthetics, volatile agents, local anesthetic drugs, opiates, and non-steroidal anti-inflammatory drugs are reviewed along with recent literature and ongoing clinical trials in this area. Regional anesthesia is increasingly emerging as a safer option with less cancer recurrence potential as compared to general anesthesia. Blood transfusion, pain, stress, use of beta-blockers, and hypothermia are other potentially important perioperative factors to consider.

Identification of altered dipeptidyl-peptidase activities as potential biomarkers for unipolar depression

BACKGROUND

Changes in circulatory aminopeptidases [dipeptidyl-peptidase-IV (DPP-IV), Prolyl-oligopeptidase (POP) and Leucine aminopeptidase (LAP)] activities have been found to be associated with psychiatric illnesses and inflammatory diseases.

METHODS

The discriminatory indices of aminopeptidases activities were assessed by enzymatic assays in plasma samples from 240 unipolar depression (UD) patients and 264 matched controls. In addition the relationship between soluble and cellular DPP-IV activity was determined in plasma and blood cells from healthy subjects.

RESULTS

Greater than 95% of the plasma DPP-IV activity could be blocked by inhibitors, demonstrating the specificity of the assay. Also, DPP-IV protein and activity levels were strongly correlated. In contrast, only 50% of the membrane-bound activity in blood cells was inhibited, which suggested that other similar peptidases may be present in these cells. UD patients had decreased plasma levels of DPP-IV and POP activities compared to healthy controls with a concomitant increase in LAP activity. Finally, testing of the LAP/DPP-IV ratio resulted in good discrimination of UD patients from controls with an area under the curve-receiver operating characteristic of 0.70.

LIMITATIONS

Further biological validation studies using different cohorts are warranted.

CONCLUSIONS

The finding that plasma DPP-IV activity was decreased and LAP activity was increased in UD patients suggests the potential value for testing the levels of these enzymes for improved classification of patients. In addition, the changes in these enzymes, suggests that the proteolytic maturation of their proneuropeptide and prohormone subtrates may also be affected in UD, resulting in altered production of the associated bioactive peptides.

Prolyl oligopeptidase, inositol phosphate signalling and lithium sensitivity

Inhibition of prolyl oligopeptidase (PO) elevates inositol phosphate (IP) signalling and reduces cell sensitivity to lithium (Li⁺). This review discusses recent evidence that shows PO acts via the multiple inositol polyphosphate phosphatase (MIPP) to regulate gene expression. As a consequence, PO inhibition causes both a transient, rapid increase in I(1,4,5)P₃ and a long-term elevation of IP signalling. This pathway is evolutionary conserved, being present in both the social amoeba Dictyostelium and human cell systems, and has potential implications for mental health.

Genetic control of lithium sensitivity and regulation of inositol biosynthetic genes

Lithium (Li(+)) is a common treatment for bipolar mood disorder, a major psychiatric illness with a lifetime prevalence of more than 1%. Risk of bipolar disorder is heavily influenced by genetic predisposition, but is a complex genetic trait and, to date, genetic studies have provided little insight into its molecular origins. An alternative approach is to investigate the genetics of Li(+) sensitivity. Using the social amoeba Dictyostelium, we previously identified prolyl oligopeptidase (PO) as a modulator of Li(+) sensitivity. In a link to the clinic, PO enzyme activity is altered in bipolar disorder patients. Further studies demonstrated that PO is a negative regulator of inositol(1,4,5)trisphosphate (IP(3)) synthesis, a Li(+) sensitive intracellular signal. However, it was unclear how PO could influence either Li(+) sensitivity or risk of bipolar disorder. Here we show that in both Dictyostelium and cultured human cells PO acts via Multiple Inositol Polyphosphate Phosphatase (Mipp1) to control gene expression. This reveals a novel, gene regulatory network that modulates inositol metabolism and Li(+) sensitivity. Among its targets is the inositol monophosphatase gene IMPA2, which has also been associated with risk of bipolar disorder in some family studies, and our observations offer a cellular signalling pathway in which PO activity and IMPA2 gene expression converge.

Plasma activity of prolyl endopeptidase in relation to psychopathology during immunotherapy with IFN-alpha in patients with renal cell carcinoma

Abnormal activity in peripheral blood of the cytosolic enzyme prolyl endopeptidase (PEP, EC 3.4.21.26, post prolyl cleaving enzyme, prolyl oligopeptidase) has been found in patients with a variety of psychiatric disorders, most consistently in mood disorders. Mood disturbance is a well-known side effect of immunotherapy with interferon-alpha (IFN-alpha). Earlier, we documented a decrease in serum PEP activity in the first 4 weeks of treatment with IFN-alpha. In 24 patients (16 men, 8 women, median age 60.5 years, range 47-72 years) with metastatic renal cell carcinoma (RCC), psychiatric assessment and blood sampling were performed before and at 4 and 8 weeks and at 6 months after initiation of treatment with IFN-alpha. No episodes of depression were observed, and the sum score and the scores on the subscales for depression and hostility of the Symptom Check List-90 (SCL-90) did not change during follow-up, whereas the anxiety scores were somewhat lower at 4 and 8 weeks compared with baseline. No change in plasma PEP activity and no relationships between change in psychiatric parameters and change in plasma PEP activity were found. As more subtle relationships between PEP activity and psychiatric status could have easily been obscured, a role for PEP in the pathophysiology of IFN-alpha-induced mood disturbance can neither be confirmed nor excluded.

Suggested functions for prolyl oligopeptidase: a puzzling paradox

Prolyl oligopeptidase (PO, E.C. 3.4.21.26) is a post-proline cleaving enzyme with endopeptidase activity towards peptides not longer than 30 amino acids. It has been purified and characterized from various mammalian and bacterial sources, but despite its thorough enzymological and structural characterization, the exact function of PO remains obscure. Many investigations have addressed the physiological role of this enzyme, mainly by the use of specific PO inhibitors, activity measurements in clinical samples and (neuro)peptide degradation studies. From the combined results emerges a puzzling paradox: how can an intracellular, cytoplasmatic oligopeptidase affect not only the amount of extracellular neuropeptides but also signal transduction and secretion? This report provides a review of the literature on the suggested functions for PO, highlighting possible pitfalls and contradictions.