Hepatic porphyrin concentration and uroporphyrinogen decarboxylase activity in hepatitis C virus infection

Hepatitis C virus core protein triggers abnormal porphyrin metabolism in human hepatocellular carcinoma cells

Porphyria cutanea tarda (PCT), the most common of the human porphyrias, arises from a deficiency of uroporphyrinogen decarboxylase. Studies have shown a high prevalence of hepatitis C virus (HCV) infection in patients with PCT. While these observations implicate HCV infection as a risk factor for PCT pathogenesis, the mechanism of interaction between the virus and porphyrin metabolism is unknown. This study aimed to assess the effect of HCV core protein on intracellular porphyrin metabolism to elucidate the link between HCV infection and PCT. The accumulation and excretion of porphyrins after treatment with 5-aminolevulinic acid, a porphyrin precursor, were compared between cells stably expressing HCV core protein and controls. Cells expressing HCV core protein had lower amounts of intracellular protoporphyrin IX and heme and had higher amounts of excreted coproporphyrin III, the oxidized form of coproporphyrinogen III, compared with controls. These observations suggest that HCV core protein affects porphyrin metabolism and facilitates the export of excess coproporphyrinogen III and/or coproporphyrin III, possibly via porphyrin transporters. Real-time PCR analysis revealed that the presence of HCV core protein increased the mRNA expression of porphyrin exporters ABCG2 and FLVCR1. Western blot analysis showed a higher expression level of FLVCR1, but not ABCG2, as well as a higher expression level of mature ALAS1, which is the rate-limiting enzyme in the heme synthesis pathway, in HCV core protein-expressing cells compared with controls. The data indicate that HCV core protein induced abnormal intracellular porphyrin metabolism, with an over-excretion of coproporphyrin III. These findings may partially account for the susceptibility of HCV-infected individuals to PCT development.

Prevalence of photosensitivity in chronic hepatitis C virus patients and its relation to serum and urinary porphyrins

BACKGROUND & AIMS

HCV is a major cause of chronic liver disease in Egypt. The aim was to study the prevalence of photosensitivity among asymptomatic HCV-infected patients and its possible relation to porphyrins levels and whether it can be considered an alarm for early diagnosis of the disease, which is the most important goal in the management.

METHODS

This study included 100 accidentally discovered HCV positive cases and 100 HCV negative healthy controls. All patients and controls were subjected to: Detailed history and clinical examination, dermatological examination including evaluation of reaction to solar exposure, measurement of serum AST, ALT, albumin, bilirubin, serum and urinary porphyrins levels.

RESULTS

The prevalence of photosensitivity among HCV-positive cases (33%) was significantly higher compared to 10% in the control group. Serum porphyrins were positive in 46 cases (46%), twenty-three cases (23%) had positive urinary porphyrins, while only four controls (4%) showed positive serum porphyrins and one (1%) showed positive urinary porphyrins, the difference was statistically significant. Cases with photosensitivity showed significantly higher prevalence of serum and urinary porphyrins existence as well as serum porphyrins levels. Levels of viraemia showed statistically significant relation to levels of porphyrins.

CONCLUSION

Asymptomatic chronic HCV infection cases showed significantly high prevalence of photosensitivity, which is related to the associated disturbance of porphyrins metabolism. Photosensitivity can thus be considered an early marker of HCV infection. Patients discovered to have recently acquired photosensitivity should be screened for HCV infection especially in endemic areas like Egypt.

Autoantibodies to human cytosol: a marker of sporadic porphyria cutanea tarda

The enzymes potentially involved in the pathogenesis of sporadic porphyria cutanea tarda (PCT) reside in liver cytosoles and microsomes. PCT is frequently associated with hepatitis C virus (HCV) infection, which is in turn associated with autoimmune manifestations. To investigate whether autoimmune reactions, possibly triggered by HCV, are involved in the pathogenesis of PCT, we measured by immunoblot autoantibodies to human cytosolic and microsomal liver fractions in 82 patients with PCT (77% with HCV infection), 105 with other liver disorders and 40 healthy subjects. Anti-liver cytosolic antibodies were more frequent in PCT patients (38/82, 46%) than in pathological controls (P < 0.05-P < 0.001) or in healthy subjects (3/40, 8%, P < 0.001). Among PCT patients, anticytosolic antibodies were more frequent in HCV positive (36/63, 57%) than in HCV negative (2/19, 11%, P < 0.05) cases. Reactivity to a 40-kDa cytosolic polypeptide was present in 20 PCT patients (19 HCV positive), being more frequent than in all pathological controls (P < 0.01-P < 0.0001). Histological activity index (P = 0.04) and antibodies to HCV (P = 0.027) - but not HCV RNA - were associated independently with anticytosolic antibodies as assessed by multivariate analysis. In contrast, frequency of antiliver microsomal antibodies was similar in PCT patients (24/82, 29%) and pathological controls (8-26%), being higher in the autoimmune hepatitis control group (23/23, 100%, P < 0.0001). In conclusion, anticytosolic antibodies, particularly to a 40-kDa polypeptide, are frequent in PCT and associated with HCV infection and severity of liver damage.