Why sickness hurts: A central mechanism for pain induced by peripheral inflammation

Low-grade systemic inflammation has been implicated in chronic pain, as well as in comorbid diseases like depression and fatigue. We have previously shown that women's pain perception and regulation is more affected by systemic inflammation than that of men. Here we investigated the neural substrates underlying these effects using an fMRI paradigm previously employed in a clinical population. Fifty-one participants (29 women) were injected with 0.6ng/kg lipopolysaccharide (LPS) or saline to induce a peripheral inflammatory response. The subjects were then tested with a pressure pain fMRI paradigm designed to capture descending pain inhibitory activity 2h after injection, and blood was sampled for cytokine analysis. The subjects injected with LPS became more pain sensitive compared to the placebo group, and the heightened pain sensitivity was paralleled by decreased activity in the ventrolateral prefrontal cortex and the rostral anterior cingulate cortex (rACC) compared to placebo; areas involved in descending pain regulation. The LPS group also had higher activity in the anterior insular cortex, an area underpinning affective and interoceptive pain processing. Women displayed overall less pain-evoked rACC activity compared to men, which may have rendered women less resilient to immune provocation, possibly explaining sex differences in LPS-induced pain sensitivity. Our findings elucidate the pain-related brain circuits affected by experimental peripheral inflammation, strengthening the theoretical link between systemic inflammation and weakened pain regulation in chronic pain disorders. The results further suggest a possible mechanism underlying the female predominance in many chronic pain disorders.

The influence of negative life events on hippocampal and amygdala volumes in old age: a life-course perspective

BACKGROUND

Psychosocial stress has been related to changes in the nervous system, with both adaptive and maladaptive consequences. The aim of this study was to examine the relationship of negative events experienced throughout the entire lifespan and hippocampal and amygdala volumes in older adults.

METHOD

In 466 non-demented old adults (age range 60-96 years, 58% female), hippocampal and amygdala volumes were segmented using Freesurfer. Negative life events and the age at which these events occurred were assessed by means of a structured questionnaire. Using generalized linear models, hippocampal and amygdala volumes were estimated with life events as independent variables. The statistical analyses were adjusted for age, gender, intracranial volume, lifestyle factors, cardiovascular risk factors, depressive symptoms, and cognitive functioning.

RESULTS

Total number of negative life events and of late-life events, but not of early-life, early-adulthood, or middle-adulthood events, was related to larger amygdala volume. There were interactions of early-life events with age and gender. Participants who reported two or more early-life events had significantly smaller amygdala and hippocampal volumes with increasing age. Furthermore, smaller hippocampal volume was found in men who reported two or more early-life events, but not in women.

CONCLUSIONS

These results suggest that the effect of negative life events on the brain depends on the time when the events occurred, with the strongest effects observed during the critical time periods of early and late life.

Do cardiovascular risk factors explain the link between white matter hyperintensities and brain volumes in old age? A population-based study

BACKGROUND AND PURPOSE

White matter hyperintensities (WMHs) and brain atrophy frequently coexist in older people. However, it is unclear whether the association between these two brain lesions is dependent on the aging process, a vascular mechanism or genetic susceptibility. It was therefore investigated whether the association between load of WMHs and brain atrophy measures is related to age, vascular risk factors (VRFs) or the APOE-ε4 allele.

METHODS

This population-based study included 492 participants (age ≥60 years, 59.6% women) free of dementia and stroke. Data on demographics, VRFs and APOE genotypes were collected through interviews, clinical examination and laboratory tests. WMHs on magnetic resonance images were assessed using manual visual rating and automatic volumetric segmentation. Hippocampal and ventricular volumes were manually delineated, whereas total gray matter (GM) volume was measured by automatic segmentation. Data were analyzed with multivariate linear regression models.

RESULTS

More global WMHs, assessed using either a visual rating scale or a volumetric approach, were significantly associated with lower GM volume and higher ventricular volume; the associations remained significant after adjusting for age, VRFs and the APOE-ε4 allele. In contrast, the association between global WMHs and hippocampal volume was no longer significant after adjusting for age, whereas adjustment for VRFs and APOE-ε4 had no influential effect.

CONCLUSION

The association of global WMHs with lower GM volume and higher ventricular volume is independent of age, VRFs and APOE-ε4 allele, suggesting that the process of cerebral microvascular disease and neurodegeneration are associated independently of the normal aging process, vascular mechanisms or genetic susceptibility.

Immunophenotype, ras oncogenes and p53 onco-suppressor gene in benzo(a)pyrene induced malignant soft tissue tumours in Wistar rats

This study was designed to identify the immunophenotypic characteristics of malignant soft tissue tumours, induced experimentally with benzo(a)pyrene (BaP), and to evaluate the immunohistochemical expression of the ras oncogene family and p53 onco-suppressor gene in these tumours, in association with prognostic factors. Seventy-five male Wistar rats were subcutaneous injected, dorsally, with a single dose of 10.08 mgr BaP. A solid, well-circumscribed tumour was formed at the injection site, in 70 of the animals, 80-100 days after the carcinogen's administration. The tumour as well as selected main organs were excised and studied after the animals' death. All the specimens were fixed in formalin 10%, embedded in paraffin and stained with H + E. The immunohistochemical avidin-biotin method was performed in the tumour sections, using the following monoclonal or polyclonal antibodies: vimentin, desmin, muscle specific actin (MSA), a-smooth muscle actin (SMA), myoglobin, smooth muscle myosin, a-1-antitrypsin, a-1-antichymotrypsin, S-100 protein, epithelial membrane antigen (EMA), K-ras, H-ras, Pan-ras and p53. The induced tumours of the animals were almost well-circumscribed, with a partly storiform cut surface. Histologically, their appearance was more conventional with high grade leiomyosarcomas; about half of them showed highly anaplastic areas, resembling other pleomorphic undifferentiated sarcomas. Pulmonary metastatic foci were detected in 37 animals. Immunohistochemically, all the tumours displayed positive expression of vimentin, MSA and SMA. Desmin was positively expressed in 40 tumours, smooth muscle myosin in 57 tumours and EMA in 12 tumours. All the tumours were negative for myoglobin, a-1-antitrypsin, a-1-antichymotrypsin and S-100 protein. In addition, five tumours showed a positive reaction for K-ras p21, 37 for H-ras p21, 41 for Pan-ras p21 and 14 for p53 protein. The overexpression of the oncoproteins H-ras p21 and Pan-ras p21 in these tumours was significantly associated with a non-advanced tumour stage (absence of metastatic focus). In conclusion, the histological as well as the immunophenotypic features of the induced tumours are more conventional with leiomyosarcomas mostly of high grade; many of them are "dedifferentiated". The identification of both ras and p53 gene products in these tumours indicates that alterations of these genes are common but not specific events, implicated in the tumourigenesis, which may become prognostic markers for this subtype of soft tissue sarcomas.

Comparison of the therapeutic effects of two vanadium complexes administered at low dose on benzo[a]pyrene-induced malignant tumors in rats

The antitumor effects of low dose administration of the vanadium(III) complexes with L-cysteine (complex 1) and N-(2-mercaptopropionyl)-glycine (complex 2) were compared on benzo[a]pyrene (BaP)-induced tumors in Wistar rats. Male Wistar rats, injected with 10.0 mg of BaP, were divided into one control (C-G) and two treatment (TR-G) groups of 17 animals each. Animals of the first treatment group were administered complex 2 (TR-2 group) and those of the second group were administered complex 1 (TR-1 group) at doses of 100 microg of vanadium per os daily, starting from the day a palpable tumor was developed till their death. BaP injection induced a 100% tumor (leiomyosarcomas) development in the animals of all groups. Administration of complex 1 to the animals resulted in a significant prolongation of the mean survival time, a complete remission of 17.6% of the tumors developed, a significant reduction of the carcinogenic potency (CP) of BaP and of the tumor growth rate (TGR) in TR-1 group animals, compared to the control and the TR-2 group. In marked contrast, complex 2 failed at the doses administered to exert any significant modulation of the above mentioned parameters. Results indicate that at low (100 micro/day) concentrations of vanadium, complex 1 exerts a significant anticarcinogenic effect on experimentally-induced leiomyosarcomas in rats, whereas complex 2 has no effect when administered at the same low concentrations of vanadium.

Dose-related preventive and therapeutic effects of antioxidants-anticarcinogens on experimentally induced malignant tumors in Wistar rats

A combination of antioxidants-anticarcinogens, consisting of vitamins C and E, selenium and 2-mercaptopropionyl glycine (2-MPG), was administered orally for the prevention (PRG) and treatment (TRG) of benzo(a)pyrene (BaP)-induced malignant tumors (leiomyosarcomas), in Wistar rats. In order to evaluate dose-related effects, a low dose vitamin (0.15 g/kg b.w. per day of vit.C and 0.05 g/kg b.w. per day of vit.E) and a high dose (1.5 g/kg b.w. per day of vit.C and 0.5 g/kg b.w. per day of vit.E) combination was administered, in prevention and treatment groups. Selenium was administered in doses of 2 microg/kg b.w. per day and 2-MPG in 15 mg/kg b.w. per day, in all groups. Daily estimations of 24 h urine volume levels of thiobarbituric acid reacting substances (MDA) were performed in 20 animals, divided into a control group, a BaP-injected group, a tricapryline-injected group and a BaP-injected and treated by the low dose combination group. Results revealed that the low dose combination failed to exert any beneficial effect on mean survival time of animals treated either preventitively or therapeutically. An increased number of animals bearing a second (lung) tumor was, in addition, found in autopsy and histological examination in the low dose combination (PRG and TRG) and the high dose TRG groups. The high dose combination groups manifested a significant prolongation of the mean survival time of animals; complete remission of tumors developed in 16.8% of the animals in the treatment group and a 5.2% prevention of tumor formation in the preventive group, without any evidence of an increased number of double tumor formation in the PRG group. Urine MDA increased significantly in animals injected by BaP during the first 10 days and since the 90th day (formation of palpable tumors) after injection, in relation to control and tricapryline-injected groups. Complete prevention of urine MDA-increased values was obtained in BaP-injected and treated by the low dose combination animals. Results indicate that high doses (megadoses) of the antioxidant-anticarcinogen vitamins C and E in combination with carefully selected other antioxidants possessing supplementary actions, are probably needed in order to achieve a sufficient prevention and treatment of malignant diseases.