Images in clinical medicine. Hemoglobinuria with malaria

Host-Derived Cytotoxic Agents in Chronic Inflammation and Disease Progression

At inflammatory sites, cytotoxic agents are released and generated from invading immune cells and damaged tissue cells. The further fate of the inflammation highly depends on the presence of antagonizing principles that are able to inactivate these host-derived cytotoxic agents. As long as the affected tissues are well equipped with ready-to-use protective mechanisms, no damage by cytotoxic agents occurs and resolution of inflammation is initiated. However, long-lasting and severe immune responses can be associated with the decline, exhaustion, or inactivation of selected antagonizing principles. Hence, cytotoxic agents are only partially inactivated and contribute to damage of yet-unperturbed cells. Consequently, a chronic inflammatory process results. In this vicious circle of permanent cell destruction, not only novel cytotoxic elements but also novel alarmins and antigens are liberated from affected cells. In severe cases, very low protection leads to organ failure, sepsis, and septic shock. In this review, the major classes of host-derived cytotoxic agents (reactive species, oxidized heme proteins and free heme, transition metal ions, serine proteases, matrix metalloproteases, and pro-inflammatory peptides), their corresponding protective principles, and resulting implications on the pathogenesis of diseases are highlighted.

[Abnormal urine color assessment: The urine wheel]

Looking at the urine for diagnostic purposes, once performed by ancient Egyptians, can still provide some valuable clues in modern medicine. Several diseases have been named after their associated urine color and this underlines the clinical value of visual urine inspection: blue diaper disease, purple urine bag syndrome, black urine disease or porphyria. Abnormal urine color could be challenging for the clinician: it may reveal neoplastic disease (urologic cancer; melanoma), cell lysis (rhabdomyolysis; hemolysis), infection (lymphatic filariasis; malaria), enzyme deficiency (porphyria; alkaptonuria), medication or food intake. In this article, we present the diagnostic approach, the mechanisms involved and the main causes of abnormal urine color.

Clinical profile and outcome of pigment-induced nephropathy

Background

Pigment nephropathy represents one of the most severe complications of rhabdomyolysis or hemolysis.

Methods

We performed a retrospective observational study to analyze the etiology, clinical manifestation, laboratory profile and outcome in patients with biopsy-proven pigment-induced nephropathy between January 2011 and December 2016. History, clinical examination findings, laboratory investigations and outcome were recorded.

Results

A total of 46 patients were included with mean follow-up of 14 ± 5.5 months. Mean age was 40.15 ± 12.3 years, 65% were males (male:female, 1.8:1) and ∼37 (80.4%) had oliguria. Mean serum creatinine at presentation and peak creatinine were 7.5 ± 2.2 and 12.1 ± 4.3 mg/dL, respectively. Evidence of rhabdomyolysis was noted in 26 patients (64%) and hemolysis in 20 patients (36%). Etiology of rhabdomyolysis include snake envenomation (10 patients), seizures (7), strenuous exercise (5), wasp sting (2) and rifampicin induced (2). The causes of hemolysis include rifampicin induced (7 patients), sepsis (5), malaria (3), mismatched blood transfusion/transfusion reaction (3) and paroxysmal nocturnal hemoglobinuria (2). On renal biopsy, two patients had acute interstitial nephritis and two had immunoglobulin A deposits in addition to pigment nephropathy. All except one (97.8%) required hemodialysis (HD) during hospital stay and mean number of HD sessions was 9 ± 2. A total of three patients with sepsis/disseminated intravascular coagulation died, all had associated hemolysis. On statistical analysis, there was no difference between AKI due to rhabdomyolysis and hemolysis except for high creatine phosphokinase in patients with rhabdomyolysis and Lactate dehydrogenase level in patients with hemolysis. At mean follow-up, five patients (12%) progressed to chronic kidney disease (CKD).

Conclusions

Pigment nephropathy due to rhabdomyolysis and hemolysis is an important cause of renal failure requiring HD. The prognosis was relatively good and depends on the etiology; however, long-term studies and follow-up are needed to assess the true incidence of CKD due to pigment nephropathy.

Hemoglobinuria-related acute kidney injury is driven by intrarenal oxidative reactions triggering a heme toxicity response

Intravascular hemolysis can result in hemoglobinuria with acute kidney injury. In this study we systematically explored two in vivo animal models and a related cell culture system to identify hemoglobinuria-triggered damage pathways. In models of stored blood transfusion and hemoglobin (Hb) exposure in guinea pigs and beagle dogs we found that hemoglobinuria led to intrarenal conversion of ferrous Hb(Fe²⁺) to ferric Hb(Fe³⁺), accumulation of free heme and Hb-cross-linking products, enhanced 4-hydroxynonenal reactivity in renal tissue, and acute tubule injury. These changes were associated in guinea pigs with activation of a renal cortex gene expression signature indicative of oxidative stress and activation of the unfolded protein response (UPR). Tubule cells of hemolytic animals demonstrated enhanced protein expression of heme oxygenase and heat shock protein and enhanced expression of acute kidney injury-related neutrophil gelatinase-associated lipocalin. These adverse changes were completely prevented by haptoglobin treatment. The in vivo findings were extrapolated to a MS-based proteome analysis of SILAC-labeled renal epithelial cells that were exposed to free heme within a concentration range estimate of renal tubule heme exposure. These experiments confirmed that free heme is a likely trigger of tubule barrier deregulation and oxidative cell damage and reinforced the hypothesis that uncontrolled free heme could trigger the UPR as an important pathway of renal injury during hemoglobinuria.

Blackwater fever like in murine malaria

Blackwater fever (BWF) is the term used to designate the occurrence of hemoglobin pigments in the urine of patients infected with malaria parasites. BWF is more often associated with Plasmodium falciparum infection in man. The pathogenesis of BWF has not been explained satisfactorily. In the present study, the clinical and pathological observations made upon CD1 mice infected with Plasmodium yoelii yoelii lethal strain with clinical signs of hemoglobinuria and acute renal failure were evaluated. From the 40 P. yoelii yoelii-infected mice, 14 presented hemoglobinuria. In the observations, it was emphasized that hemoglobinuria occurred in the animals 1-2 days before they die. At 6 days post-infection, infected hemoglobinuric mice (HM) exhibited clinical signs such as dark red urine, apnea, and evident oliguria and hematuria; urine microscopical examination showed very few red blood cells. The entire non hemoglobinuric infected mice had a high parasitemia preceding the time of death, while the HM parasitemia was just detectable. In HM, marked hepatosplenomegaly, anemia, and renal and hepatic dysfunction were observed with the blood chemistry analysis at 6 days post-infection. Severe renal lesions were demonstrated in histopathological and scanning electron microscopy samples. Occlusion and necrosis of convoluted tubules were the main lesions found. The conditions required for the experimental production of hemoglobinuria in CD1 mouse infected by P. yoelii yoelii is still unknown. The clinical picture of a BWF, like in our rodents, was produced exclusively by the interaction between the parasite and its host. Results showed that hemoglobinuria in CD1 mice infected with P. yoelii yoelii and BWF in man infected with P. falciparum are similar in their pathogenesis.